Patent Description:
As is known, every vehicle with an internal combustion engine, powered completely or partly by gas (such as for example LPG, methane CH4, hydrogen H2, etc.) has a tank/cylinder for storing the same fuel at high pressure (<NUM>. 6MPa for LPG, 20MPA for methane CH4, 70MPa for hydrogen H2, etc.) to increase the mass capacity thereof.

Instead, the use of gas in the internal combustion engine always takes place at a pressure reduced to a few tenths of MPa above the intake pressure. This pressure reduction, which in the case of LPG is also associated with a phase change (from liquid to gas), is always associated with a removal of heat from the device (known as "lung", pressure reducer, evaporator) which therefore in turn absorbs heat from the outside, lowering its temperature.

For an average LPG-powered 61kW combustion engine vehicle, the thermal power absorbed is estimated to range from 150W to over 3kW.

This absorption of heat inevitably leads the pressure reduction device to lose temperature, until it reaches levels that prevent it from functioning properly due to two phenomena.

The first phenomenon consists in reaching temperatures at which the movable elements (such as springs, membranes, etc.) of the pressure reducer lose their pressure regulation properties (for methane, hydrogen).

The second phenomenon consists in the fact that the temperature of the body/gas outlet is lower than the dew point of the gas itself which therefore would not be able to remain in the gaseous phase (in the case of LPG).

To overcome these problems, it is usual to keep the pressure reducer heated by the cooling liquid coming from the engine cooling system.

This method, simple and archaic, satisfies the primary need to guarantee the correct operation of the pressure reducer (and therefore of the engine) but is nowadays not very efficient from an energy point of view.

In fact, the known solutions simply provide for a thermal exchange between the engine coolant fluid, appropriately withdrawn by a branch of the system, and the pressure reducer which is therefore thermostatted substantially at the same temperature of the engine.

In this way, however, a non-negligible amount of cooling power of the pressure reducer and, above all, already available since it is freed automatically by the expansion of the fuel gas, is dissipated.

It is therefore clear that the known solutions are not able to guarantee the aforementioned energy efficiency specifications/requirements. Solutions according to the preamble of claim <NUM> are disclosed by <CIT> and <CIT>.

The need of solving the drawbacks and limitations mentioned with reference to the prior art is therefore felt.

Therefore, the need is felt to provide a fuel supply system for vehicles with a pressure reducer that is energy efficient.

This requirement is met by a fuel supply system for vehicles with pressure reducer according to claim <NUM>.

Further features and advantages of the present invention will appear more clearly from the following description of preferred non-limiting embodiments thereof, in which:.

Elements or parts of elements in common to the embodiments described below are referred to with the same reference numerals.

With reference to the above figures, reference numeral <NUM> globally indicates an overall schematic view of a fuel supply system for motor applications, such as for example vehicles <NUM> according to the present invention.

It should be noted that the present invention may be applied to any type of vehicle <NUM>, such as a motor vehicle, a bus, a truck and the like.

The concept of engine application must be understood in a broad sense, including for example generating sets, a cogeneration plant, etc..

For the purposes of the present invention, the aforementioned applications must be considered in an explanatory and non-exhaustive manner.

In particular, the present invention applies to supply systems for internal combustion engines or endothermic engines, preferably fed, at least partially, with so-called alternative fuels such as LPG, methane, hydrogen.

Said fuels, which are in the gaseous state in ambient conditions, are normally stored at high pressure inside a tank <NUM>, which is part of the supply system <NUM>.

For example, as seen, storage pressures of <NUM>. 6MPa are reached for LPG, 20MPA for methane CH4, 70MPa for hydrogen H2, etc..

The supply system <NUM> therefore comprises a pressure reducer, fluidly connected in input to said fuel tank <NUM> containing fuel compressed to an input pressure Pi, and adapted to feed the fuel to the internal combustion engine <NUM>. In particular, the fuel is fed in the gaseous phase, at a delivery pressure Pm lower than the inlet pressure Pi.

The fluid at the delivery pressure Pm is then sent to special injectors <NUM> which inject it directly or indirectly into the combustion chamber <NUM> of the internal combustion engine <NUM>.

Therefore, in a known manner, the pressure reducer <NUM> reduces the fuel pressure from the input value Pi to a delivery value Pm, so as to correctly supply the internal combustion engine <NUM>.

