FIELD OF THE INVENTION The present invention concerns a device for delivering a gaseous mixture, a corresponding delivery apparatus and corresponding method of use, suitable for use in a delivery apparatus in which a mixture of two gases is used.

In particular, the present invention concerns a delivery device, and the corresponding method of use, suitable to be used in a delivery apparatus comprising a combustion apparatus in which a mixture of combustible gas and air is used as fuel.

By way of a non-restrictive example, the combustion apparatuses in question may comprise burners such as boilers, storage water heaters, stoves, ovens, fireplaces, or other similar or comparable apparatuses. BACKGROUND OF THE INVENTION

It is known that combustion apparatuses fed by a mixture of air and second gas, or combustible gaseous mixture, are provided with a delivery device which allows to regulate the quantity of second gas to be sent to a mixing zone in order to mix it with comburent air. The delivery device generally comprises a duct for feeding the first gas and a duct for feeding the second gas, which join in a common duct in a mixing zone.

Feed means are generally provided along the second gas duct, generally a valve device comprising an aperture which is selectively opened and closed by means of a safety solenoid valve and a pressure regulator. In some cases, there may also be a flow regulator which varies the passage section of the second gas.

The second gas fed into the delivery device, and therefore to the burner, can contain one or more natural gases, such as methane, LPG (liquefied petroleum gas), or hydrogen.

The gaseous mixture that is sent to the burner when fully operational normally has to comply with a specific first gas/second gas ratio, with respect to the first gas/second gas stoichiometric value defined by the , λ (lambda) coefficient, to allow high efficiency of the system and at the same time to guarantee complete combustion of the gas, limiting the generation of combustion residues. In combustion apparatuses that use natural gas or LPG, usually in the combustion chamber there is a detector of the first gas/second gas ratio, or ionization electrode, which is able to supply a feedback signal which is used to regulate the flow rates of gas and air; this method is generally known as the SCOT method.

However, when a second gas with a high percentage of hydrogen is used, in particular 100% hydrogen, it is not possible to use said ionization electrodes, and therefore to use a feedback control based on an ionization electrode, since the signal of the ionization current would be insufficient for a correct control. When a gas with a high percentage of hydrogen is used, in particular 100% hydrogen, it is necessary to ensure that at the time of ignition there is no excess quantity of hydrogen in the combustion chamber, which could lead to explosions or flashbacks. In this case, it is advisable for the lambda coefficient to be set, during the ignition step, to higher values than those of the fully operational step, and it can then be subsequently modified.

In order to be able to guarantee the supply of a mixture having a suitable composition it is therefore necessary to use two or more sensors suitable to at least measure the flow rate of the first and second gas, and therefore it is necessary to provide spaces suitable to house them, as well as to position them in an appropriate manner along the respective ducts in order to enable the necessary measurements to be obtained. The positioning of the sensors and of the respective wiring therefore requires that suitable sizes and housing seatings are provided, and that complex operations in small and therefore inaccessible spaces are carried out, making it very complex both to verify the operation of the sensors and also to replace them if necessary.

Document GB2566143A describes a venturi nozzle for mixing two fluids, in particular air and gas.

DE10348324B3 and US20I8/274781AI describe known types of gas delivery devices. There is therefore a need to perfect a delivery device which can overcome at least one of the disadvantages of the state of the art.

One purpose of the present invention is to provide a delivery device that is compact and simple to use and implement. One purpose of the present invention is to provide a delivery device whose operation is not affected by possible wear or damage to its parts or components.

One purpose of the present invention is to provide a delivery device which allows to quickly and easily carry out any functional checks or replacement of the components.

One purpose of the present invention is to provide a delivery device, and to perfect a corresponding method of use, which guarantees in every situation a correct feed of the gaseous mixture into combustion apparatuses both when traditional fuels such as natural gas, methane or LPG are used, and also in the case of gases with a high percentage of hydrogen, and also with 100% hydrogen.

Another purpose is to provide a delivery apparatus which prevents the risk of explosions or flashbacks, especially in the ignition step.

Another purpose is to perfect a method for using a delivery apparatus which allows effective and safe delivery of the fuel without needing to provide the use of combustion detectors, or lambda sensors.

A further purpose of the invention is also to provide a delivery apparatus which can possibly be converted with minimal modifications, in order to be used with different types of gases.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with one aspect of the invention, there is provided a device for delivering a gaseous mixture of a first gas and a second gas which comprises a body that defines a first duct in which the first gas flows and a second duct in which the second gas flows, wherein the first duct and the second duct join together in a mixing zone.

The delivery device comprises a first sensor configured to determine a flow rate of the first gas, and at least one of either a second or a third sensor configured to determine a flow rate of the second gas, wherein the first sensor, the second and/or third sensor are positioned adjacent to each other and installed on a same side of the body.

In accordance with some embodiments of the invention, only the first sensor and the second sensor can be provided. According to other variants, a third sensor can also be provided, which is also configured to determine a flow rate of the second gas and is disposed on the same side of the body where the first and second sensor are positioned.

In another example of the invention, the first sensor, the second sensor and the possible third sensor are positioned in a recesses formed in the body and are kept in position by a containing plate.

In another example of the invention, the containing plate is attached to the body by means of attachment means and comprises at least one aperture configured to allow access to the first sensor, to the second sensor and to the third sensor.

In yet another example of the invention, the at least one aperture is configured to allow access to connectors for the power supply and/or data exchange of the first sensor, of the second sensor and of the third sensor.

According to some embodiments, the delivery device comprises a printed circuit board installed in the recess, with/on which there are connected and/or installed the first, second and/or third sensor, and an integrated control unit configured to control at least the operation of the first, second and/or third sensor.

According to other variants, the first sensor, the second sensor and the possible third sensor are positioned inside a containing casing, which is connected externally to the support body by means of attachment members of the removable type. According to these embodiments, through holes are provided on the support body for the passage of respective air flows from the support body to the sensors, and vice versa.

According to some embodiments, in the connection zone of the containing casing, the support body is closed by a removable closing plate on which the through holes are made.

According to some embodiments, the first, the second and the possible third sensor can all be installed on a same printed circuit board, or PCB, inserted in the containing casing. In this way, it is sufficient to insert and attach the board with the sensors in the casing and then align the sensors with the through holes and attach the containing casing to the support body.

