MECHATRONIC BURNER OF A COOKER HOB, COOKER HOB COMPRISING

THE BURNER, AND METHOD OF IMPLEMENTING THE COKER HOB

The present invention relates to a mechatronic burner of a cooker hob.

In the prior art gas cooker hobs are known comprising atmospheric burners.

Combustible and oxidizer (air) are mixed upstream of the combustion process, supplying a quantity of oxygen sufficient to oxidize all the supplied combustible or a part of it.

Atmospheric burners mounted with cooker hobs comprise valves for varying a flow rate of combustible gas with the purpose of varying a supplied thermal power, at least one ejector, at least one burner head, at least one flame sensor (FFD, Flame Failure Device) which interrupts the flow of combustible gas when the combustion is not detected, and at least one igniter.

The two most important components relating to burner performance are the ejector and the burner head or plate. The latter component has the function of stabilizing and anchoring the flame in the desired position and allowing the combustion process to be carried out in the desired manner to efficiently transmit heat to the container or dish to be heated.

The performance and goodness of the final chemical conversion process are strictly connected to the supply conditions upstream of the flame, and therefore to the reactant mixture obtained through the combination of ejector and burner head.

The ejector is a component that allows the energization of a low-energy fluid (secondary fluid), in this case air, through a jet with high kinetic energy (primary fluid) which in cooker hobs is the combustible gas. This solution allows exchanging amounts of momentum and mechanical energy without the use of moving parts.

Disadvantageously, the cooker hob thus described is not able to optimize its operation while considering the variations in the boundary conditions to which it may be subjected .

The object of the present invention is to provide a burner for a cooker hob which overcomes the disadvantages of the known art, is more energy efficient, limits unwanted emissions, guarantees safety and cooking precision .

According to the invention, this object is achieved with a burner of a cooker hob according to claim 1.

Another object of the present invention is to provide a mesoburner, where the term mesoburner refers to a burner of compact dimensions, that co-operates with the burner of claim 1 of a cooker hob, which overcomes the disadvantages of the known art, is more energy efficient, limits unwanted emissions, guarantees safety and cooking precision, is able to adapt its operation to variations in the composition of the combustible gas.

According to the invention this further object is achieved with a mesoburner that co-operates with a burner of a cooker hob according to claim 5.

A further object of the present invention is to provide a cooker hob which overcomes the disadvantages of the known art, is more energy efficient, limits unwanted emissions, guarantees safety and cooking precision .

According to the invention, this further object is achieved by a cooker hob according to claim 12 and 13.

A still further object of the present invention is to provide a method for implementing a cooker hob which overcomes the disadvantages of the known art.

According to the invention this still further object is achieved with a method for implementing a cooker hob according to claim 14.

Another still further object of the present invention is to provide a method for operating a cooker hob which overcomes the disadvantages of the known art.

According to the invention, this another still further object is achieved with a method for operating a cooker hob according to claim 15.

Other characteristics are envisaged in the dependent claims.

The features and advantages of the present invention will be more apparent from the following description, which is to be understood as exemplifying and not limiting, with reference to the appended schematic drawings, wherein:

figure 1 is a diagram of the atmospheric burner according to the present invention;

figure 2 is a detail of figure 1 showing a diagram of an atmospheric burner;

figure 3 is a detail of figures 1 and 2 showing a diagram of electrical connections between the control unit and sensors/actuators;

figure 4A is a detailed diagram of the preceding figures showing the burner with primary combustion air supply, inhaling it below the cooker hob. (Air from below) ;

figure 4B is a detailed diagram of the preceding figures showing an alternative burner with primary combustion air supply, inhaling it above the cooker hob. (Air from above) ;

figures 5A, 5B, 5C, 5D are detailed diagrams of the preceding figures showing alternative injectors and ejectors of the burner according to alternative geometries such as to integrate some of the possible types of air flow rate regulators;

figure 6 is a diagram of the alternative atmospheric burner of the present invention comprising a mesoburner; figure 7 is a detailed diagram of figure 6 showing the cooker hob comprising the mesoburner;

figure 8 is a detailed system diagram of figures 6 and 7 showing the compartment wherein the mesoburner is located;

figure 9 is a diagram of the mesoburner of figures 6-8;

figure 10 is a detailed diagram of figures 6-9 showing electrical connections between the control unit and sensors/actuators of the burner and the mesoburner; figure 11 is a representation of the detail relating to the introduction of the mixture of combusted gases and air near the flame front anchored to the burner, where this flow comes from the compartment of the mesoburner;

figure 12 shows a graph of a stability field of the mesoburner with a specific thermal load at the ports of the mesoburner on the abscissa and the primary air fraction on the ordinate;

figure 13 shows a graph of a trend of the volumetric ratio between the flow rate of inhaled air with respect to the flow rate of combustible gas supplied with the variation of the flow rate of combustible gas for certain values of the temperature of the combustible gas, of the primary combustion air, of the burner and for combustible gas provided with a defined molar mass;

figure 14 shows a graph describing a link between equivalence ratio and ionization current measured for certain values of total flow rate, temperature of the reactant mixture upstream of the burner head, burner temperature and composition of the combustible gas;

figure 15 shows a graph which describes the trend of the volumetric ratio between the flow rate of the inhaled air with respect to the flow rate of combustible gas supplied with the variation of the flow rate of combustible gas for certain values of the temperature of the combustible gas, of the primary combustion air, of the burner, for combustible gas provided with a defined molar mass and for a defined position of the air regulator;

figures 16, 17 and 18 show a flow chart which comprises steps of the operating method of the cooker hob according to the present invention.

With reference to the aforementioned figures and in particular figures 1-5D, a cooker hob 100 is shown comprising at least one atmospheric burner 10.

Usually the cooker hob 100 comprises two or more burners 10.

As shown in particular in figure 2, the burner 10 comprises at least one ejector 20 and at least one head 30.

The ejector 20 comprises an ejector duct 21, an injector 40 and an air flow rate regulating system 50.

The burner 10 is able to regulate its operation by responding to changes in boundary conditions by means of the regulator of an air flow rate 51/52, where the air is inhaled by the ejector 20. The inhaled air flow rate regulating system 50 comprises at least one electromechanical actuator 53 for regulating the primary combustion air flow rate. The cooker hob 100 comprises at least one control unit 200 which controls and commands the at least one electromechanical actuator 53 of the air flow rate regulating system 50.

The control unit 200 comprises at least one processor and at least one memory.

The boundary conditions that can vary are relative to the following observables: a temperature of a combustible gas T _gas supplied by the injector 40, a temperature of air T _air inhaled by the ejector 20, a temperature T _b of the burner 10, a thermal power P _gas supplied by the head 30 of the burner 10. In addition to the variables previously described, the chemical composition of the combustible x _gas is also a parameter that can be subject to changes, thus influencing burner operation. To take into account the latter parameter, however, a burner of compact size must be introduced, which in the present discussion has been renamed with the term mesoburner, as shown in figures 6-11.

As shown in particular in figure 2, the head 30 of the burner 10 comprises holes 31 adapted to firmly anchor the flames generated by the combustion of the reactant mixture given by comburent and combustible.

The burner 10 comprises at least one injector 40 which supplies the ejector duct 21 with combustible gas 301 by means of one or more nozzles or orifices 41. The combustible gas 301 has a modest flow rate, but flowing through at least one orifice 41 of the injector 40 increases its speed and the high-speed flow of the gas 301 that exits the orifice 41 allows recalling air 310 from the surrounding environment, hence the term atmospheric burner 10.

As shown in particular in figures 2, 4A-4B, 5A-5D, the orifice 41 of the injector 40 comprises a duct generally axially aligned with an axis along which the ejector duct 21 of the ejector 20 extends.

As shown in particular in figure 2, the ejector duct 21, depending on the chosen design, can have a cylindrical or Venturi geometry. Preferably as shown in figures 2 and 5A-5D, the section of the ejector duct 21 comprises a convergent section which defines a head mixing area 22 which is the inlet area of the ejector duct 21, in which there is an air recall environment 310 due to the gas flow 301 coming from the orifice 41 of the injector 40, a throat section 23 and a divergent section defining a mixing duct 24, in which the mixing between the reactants takes place, that is, the region where the mixing between air 310 and combustible 301 takes place.

The geometry of the injector 40, the geometry of the head mixing area 22, of the throat 23 and of the mixing duct 24 of the ejector duct 21 are the main geometric parameters that determine the ratio between the quantity of air inhaled and the gas supplied.

As shown in particular in figure 2, at one end of the mixing duct 24 there is the connection with the head 30 of the burner 10 and it is thus possible to define a fluid-dynamic circuit and relative pressure drops of the atmospheric burner 10.

Once the geometry of the burner 10 is assigned, i.e. of the group comprising the ejector 20 and head 30 of the burner 10, the thermo-fluid-dynamic properties of the primary and secondary fluid, the flow rate of combustible gas and the possible boundary conditions connected to the use of the object, the result of the combustion process and its quality can be defined.

To introduce a control parameter on the process, in addition to the regulation of the gas flow rate, the air regulating system 50 is inserted, which allows modifying the geometry of the ejector 20 to reduce or increase the quantity of air inhaled. Some alternative types of air regulators 52 are shown in figures 5A-5D.

Modifying the geometry of the ejector 20 means modifying the air inlet section or geometric parameters by means of the air flow rate regulating system 50. For example a moving obstacle 51 can be introduced.

Figures 5A-5D show an enlargement of the ejector 20 between the injector 40 and the ejector duct 21 and presents different types of air flow regulators 52 which are alternative to each other, driven by electromechanical actuators 53 as shown in figure 1. Flow rate regulators 51, 52 operated by electromechanical actuators 53 modify the ratio between the flow rates of the supplied combustible gas 301 and the inhaled ambient air 310 that flow into the head mixing area 22 of the ejector duct 21.

The actuator 53 automatically regulates the ratio between the flow rates of the combustible gas 301 and the ambient air 310 which flow into the head mixing area 22, automatically responding to changes in the boundary conditions. This actuator 53 can thus be connected to the control unit 200 which gives instructions for controlling the combustion process. By acting on the inhaled air 310 it is in fact able to control the equivalence ratio of the combustible- comburent mixture, defined as the ratio between the air 310 - combustible 301 ratio that should be present in stoichiometric conditions with respect to that actually achieved. This parameter is of fundamental importance as it affects the stability, temperatures and emissions of combustion processes. It is in fact the main parameter subject to monitoring in combustion processes on a domestic and industrial scale, in transport and in the generation of electrical power.

