" FUEL SYSTEM FOR A SPARK IGNITION ENGINE"

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Field of the invention

The present invention relates to the field of spark ignition engines and in particular to fuel supply systems .

State of the art

Hydromethane is a gaseous mixture composed of 10%-30% by volume of hydrogen and 70%-90% by volume of methane , mainly used in the automotive field as fuel . The presence of hydrogen helps to improve engine combustion ef ficiency and reduce CO2 equivalent and NOx emissions into the atmosphere , as hydrogen is a clean energy source .

Both the methane gas and the hydrogen gas constituting hydromethane can be produced biologically or through synthesis processes , increasing the use of renewable energy sources and further contributing to the decarbonisation obj ectives of the automotive field .

Given the properties of hydromethane , it was thought in the past to distribute methane with added hydrogen at about 10% by volume , to exploit the advantages of the mixture . This arti ficially generated hydromethane is generally referred to as " industrial hydromethane" .

However, the di f fusion of hydromethane is poor and the percentages of hydrogen are not constant . In view of a greater di f fusion of the hydrogen vector in the energy system, the gas distribution system envisages a partial use of the methane gas networks to inj ect hydrogen and in this way be able to convey it from the point of production to the point of use . Recent studies have demonstrated the compatibility of low pressure methane gas distribution networks up to hydrogen percentages of the order of 10- 15% (by volume ) .

It is therefore possible that in the future the gas distribution system will contain this type of mixture . However, this approach is still unclear at European level , neither in terms of timing nor in terms of location of the hydrogen inj ection points .

From the point of view of use through the automotive system, this approach is therefore still highly uncertain . Furthermore , considering the case of using methane in liquid form ( LNG ) , it is not possible to mix hydrogen in the liquefied methane due to the di f ferent liquefaction temperatures . Therefore , currently, it is not possible to predict a capillary di f fusion of hydromethane .

Unless speci fically excluded in the detailed description that follows , what is described in this chapter is to be considered as an integral part of the detailed description . Summary of the invention

The obj ect of the present invention is to propose a solution to the problems inherent in the use of hydromethane .

The basic idea of the present invention is to propose a methane and hydrogen inj ection system so that the hydromethane mixture is created directly on board the vehicle during its combustion .

More particularly, according to the present invention, each cylinder is associated with two inj ectors , a first inj ector of which is arranged to inj ect methane in gaseous form and a second inj ector arranged to inj ect hydrogen in gaseous form .

It is clear that the two species of methane and hydrogen are stored separately on board the vehicle using separate accumulation tanks .

According to the present invention, the two inj ectors are associated together so as to inj ect the respective species into a common inj ection channel , able to be operatively associated with the intake mani fold of the relative cylinder .

The common inj ection channel is a distinct and separate component from the intake mani fold, therefore , the mixing of methane and hydrogen takes place in the common channel . Furthermore , it is understood that the power supply to the engine is indirect , as the common duct is not connected directly with the engine head, but indirectly through the intake mani fold .

Each inj ector of the multi-species inj ector defines a development axis , so that the development axis of one inj ector is incident with the development axis of the other inj ector defining a Y configuration in combination with the common inj ection channel .

According to a preferred variant of the invention, the common inj ection channel is made in a body which is in one piece with the casings of the two inj ectors defining a Y- shaped multi-species inj ection device .

The multi-species inj ection device can be associated directly with the relevant intake mani fold or via an optionally flexible extension .

According to a preferred implementation of the invention, an internal combustion engine comprises at least one multispecies inj ection device . More particularly, the multispecies inj ection device defines a containment plane and in which the containment plane is perpendicular to or incident with a crankshaft of the internal combustion engine when operatively associated with the internal combustion engine . Advantageously, the multi-species inj ection system allows not only to simpli fy the assembly of the internal combustion engine , but also allows to limit the dimensions of the inj ection system .

When the internal combustion engine comprises two or more cylinders arranged in line , the corresponding two or more multi-species inj ection systems share two rails for the distribution of the two fuels , preferably arranged parallel to the crankshaft of the internal combustion engine . According to a further preferred aspect of the invention, the ratio between methane and hydrogen has varied over time as a function of some factors :

- Operating point of the engine ,

- Ambient temperature and/or engine coolant temperature ,

- Characteristics of methane ,

- Fuel levels in methane and hydrogen tanks .

Therefore , in at least one operating condition of the engine both gaseous species are inj ected simultaneously but with a ratio which varies over time .

In fact , the concept of a mixture implies that both gaseous species must be present .

The dependent claims describe preferred variants of the invention, forming an integral part of the present description .

Brief description of the figure

Further obj ects and advantages of the present invention will become clear from the detailed description that follows of an embodiment of the same ( and of its variants ) and from the annexed drawings given for purely explanatory and non-limiting purposes , in which : Figs. 1 and 2 show an embodiment of a multi-species injection device respectively according to a side view and according to a corresponding longitudinal section;

Fig. 3 shows a perspective view of a group of multispecies injectors according to the previous figures of an internal combustion engine;

Fig. 4 shows a spark ignition engine implementing a device according to figures 1 - 3.

The same reference numbers and letters in the figures identify the same elements or components or functions.

It should also be noted that the terms "first", "second", "third", "superior", "inferior" and the like may be used herein to distinguish various items. These terms do not imply a spatial, sequential, or hierarchical order for the modified items unless specifically indicated or inferred from the text.

The elements and characteristics illustrated in the various preferred embodiments, including the drawings, can be combined with each other without however departing from the scope of protection of the present application as described below .

Detailed description of preferred embodiment

Figure 1 shows an example of a multi-species injection MJ device according to the present invention. In particular, it is configured for the injection of two different gaseous species .