According to some embodiments, an integrated control unit can also be provided on the electronic board.

According to some embodiments, the containing casing can be provided with protruding ducts configured to be inserted in the through holes and allow the flow of respective air flows toward the sensors and toward the support body, respectively. The fact that the sensors are all disposed on a same side of the body of the device allows to achieve at least the following advantages:

- optimize the occupied space and simplify the construction of withdrawal and/or re-introduction channels;

- allow easy maintenance and/or replacement of one or more sensors;

- use a single containing casing for all sensors; - use a single printed circuit board suitable to power and control the operation of all the sensors, which is installed directly on the body.

In one example of the invention, the first sensor, the second sensor and the third sensor are selected from a differential pressure sensor and a flow sensor, in particular of the thermal-mass type. In another example of the invention, the first sensor is configured to determine the flow rate of the first gas in the first duct, between an inlet aperture and a narrowing.

In another example of the invention, the second sensor and the third sensor are configured to measure a pressure difference between a point of the first duct upstream of the narrowing and a point of the second duct.

In another aspect of the invention, there is provided an apparatus for delivering a gaseous mixture which comprises a delivery device and a ventilation device configured to regulate the flow rate, Q _A , of the first gas in the first duct.

In an example of the invention, the apparatus for delivering a gaseous mixture comprises a control unit configured to control the ventilation device in order to regulate the flow rate of the first gas by controlling a rotation speed of a rotating element of the ventilation device.

In another aspect of the invention, there is provided a method for using an apparatus for delivering a gaseous mixture, comprising:

- supplying the first gas in the first duct and supplying the second gas in the second duct;

- obtaining a gaseous mixture of the first gas and the second gas by regulating the flow rate of the first gas through the regulation of a rotation speed of a rotating element of the ventilation device, in such a way that the ratio between the flow rate of the first gas and the flow rate of the second gas corresponds to a predefined value of a A, coefficient;

- delivering the gaseous mixture of the first gas and the second gas to a gas user device.

In an example of the invention, the method also provides to regulate the flow rate of the first gas in such a way that the following relation is satisfied: A = in which Q _A is the flow rate of the first gas, R is a stoichiometric ratio relative to the second gas, Q _G is the flow rate of the second gas, and the λ coefficient corresponds to the predefined value.

In another example of the invention, the λ coefficient is comprised in a first interval between 2 and 5, in an initial step of the method, and it is comprised in a second interval between 1.2 and 2 in a step that follows the initial step, wherein, when the gas user device is a burner, the initial step corresponds to a step of ignition of the gas user device.

DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein: - fig. la is a schematic view of a first variant of a delivery apparatus according to the present invention in a first configuration;

- fig. lb is a schematic view of a delivery apparatus according to the present invention in a second configuration;

- fig. 2a is an isometric view of a device for delivering a gaseous mixture according to the present invention;

- fig. 2b is a top view of the delivery device of fig. 2a;

- figs. 3a, 3b, and 3c are sections of the delivery device according to the plane Illa, Illb, and IIIc, respectively, indicated in fig. 2b; - fig. 4a is an isometric view of a delivery apparatus according to the present invention in accordance with a variant;

- fig. 4b is a partial view sectioned along the plane IV of fig. 4a;

- fig. 5 schematically shows a method for using an apparatus for delivering a gaseous mixture according to an example of the invention;

- fig. 6 schematically shows another method for using an apparatus for delivering a gaseous mixture according to an example of the invention;

- fig. 7a is an exploded isometric view of a delivery apparatus according to the present invention in accordance with another variant; - fig. 7b is an exploded view of a component of the apparatus of fig. 7a;

- fig. 7c is a partial section view of the apparatus of fig. 7a in an assembled condition.

We must clarify that in the present description the phraseology and terminology used, as well as the figures in the attached drawings also as described, have the sole function of better illustrating and explaining the present invention, their function being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION

With reference to fig. la, an apparatus 200 for delivering a gaseous mixture M comprises a mixing and delivery device 10 and is configured to cooperate with a gas user apparatus 50. The gaseous mixture M is a mixture of a first gas A and a second gas G.

In an example of the invention, the gas user apparatus 50 is a combustion apparatus, a burner. In this case, the first gas A is air, and the second gas G is a combustible gas such as natural gas, methane, LPG (Liquefied Petroleum Gas), a mixture of natural gases but also a mixture of gases containing hydrogen. In particular, the device 10 is suitable to use a second gas G with high percentages of hydrogen, even higher than 30-40%, preferably higher than 50-60%, and even more in particular containing only 100% hydrogen. The gaseous mixture M is defined by a volume ratio of the first gas A to the second gas G with respect to the stoichiometric volume ratio, also called the Z (lambda) coefficient.

When the second gas G is a combustible gas, the Z coefficient can be adjusted so as to assume different values according to the combustion step, such as the ignition value Zi or the steady state or normal operation value 2.

In one example, in the ignition step the value Zi can be comprised in a first interval I ₁ ; in normal operation, the value Z2 can be comprised in a second interval I2. In another example, in the case of hydrogen in very high volume percentages, or at 100%, it is necessary for the value Zi to assume a high value, greater than 1 (high excess of the first gas), in order to prevent dangerous flashback phenomena caused by the high propagation speed of the hydrogen-oxygen combustion, which in some cases could irreparably damage some components of the combustion apparatus and create dangerous situations. In this particular case, the value Z-i can be equal to at least 3-4 times the value Z2. In the case of 100% hydrogen, the intervalI ₁ can be substantially comprised between 2 and 5, preferably equal to about 4, and the interval I2 can be comprised between about 1.2 and 2, and preferably equal to about 1.3 - 1.5. Also with other types of second gas G, the value Zi can be different from the value Z2 during normal operation: in the case of ignitions with very low temperatures, for example, it is usually advisable for there to be a higher quantity of the second gas G. For example, typical values of Zi during ignition for a second gas G other than hydrogen could be comprised between 1 and 2. As another example, in the case of natural gases, the intervalI ₁ can be comprised between 1 and 4 and the interval I2 can be comprised between 1 and 2, preferably between 1.2 and 1.5.

Drawings 2a, 2b, 3 a, 3 b, 3 c, 4a, 4b, 7a, 7b and 7c show a mixing and delivery device 10 that can be used in the delivery apparatus 200 according to one example of the invention. The device 10 comprises a body 15 which defines a first duct 11 for feeding the first gas A and a second duct 12 for feeding the second gas G.