The air inhaled 310 through the operating principle of the ejector 20 is called primary air 310 to distinguish it from the air with which the flame generated by the combustion process will come into contact, which is instead identified as secondary air 320.

Depending on whether the primary air 310 is inhaled below as shown in figure 4A or alternatively above a surface 101 of the cooker hob 100 as shown in figure 4B, the terms used are burners 10 with supply from below (Air from below) or from above (Air from above) . A schematic representation of the two technologies is shown in figures 4A and 4B. Both solutions are widespread and despite the obvious aesthetic differences, they base their operation on the same physical principles.

As shown in particular in figure 1, the variable geometry atmospheric burners 10 are integrated with the surface 101 of the cooker hob 100.

The cooker hob 100 comprises support grids 110 for pots 120 or for other kitchen tools. The support grids 110 comprise at least one portion adapted to keep the pan 120 raised at a certain height above the burners 10.

The cooker hob 100 comprises a means for regulating the flow rate of combustible gas 130 sent by means of a duct 134 of the combustible gas 301 towards the injector 40. Said means for regulating the flow rate of combustible gas 130 allows controlling the thermal power supplied by the head 30 of the burner 10. The means for regulating the flow of combustible gas 130, and therefore the flow rate of gas 301, usually comprises a knob 131 to be handled by a user, a valve or tap 132 for the combustible gas 301. The valve 132 is adapted to pass at least from an open position to a closed position. The cooker hob 100 also comprises a position transducer 133 for indicating the position of the valve 132. For example, the transducer 133 comprises an encoder which detects the actual position of the valve 132 of gas regulation 301. Alternatively to that which is shown in figure 1, the valve 132 could be of the electronic type and in this case the regulation could still take place through a knob 131 or through other interfaces integrated in the cooker hob (for example buttons) . Using electronic valves, the position of the valve 132 of the combustible gas 301 could be known without using an encoder but knowing the instructions given by the control unit 200 to the valve itself based on if and how open it is.

The cooker hob 100 comprises a combustible gas temperature sensor 140 for detecting the temperature of the combustible gas 301. The combustible gas temperature sensor 140 is for example a thermocouple. The combustible gas temperature sensor 140 is positioned inside the duct 134 of combustible gas 301 supply or inserted in the body of the injector 40, as shown in figure 1. The cooker hob 100 comprises an air temperature sensor 150 for measuring the temperature of the primary air 310. The air temperature sensor 150 is a thermocouple for example. The air temperature sensor 150 is positioned in a place adapted to measure the temperature of the primary air 310, for example it is located outside the ejector duct 21 and outside the injector 40, positioned near the entrance to the head mixing area 22 of the ejector duct 21.

The burner 10 comprises at least one temperature sensor inserted for example in said at least one head 30. This sensor can be for example a thermocouple placed in contact with the head 30 or other appropriately chosen parts of the burner 10.

The burner 10 comprises the air flow rate regulating system 50 which comprises the electromechanical actuator 53 which comprises for example an encoder and a shutter 51/52 adapted to pass from at least an open position to a closed position, so as to regulate the flow rate of the air 310 - combustible gas 301 mixture entering the ejector duct 21.

The at least one head 30 of the burner 10 comprises at least one igniter 36 for triggering the combustion process of the mixture and at least one flame sensor 37 (flame failure device, FFD) adapted to interrupt the supply of combustible gas 301 if the presence of a flame is not detected.

Taking into account the thermo-fluid-dynamics underlying the operation of the atmospheric burner 10, the introduction of the variable geometry and of the sensors, which are measuring means, 133, 140, 150, 35 shown above, allows regulating the ratio between the volume of inhaled air 310 and volume of supplied combustible gas 301, in the hypothesis that the combustible gas 301 has a certain chemical composition, ideally able to represent the combustibles actually distributed in the market wherein the cooker hob 100 is used well. The fuel chemical composition to be considered could be also transmitted to the control unit 200 from an external source thanks to a suitable interface, for instance through the use of IoT (Internet of Things) concepts that involve the connection of household appliances to internet. In that way the control unit can update the fuel chemical composition of reference according to the data provided by the fuel supplier.

This regulation has the object of imposing the desired equivalence ratio for each burner 10 with the variation of the thermal power supplied by the user, the temperature of the burner 10, of the air 150 and of the combustible gas 140.

It is also possible to set a specific initial position of the air regulating system 50, suitable for a ready lighting of the burner 10, to then modify the geometry of the ejector 20 to obtain instead the optimal conditions in terms of energy efficiency, limitation of unwanted emissions, safety and amplitude of the regulation range of the supplied power based on the signals obtained.

The situation described up to now substantially entails the modification of commercially available burners 10 or the implementation of new burners to include the air regulating systems 50, the regulators 51-52, the relative actuators 53 and the various measuring means 133, 140, 150, 35 to connect to the burners 10 and to the valves 132 of the combustible gas 301 of each of them.

The cooker hob 100 comprises at least one electronic control unit 200, suitably located, which is adapted to receive the signals relating to the presence of flame, the signals relating to the measured parameters pertaining to each burner 10 (opening of the gas valve 132, inhaled air temperature 310, supplied combustible gas temperature 301, burner temperature 10, position of the air regulating system 50) and to give instructions to the actuator 53 of the air regulator 51-52 based on algorithms implemented in the same control unit 200.

It is possible to envisage that the ideal position of the control unit 200 is below the surface 101 of the cooker hob 100.

In particular, the flame failure signal FFD is a signal required by the control unit 200 in order to know if the single burner 10 of the cooker hob 100 is at that moment off, which therefore allows the control unit 200 to know whether or not to set the air regulating system 50 in ideal conditions for lighting without making further adjustments.

The control unit 200 is electrically connected to the sensor for detecting the temperature of the burner 35, to the flame sensor 37, to the air flow rate regulating system 50, to the combustible gas temperature sensor 140, to the air temperature sensor 150, to the means for regulating the flow of combustible gas 130, as shown in the diagrams of figures 1 and 3, so that the data: the temperature of combustible gas T _gas , the temperature of the inhaled primary air T _aria , the temperature of the burner T _b and the supplied thermal power P _gas are data transmitted to the control unit 200.

The combustible gas 301 supply can be managed directly by the user, exactly as is the case today in the most common cooker hobs on the market. Alternatively it is possible, by implementing electronic valves, that the control unit 200 can act on the valve 132 of the flow regulator 130. In this way the regulation aimed at obtaining a more energy-efficient burner, which limits unwanted emissions, guarantees safety and precision in cooking could have the advantage not only of air flow rate regulating systems 50 but also of regulations implemented on the flow rate of combustible gas 301. It should be noted that in practice it is the user who chooses the supplied thermal power based on the requirements of the cooking process he/she wishes to implement. The introduction of regulations of the control unit 200 on the valve 132 for purposes other than those related to the safety of use of the cooker hob 100 should therefore be limited in their magnitude.

From the user's point of view, therefore, there may not be any difference in the methods of use or in the appearance of the cooker 100 with respect to that which is present on the market. All the modifications and additional components can in fact be located below the surface 101 of the cooker hob 100 and in the case of burners 10 with inhalation from above below the head 30 of the burner 10.

Alternatively, as shown in figures 6-11, it is possible to provide that the cooker hob 100 also comprises a mesoburner 60.

The mesoburner 60 co-operates with the burner 10 of the cooker hob 100, allowing a synergistic effect to be obtained for the present invention.

Considering the composition of the combustible x _gas requires that the cooker hob 100 comprises an additional component hereinafter called mesoburner 60.

The mesoburner 60 is a burner of compact and lesser dimensions than those of the other burners 10 and is used in the present invention to obtain useful measurements for the purposes of correct regulation of the main burners 10 designed for cooking and mounted with the cooker hob 100.

The mesoburner 60 is placed in a compartment suitable for ensuring the reliability of the measurements, is equipped with a specific supply line and ancillary components connected to its installation in the cooker hob 100 and its operation.

The mesoburner 60 allows regulating the flow rate of air inhaled by each burner 10, advantageously optimizing its operation in terms of energy efficiency, limiting unwanted emissions, safety and cooking precision, thanks to the detection of the following parameters: flow rate of combustible gas flowing in the mesoburner 60, temperature of the combustible gas supplied to the mesoburner 60, temperature of the air inhaled by the mesoburner 60, temperature of the mesoburner 60, ionization current measured on the mesoburner 60, flow rate of combustible gas supplied to the single burner 10 examined, temperature of the combustible gas supplied to the single burner 10 examined, temperature of the air inhaled by the single burner 10 examined, temperature of the single burner 10 examined .

The variable geometry atmospheric burners 10 described above also comprising the mesoburner 60 can also consider variations in the composition of the combustible gas 301 in the regulation of the combustion. It is necessary to introduce the mesoburner 60 which is a small atmospheric burner not designed directly for cooking .

It is sufficient that there is at least one mesoburner 60 for the entire cooker hob 100, unlike the burners 10 which can be multiple burners 10 of the cooker hob 100. The mesoburner 60 must be inserted in a compartment to be protected from possible dirt and damage. The most suitable placement is below the surface 101 of the cooker hob 100.

As shown in particular in figure 9, the mesoburner 60 has limited dimensions. The mesoburner 60 comprises an igniter 66, an ejector duct 62, a head 63 and an electrode 64, located above the head 63 of the mesoburner 60, a sensor for detecting the temperature of the mesoburner 65. The electrode 64 measures an electric current defined as an ionization current. It has been found that the flames of hydrocarbons generate ions during combustion, even if in very modest concentrations. By imposing a potential difference between two electrodes 64, connected to each other and located upstream and downstream of a flame front 106 of the mesoburner 60, the presence of such ions gives rise to the passage of a current which is measured by means of an ionization current sensor 68, which for example is a circuit for measuring the ionization current that can also be used for detecting the FFD signal. The ionization current sensor 68 comprises an ammeter and a power supply connected to the two electrodes 64 located above and below the flame front 106. Beyond the complex chemistry that exists at the foundation of the empirical results found, which is still the subject of studies today, in practice the measurement of the ionization current makes it possible to assess the presence of combustion processes (FFD signal) and to correlate the current circulating in the system to the equivalence ratio with which the burner 10 is operating if natural gas such as combustible is used, having methane as its predominant component. The possibility of correlating ionization currents and equivalence ratios for other combustibles is still to be verified.