In this significant pressure reduction, there is a considerable lowering of the temperature of a body <NUM> of the pressure reducer, due to the absorption of heat by the expanding gas. In order to prevent the body <NUM> of the pressure reducer <NUM> from reaching too low temperatures, the heat exchange between the pressure reducer and at least one exchanger fluid is provided.

The fuel supply system <NUM> comprises at least one exchanger fluid passing through at least one conveying duct <NUM> so as to at least partially lap a portion of the body <NUM> of the pressure reducer <NUM> to increase the temperature of said body <NUM> and simultaneously reduce the temperature of said exchanger fluid.

According to the invention, said conveying duct <NUM> is provided with at least an adjustment mean <NUM> suitable to regulate the flow rate of the exchanger fluid that laps the body <NUM> of the pressure reducer <NUM>, so as to bring the body <NUM> of the pressure reducer <NUM> to a temperature higher than a predetermined minimum value.

In particular, said minimum temperature value is equal to the freezing temperature of atmospheric humidity or of that possibly contained in the supply gas under the conditions of use (in the case of use of methane/hydrogen as fuel); the minimum temperature value is above the boiling temperature of the fuel in the gaseous phase at the delivery pressure Pm, in the case of use of LPG as fuel.

In other words, the adjustment mean <NUM> is operated so as to regulate the flow of exchanging fluid to regulate the temperature of the body <NUM> of the pressure reducer <NUM>.

There are various possible embodiments of said adjustment mean <NUM>.

For example, the adjustment mean <NUM> may comprise a throttle valve.

It is also possible to use, as an adjustment mean <NUM>, a thermostatic valve or a proportional valve, both suitable for regulating said flow of exchanger fluid.

It is also possible to use, as an adjustment mean <NUM>, a variable displacement pump.

In particular, in order to carry out the heat exchange necessary to thermostat/heat the body <NUM> of the pressure reducer <NUM>, it is possible to use different types of exchanger flows.

It should be noted that the temperature control of the pressure reducer body <NUM> preferably takes place by means of a temperature sensor <NUM>, preferably arranged in contact with said body <NUM>.

The temperature sensor <NUM> is able to generate a signal which is sent to a control unit <NUM> of the power supply system <NUM>.

Said control unit <NUM> can be specific to the fuel supply system and therefore adapted to interface with a control unit of the internal combustion engine <NUM>, or it can be integrated in the control unit of the internal combustion engine <NUM>.

According to the invention, said at least one conveying duct <NUM> comprises a ventilation duct of a vehicle air conditioning system: therefore in this solution the exchanger fluid is the flow of air F destined to be introduced into the passenger compartment of the vehicle <NUM>.

Preferably, an air/air exchanger <NUM> is provided in this solution which facilitates the heat exchange between the air of the air conditioning system and the body <NUM> of the pressure reducer <NUM>.

According to a further possible embodiment, said at least one conveying duct <NUM> further comprises a branch duct of a cooling liquid of the internal combustion engine <NUM>, so as to convey the cooling liquid towards the pressure reducer <NUM>. This cooling system will in turn be at least a recirculation pump <NUM>, suitable for moving or recirculating the liquid inside said system in a known manner.

According to a further possible embodiment, said at least one conveying duct <NUM> extends to at least partially lap an exhaust gas recirculation valve <NUM> (EGR) of the internal combustion engine <NUM>.

Preferably, in such embodiment, the at least one conveying duct <NUM> extends to at least partially lap a heat exchanger <NUM> fluidly connected with said exhaust gas recirculation valve <NUM> (EGR).

It is also possible to make an exhaust gas recirculation valve <NUM> at least partially integrated into the body <NUM> of said pressure reducer <NUM>, so as to directly yield heat from the exhaust gas recirculation valve <NUM> to the pressure reducer <NUM> itself.

The possible condensate liquid, i.e. water, generated by the heat exchange between the exchanger fluid and the body <NUM> of the pressure reducer can be collected and conveyed in a water tank (not shown) to be used for water injection phases in the internal combustion engine. Other uses are also possible, such as for example the use of water produced in headlamp cleaning systems or also for cleaning the windscreen or rear window.

The operation of a fuel supply system for vehicles with pressure reducer according to the present invention will now be described.

According to the invention, the method of adjusting a fuel supply system for vehicles supplied with alternative fuels with a pressure reducer comprises the steps of:.