The first duct 11 is configured to allow the entry of the first gas A through an inlet aperture 10a and the delivery of the mixture M of the first gas A and second gas G through a delivery aperture 10b (fig. 3a).

According to some embodiments, the first duct 11 can comprise, downstream of the inlet aperture 10a, a laminator element 20 configured to make the flow of the first gas A laminar and generate a pressure difference between the zones located upstream and downstream thereof. The laminator element 20, when present, is located upstream of a section narrowing 18 present in the first duct 11 of the device 10 and defining a Venturi effect nozzle upstream of the mixing zone 13.

The narrowing 18 can be formed by the body 15 or it can be defined by a tapered portion 14 of the first duct 11 having a variable section, which progressively decreases, linearly or according to a curvilinear trend, in the direction of flow of the first gas A.

In the example case, the tapered portion 14 has, in section view, a curvilinear linear wall 14a with concavity facing inward. The tapered portion 14 can be formed by a suitable shape of the first duct 11 itself, or it can be a separate component inserted in the first duct 11 , possibly cooperating with an internal wall 11 a thereof, or with a seating made therein to obtain a sealed coupling. Suitable gaskets can also be provided.

In accordance with some embodiments, the tapered portion 14 is connected to the laminator element 20 by means of hooking members 16. By way of example, these hooking members 16 can comprise a pair of protruding tabs suitable to be inserted in special seatings provided on the laminator element 20.

In accordance with some embodiments, both the first duct 11 and the second duct 12, as well as a mixing duct 39 delimiting the mixing zone 13, are integrated in the body 15. The mixing duct 39 can be made in continuity and/or in a single body with the first duct 11, and define a part of the latter or be separate.

The mixing duct 39 comprises a mouthpiece 40 having a diameter greater than that of the narrowing 18 and located coaxially therewith, whereby between the narrowing 18 and the mouthpiece 40 there is defined a passage 41 for the second gas G.

According to some embodiments, the mixing duct 39 can have a section that increases from the mouthpiece 40 toward the delivery aperture 10b of the delivery device 10, whereby the mixing between the first A and the second G gas is facilitated.

The second duct 12 comprises an inlet aperture 12a configured to allow the entry of the second gas G and an outlet aperture 12b which flows into the first duct 11 in correspondence with the narrowing 18 and which allows the introduction of the second gas G into the mixing zone 13.

Preferably, the second duct 12 flows into an accumulation chamber 43, which extends around the tapered portion 14 and the narrowing 18 and communicates with the mouthpiece 40 through the passage 41.

The second duct 12 can comprise, upstream of the outlet aperture 12b, a nozzle 12c, or a choke, configured to allow the delivery of the second gas G into the accumulation zone 43 through the outlet aperture 12b.

The second duct 12 comprises a coupling portion 12d configured to allow the coupling, or attachment, to an external element such as a second source S2 of the second gas G, a pipe, a duct, and suchlike. In fig. 2 the coupling portion 12d is shown as a threaded element. The person of skill in the art will understand that the coupling portion 12d can consist of any element whatsoever which allows a secure coupling, that is, one without leakages, between two elements of a fluidic, hydraulic or pneumatic system.

The device 10 also comprises a first coupling element 15a positioned in correspondence with the inlet aperture 10a and a second coupling element 15b positioned in correspondence with the delivery aperture 10b. The first coupling element 15a and the second coupling element 15b, for example flanges, are configured to allow the coupling or attachment of the device 10 with, respectively, a first source S 1 of the first gas A and the user device 50. The first gas A delivered by the source enters the first duct 11 through the inlet aperture 10a and flows toward the delivery aperture 10b. If the laminator element 20 is present, in its path inside the first duct 11 , the flow of the first gas A is made laminar by the laminator element 20, which typically comprises a plurality of laminator ducts 20a having a longitudinal size, in a direction parallel to the direction of the flow of the first gas A, much greater than a transverse size in a direction transverse with respect to the direction of the flow of the first gas A.

The laminator element 20 generally consists of a plurality of tightly packed pipes, which are parallel to the first duct 11 and have a length, measured in the direction of the flow of the first gas A, which greatly exceeds the size of their internal diameter, measured in a direction transverse with respect to the direction of the flow of the first gas A. The laminator element 20 is inserted in the first duct 11 in such a way as to entirely occupy its cross section, so that the flow of the first gas A becomes laminar after passing through the plurality of laminator ducts 20a of the laminator element 20, or in any case its pressure decreases.

The structure of the laminator element 20 will not be further explored here. The person of skill in the art will know which devices or elements to use in order to make the flow of the first gas A laminar upstream of the narrowing 18. The first gas A reaches the narrowing 18 in which, due to the Bernoulli effect, it increases its speed, creating at the same time a decrease in its pressure.

In correspondence with the narrowing 18, thanks to the Venturi effect generated by the latter, the second gas G which flows in the second duct 12 and in the accumulation chamber 43 passes through the passage 41 and enters the mixing zone 13, where it mixes with the first gas A, forming a gaseous mixture M.

The mixing zone 13 can be a terminal part of the first duct 11 , that is, the mixing duct 39, where the first gas A and the second gas G meet and mix to form the gaseous mixture M which is delivered to the gas user device 50 through the delivery aperture 10b. The device 10 also comprises a plurality of sensors 30 configured to measure physical characteristics of the flow of the first gas A and of the flow of the second gas G.

In accordance with one aspect of the present invention, the plurality of sensors 30 is installed on the body 15 of the device 10. According to some embodiments, the plurality of sensors is integrated in the body 15 of the device 10.

According to other variants, the plurality of sensors 30 is attached on the body 15 of the device 10.

The plurality of sensors 30 comprises a first sensor 30a configured to determine a flow rate of the flow of the first gas A and at least one second sensor 30b configured to measure a pressure difference between the first duct 11 and the second duct 12. The measurements obtained thanks to the first sensor 30a and the at least one second sensor 30b are used together to determine the ratio between a flow of the first gas A and a flow of the second gas G.

According to other embodiments, there are both a second sensor 30b and also a third sensor 30c, both configured to detect the pressure difference between the first 11 and the second duct 12. Each of the plurality of sensors 30 can be a pressure sensor of the differential type for measuring the pressure difference of a gas between two zones of a duct or, preferably, a flow sensor for determining the pressure difference between two zones of a duct by measuring a flow of the gas.