As anticipated, the measurement of the ionization currents presupposes the use of an electrode 64 positioned above the head 63 of the mesoburner 60

(downstream of the flame front 106) and another electrode 64 under the head 63 of the mesoburner 60 (upstream of the flame front 106) .

Alternatively, the function of the electrode 64 upstream of the combustion process can be carried out by the mesoburner 60 itself, which must be made with conductive material.

The two electrodes 64 are connected to each other, integrating the measurement system of the circulating current. In the following there will be no further mention of the mesoburner 60 as electrode 64, but with this term only the one downstream of the flame front 106 will be indicated, immersed in the exhaust gases of the mixture burned by the mesoburner 60.

The electrode 64 is made of metal alloys resistant to high temperatures and can have different geometries. For example, planar geometries have been studied, using a metal mesh parallel to the plane of the mesoburner 60 with sufficient extension to cover the entire surface of the head 63 of the mesoburner 60 on which the flame 106 is stabilized, and alternatively a simpler cylindrical geometry, thus positioning the electrode 64 with its axis parallel to the head 63 of the mesoburner 60. The distance between the electrode 64 and the mesoburner 60 as well as the voltage are important parameters, since they influence the signal relative to the ionization current obtained. Without reporting any further considerations, it can be briefly said that combustion control based on ionization currents is an ideal solution from a technical and commercial point of view for products intended for mass consumption, able to provide a signal for regulation based on the generation of electrically charged species in the flame front 106, primarily a function of the specific burner analysed, of the equivalence ratio, of the fuel flow rate or the air- gas mixture flow rate, of the geometry and position of the adopted electrode 64 and of the imposed electric field .

It is thus possible to know the equivalence ratio with which the mesoburner 60 operates and consequently to set the regulation to be adopted on the burners 10 designed specifically for cooking, comparing the operating conditions of the mesoburner 60 with those of the single burner 10 which must be regulated, one 10 independently from the other 10 of the plurality of burners 10 of the cooker hob 100.

In detail, the mesoburner 60 is a compact atmospheric burner like the one shown in figures 8 and 9 which comprises, in addition to the igniter 66, which is an ignition system, also a flowmeter or pressure transducer 71 for determining or validating the flow rate of flowing combustible gas 302, a combustible gas temperature sensor 141 (for example a thermocouple) inserted in a gas supply duct 46 or in the body of an injector, an air temperature sensor 151 (for example a thermocouple) located near the inlet of an ejector duct 62 of the mesoburner 60, a temperature sensor of the mesoburner 65 (for example a thermocouple) integrated in the head 63 of the mesoburner 60, one or more electrodes 64 and a circuit measuring the ionization current 68.

It is envisaged that the mesoburner 60 can be preferentially covered by solid walls 81 arranged for avoiding secondary air inflows before the exhaust gases generated by the flame front 106 come into contact with the electrode 64.

The cooker hob 100 also comprises the control unit 200 electrically connected with the sensors and the actuators 26, 135, 66, 68, 71, 65, 151, 141, 160, 37, 130, 35, 150, 140, 50 of both the burners 10 and the mesoburner 60 as shown in particular in figures 6 and 10.

The control unit 200 controls the opening of a gas valve 135 when at least one of the burners 10 of the cooker hob 100 is lit and therefore the ignition procedures of the mesoburner 60, of safety and of cooling .

As shown in particular in figure 8, preferably the mesoburner 60 is installed in a special compartment 80 to protect the mesoburner from damage or dirt. This compartment 80 is provided with a fan 26 (also controlled by the control unit 200) for the inhalation of an air flow rate 311 greater than that which in any condition may be required by the mesoburner 60. The motion of the aforesaid air flow 311 inside the compartment must not affect the operation of the ejector 62 of the mesoburner 60, so that the latter can behave exactly as if it were in still air. At the same time the shape of the compartment 80 must prevent the combusted gases 330 from being inhaled together with the primary air 312 since this would affect the measurements linked to the ionization current. Still referring to the measurements connected to the ionization current, it may be necessary to introduce solid walls 81, made of ceramic material, that prevent the mixing of combusted gases 330 with secondary air until they have come into contact with the electrode 64.

As shown in figure 8, a grid or a cage 84 is preferentially provided comprising a plurality of through openings 83 adapted to the passage of air, making it air that is as still as possible. The cage 84 encloses the mesoburner 60 inside. The plurality of through openings 83 of the cage 84 allows a homogeneous and stationary flow of air to be obtained near the ejector duct 62 which will then inhale the combustion air 312 of the mesoburner 60.

At the outlet of the compartment 80, since the exhaust gases 340 of the mesoburner have an enthalpy content which cannot be released into the environment without producing a useful effect for cooking and, in addition to this, could contain fractions of non- combusted substances, the aforementioned exhaust gases must be sent to one of the burners 10 which are lit in that moment . To realize this redirecting of the gases 340 which comprise the combusted gases 330 and the remaining portion of the air 311 entering the compartment 80 of the mesoburner 60, it is necessary to provide a motorized node 160 connected to the compartment 80 and to various ducts 163 leading to the release points 165 of the exhaust gases 340 near each burner 10, as shown in particular in figures 6, 7 and 11.

To avoid losses from the energy point of view and to avoid the establishment of excessively hot regions, it is advisable that the compartment 80 of the mesoburner 60 be thermally insulated, at least at its top, as it is advisable to thermally insulate the outlet duct 85 connected to the compartment 80, the distribution node 160 and the ducts 163 which branch out towards the different burners 10.

The regulation of the combustion process takes account of the fact that the mixture of combusted gases 330 and air coming from the mesoburner 60 is sent only to one or some of the burners 10 which are lit in that moment. It follows that it is necessary to know the position in which an actuator 162 is placed which controls the motorized node 160. In this way the choice of the equivalence ratio sought in each burner 10 will not only be based on the thermal power supplied by the user and on the temperature of the burner 10 but also on the consideration of this additional flow. This can be important in particular in the presence of burners 10 with inhalation of the primary air 310 above the surface 101 of the cooker hob 100.

In the eyes of the user, the only difference with respect to a traditional cooker hob 100 would therefore be in the sections supplying the gas mixture 340 coming from the mesoburner 60 to the different burners 10.

In particular it is possible to note in figures 6 and 11 how the mixture 340 coming from the compartment of the mesoburner 80 is sent through the duct 85, the motorized node 160, the duct 163 to a manifold 164 positioned near the burner 10 such as to release said mixture 340 near the flame front 107 of the burner 10, through ports 165, at the same time mixing with the secondary air 320.

A diagram showing the various components mentioned so far and the variables which must be known in order to set the combustion regulation strategies, identified for each of them, is shown in figure 7.

At the end of cooking, once all the burners 10 have been turned off and consequently the control unit 200 has also turned off the mesoburner 60, it is possible to exploit the presence of the fan 26 to sequentially cool the burners 10 used. For this purpose, the number of revolutions per minute of the fan 26 can be increased so as to reduce the time required for cooling the individual burners 10.

That which has been said so far allows summarizing the task to be carried out by the control unit 200.

First of all, the control unit 200 detects the lighting of the burners 10. When the FFD signal of at least one burner 10 signals the presence of a flame (due to activation of the cooker hob 100 by the user), the control unit 200 starts the lighting of the mesoburner 60. It should be noted that the intention of the user to turn on the cooker hob 100 is known thanks to the transducer 133 of the position of the combustible gas valve 132 which, once a signal is detected outside the region corresponding to zero flow rate, can alert the control unit 200. Alternatively, it can be known thanks to the signal directly sent to the control unit if it is designed to control an electronic-type valve 132.

An ignition process could first include the placement of the motorized node in the position suitable to send the mixture 340 of the mesoburner 60 to the burner 10 which is lit. Subsequently the control unit 200 can start the fan 26 to carry out the washing of the compartment 80 and after a short time open the combustible gas valve 132 with the simultaneous activation of the ignition circuit 66 of the mesoburner 60 and of the circuit designed for detecting the ionization current 68.

Once the circuit designed for measuring the ionization current 68 has detected the presence of a flame (FFD signal), the control unit 200 can interrupt the power supply to the ignition circuit of the mesoburner 60. If the flame is not detected within a certain period of time it is possible to interrupt all the activities and restart the lighting procedure. After a certain number of failed attempts, the control unit 200 can interrupt the procedure and send a system lock signal. Still for safety reasons, it is opportune to detect that upon the start signal the fan 26 is actually operating or that there are no obstructions to the outflow of the mixture 340.

If another burner 10 is activated, the motorized node 160 can either divide the flow between several burners 10 or continue to send all the flow 340 to only one . When the cooking is finished and all the burners 10 are turned off, the control unit 200 must interrupt the flow rate of supplied combustible 302 to the mesoburner 60, closing the gas valve 135. At this point the fan 26 can continue to operate to wash the compartment 80 of the mesoburner 60 and sequentially cool the burners 10 which have been used. For this purpose, the temperature- related signal of the various burners 10 can be used to identify when it is appropriate to change the position of the motorized node 160, and consequently the burner 10 to be cooled. It should be noted that each time the user turns off a burner 10 the control unit 200 can act on the air regulator of that specific burner 10 to bring it to the optimal position for the ignition conditions.

At the moment in which the mesoburner 60 is active it is possible to use it as previously mentioned to obtain measurements relating to the actual equivalence ratio with which it is operating and consequently to regulate the burners 10 lit at that moment.

The control unit 200 measures the flow of combustible gas supplied 302 to the mesoburner 60 or checks that the mains supply pressure is suitable for obtaining a correct measure of the equivalence ratio. After this, the control unit 200 can therefore receive the signal from the mesoburner 60 relating to the measured ionization current, the temperature of the combustible gas supplied 302, the temperature of the inhaled air 312, and the temperature of the mesoburner 60. Once these variables are received in input they can be used, making use of appropriate algorithms implemented therein, to regulate the combustion for each of the other burners once it knows, for each of them, the degree of opening of the tap 132 of the gas set by the user, the temperature of the injected combustible gas 301, the temperature of the inhaled air 310, the temperature 35 of the burner 10, the position of the air regulating system 50 and whether the flow rate of combusted gases 330 and air 340 coming from the mesoburner 60 is sent to the specific burner 10 analysed.

In particular, the control unit 200 thus has the conditions to calculate the appropriate position of the air regulating system 50, check whether this coincides with the current one and, if not, send instructions to the actuator 53 relating to how much to move the air regulator 51, 52.