It comprises a pair of injectors JI, J2 associated together so as to produce a hydromethane mixture directly on board the vehicle during its combustion.

In other words, the mixture produced is in no way stored for later use. The mixture produced is injected directly into the intake manifold of a cylinder during its operation, in order to burn it.

It is also worth noting that an injector cannot be confused with a simple valve, as the injector is responsible for dosing the fuel over time, also making multiple injections in the same engine power cycle. Indeed, a simple valve does not have the characteristics to open and close as quickly as an injector.

The first injector JI is arranged to inject methane in gaseous form, while the second injector J2 is arranged to inject hydrogen in gaseous form.

According to the present invention, the two injectors are associated together so as to inject the respective species into a common injection channel CMC, able to be operatively connected to the intake manifold of the relative cylinder. As can be seen in figures 1 and 2, each injector JI and J2 defines a development axis, respectively X and Y, so that the development axis of the first injector JI is incident with the development axis of the second injector J2, defining a configuration V-shaped . More speci fically, according to a preferred variant of the invention, the inj ectors define a Y-shaped configuration with the common inj ection channel CMC .

Preferably, the angle between the X-axis and the Y-axis is between 10 ° and 90 ° .

At the free ends of the V configuration there are electrical connectors CN1 and CN2 , which allow to independently control the operation of the respective inj ectors JI and J2 .

The common channel CMC can have any shape . It is connected to inj ectors JI and J2 at the vertex defined by the point of incidence of straight lines X and Y . It can have a straight or curved shape . Preferably, it has a rectilinear shape and the relative development axis is the bi field of the angle identi fied by the intersection of the X and Y axes .

However, the development axis Z of the common channel CMC can coincide with the X axis or with the Y axis .

I f we consider a containment plane in which the X and Y axes lie , the Z axis of the common channel can also belong to the same plane or it can be incident with it .

According to a preferred variant of the invention, the common inj ection channel is made in a body, which is in one piece with the casings of the two inj ectors . The common inj ection channel of the multi-species inj ection device can be associated directly with the relative intake mani fold or by means of an optionally flexible extension .

With reference to figure 1 , the body of the device MJ comprises a first port R1 and a second port R2 intended to be connected to respective distribution rails of the two types . The doors are perpendicular to the containment plane identi fied by the X and Y axes .

According to a preferred implementation of the invention, an internal combustion engine comprises at least one multispecies inj ection device . More speci fically, the X and Y axes of the multi-species inj ection device identi fy a containment plane which can be perpendicular to or incident with the crank shaft of the internal combustion engine when operatively associated with the engine itsel f .

Advantageously, the multi-species inj ection system allows not only to simpli fy the assembly of the internal combustion engine , but also allows to limit the dimensions of the inj ection system .

When the internal combustion engine comprises two or more cylinders arranged in line , the corresponding two or more multi-species inj ection systems are arranged so that the relative planes identi fied by the X and Y axes are parallel to each other .

This fact makes it possible to adopt two ducts ( rails ) for the distribution of the two fuels that are perfectly straight and arranged parallel to each other and to the crankshaft of the internal combustion engine .

According to another aspect of the present invention, the hydromethane mixture is varied over time in relation to the operating conditions of the vehicle .

It is known that hydrogen has a much lower resistance to detonation than methane ; the latter has an equivalent octane number closely linked to the composition of the distributed methane .

By virtue of these di f ferences in the combustion properties of the two species , it can be expected to operate the internal combustion engine with a mixture rich in hydrogen :

1 ) at minimum ( idle )

2 ) in cruising conditions with torque output lower than a pre-set percentage ( e . g . 35% ) of the maximum torque output ,

3 ) in conditions of very cold intake air and/or still cold engine water .

Conversely, when the temperature of the engine and/or ambient air and/or the engine rotation speed exceeds a predetermined threshold, it is advantageous to limit the percentage of hydrogen so as to guarantee an adequate average octane number .

According to another preferred aspect of the invention, the addition of hydrogen depends on the quality of the methane . Hydrogen is known to help improve combustion. It is also known that pure methane does not exist and that the presence of heavier hydrocarbons (e.g. ethane, propane) and/or inert gases (e.g. N2, CO2 ) can lead to variations in its resistance to detonation.

It is worth highlighting that in the context of the present invention when we speak of a mixture we always refer to a mixture of hydrogen and methane, neglecting the fact that methane in itself represents a mixture of other species.

Therefore according to one aspect of the invention, the percentage of hydrogen injected into the engine can vary in relation to the availability of the two species.

In fact, if the residual amount of methane is limited, to extend the vehicle's range it is possible to increase the percentage of injected hydrogen up to the maximum design limit. Conversely, when the residual quantity of hydrogen is limited, the percentage of injected hydrogen can be reduced or cancelled.

Obviously, in relation to the percentage of injected hydrogen, the ignition times can be suitably varied taking into account the different composition of the mixture entering the engine.

The management of the species injected into the engine is achieved by means of an ECU processing unit, which controls the internal combustion engine and its subsystems. The processing unit is arranged and connected with each multi-species inj ector so as to be able to selectively and independently control the operation of the methane inj ector and the hydrogen inj ector .

Figure 3 shows a group of multi-species inj ectors according to the present invention interconnected by means of the duct R, generally referred to as the rail . Preferably, it houses two separate and parallel ducts to convey hydrogen and methane . Two temperature sensors TS 1 and TS2 are associated with the rail to measure the temperature of the two fuel species for the purpose of regulating the combustion and mixing parameters of the same species immediately before the relative combustion .

Variants of the non-limiting examples described are possible , without however departing from the scope of protection of the present invention, including all embodiments equivalent , for a person skilled in the art , to the content of the attached claims .

From the description given above , the person skilled in the art is capable of reali zing the obj ect of the invention without introducing further constructive details .