The plurality of sensors 30, 30a, 30b, 30c is positioned externally to the first duct 11 and is in fluidic connection with it through channels formed in the body 15 of the device 10.

In detail, the first sensor 30a is in fluidic connection with a front zone 31 of the first duct 11 , upstream of the laminator element 20 when this is present, through a first front channel 33 a, and with a rear zone 32 of the first duct 11 , downstream of the front zone 31 and upstream of the narrowing 18, through a first rear channel 34a. When the laminator element 20 is not present, the rear zone 32 can be located inside the tapered portion 14 in proximity to the narrowing 18. When the laminator element 20 is present, the rear zone 32 can be located between the laminator element 20 and the tapered portion 14. The second sensor 30b is in fluidic connection with the front zone 31 of the first duct 11 , upstream of the laminator element 20 when this is present, through a second front channel, not shown, and with a measurement zone 35 of the second duct 12 through a second rear channel 34b.

The third sensor 30c is in fluidic connection with the front zone 31 of the first duct 11 , upstream of the laminator element 20 when this is present, through a third front channel, not shown, and with a measurement zone 35 of the second duct 12 through a third rear channel 34c.

The first 33 a, second, and third front channel are formed in the body 15 of the device 10 and comprise a series of turns and bends for fluidly connecting the sensor associated therewith with the front zone 31 of the first duct 11. Moreover, the first

33 a, second, and third front channel can be formed in such a way as to comprise a path around the circumference of the first duct 11.

If the sensors 30 are flow sensors, the front and/or rear channels also have the function of carrying the gas toward the respective sensors 30 and reintroducing it into the main flow.

In detail, the first sensor 30a, the second sensor 30b and the possible third sensor 30c are positioned adjacent to each other on a same side of the body 15, in proximity to and/or in correspondence with an external surface thereof.

According to some embodiments, for example described with reference to figs. 2a-4b, the plurality of sensors 30, 30a, 30b, and 30c can be positioned in one or more recesses 23 formed in the body 15, and it can be kept in position by a containing plate 37, attached to the body 15 by means of attachment means 38 such as screws, bolts and suchlike, which comprises at least one aperture 37a configured to allow access to the plurality of sensors 30, in particular to allow access to the connectors for power supply and/or data exchange.

This disposition of the sensors 30a, 30b, and 30c achieves the advantage of optimizing the space occupied by the device 10 and allows a rapid connection or disconnection of the sensors 30a, 30b, and 30c to prepare the device 10. Furthermore, this solution facilitates maintenance of the sensors 30a, 30b, and 30c.

In the example shown in figs. 2a and 2b, the sensors 30 are positioned adjacent to each other and kept in position by the containing plate 37.

This configuration facilitates the operations of repair, maintenance, installation, or replacement of the device 10 and of the sensors 30.

According to the embodiment of figs. 2a- 2b and 3 a, three recesses 23 can be provided in the body 15, each suitable to house a sensor 30a, 30b, 30c, and each aligned with a respective aperture 37a of the containing plate 37.

According to a variant, for example described with reference to figs. 4a-4b, a single recess 23 is provided in the body 15 in which all the sensors 30 are housed.

In accordance with this variant, the sensors 30 can all be housed in a containing casing 44, for example made of plastic material, which is in turn inserted in the recess 23.

The sensors 30 can each be connected to an external control unit, for example to the control unit 230 of the delivery apparatus 200.

Additionally, or alternatively, the device 10 can comprise an integrated control unit 45, configured to control at least part of the operation of the sensors 30, which can be installed inside the body 15. The integrated control unit 45 can be connected to and communicate with the control unit 230.

According to the embodiment of figs. 4a-4b, the integrated control unit 45 can be created on a printed circuit board 46, or PCB.

In this embodiment, the sensors 30 can be connected to and/or integrated in the board 46.

In particular, the board 46 can be disposed in the recess 23, inside the containing casing 44, if present, positioned above them, on the side opposite the withdrawal points 24a, 24b, 24c which communicate with the respective front and/or rear channels. In this case, there can be provided just one aperture 37a for the connection of the board 46 to suitable connectors for data exchange and/or electric power supply.

However, the person of skill in the art will understand that the position of the plurality of sensors 30 on the side of the inlet aperture 12a of the second duct 12 and adjacent thereto, as shown in the drawings, is not a necessary characteristic of the invention, and that it can vary according to technical needs and/or contingencies.

According to other embodiments, for example described with reference to figs. 7a-7c, the sensors 30 can be inserted in a containing casing 144, which is connected externally to the body 15 by means of attachment members 47 of the removable type, for example screws.

According to these embodiments, through holes 48 are provided on the body 15 for the passage of respective air flows A from the body 15 to the sensors 30, and vice versa.

The through holes 48 are put in fluidic communication with the respective front and rear channels 33, 34.

According to some embodiments, in the connection zone of the containing casing 144 the body 15 is closed by a removable closing plate 137 on which the through holes 48 are made. The closing plate 137 can also be connected to the body 15 by means of screws 47 or suchlike. According to some embodiments, the first 30a, the second 30b and the possible third sensor 30c can all be installed on a same printed circuit board 46, or PCB, inserted in the containing casing 144.

This solution further facilitates the assembly of the sensors 30 on the body, since it is possible to insert and attach the board 46 with the sensors 30 in the containing casing 144 and subsequently align the sensors 30 with the through holes 48 and attach the containing casing 144 to the body 15.

According to some embodiments, an integrated control unit 45 can also be provided on the board 46.

According to some embodiments, the containing casing 144 can be provided with ducts 145 protruding externally from a bottom wall 146 and configured to be inserted in the through holes 48 and allow the flow of respective air flows toward the sensors 30 and toward the body 15, respectively. In this solution, gasket elements 149 can be provided, for example O-rings, disposed during use between the ducts 145 and the through holes 48 in order to prevent possible leakages of the air flow.