Alternatively, when the cooker hob 100 does not comprise any mesoburner 60 and a variable geometry atmospheric burner 10 is to be implemented without a mesoburner 60, the steps of the method which will be described below can be omitted from the first step to the eighth step.

Alternatively, it is possible to predict that if only four observables were to be taken into account, T _gas , T _aria , T _b , P _gas , the aforementioned mesoburner 60 would not be necessary. Without installing the mesoburner 60 it is possible to regulate the flow rate of air inhaled by each burner 10, optimizing its operation in terms of energy efficiency, limiting unwanted emissions, safety and cooking precision, assuming or receiving as an external information a certain reference combustible composition and thanks to the detection of the following parameters: flow rate of combustible gas supplied V _gas to the single burner 10 examined, temperature of the combustible gas supplied T _gas to the single burner 10 examined, temperature of the air inhaled T _aria by the single burner 10 examined, temperature T _b of the single burner 10 examined.

Alternatively, the invention described up to here can be implemented in different ways, making use of multiple engineering and experimental approaches. One of these approaches is described below.

As regards the method for implementing the mesoburner' s 60 macro-components and one or more burners 10, the method for implementing the cooker hob 100 comprises twelve steps.

The chronological sequence of the steps of the method is not to be considered as binding, nor is the implementation methodology described, which are both intended only to prove the feasibility of the object.

The steps for the implementation method of the macro-components mesoburner 's 60 and burners 10 refer to mathematical equations.

For greater clarity the symbols used in the mathematical equations that follow are listed below:

quivalence ratio

volumetric flow rate of combustible gas

volumetric air flow rate

volumetric flow rate of the air-

combustible mixture

r _gas combustible gas density

r _aria air density

s ratio between the supplied combustible gas density and that of the inhaled air

MM _gas combustible gas molar mass MM _aria air molar mass

R volumetric ratio between the air inhaled by the ejector and the combustible gas supplied

R m _stch mass ratio in stoichiometric air- combustible gas conditions

A _i passage area of the combustible gas nozzle

A _b passage area of the burner ports

A _g throat area of the ejector

D _g throat diameter of the ejector

D _i combustible gas nozzle diameter

p _atm atmospheric pressure

D _p pressure difference between upstream and downstream of the combustible gas nozzle

C _d-i flow coefficient of the combustible gas flow rate

w ejector flow rate reduction coefficient

C _d-b outflow coefficient of the burner ports

C _l ejector pressure loss coefficient

PA primary air fraction

PCS higher heating value of the combustible expressed in mass terms

thermal power molar flow rate of the j-th species

X _j mole or volumetric fraction of a given j- th species in the mixture

X _gas chemical composition of the combustible

R universal constant of gases

T _gas temperature of the supplied combustible gas T _aria temperature of the air inhaled by the ejector

T _mix temperature of the air-combustible gas mixture

T _b burner temperature

/ _ion ionization current

c _Pgas molar specific heat at constant pressure of the combustible gas

C _{p aria} molar specific heat at constant air pressure

c _{p ,} mass specific heat of the body to be heated

M _p equivalent mass of the body to be heated

DT difference between initial and final temperature of the heated body for efficiency tests

t time

geometria position taken by the air regulator of the ejector

gas _meso binary variable linked to the supply of the gases coming from the mesoburner

P _gas thermal power supplied by the burner.

In particular, the sequence of steps of an implementation method of the cooker hob 100 comprising the mesoburner 60 is shown.

The first step to the seventh step of the method are steps for implementing the mesoburner 60.

A first step involves a choice of the nominal power of the mesoburner 60.

The nominal power of the mesoburner 60 is calculated starting from equation 1 shown below and is therefore given by the product of the nominal combustible gas flow rate of the combustible gas 302 taken as a reference (for example G20) for the corresponding heating value (conventionally the higher heating value is assumed) . This must be chosen carefully by the designer. In fact, this power must be the result of the compromise given by seeking to minimize the thermal power supplied to the mesoburner 60, so as to make it as negligible as possible with respect to that supplied to the burners 10 designed for cooking, without however causing an excessive miniaturization of the mesoburner 60 itself, which would compromise the cost of the device and its reproducibility on an industrial scale.

Equation 2 below can be a useful reference from this point of view since it allows evaluating the diameter the nozzle of the injector will have (calculating it starting from the area A _i ) with the variation of the combustible gas flow rate 302 by setting certain parameters that can be set or estimated starting from values reported in the literature (as in the case of the outflow coefficient, C _d-i ) .

Subsequently using equation 4 shown above considering an opportune value of the coefficient of flow rate reduction w starting from that which is reported in the literature, it is possible to obtain a first estimate of the throat diameter of the ejector 62 to have a determined value of R (equation 3) which indicates the ratio between the air inhaled 312 and the gas injected 302 in volumetric terms (for example by first choosing a fairly rich mixture, which involves more stable flames and reduced throat diameters) and thus a certain F (equation 5) and a certain total volumetric flow rate in isothermal conditions (equation 6) . These last two parameters are in turn useful for a first geometric sizing of the head 63 of the mesoburner 60. It should be noted that by knowing the throat diameter, it is possible to estimate what the length of the mixing duct of the ejector 62 should be starting from the recommendations found in the technical literature. In this way, on the whole there is a preliminary evaluation of the dimensions of the mesoburner 60 starting from the chosen nominal power, being able to evaluate its suitability or not. A second step involves the sizing of the head 63 of the mesoburner 60.

The head 63 of the mesoburner 60 can be made with different configurations ranging from porous septa to perforated plates with ports of varying geometry and size. The fundamental aspect to consider is the cost of the choice made and its reproducibility on an industrial scale .

For the choice of the total passage section of the combustible mixture through the head 63 of the mesoburner 60, where the flame 106 will be anchored, reference can be made to equation 7, obtained by isothermal conditions and hypotheses applicable to atmospheric burners 10 in practice. In doing so it is possible to estimate the coefficients linked to the pressure losses C _d-b and C _l consistently with what is reported in the technical literature. For the actual dimensions of the individual ports, their geometry and spatial distribution, reference should be made to the known concepts related to the speed of propagation of the flame front 106, the diameter of quenching and to the empirical surveys detailed in the literature.

It should be noted that the previously adopted equation 4 is reported as valid for burners where the size of the burner ports is such as to make their effect on the inhaled air negligible. In particular, it is recommended that the ratio between the outflow area from the burner ports and the area of the ejector throat section is greater than 1.5. If this is not verified for the previously obtained passage sections, use can be made of equation 8 to recalculate the term D _g . The choice of the materials with which to make the head of the mesoburner 60 is also an important parameter and it is possible to adopt, for example, metals already commonly used for the production of burners.

The design must also include those fundamental elements for the operation of the mesoburner 60 such as the igniter 66, the ionization electrode 64 and any solid walls 81 (made for example with ceramic material) arranged to avoid the introduction of secondary air before the combusted gases 330 reach the electrode 64.

Once the configuration has been chosen, the head 63 of the mesoburner 60 can be connected to a duct in which a flow rate of combustible gas 302 and one of known air are supplied.

The supply can for example be carried out by means of flowmeters connected to cylinders containing the combustible under pressure and to compressed air transport ducts. It should be noted that the duct upstream of the burner head must be long enough to allow a complete mixing of the reactants. Once the flow rate and the composition of the flows is known, it is possible to reconstruct the stability field 501 of the mesoburner 60 as shown in figure 12, which shows the specific thermal power on the burner ports on the abscissa 912 and the fraction of primary air on the ordinate 913, identifying the regions of flash back 502, flame lift 503 and sooting 504 through observation of the flame. In detail, video footage can be taken to detect that for a given nominal combustible gas flow rate 302, with an increase in primary air 312 it is possible to reach instability conditions 503 (flame lift), or on the contrary reducing the primary air 312 (and therefore increasing F) , it is possible to reach the appearance of a yellow colour, which in hydrocarbon flames 504 signals the presence of fine carbonaceous particulate. Still using video footage, it is possible to identify the instant in which, by reducing the flow rate of combustible gas 302, flash back will occur. Therefore moving along two coordinates (combustible gas flow rate and fraction of supplied primary air) it is possible to obtain a graph like the one shown in figure 12.

The fraction of primary air (PA) is calculated as the ratio between the air actually supplied with respect to the air that should theoretically be supplied to oxidize all the supplied combustible (for example G20) and is clearly a parameter linked to F and R (equations 5 and 9) .

PA = F ^-1 (9)

The specific thermal power at the burner ports (Burner Port Loading) is nothing more than the ratio between the thermal power supplied (equation 1) and the total area of the burner ports.

Obtaining this graph therefore allows validating the design chosen as a function of the nominal power chosen, or alternatively, allows modifying the nominal power as a function of the operating range of the head 63 of the mesoburner 60 which has been characterized.

A third step of the method provides for the sizing of the ejector 62 of the mesoburner 60.

Having obtained the operating range of the head 63 of the mesoburner 60 and knowing the nominal thermal power, it is possible to choose the value of R which one wishes to always achieve under nominal conditions.

The choice of R must firstly aim to provide flammable mixtures and flames that fall within the stability field 501 previously defined when the boundary conditions vary (composition of the combustible gas, temperatures, etc.) and secondly adapted to obtain a signal as suitable as possible for obtaining the measurements connected to the ionization current. The measured signal will in fact be maximum for a given F (around 1.1) but working near this value can lead to signals that may not be unique and would involve the installation of additional systems to clarify doubtful situations. It would therefore be ideal to always operate with an R such as to give the highest possible current values and at the same time always in increasing or decreasing monotone sections.

Once this R has been chosen, it is possible to proceed with the design of the ejector 62 which can take place by means of empirical expressions (equations 2, 4 and other fluid-dynamic correlations) or by means of other tools such as CFD (computational fluid dynamics) . For this purpose it may be useful to experimentally evaluate the pressure losses connected to the head 63 of the mesoburner 60, for example by evaluating the total pressure difference upstream and downstream of the head 63 of the mesoburner 60 itself as the total flow rate varies, implementing this information in the calculation algorithms that will be used.

Once a first geometry of the ejector 62 has been obtained and carried out, it is possible to integrate it with the head 63 of the mesoburner 60 and carry out tests to evaluate the actual value of R under nominal conditions .