In accordance with some embodiments, a pair of ducts 145 can be provided, which act respectively as inlet and outlet for each of the sensors 30 present. According to some embodiments, the ducts 145 can be made directly on the casing 144 if this has a box-like shape, or on a support element 147 configured to be inserted in the containing casing 144. In this case, the support element 147 can also have the function of positioning and closing the board 46 and/or the sensors 30 disposed inside the containing casing 144. According to some embodiments, for example shown in figs. 7b and 7c, the containing casing 144 comprises a covering element 148, closed on five sides, configured to define the upper and lateral walls of the containing casing 144, and the support element 147, inserted during use in the covering element 148, can be provided with the bottom wall 146 which closes the containing casing on the opposite side with respect to the covering element 148.

When the first sensor 30a is a flow and/or thermal-mass sensor, the first gas A enters the first front channel 33a and exits from the first rear channel 34a reentering the first duct 11. In this way, the first sensor 30a detects a flow S21 which can then be converted into a pressure differential ΔP2i=P2-P ₁ where P2 is the pressure value inside the first duct 11 in correspondence with the rear zone 32 and P ₁ is the pressure value inside the first duct 11 in correspondence with the front zone 31.

In the case of a sensor of the differential type, there is a membrane which separates the first gas A entering from the first front duct 33a from the gas entering from the first rear duct 33b, and as a function of the deformation and position of the membrane it is possible to determine the pressure differential ΔP21 between the front 31 and rear 32 zones. Similarly, the second and third sensor 30b and 30c, when created as flow sensors, respectively, detect a flow of the first gas A from the duct 11 to the duct 12 and determine, on the basis of the flow detected, a pressure difference.

The first gas A enters, respectively, in the second and third front channel and exits from the second and third rear channel 34b and 34c, entering in the second duct 12. In this way, the second and third sensor 30b and 30c each detect a flow S31 which can be converted into a pressure differential A?3i=P3-P ₁ where P3 is the pressure value inside the second duct 12 in correspondence with the measurement zone 35 and P ₁ is the pressure value inside the first duct 11 in correspondence with the front zone 31. The flow of the portion of first gas A on which a measurement is performed by the second and third sensor 30b and 30c, respectively, passes from the first duct 11 to the second duct 12 passing through the second rear channel 34b and the third rear channel 34c, respectively.

The flow of the portion of first gas A is preferably always directed from the first 11 to the second duct 12, in order to prevent the second gas G from entering the second and/or third sensor 30b and 30c, respectively, damaging them, or even escaping into the first duct 11 , potentially causing a flashback.

If the second gas G used is known and the second and/or third sensor 30b and 30c, respectively, are created as sensors of the thermo-mass type, they can also measure its mass.

If the second 30b and third 30c sensor are differential pressure sensors, the pressure difference is calculated as a function of the deformation/position of a membrane which separates the respective front and rear channels.

The delivery apparatus 200 also comprises a ventilation device 210 configured to move the first gas A and positioned downstream or upstream of the device 10. Optionally, the ventilation device 210 is positioned inside the first duct 11. For example, fig. la shows the ventilation device 210 disposed upstream of the mixing zone 13 and operating in suction mode, while in fig. lb the ventilation device 210 is disposed downstream of the mixing zone 13 and operates in thrust mode.

The action of the ventilation device 210 operating in suction mode, that is, downstream of the mixing zone 13, also contributes to suck in the second gas G present in the second duct 12 together with the pressure of the second gas G itself. However, this effect can also be achieved with the ventilation device 210 operating in thrust mode, that is, upstream of the mixing zone 13.

The apparatus can further comprise a speed sensor 42 to measure the rotation speed of the ventilation device 210.

The speed sensor 42 is suitable to detect the drive level of the ventilation device 210, that is, its real operation. For example, the speed sensor 42 is suitable to detect the number of revolutions of a fan of the ventilation device 210, and it can be a Hall effect sensor, an encoder or suchlike, preferably it is a Hall effect sensor connected to the ventilation device 210 and sensitive to the variation of the magnetic field created by an object located on the rotating part of the ventilation device 210.

The apparatus 200 can comprise a valve device 250, comprising the regulating means 260 and the safety means 270.

The safety means 270 are configured to allow or prevent the flow of the second gas G in the second duct 12 and can comprise one or more safety solenoid valves, which can be commanded selectively. In particular, when the safety means 270 are in a closed condition, the second gas G does not flow in the second duct 12.

In one example, the regulating means 260 are configured to regulate the flow of the second gas G flowing in the duct 12.

For example, the regulating means 260 comprises at least one of either a flow modulator or a pressure modulator.

By means of the regulating means 260 it is therefore possible to modify the flow of the second gas G in the duct 12 and therefore its percentage in the mixture M.

By means of the regulating means 260 it is possible to modify the flow of the second gas G in the duct 12 and to modify the value of the λ coefficient during the operation of the gas user device 50.

In particular, it is possible to obtain, in the step of ignition of the gas user device 50, a value λi of the λ coefficient comprised in the first intervalI ₁ and, in the steady state step, a value 2 λ of the λ coefficient comprised in the second interval I2. The apparatus 200 comprises a control unit 230 configured to regulate its operation.

The control unit 230 is configured to receive data from the first sensor 30a and from the second and third sensor, 30b and 30c, respectively, and process them to appropriately regulate the operation of the apparatus 200.

The control unit 230 is also configured to process the data detected by the first sensor 30a and by the speed sensor 42 in order to control that the ratio between the flow rate of the first gas A and the rotation speed of the ventilation device 210 remains substantially constant within a range of a predetermined initial ratio thereof, by suitably regulating the ventilation device 210.

Since the ventilation device 210 controls the feed of the first gas A into the first duct 11 , controlling the ventilation device 210 allows to control the quantity of first gas A introduced in the first duct 11 and therefore the abundance of the first gas A in the gaseous mixture M. The control unit 230 can include storage and processing devices able to store and execute control algorithms, in particular software or firmware for managing the operation of the apparatus 200.

Moreover, the control unit 230 can be connected to a user interface, to the gas user device 50, to the first and second source SI and S2, respectively, and to each drivable element, for example the valve device 250, by means of a physical medium, such as a cable, a wire or a conductive trace, or by means of wireless technology, such as Wi-Fi, Bluetooth, inductive coupling, capacitive coupling, radio frequencies for short, medium, and long range transmissions and suchlike.