To do so it is sufficient to supply a known flow rate of combustible gas 302, of known composition, and at the same time isolate the head 63 of the mesoburner 60 from possible inflows of secondary ambient air, measuring the composition of the combusted gases. In fact, it must be remembered that compared to the previous point, the air flow rate 312 is no longer imposed but is inhaled by the ejector 62, resulting in an unknown parameter, difficult to measure at the inlet of the ejector 62. To obtain the composition of the gases it is sufficient to use an analyser of the composition of the combusted gases connected to a probe designed to withdraw the gases directly from the discharge of the mesoburner 60.

At this point, using atomic balances and knowing the composition of the combustible 302 and the ambient air inhaled 312 by the mesoburner 60, it is possible to obtain F and the actual ratio R. For example, assume operating with G20 gas (100% CH ₄ ) in conditions where it can be assumed that all the hydrogen present in the combustible goes to make H ₂ O and that the only other combustion products relevant for the definition of F are CO, CO ₂ and O ₂ . The following balance results in terms of molar flow rates:

The values measured by the analyser are generally on an anhydrous basis and show the molar fractions of the type measured (in this example CO, CO ₂ and O ₂ ) .

The molar fraction of N ₂ in the exhaust gases can be obtained as the complement to one of the molar fractions reported by the analyser: x _N2 = 1— x _CO2 — x _CO — x _O2

Since the molar flow rate of combustible is known from an atomic balance on the carbon, we have:

Knowing the molar flow rate of methane, having the total molar flow rate of dry gases is therefore immediate :

Once the total molar flow rate of dry exhaust gases has been calculated, this gives the molar flow rate of each individual type measured by the analyser:

Since the hypothesis has been made that all the hydrogen contained in the methane goes to make water, subsequently condensed, there is also the molar flow rate of the same thanks to an atomic balance on the hydrogen :

With an atomic balance on the oxygen it is therefore possible to determine the molar flow rate of supplied air since this is approximable in a mixture having a chemical composition equal to 21% O ₂ and 79% N ₂ .

It should be noted that in the example given, since the combustible is devoid of nitrogen fractions, the molar flow rate of air could have been calculated starting from the molar flow rate of nitrogen.

Once the molar flow rate of air is obtained, R and F are immediately obtained, since the molar and volumetric flow rates are bound by the ideal gases state law and that both the volumetric flow rate of the supplied gas and that of the inhaled air are at atmospheric pressure.

The solution model described above can of course be extended considering the measurement or estimation of any other combustion products such as H ₂ , unburned hydrocarbons (HC) , nitrogen oxides (NO _X) or any traces of water due to the incomplete dehydration of the exhaust gases .

Similarly, the approach used is applicable to combustibles of different known composition.

Once R is obtained, it is possible to evaluate if this is close to the value to be obtained or if it is necessary to modify the geometry of the ejector 62.

A fourth step of the method involves obtaining the expression of R _meso .

Once the definitive atmospheric mesoburner 60 is obtained, consisting of the ejector 62 and the head of the mesoburner 63, it is possible to proceed with the definition of the expression of R _meso , where the "meso" subscript is used to specify that it is the expression of R referred to the mesoburner 60 component.

To do so it is possible to make use of the same test bench used for the validation of the geometry of the ejector 62, therefore adopting a derivation of the known air-combustible ratio, the flow rate and composition of the combustible gas 302 and the composition of the exhaust gases 330, avoiding the inhalation of secondary air.

In this case, however, systems capable of controlling certain thermo-physical parameters must be introduced. In particular, the trend of R _meso must be assessed with the variation of the flow rate of combustible gas 302, temperature of combustible gas, temperature of the air, mesoburner temperature, composition of the combustible gas.

The flow rate and composition of the combustible gas are already under control since it is possible to supply combustible gas 302 of known composition by means of a cylinder and regulate the flow rate through a specific laboratory flowmeter. In particular, it is important to know the molar mass of the combustible gas since for an ideal gas at a given pressure and temperature, it is what allows obtaining its density.

The temperature of the combustible gas cam be measured/estimated in two ways from an application perspective: by inserting a temperature sensor 141 (for example a thermocouple) in the gas supply duct itself or in the body of the injector 45 of the ejector 62. The injector is in fact the element that due to its proximity to the burner may be subject to greater heating and given the reduced passage section and the high speed of circulation of the combustible gas inside it, will predominantly contribute to determining the actual temperature of the outflowing combustible gas.

For the arbitrary control during the experimental tests of the temperature of the combustible gas 302 it is sufficient, for example, to install a supply duct of the combustible gas heated by means of electric resistance, with thermal power supplied by the modular Joule effect, upstream of the injector 45.

The ambient air temperature can be controlled by inserting the mesoburner 60, or at least the part involved in air inhalation, in an air-conditioned environment. The air temperature measurement can be obtained by placing a thermocouple 151 near the inlet to the duct of the ejector 62.

The temperature of the mesoburner can likewise be measured by inserting a thermocouple 65 inside the head 63 of the mesoburner 60, in a cavity made of the metallic material of which it is composed, ensuring a suitable contact between the two components.

However, the problem with this parameter does not lie in its size but in its control. In fact, due to the very nature of the mesoburner 60 it will start from an initial temperature, equal to the room temperature, and will undertake a heating transient which will bring it to temperatures near the head 63 of the mesoburner 60 also of some hundreds of Celsius degrees higher.

The analysis relating to the effect of the temperature of the mesoburner cannot therefore be carried out in stationary conditions but it will be necessary to measure the progress of R over time as the aforesaid temperature changes.

In this way it is possible to determine curves such as those shown in figure 13 as the various parameters initially mentioned vary.

Once the different curves that link R _meso to the thermo-physical variables of interest are obtained, a function can be reconstructed that, taking equation 4 as a model example, would result in:

Where applying the ideal gases state law, considering air and gas at a pressure equal to atmospheric pressure, the following is obtained:

The expression of pressure losses/flow rate reduction can be approached by searching for different suitable formulations.

For example, one such equation could be:

Where m _rif is the flow rate reduction coefficient that would occur with all the quantities measured in reference conditions and where a, b, g, d indicate experimentally derived coefficients or functions that involve all or part of the other measured parameters, still obtained through analysis of the empirical results.

The effective applicability of one model or another is to be verified during the reprocessing of the measured data, taking into account the choice that best lends itself to minimizing the uncertainties related to the formulation of R _meso through analytical expression.

A fifth step of the method involves a determination of the link F _meso -I _Ion , where the subscript "meso" specifies that it is the expression of F referred to the mesoburner 60 component.

The determination of the equivalence ratio with which the mesoburner 60 actually operates (F _meso ) in the presence of any variation of the boundary conditions is of fundamental importance since it allows setting combustion regulation strategies that also take into account the variation of the composition of the combustible gas in the case of use of natural gas primarily composed of methane. The applicability of the same system for operating with other combustibles such as, for example, LPG mixtures is instead still to be verified .

It is necessary to make the measuring circuit of the ionization current 68, assuming that it will be necessary to impose differences in potential between electrode 64 and mesoburner 60 of about 300-400 V and that the measured currents will be around nA-mA. Naturally these evaluations are based on the data found in the literature.

It is also important that the electrode 64 has been placed since the beginning of the design (second step of the method) at a suitable distance ( indicatively less than 10 mm) from the ports 61 of the mesoburner 60 and that it has been subjected to an ageing process so that the measured signal does not vary over time. The applied voltage can be alternating or direct and the ionization current measurement circuit can also be used as the FFD system of the mesoburner 60.

At this point it is possible to start an experimental campaign aimed at obtaining the steps of the procedure that will allow reconstructing curves such as the one shown in the graph in figure 14 that link the ionization current to the actual equivalence ratio. The parameters of interest will be the chemical composition of the combustible, the total flow rate of the flowing mixture, the temperature of this mixture and the temperature of the mesoburner.

The tests can be carried out with combustibles of different composition, taking as a reference, for example, the limit gases for the operating tests of the cooker hobs to be used in different markets. Clearly the actual composition of the combustible gas will be unknown in commercial use but the regulating systems currently based on the ionization current base their operation on being able to reconstruct curves that bind applicable F- I ion effectively for substantial combustion regulations while considering uncertainties due to a lack of knowledge of the actual reactant chemical types. Therefore carrying out tests with combustible gases of different composition allows quantifying the uncertainties of the correlations obtained and consequently the uncertainty that will arise when the regulating strategies are adopted.

To obtain the aforementioned curves it is possible to create a test bench where the head 63 of the mesoburner 60 is connected to a duct designed for the complete mixing of combustible gas and air, equipped with a heating system of this mixture through an electric heater that can be regulated in order to be able to impose the temperature of the mixture upstream of the head 63 of the mesoburner 60.

The temperature of the mesoburner is an easily measurable parameter, but it is not as easy to control. As already described in the fourth step of the method, the burner will in fact tend to vary its temperature, warming up with respect to the initial lighting conditions .

A system commonly adopted to control this phenomenon is that of circulating a cooling liquid in the head of the burner in order to control its temperature and evaluate its effects.

This therefore makes it necessary to design a head

63 of the mesoburner 60 which can detach from that which will then be applied in the product suitable for commercial diffusion but which instead integrates a cooling circuit designed to stabilize the temperature of the mesoburner 60 to certain values, so as to be able to then apply the results obtained in the object lacking such a heat dissipation system.

Thus by making use of two flowmeters designed to supply known flow rates of combustible gas 302 of known composition and of air 312, it is possible to impose the total flow rate of the mesoburner 60 and the equivalence ratio, measuring the value of the ionization current for set values of the temperature of the mixture and the mesoburner (figure 14) .

An expression can therefore be obtained that in general terms results in:

It should be noted, in fact, that the total flow rate, the temperature of the mixture and of the mesoburner are the main parameters which, for a given equivalence ratio, determine the relative distance of the flame front with respect to the head 63 of the mesoburner 60 and to the electrode 64, simultaneously affecting the temperature of the reaction area, thus also taking into account the non-adiabat ic nature of the flame front 106 itself.

However, the above ratio contains two terms that are not measured in the commercial application. In fact, the temperature of the mixture and the volumetric flow rate of the mixture are not parameters measured in that which will be the design of the mesoburner 60 for mass distribution .

Firstly, however, it can be noted that the temperature of the mixture will be close to that of the air supplied, since it has a flow rate which is considerably higher than that of the combustible gas

(remember that the stoichiometric air-combustible ratio between for example methane gas and air in molar terms is equal to 9.5) . It is therefore possible to obtain the temperature of the mixture considering it equal to that of the air, or to be more precise by approximately weighing the temperature of the combustible gas and that of the air considering a specific heat of air and suitable combustible gas and a value of R _meso equal for example to that which should be achieved in the reference conditions of the third step of the method (equation 15) .