When the first gas A is air and the second gas G is a combustible gas, the control unit 230 can calculate the value of the λ coefficient on the basis of the data detected by the first sensor 30a, by the at least one second sensor 30b, and optionally by the speed sensor (not shown in the drawings). In more detail, by using the first sensor 30a, and optionally the speed sensor, the measurement of the volume of a first gas A is obtained, and from the combination of the measurements performed by the first, second, and third sensor, respectively, 30a, 30b, and 30c, the measurement of the volume of the second gas G is obtained.

The control unit 230 allows for a precise volumetric control of the first gas A and of the second gas G, and it can calculate the mass flow rate of the first gas A, the composition of the first gas A being known.

If the composition of the second gas G is known, the control unit 230 also allows to calculate the mass flow rate of the second gas G. In particular, the control unit 230 allows, by controlling the regulating means 260, to modify the flow rate of the second gas G in the duct 12 and therefore modify the value of the λ coefficient during the operation of the gas user device 50, the burner.

When the first sensor 30a is a differential pressure sensor, the control unit 230 receives a datum from the first sensor 30a indicating the pressure difference ΔP?i between a first pressure value P ₁ measured in correspondence with the front zone 31 and a second pressure value P ₂ measured in correspondence with the rear zone

32, ΔP ₂₁ =P ₂ -P ₁ .

Optionally, the creation by the laminator element 20 of a laminar flow of the first gas A allows to use the Hagen-Poiseuille law to describe the linear relation between the flow rate of the first gas Q _A and the pressure difference ΔP ₂₁ : Q _A oc ΔP ₂₁ .

Conversely, without the laminator element, the flow rate of a non-laminar flow of the first gas A can be expressed by the following relation: where K is a coefficient that depends on geometric factors of the first duct and on physical characteristics of the fluid. The laminator element 20 allows to improve the reading sensitivity of the first sensor 30a at low flow rates, since it linearizes the relations between Q _A and ΔP ₂₁ and generates a pressure drop at its ends which can be detected by the first sensor 30a.

The same argument is valid when the first sensor 30a measures a flow rate of a gas. In this case, if the tapping of the first gas A with respect to the flow in the first duct 11 is negligible, the relations expressed above which link the pressure to the flow rate allow to obtain a pressure difference starting from a flow rate measurement.

The control unit 230 obtains a datum from the second sensor 30b and/or from the third sensor 30c indicating a pressure difference ΔP31 between the pressure P3 measured in the measurement zone 35 of the second duct 12 and the pressure Pi measured in the front zone 31 of the first duct 11.

The control unit 230, from the data received from the second sensor 30b and/or from the third sensor 30c, calculates a pressure difference value ΔP31, ΔP ₃₁ = P ₃ — P ₁

Knowing that the flow of the second gas G is not laminar, its flow rate Q _G can be expressed through the following relation:

Where KG is a coefficient that depends on geometric factors of the second duct and on the physical characteristics of the fluid, ΔP23 corresponds to the difference between the pressure P2 measured in correspondence with the rear zone 32 of the first duct 11 and the pressure P3 measured in correspondence with the measurement zone 35 of the second duct 12, ΔP ₂₃ = P ₂ — P ₃ .

The control unit 230 calculates ΔP23 using the value ΔP21 measured by the first sensor 30a and the value ΔP31 measured by the second and/or third sensor 30b and/or 30c, respectively:

The measurement of the flow rates of the first gas A, Q _A , and of the second gas G, Q _G , allows to calculate the λ coefficient using the following formula: where the λ coefficient is in the denominator and R is the known stoichiometric ratio between the first gas A and the second gas G.

From which the λ coefficient can be expressed as: in which the flow rate Q _G is calculated by substituting the relation (1) into (4), and Q _A can be either measured directly by the first sensor 30a or obtained from pressure measurements, when the sensor 30a measures a pressure difference.

The value of the flow rate of the second gas Q _G also depends on the pressure drops existing between the respective withdrawal zones 32, 35, which can be considered by providing a possible correction factor.

According to the relation (4), each variation of at least one of the flow rates of the first gas Q _A and of the second gas Q _G affects the value of the A, coefficient.

For this reason, the control unit 230 controls the regulating means 260 in order to regulate the flow rate of the second gas G. In more detail, the control unit 230 can be configured to regulate the regulating means 260 whenever it is necessary to vary the A, coefficient of the mixture M. In one example, the control unit 230 also controls the ventilation device 210 in order to regulate the flow rate Q _A of the first gas A to thus vary the λ coefficient of the mixture M.

When the gas user device 50 is a burner, the control unit 230 can also be configured to receive data from a flame presence sensor, for example an optical sensor, a thermocouple, a (ultraviolet) UV sensor, or suchlike. The flame presence sensor can be positioned in correspondence with the combustion chamber of the gas user device 50, the burner, for example outside an optical window in the case of an optical sensor, or inside the chamber in the case of a thermocouple. If 100% hydrogen is used, an optical sensor is used as a sensor to verify the presence of the flame F.

With reference to fig. 5, the delivery apparatus 200 described heretofore is used in a method of use which comprises the following steps. Although various examples of the method will be described, the person of skill in the art will understand that the various examples can be combined together without thereby departing from the scope of the invention.

A first step SI 00 provides to supply the first gas A in the first duct 11 of the device 10.

In one example, the first step SI 00 provides to connect the device 10 to a first source S 1 of first gas A. The first source S 1 consists of a gas container, for example a cylinder, containing a gas or a gaseous mixture containing, for example, a high percentage of nitrogen. In another example, the first source S 1 is a duct, a pipe, a conduit forming part of a plant that transports the first gas A. Optionally, the first gas A is air and the first source S 1 is none other than the environment. Optionally, the first step SI 00 provides that the control unit 230 activates the ventilation device 210 to create a flow of the first gas A inside the duct 11 toward the gas user device 50. The control unit 230 is also configured to control (increase or decrease) a rotation speed of the ventilation device 210 in order to increase or decrease, respectively, a flow rate Q _A of the first gas A inside the duct 11. A second step S 110 provides to supply the second gas G in the second duct 12 of the device 10.

In one example, the second step SI 10 provides to connect the device 10 to a second source S2 of second gas G. The second source S2 consists of a gas container, for example a cylinder, containing a gas or a gaseous mixture. In another example, the second source S2 is a duct, a pipe, a conduit forming part of a plant that transports the second gas G. Optionally, the second gas G is a combustible gas. An optional step SI 15 provides to determine the flow rate Q _A of the first gas A by means of the first sensor 30a and/or the flow rate Q _G of the second gas G by means of at least one of either the second sensor 30b or the third sensor 30c. We refer to what has already been described in relation to the plurality of sensors 30 for further details on determining the first flow rate Q _A and the second flow rate Q _G .