As for the total flow rate, this is linked to the expression R _meso obtained in the fourth step of the method and to the flow rate of combustible gas 302 supplied to the mesoburner 60, which is a measurable parameter, as described by equation 6 for the case in which air and gas have the same temperature.

Note how the composition of the combustible, which is unknown in the use of the mesoburner 60 beyond the laboratory tests, but of which the predominant types (for example methane for natural gas) can be known, does not perceptibly influence the total flow rate since:

Considering instead the case of different temperatures between combustible gas and inhaled air, equation 4 can be modified taking the molar volumes into account :

It follows that thanks to the expression of R _meso obtained in step 4, it is possible to rewrite equation 14 considering how the variations of the temperature of air, combustible gas and mesoburner modify the value of the total flow rate for an assigned or measured flow rate of combustible gas, thus obtaining an expression of the type:

Equation 16 is therefore applicable to the mesoburner 60 complete with an uncooled head 63, an ejector 62 and sensors designed for measuring the various variables .

Since it is to be expected that the predominant dependence in the expression of the equivalence ratio is that of the ionization current, it is possible that an expression in the form of equation 17 is suitable for a correct representation of this magnitude.

Where a, b, c, d indicate, as in the case of equation 13, experimentally derived coefficients or functions that totally or partially incorporate the different measured variables.

A sixth step of the method provides for the creation of a gas supply line to the mesoburner 60 and of the sensors to be implemented in the atmospheric mesoburner 60.

The gas supply line must first include a solenoid valve, in particular a simple, normally closed valve 135, which opens when the cooker hob 100 is used and the mesoburner 60 must be started, to set the combustion regulation strategies accordingly based on it.

It is not in principle necessary to provide proportional valves since the most convenient solution from the point of view of the measurements that are to be carried out on the mesoburner 60 is to possibly operate with a constant combustible gas flow rate. Operating with a non-proportional valve, therefore, the effective flow rate is influenced by the gas supply pressure to the cooker hob 100 and by the composition of the combustible gas, parameters respectively related to the terms Dp and r _gas of equation 2. As seen above, the density of the combustible gas has in principle a negligible effect in determining the total flow rate flowing in the mesoburner 60, which as seen is a parameter of fundamental importance for the correlation between F _meso and I _ion , while variations in the mains pressure are not negligible.

At this point it is important to consider aspects of the flow rate of combustible gas and the effect it has on R _meso and the link F _meso - I _ion .

The trend of R _meso shown in figure 13 shows how over a certain flow rate of combustible gas the value of R tends to become independent of settling at an almost

constant value. The results obtained in burners used in boilers show how beyond a certain thermal power (and therefore total flow rate supplied by the burner supply fan of the boiler itself) , for determined F, there are almost constant values of I _ion .

Alternatively, if these two considerations are applicable to the mesoburner 60, the insertion of a flowmeter 71 could therefore be omitted, but it would be sufficient to use a pressure transducer 71 designed to validate the gas flow rate as suitable for the application of the algorithms that describe R _meso and F _meso previously obtained simply by checking that the supply pressure falls within a certain range.

Alternatively, if this were not the case, a flowmeter 71 should be instead used, designed exclusively for reading the flowing flow rate, choosing the most suitable technical solution, aiming above all at the maximum reliability of the component and its cost- effectiveness .

At this point it is possible to summarize the components that are theoretically necessary for the use of the algorithms obtained so far, considering the final design of the mesoburner 60 for mass production:

• Flowmeter or pressure transducer 71 for the determination or validation of

• Temperature sensor 141 inserted in the combustible gas supply duct or in the body of the injector 45

• Air temperature sensor 151 located near the inhalation duct of the ejector 62 • Temperature sensor 65 integrated in the head 63 of the mesoburner 60

• Electrode 64 and measuring circuit of I _ion 68.

A seventh step of the method involves the implementation of the ancillary components of the mesoburner 60.

Being a component designed primarily for a measurement function, the mesoburner 60 must be placed in a special compartment 80, protected from any damage or dirt .

The air 311 supplied to the compartment is inhaled through a common fan 26 (for example a fan driven by a brushless DC electric motor) . The flow rate of air 311 must be greater than that which the mesoburner 60 can possibly require in any case. The electric motor should also include verification systems that match the actual operation of the received start signal and that the number of revolutions per minute is close to the expected value. The power of the fan 26 must be such as to overcome the pressure losses in the compartment and in the ducts designed for sending the mixture given by the excess air and by the exhaust gases 340 of the mesoburner 60 to the different burners 10 of the cooker hob 100.

It is certainly simpler to design the compartment 80 and the distribution ducts 163, make such components, evaluate the curve that links the pressure drops to the flow rate of the flowing mixture and on the basis of these results design or select the design of the fan 26 and the relative electric motor.

The compartment 80 must be designed to ensure that the fluid-dynamic field generated by the forced flow given by the fan 26 does not affect the operation of the mesoburner 60, causing it to operate exactly as if it were in still air conditions. Furthermore, it must be constructed in such a way that the combusted gases 330 exiting the mesoburner 60 cannot be inhaled by the mesoburner 60 itself, thus avoiding that any redirected stale air invalidate the measurements and consequently the regulation strategies. This design can be based on theoretical, empirical or CFD-use approaches.

The expressions obtained by R _meso and by the link F _meso -I _ion must in fact be unchanged. To do so, the compartment must be made in such a way that downstream of the fan 26 the kinetic term of the flow is converted into static pressure (suitable expansion) to minimize the verifiable speeds. Subsequently it is advisable for the air to reach the ejector 62 through, for example, a perforated grid 83, 84, such as to uniform the field of motion and minimize the actual speeds so as to recreate a situation similar to having the mesoburner 60 operating in still ambient air. Finally it is sufficient to create solid walls or preferential paths for the excess air so as to make it impossible to recirculate combusted gases 330 at the inlet of the mesoburner 60.

Since the mesoburner 60 can be single for an entire cooker hob 100, which on the contrary integrates several burners 10, it is necessary to ensure that the flow exiting the compartment 80 can be directed only to one or more of the burners 10 which are actually lit at that time. To do this it is possible to insert, downstream of the main outlet duct 85 from the compartment 80, a motorized distribution node 160 of the exhaust gases to the various channels 163 leading to the individual burners 10.

The node 160 can be made as a hollow cylinder provided with an opening for the inlet of the flow from the top or from the bottom, and provided with a single hole on the lateral surface. If placed in the condition to rotate on its own axis, for example by means of a stepper motor, this can be inserted in another fixed, hollow cylinder coaxial to it, provided with different holes from which the various relevant ducts 163 of the single burner 10 depart.

In this way, depending on the burner 10 lit, the lateral hole of the innermost cylinder can be made coaxial exclusively with the hole of the duct 163 which is to be supplied.

There are other ways of creating a node 160 of this type, but once again it is fundamental that they have low costs and robust solutions equal to the one proposed here .

Since the need to send the gases leaving the mesoburner 60 to the various main burners 10 arises from the need to oxidize any non-combusted gases generated by the mesoburner 60, but above all to prevent the enthalpy content of these exhaust gases from being dispersed in the environment without generating any useful effect for cooking, it is advisable that the compartment 80, the distribution node 160 and the various ducts 163 are suitably insulated.

Once the cooking process is finished, all the burners 10 and the mesoburner 60 are turned off, the fan 26 can be used to quickly cool the different burners 10, thus reducing the time in which, due to the high temperatures present, the cooker hob 100 can damage the user if touched.

The eighth to the twelfth step of the method for implementing the cooker hob 100 are steps for the implementation of one or more burners 10.

For the implementation of the mechatronic cooker hob 100, it is possible to design new burners 10 or to start from models already on the market, making only the necessary modifications.

In the present embodiment, reference will be made to the latter case, which allows considerable savings in terms of costs related to product engineering.

An eighth step of the method involves the implementation of the supply sections of the gases coming from the mesoburner 60.

The gases 340 coming from the mesoburner 60 must be supplied to the flames of the burners 10 so that any non-combusted matter is oxidized and that the enthalpic content of this mixture is not dispersed in the environment but goes to heat the pot 120.

The design of these entry sections can be imagined aimed at ensuring rapid mixing with the secondary air 320 and at the establishment of a flow field at the base of the pot 120 which is optimal for heat exchange (for example by imposing a swirl flow thanks to this forced flow) . To do so it is sufficient to create the entry points 165 of the gases 340 coming from the mesoburner 60 with a suitable geometry. However, it should be pointed out that in the case wherein the burners 10 selected are of the type with inhalation of the primary combustion air 310 above the surface 101 of the cooker hob 100, the gases 340 coming from the mesoburner 60 could also mix with this flow. This situation should be taken into consideration in determining the optimum equivalence ratio of the burners 10, as will be seen in the ninth step of the cooker hob 100 implementation method.

An exemplary embodiment of the supply sections is a metallic crown 166 which can be removed for cleaning operations, which envelops the burner 10, being coaxial to it, in which holes 165 of different geometry are formed, possibly inclined to generate a swirl flow or to allow the mixture produced by the mesoburner 60 to come into contact with the flames of the burners 10 at a given angle. Below this crown there must be an annular manifold 164 present into which the duct 163 coming from the distribution node 160 of the mesoburner 60 is introduced.

Considering how when the cooker hob 100 is off the fan 26 can be used for rapid cooling of the burners 10 (cooling function) , the design of the supply sections can also be aimed primarily at this activity.

A ninth step of the method provides for the definition of the optimal equivalence ratio (F _nom ) .

After selecting the burners 10 to be used, the optimal operating conditions can be experimentally evaluated .

By working exclusively on the head 30 of the burner

10 it is possible to carry out energy efficiency tests first. There are specific rules that establish how to carry out such tests so that the data detected in different products can be compared with one another.

In general terms, the efficiency can be measured by evaluating the ratio between the amount of heat transferred to the water contained in the pan 120 which must be heated with respect to the thermal power supplied by the burner 10. Once the size of the pot 120, the material of the pot 120, the quantity of water contained therein and the preheating times of the burner 10 of the grids 110 supporting the pot 120 are defined, it is possible to place the pot 120 above the burner 10 and measure its temperature change over time by inserting a thermocouple in the water.

Once the flow rate of the supplied combustible and its composition are known, the thermal power delivered is known and thus the efficiency is obtained as described by equation 18 :

Therefore by supplying a known flow rate of combustible gas 301 and a known flow rate of air 310 to the head 30 of the burner 10 by means of suitable flowmeters, it is possible to find the optimal equivalence ratio which we will call F _nom of each burner 10 as the main boundary conditions vary.

The prevailing known or measurable boundary conditions in determining the performance of the burner 10 are the flow rate of the combustible gas supplied (and therefore the thermal power supplied) and the fact that at that burner 10 in that moment the gases coming from the mesoburner 60 are supplied or not.

The flow rate of combustible gas is clearly known during experimental tests but is not known in the burners 10 designed for commercial diffusion. In fact, it would not be economically possible to introduce a flowmeter in all the burners 10. In the commercial burners 10 used for cooking, the power supplied, and therefore the flow rate of combustible gas, is controlled directly by the user of the cooker hob 100 who sets the opening of the valve 132 of the tap of combustible gas 301 and therefore the term Dp in equation 2. Because of this, it is possible to omit the direct measurement of the flow rate of combustible gas and only detect the position of the gas valve (P _gas ) for example by applying an encoder 133 that indicates the degree of closure of the tap itself. It is in fact normal to expect that the mains pressure is close to the nominal values and that the main pressure variations are linked to the user's choices. Alternatively, if the tap 132 were of the electronic type, the position could also be calculated starting from the electric regulation signal sent to it.

The supply or lack of supply of the flow 340 coming from the mesoburner 60 can influence the detection of F _nom and it is therefore advisable to carry out the tests both in the presence of this gas flow rate and in its absence. It should be noted that this is relevant in particular in the presence of burners 10 with the inhalation of air 310 above the surface 101 of the cooker hob 100. This variable, defined as gas _meso , can in fact be a term that admits two values, 0 and 1, depending on whether the flow rate of gas 340 coming from the mesoburner 60 is not supplied to the burner 10 (assumed value: 0) or is (assumed value: 1) .

By applying the same experimental system it is possible to evaluate not only the efficiency but also the emissions of the main undesired chemical types, in particular CO and N _x .

For example, by placing the pan 120 inside a duct coaxial thereto but with a larger diameter, such as to create a gap between the pan 120 and the duct itself, the gases that rise up along the lateral surface of the pot can be taken and their composition evaluated.

To compare different operating conditions, for example, an approach aimed at expressing the mole fraction of CO and _x could be applied, referred to dry gases, compared to a specific mole fraction of oxygen. This method is in fact convenient because it avoids introducing more complex data processing systems.

If a flow is considered containing a specific fraction of pollutants expressed in ppmvd (volumetric parts per million of dry gases) and having a certain mole fraction of oxygen (y% O ₂ ) , it is possible to report this fraction referring to a specific mole fraction of oxygen (x% O ₂ ) through equation 19:

Thus having the value expressed in ppmvd of the different chemical types analysed and the mole fraction of O ₂ thanks to the measurement carried out by the exhaust gases analyser, values can be obtained that compare the emissions with the change in supplied equivalence ratio and the variables on which the search for F _nom is set.

In addition to energy efficiency and the content of unwanted types, the choice of F _nom can also be based on considerations concerning the cooking precision and the safety of the device.

Since it is supposed to modify burners 10 already commercially available, it is possible to consider arranging the operating range of the burner 10 without having to perform other tests. To improve cooking precision it is the designer's goal to maximize the possible regulation range and therefore the ratio between maximum and minimum burner power 10. However, this can lead to conditions close to the stability limits defined by the operating range and typically this ratio is limited in commercial burners 10, which operate on a fixed geometry, at values comprised between 2 and 3. Taking into account the fact that thanks to the mechatronic burner 10 it is possible to vary the geometry to respond to changes in the boundary conditions, it is possible to try to expand this range by ensuring that at the critical points F _nom it is not linked only to performance parameters ( h and unwanted emissions) but also to the ability to have a system able to operate stably and have time to adjust accordingly in the presence of sudden and significant variations in the boundary conditions.

Since the burner 10 will undertake a thermal transient from the moment of lighting until reaching stationary conditions, it is possible to carry out tests which take this into consideration in order to eventually vary the optimum equivalence ratio as a function of the burner temperature. In particular, it is possible to start from a burner at room temperature, turn it on and monitor the emissions as the temperature increases, imposing a constant equivalence ratio thanks to the flowmeters. This repeated analysis for different equivalence ratios allows implementing possible corrections of the previously obtained nominal equivalence ratio, again for different thermal powers and in the presence or absence of the flow 340 coming from the mesoburner 60.

That which has been described up to now therefore provides the elements for defining the optimum equivalence ratio to be achieved during cooking, keeping it constant as the boundary conditions vary: F _nom F _nom (P _gas , as _meso ) (20)

A tenth step of the method involves implementing atmospheric burners with variable geometry.

In order to be able to regulate the combustion process by varying the flow rate of the inhaled air 310 in order to operate with the desired equivalence ratio, it is necessary to introduce motorized systems that allow varying the geometry of the atmospheric burners 10.

It is therefore necessary to install air flow rate regulating systems 50 on the ejector 20. These are usually manually regulated and there are several technical solutions reported in the literature.

In order to be able to carry out an automatic regulation, it is necessary to introduce actuators 53 which allow the translation of the components, for example associating a determined physical displacement (for example a forward or backward movement of a shutter 51, 52 of a given value of millimetres) to the number of steps performed by a stepper motor with respect to an assigned initial position.

The insertion of similar devices is simple and low- cost in atmospheric burners 10 with inhalation of the primary air 310 below the surface 101 of the cooker hob 100 and is more complex in burners 10 with inhalation of the air above the surface 101 of the cooker hob 100, since the moving components can be touched by the user during cleaning procedures and can be soiled due to the cooking process.

An eleventh step of the method provides for the definition of the expression of R.

Similarly to what has been done for the mesoburner 60 in the fourth step of the method, it is necessary to obtain the expression of R for the various atmospheric burners 10 for which F _nom has been defined (as indicated in the ninth step of the method) and a system for regulating the inhaled air has been installed (as indicated in the tenth step of the method) .

It is therefore possible to supply a known flow rate of combustible gas 301 of known composition to the burner 10 which is the object of the experimental test, and analyse the composition of the exhaust gases with the methods described in the fourth step of the method, obtaining the expression of R.

However, with respect to what has been described in the fourth step of the method, there is one more variable to be considered in the description of the function of R, since now the geometry of the ejector 20 is variable. Thus curves such as the one shown in figure 15 can be reconstructed for each of the burners 10 which will be adopted in the cooker hob 100. Going therefore to write the expression of R:

Where the complex expression of the flow rate reduction coefficient can be imagined as assuming for example a form similar to equation 13, of the type:

Where w _rif is the flow rate reduction coefficient that would occur with all the quantities measured in reference conditions and where a' , b' , g' , d' , indicate experimentally derived coefficients or functions that involve all or part of the other measured parameters, still obtained through analysis of the empirical results.

A twelfth step of the method involves the implementation of sensors and actuators to be implemented in the atmospheric burners.

The different atmospheric burners that will be installed in the cooker hob must therefore have:

• transducer 133 for the position of the combustible gas tap 132. For example, an encoder can be used which allows detecting the actual position of the valve 132 controlled by the user; • temperature sensor 140 inserted in the combustible gas supply duct 134 or in the body of the injector 40;

• air temperature sensor 150 located near the inhalation duct 21 of the ejector 20;

• temperature sensor 35 integrated in the burner

10;

• electromechanical actuator 53 (for example a stepper motor) designed to control the air regulator 51, 52 possibly equipped with an encoder.

As regards the operating method of the cooker hob 100 by means of the control unit 200, the method can comprise steps outlined in the flow charts of figures 16, 17 and 18.

In the steps of the method for the operation of the macro-components of the mesoburner 60, burners 10 and control unit 200, reference is made to mathematical equations which have the same symbols used above to describe the method for implementing the cooker hob 100. In the course of the discussion, for greater clarity, all the variables that refer to the mesoburner will be indicated with the subscript "meso", while in the absence of this subscript the variables will be connected to the single burner examined. The term I _ion is an exception which is clearly linked exclusively to the measurements carried out on the mesoburner.

The control unit 200 has the task of receiving the various input signals coming from the sensors located in the cooker hob 100, processing them and, thanks to the algorithms implemented therein, issuing different instructions . These instructions concern:

• the functions related to the ignition of the mesoburner 60 (and possibly also of the other burners 10) ;

• the safety functions of the cooker hob 100;

• the control functions of the combustion process ;

• the cooling function;

Taking a moment to discuss the combustion regulation logic, figures 16-18 show examples of flow diagrams concerning this aspect and which could therefore be integrated in the control unit 200.

The details of the lighting process of the mesoburner 60, the logics concerning the "safety" of the device, and the cooling function are therefore excluded from the diagrams.

For the sake of simplicity, the exit conditions from the loops shown in the diagrams have also been omitted because they are irrelevant for immediately conveying the combustion regulation method. These exit conditions can be blocks due to safety conditions (for example a failed flame detection) or more simply the fact that the user has turned off the burner 10 after finishing cooking .

The description of the possibility that the control unit can also act on the degree of opening of the valve 132, thus also changing the flow rate of combustible gas supplied to the single burner 10 examined, has also been omitted .

The diagrams describe the operating method of the cooker hob 100 to regulate the combustion process. Figure 16 shows the flow diagram for obtaining the equivalence ratio F _meso .

The first step 600 connected to the regulation of the combustion process through the use of the mesoburner 60 consists in defining the actual equivalence ratio of this compact burner. A first preliminary step 604 is connected to the evaluation of the suitability of the flow rate of combustible gas in order to obtain correct correlations between the ionization current and the equivalence ratio. Considerations in this regard have already been set forth in the sixth step of the method for implementing the cooker hob 100 and will not be resumed here.