A third step SI 20 provides to obtain a gaseous mixture M of the first gas A and of the second gas G.

The third step provides that the control unit 230 controls the mixing of the first gas A and of the second gas G, in the first duct 11 , into a gaseous mixture M according to a predefined ratio and/or on the basis of the values of the first flow rate Q _A and of the second flow rate Q _G determined. When the second gas G is a combustible gas, the predefined ratio coincides with the λ coefficient.

As described above, the ratio between the flow rate Q _A of the first gas A and the flow rate Q _G of the second gas G is proportional to the λ coefficient. We refer to what has already been described for further details.

The step SI 20 of controlling the mixing of the first gas A and of the second gas G comprises the control unit 230 controlling at least one of either the ventilation device 210 or the regulating means 260.

The control unit 230 controls the ventilation device 210 on the basis of the predefined value of relative abundance between the first gas A and the second gas

G, that is, on the basis of the predefined value of the λ coefficient.

In one example, the control unit 230 controls a rotation speed ω of the ventilation device 210. It is clear to the person of skill in the art that, with the same cross section of the duct in which a fluid flows, the flow rate is directly proportional to the speed of the fluid itself. In this specific case, the speed of the first gas A is directly proportional to the rotation speed ω of the ventilation device 210.

For these reasons, for a fluid flowing in a duct without sources or wells, and moved exclusively by a rotary ventilation device, the following relation is valid: Q = c . ω (5) where Q is the flow rate, c is a constant, and ω is the rotation speed of the ventilation device.

When the second gas G is a combustible gas, in order to maintain a good quality of combustion it is necessary for the ventilation device 210 to have a rotation speed such as to reach a determinate flow rate of the first gas A which depends on the combustion apparatus and on the type of second gas G used.

In another example, the control unit 230 controls the regulating means 260 in order to modify the flow rate Q _G of the second gas G in the second duct 12. The second regulating means 260 can comprise at least one of either a flow modulator or a pressure modulator.

The control unit 230 controls the regulating means 260, which can comprise at least one of either a flow modulator or a pressure modulator, in order to modify the flow rate Q _G of the second gas G in the second duct 12. The regulating means 260 can comprise, for example, a shutter, a valve or suchlike, and an actuation member for moving the shutter or the valve or suchlike in order to determine the quantity, that is, the flow rate Q _G , of the second gas G delivered.

From the relation obtained above in the text, it can be seen that controlling one of either the flow rate Q _A of the first gas A or the flow rate Q _G of the second gas G, being a combustible gas, allows to control the value of the A coefficient, so that it assumes different values according to the phase of the combustion, such as the value λ ₁ , comprised in a first interval I ₁ , during the ignition of the gas user device 50, the burner, or the value ₂ , comprised in a second interval I ₂ , during steady state operation.

As already described, in the case of hydrogen at very high volume percentages or at 100%, the interval I ₁ can be comprised substantially between 2 and 5, preferably equal to about 4, and the interval I2 can be comprised between about 1.2 and 2, and preferably equal to about 1.3 - 1.5. Typical values of λi during ignition for the second gas G different from hydrogen could be comprised between 1 and 2. In the case of natural gases, the interval I ₁ can be comprised between 1 and 4 and the interval I2 can be comprised between 1 and 2, preferably between 1.2 and 1.5. In another example of the invention, there is provided a method for using an assembly that comprises the delivery apparatus 200 and a gas user device 50, this being a combustion apparatus, a burner.

A fourth step S 130 provides to deliver the gaseous mixture M to a gas user device 50.

The steps of the method described in relation to fig, 5 are performed by the control unit 230.

Optionally, as shown in fig. 6, the method provides an initial step S200, prior to the first step SI 00, of detecting a request for ignition of the combustion apparatus, by a user of the gas user device 50, which contains information relating to the heat value Qc required, indicative of a temperature desired by the user. The information relating to the heat value Qc required is entered by the user on an interface (not shown in the drawings) such as a screen, keyboard, keypad, touchscreen and suchlike, electrically connected to the control unit 230. The connection between the control unit 230 and the interface can occur by means of a physical medium, such as a cable, a wire, a conductive trace, or by means of wireless technology, such as Wi-Fi, Bluetooth, inductive coupling, capacitive coupling, radio frequencies for short, medium, and long range transmissions and suchlike. When the gas user device 50 is a burner used to heat water, the heat value Qc refers to the heat that the burner has to generate in order to heat water or other fluids for these to reach a preset or user-set temperature value.

If the control unit 230 determines that the ignition request has been received, the control unit 230 controls the ignition of the burner flame. The control of the ignition of the burner flame comprises the steps of the method described in relation to fig. 4. In the first step SI 00, the control unit 230 controls the supply of the flow rate Q _A of the first gas A through the first duct 11.

As expressed in relation (5), the flow rate Q _A of the first gas A and the rotation speed ω of the ventilation device 210 are directly proportional. For this reason, controlling the flow rate Q _A of the first gas A comprises measuring the flow rate Q _A by means of the first sensor 30a and controlling the rotation speed of the ventilation device 210 in order to achieve the desired flow rate Q _A .

The measured value of the flow rate Q _A of the first gas is compared by the control unit 230 with a pre-established value Q _A0 of the flow rate of the first gas in a step of preparing for ignition.

The pre-established value Q _A0 depends on the type of first gas A and second gas G, on the characteristics of the device 10 and/or of the apparatus 200, and/or on the heat value Qc required, and it can be preset and stored in the control unit 230. The pre-established value Q _A0 corresponds to a flow rate value of the first gas A required to obtain the heat value Qc from the gas user device 50. The pre- established value Q _A0 of the flow rate of the first gas A required for ignition can be stored in the control unit 230.

In this step, the valve device 250 remains closed to prevent the inflow of second gas G along the second duct 12.

The control unit 230 controls the rotation speed ω of the ventilation device 210 so that the measured flow rate Q _A reaches the value Q _A0 .

As regards the measurement of the flow rate Q _A of the first gas A, we refer to what described in relation to the apparatus, which we will not repeat here for brevity.