The method 600 provides for the successful lighting of at least one burner 601, the start of the lighting procedure of the mesoburner 602. A check is then made to verify whether the mesoburner 60 has successfully been lit 603. If the mesoburner 60 has successfully been lit then the flow rate of the gas 604 of the mesoburner 60 is evaluated. If the gas flow rate of the mesoburner 60 is suitable 606 then the parameters I _ion 607, T _gas-meso 608, T _aria-meso 609, T _b-meso 610, 611 are measured. In

general terms the diagram includes, between the input variables necessary for the definition of F _meso , also the volumetric flow rate of combustible gas so as to have a more general description of the regulation algorithms. Having said this, it is therefore possible to understand how once the signals relating to I _ion , T _gas-meso , T _aria-meso , T _b-meso , are received from the control unit 200,

which are in turn measured thanks to the sensors summarized in the sixth step of the implementation method of the cooker hob 100, it is possible to obtain the value of F _meso 612 making use of equation 16 and eventually, in case the detections demonstrate its suitability, of its formulation according to equation 17 and therefore to continue 700 in figure 17.

If the burner was not successfully 603 lit, then the lighting attempts would be repeated 605. If the attempts are less than a certain predetermined number N, then the start of the mesoburner lighting process 602 is returned to. If, on the other hand, the mesoburner 60 does not light after N attempts, then the process continues with step 800 of figure 18.

If the gas flow rate 606 is not suitable, then the process continues with step 800 of figure 18.

At this point it is convenient to rewrite the actual value of F _meso obtained by comparing it to a value that should be had in nominal conditions (for example, the design value of R mentioned in the third step of the cooker hob 100 implementation method can be assumed for which a given composition of the combustible gas and a given ratio of air and combustible gas temperatures corresponds to a precise F _meso-nom ) .

In fact, this means expressing a relationship between the actual equivalence ratio, which is a variable term, and a nominal equivalence ratio, which is therefore a constant, with the aim of immediately transmitting an indication of how much difference there is between the actual operating conditions and the reference conditions, thus providing an idea of the entity of the regulation of the combustion process that must be adopted with equal immediacy.

This relationship can be defined as:

In the method 700 of figure 17, the geometry required to obtain the desired equivalence ratio F _nom is calculated.

The process of regulating the combustion 700 is to be carried out in the event that the mesoburner 60 is operating and the boundary conditions are suitable for the application of the algorithms connected thereto, as is verified 701.

Firstly it is possible to identify 712 for the generic burner 10 examined the optimal equivalence ratio, identified by the control unit once it knows the variables P _gas , T _b and gas _meso and equation number 20, i.e. measured 710, 709 and 711.

For analytical convenience with respect to the definition of the term K ₁ described by equation 23, the value of F _nom can therefore be written, obtained by comparing it to the nominal equivalence ratio of the mesoburner 60 (which, as already discussed, is a constant term) :

At this point it is possible to introduce another term that we will define K ₃ which aims to introduce a regulation correction connected to motives of safety. The ninth step of implementing the cooker hob 100 describes how the definition of the term F _nom , if aimed at maximizing the regulation range, in the most extreme conditions of this range should no longer be based solely on considerations related to performance terms (efficiency and emissions) but also to concepts aimed at ensuring the burner's 10 capacity to operate in stable conditions in the presence of sudden changes in boundary conditions. This must also include the fact that for every measure taken and correlation adopted, a well- defined uncertainty corresponds. These uncertainties must be propagated up to the definition of the uncertainty of the geometric regulation of the ejector 20. In particular it is reasonable to expect that the uncertainty will be all the more so the more important the regulation required by the system and the closer it is to the conditions of system instability.

For that which has been described thus far, it is clear that K ₃ can express a correction of F _nom , which we will call F' _nom , and which can be written as:

In this way it is possible to obtain the equivalence ratio that the system will aim to achieve through the regulation of the ejector 20.

Through simple mathematical steps the following is obtained:

Once K is obtained, it is therefore possible to calculate the geometric regulation of the ejector 20 of the single burner 10 examined in order to obtain the desired equivalence ratio F' _nom .

By omitting the analytical steps, referring to the equation of ideal gases state, remembering that air and combustible gas are at the same pressure and that both the mesoburner 60 and every other burner 10 of the cooker hob 100 receive a combustible gas 301, 302 of the same composition (and therefore the same Rm _stch and the same molar mass MM _gas ) , the following is obtained:

From which the geometric regulation to impose, once the parameters T _aria-meso 702, T _gas-meso 703, T _b-meso 704, F _meso 705, 706, T _aria 707, T _gas 708, T _b 709, P _gas 710,

gas _meso 711 are known, resolving explicitly, if possible, or iteratively with equation 29:

The control unit 200 is therefore able, thanks to the correlations that describe R and R _meso obtained in the fourth and in the eleventh step of the method for implementing the cooker hob 100, to calculate 712, thanks to the input variables 702, 703, 704, 705, 706, 707, 708, 709, 710, 711, the necessary position of the air regulating system 50 to obtain the optimum desired equivalence ratio. If the actual geometry 713 is different from the calculated geometry 712, 714 then it is necessary to modify the geometry of the burner 10 i- th 715 and then return to the method 604 of the diagram of figure 16, otherwise if the effective geometry is equal to the calculated geometry 714 then the method 604 of the diagram of figure 16 is returned to without making any adjustments. Therefore, as can be seen from the procedure 700, it is possible to check whether the air regulating system 50 is already in the correct position and otherwise provide instructions to the electromechanical actuator 53 on how much to move.

If the flow rate of the combustible gas is not suitable 606 or if the number of attempts to light the burner is greater than a number N of attempts 605, then the operating method proceeds in 800 of figure 18, where the burner 10 i-th is active 801.

The method 800 calculates the geometry required to obtain the desired equivalence ratio F _nom .

The third flow chart 800 relates to the situation wherein the mesoburner 60 is not operating or the measurement of the equivalence ratio through the ionization current cannot be considered reliable. However, it should be emphasized that the situation described by the diagram 800 is also applicable to mechatronic cooker hobs 100 without a mesoburner 60. In fact, the absence of the mesoburner 60 prevents carrying out regulations which take into account the variability of the composition of the combustible gas, but mechatronic cooker hobs 100 can be made which are able to take into account all the other variables of interest ( P _gas , T _gas , T _aria , T _b ) , measuring them 802, 803, 804 and 805 as envisaged in the embodiment example where the mesoburner is missing 60.

The operating method 800 therefore makes it possible to operate the cooker hob 100 even without the mesoburner 60.

In detail, it is possible to assume that the combustible has a reference composition, ideally the one that best represents the quality of the combustible gas 301, 302 distributed in the market where the cooker hob 100 is used, and thus to evaluate the effective geometry 807 and use equation 21 to calculate the required geometry 806 to have the desired equivalence ratio. If the actual geometry 807 is different from the calculated geometry 806, 808 then it is necessary to modify 809 the geometry of the i-th mesoburner and then verify, if the mesoburner is present, 810 if the mesoburner 60 is lit. If the burner is not lit then the measurements 802, 803, 804, 805 are returned to, otherwise if the mesoburner 60 is lit then the method 604 of the diagram of figure 16 is returned to. If the cooker hob 100 did not use the mesoburner 60 in 808 and 809, reading the measurements 802, 803, 804, 805 is always returned to.

Defining the molar mass MM _gas-rif of this reference combustible and with Rm _stch-rif the corresponding stoichiometric air-combustible mass ratio, defining firstly F' _om (referring therefore to equation 20 and possibly integrating it with the corrections due to the considerations previously expressed regarding the uncertainty of measurements and correlations), the following is obtained:

From which the geometric position of the air regulating system 50 is obtained by solving, possibly in an iterative way, the equation:

Finally, note that the expressions of R were obtained in the embodiment described above using equation 4. As seen, this expression is reported to be valid for burners 10 having an area of the passage sections of the ports to which the flames are anchored which is negligible from the point of view of the effect on R and more precisely it is reported that the ratio between A _b and A _g is greater than 1.5.

If this is not verified, equation 5 can be adopted. Since this expression is obtained analytically for isothermal conditions, it can be rewritten by explaining the ratio between the density of the combustible gas and that of the air according to the law of ideal gases and letting the additional effects related to the variations of T _gas , T _aria and T _b fall in the coefficients of pressure loss .

In particular the following can be written:

From which derives the rewriting of equations 9 and

18 in the form:

Observing the expressions 34 and 35 it is immediately noted that in applying them in equation 27, the algebraic simplification of the term MM _gas is not obtained (which is unknown) as was the case previously discussed. At this point it is proper to analyse equation 5.

Equation 5 can indeed be rewritten as:

R = A + B (36)

Where :

With reference to natural gas and observing that the stoichiometric molar ratio between air and methane is 9.5, it can be noted that the term A has a modest weight in the determination of R. In fact, the form of A is equal in the conditions mentioned above to about 8% of B . Still referring to natural gas, it can be noted that A varies little, even assuming important changes in the composition such as passing from G20 gas to G21 and G222 gas (+8% and - 7% respectively) . On the whole it can therefore be allowed to introduce in the term A a properly chosen reference molar mass, just as it is possible to always replace this value in terms that will multiply or divide A, without giving rise to significant regulation errors.

In detail, equation 29 can therefore be rewritten as :

It should be noted that what is stated above can also be implemented if equation 4 or equation 5 can have one applicable to R and the other to R _meso or vice versa. In fact, it is always sufficient to replace the molar mass of the combustible gas with a reference value in all the terms of the final expression obtained connected to term A of equation 36.

For completeness of the discussion, it is also possible to report the expression of the geometrical regulation in the event that the mesoburner 60 is not functioning or is absent, taking into account equation 35 and thus replacing equation 31 with:

Finally, it should be emphasized that although the equations describing R reported in the literature known to the author (equation 4 and 7) have been used so far, it is possible to apply the regulation based on the presence of the mesoburner 60 in more general terms for expressions that, following empirical surveys or a specific design, can have the following formulations:

Where it is verified that:

The following is obtained:

· the expression of R and R _meso is rewritten in general terms as the product of two independent functions (respectively f and g, and f _meso and g _meso ) where the first takes into account all the physical variables of interest except the chemical composition of the combustible gas, which is instead specifically the only variable on which the second function depends.

It has been assumed that variations in the composition have the same effect on the burners analysed and on the mesoburner 60, taking into account that the combustible is the same for all the aforementioned components and as suggested by equations 4 and 7.

As described above, equation 27 can therefore be reformulated in general terms by applying the equation of ideal gases state, for combustible gas and air at atmospheric pressure, so as to isolate the term f and thus obtain the geometric regulation to be implemented on the individual burner examined through equation 42:

The invention thus conceived is susceptible to many modifications and variants, all falling within the same inventive concept; furthermore, all details can be replaced by equivalent technical elements. In practice, the materials used, as well as the dimensions, can be of any type according to the technical requirements.