Advantageously, the measurement of the flow rate Q _A of the first gas A and of the rotation speed ω of the ventilation device 210, and the analysis of their ratio can allow to detect possible anomalies of the pneumatic system of the combustion apparatus during its operation. In fact, partial blockages on the flue or on the combustion fume exhaust paths, or the presence of wind with a flow opposite to the forced ventilation, could make ignition of the combustion apparatus unsafe.

If the measured value of the flow rate Q _A deviates from the flow rate value Q _A0 of the first gas A required for the ignition of the gas G user device, it is necessary to verify whether a pre-established time out time period T _TO has already elapsed since the execution of the ignition step began. If the time period T _TO has not elapsed, the method provides to control the rotation speed ω of the ventilation device 210 until the measured flow rate Q _A of the first gas A corresponds to the flow rate Q _A0 of the first gas A required for ignition. In the event the measured value Q _A is greater than the value Q _A0 , the control unit 230 controls the ventilation device 210 in order to decrease the number of revolutions per unit of time. Conversely, in the event the measured value Q _A is lower than the value Q _A0 , the control unit 230 controls the ventilation device 210 in order to increase the number of revolutions per unit of time.

The method provides to retry the ignition procedure of the gas user device 50 at a later time, or provide for a finite number of attempts to prepare for ignition.

The plurality of sensors 30a, 30b, and 30c in this step guarantee the measurement of the flow rate Q _A of the first gas ; moreover, they also play a role in identifying a malfunction of one of the three sensors 30a, 30b, and 30c and preventing the continuation of the ignition operations of the combustion apparatus.

When the time period T _TO has elapsed, the method comprises turning off the ventilation device 210. The method can return to the step of receiving the information relating to a value of the quantity of heat Qc required, and repeat the step of ignition for a further time period T _TO .

In the event that the measured flow rate Q _A of the first gas A corresponds, during the period T _TO , to the flow rate Q _A0 of the first gas A necessary for ignition, the method continues with the scintillation step.

In this step, the control unit 230 controls the activation of a scintillator above the gas user device 50, the burner, and the opening of the valve device 250 to allow the second gas G to flow in the second duct 12 and therefore mix with the first gas A in the mixing zone 13 of the first duct 11.

The control occurs directly through the control unit 230 which sends a signal that activates the scintillator device, or it occurs through the transmission of a command by the control unit 230 to the gas user device 50 or to an element thereof, such as the burner.

During the ignition step, the control unit 230 controls a flow rate Q _G of the second gas G in the second duct 12. As widely disclosed above, the relation that exists between the value of the parameter A, and the flow rate of the first gas A and of the second gas G, Q _A and Q _G , respectively, is given by: where R is the stoichiometric ratio between gas A and gas G.

The method then provides that the control unit 230 controls the regulating means 260 in such a way that the relation satisfied for λ, = λ ₁ , where λ ₁ is the value of the A, coefficient during the ignition step of the gas user device 50, and where the value of the flow rate Q _A has been set in the step of preparation for ignition.

The first value λ ₁ of the A coefficient can be defined during the steps of construction, installation, overhaul, or suchlike of the combustion apparatus and stored in the control unit 230. The ignition step can also comprise continuously determining the value of the flow rate Q _G through the measurements obtained by the plurality of sensors 30a, 30b, and 30c.

The ignition step can also comprise continuously determining the value of the flow rate Q _A through the measurements obtained by the first sensor 30a. The control unit 230 also determines whether the measured value of the parameter λ corresponds to the first value Ai. In the event that the value of the parameter A does not correspond to the value Ai, the method can provide to continue to regulate the flow rate Q _G of the second gas G by means of the regulation means 260, or the flow rate Q _A of the first gas A by means of the ventilation device 210, until a pre-established safety period T _SAFE for the ignition step has elapsed.

In the event that the value of the parameter λ corresponds to the value Ai, the ignition step S220 provides to detect the flame in the gas user device 50 by means of a flame sensor.

If the flame is not detected, the method provides to close the valve device 250 in order to stop the flow of the second gas G, switch off the ventilation device 210 and return to the detection of an ignition request.

If the flame is correctly detected, the method provides to activate normal operation in the operating step S230.

In the operating step, the control unit 230 provides to control the user device 50 of gas A to bum the gaseous mixture M in a routine operating state, verifying that the parameter A assumes the value λ ₂ . The operating step comprises the steps S100, S110, S115, S120, and S130.

The transition to normal operation can provide to measure, by means of the sensor 30a, an initial flow rate value Q _A0 of the first gas A and an initial rotation speed value ω ₀ of the ventilation device, and calculate the initial parameter co given by the ratio:

The parameter c ₀ can be stored in control unit 230. The operating step can also provide that the control unit 230 detects, as input datum, a second predefined value λ ₂ of the λ coefficient. For example, the second value λ ₂ of the λ coefficient can be read by the control unit 230, where it may have been stored during the steps of construction, installation, overhaul, or suchlike of the combustion apparatus.

The operating step can provide to calculate the flow rate Q _G of the second gas G on the basis of the previously disclosed relation (6), in which the λ coefficient assumes the value λ ₂ .

For this calculation, it can be provided to set a value of the rotation speed to achieve a value of the flow rate of the first gas A required on the basis of the value of the quantity of heat Qc required.

The operating step can then provide to calculate the difference between the flow rate Q _G of the second gas G calculated as necessary, and the real gas flow rate.

The operating step can also provide that the control unit 230 regulates the flow of the second gas G to be supplied by means of the regulating means 260, and to measure the real flow rate of the second gas G, by means of the second and/or the third sensor 30b and 30c, respectively, and the flow of the second gas G real value of the rotation speed ω of the ventilation device 210, by means of the speed sensor 42. In one example of the invention, the operating step can provide to vary the rotation speed ω of the ventilation device 210, and therefore the flow of the first gas A, and the lambda λ coefficient, according to the power requirements of the combustion apparatus.

In this case, the method can comprise the control unit 230 once again detecting the value of the lambda λ ₂ coefficient, and once again calculating the flow rate of the second gas G, on the basis of the relation (6).

It is clear that modifications and/or additions of parts may be made to the delivery device 10, to the delivery apparatus 200 and to the method as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of device for delivering a combustible gaseous mixture M and corresponding method of use, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.