The adjustment method according to the invention further comprises the steps of connecting the at least one conveying duct <NUM> to a ventilation duct of an air conditioning system of the vehicle, so as to perform a thermal exchange between the pressure reducer <NUM> and a fluid of said air conditioning system.

The adjustment method may comprise the steps of connecting said at least one conveying duct <NUM> to an exhaust gas recirculation valve <NUM> so as to perform a thermal exchange between the pressure reducer <NUM> and the exhaust gas recirculation valve.

The method may comprise the step of adjusting the temperature of the internal combustion engine <NUM> by varying the heat exchange between the engine coolant liquid <NUM> and the pressure reducer <NUM> and/or the heat exchange between the exhaust gas recirculation valve <NUM> and the pressure reducer <NUM>.

In other words, it is possible to simultaneously carry out thermal exchanges between different exchanger flows, each passing through a specific conveying duct.

The method may also comprise the step of assisting and/or replacing the conditioning system of the passenger compartment by regulating the heat exchange between the pressure regulator <NUM> and an air flow of the conditioning system.

The method may also comprise the step of condensing the ambient humidity and producing water in the liquid phase, to be used for water injection techniques in said internal combustion engine.

In essence, the pressure reducer is no longer heated to the temperature of the engine coolant (about <NUM>-<NUM>), as in the prior art solutions, but to a lower one, controlled and just enough to guarantee its functionality, generally but not necessarily, a few degrees above zero °C (in the case of methane and hydrogen supply) or above the boiling temperature of the outgoing gas in the case of LPG supply.

This 'reduced' heating, compared to known solutions, provides low temperature surfaces or a fluid that can be used for:.

As can be appreciated from the description, the present invention allows overcoming the drawbacks of the prior art.

In fact, the present invention allows avoiding dispersing the heat (absorption of heat, cooling) which is generated in the pressure reducer of gas-powered vehicles (LPG, CH4, H2, etc.), and use it instead as a free source of "waste" energy for other purposes which today, in the prior art, instead require the use of primary energy.

The advantages that can be obtained are several, such as:.

A further advantage is given by the fact that, in the case of a fluid connection (i.e. heat exchange) between the pressure reducer and the exhaust gas recirculation valve (EGR), the passage time of the engine from the supply with liquid fuel (typically petrol) to gaseous fuel supply (alternative, such as the LPG), is significantly reduced.

In fact, EGR is able to heat up significantly before the engine coolant and therefore is able to heat the pressure reducer in much shorter times than conventional solutions (which use the coolant as a heat source).

This means that the pressure reducer will go to temperature very quickly and therefore it will be possible to switch first from the conventional supply (petrol or diesel) to the alternative fuel supply (methane, LPG, hydrogen): this implies a reduction in consumption and polluting emissions.

Moreover, the present invention allows optimizing, or reducing, the thermostatting of the internal combustion engine. In fact, in the known solutions, the heating of the pressure reducer device is delegated, as seen, to a branching of the coolant in a passive manner. In this a relatively high amount of heat is dissipated to heat the reducer device, moreover, at a temperature well above that required for the correct operation of the reducer device itself. Therefore, in the known solutions, the heating of the engine is delayed, since a non-negligible quantity of heat is dissipated through the coolant unnecessarily: this results in less than optimal management of the engine temperature.

Moreover, the increase in cost of the present invention, compared with the solutions of the prior art, although variable depending on the complexity of implementation, is potentially zero if this type of system is introduced in a vehicle already designed for supply with gaseous fuels.

Therefore, the present invention can be easily applied as retrofitting to a pre-existing supply system, without requiring particular distortions and/or adaptations.

Claim 1:
Fuel supply system (<NUM>) for motor applications supplied with gaseous fuels with pressure reducer comprising:
- a pressure reducer (<NUM>), fluidly connected in input to a fuel tank (<NUM>) containing compressed fuel at an input pressure (Pi), and suitable for supplying said fuel in output, in the gas phase, to an internal combustion engine (<NUM>), at a delivery pressure (Pm) lower than the input pressure (Pi),
- at least one exchanger fluid passing through at least one conveying duct (<NUM>) so as to at least partially lap a portion of a body (<NUM>) of the pressure reducer (<NUM>) to increase the temperature of said body (<NUM>) and simultaneously reduce the temperature of said exchanger fluid,
wherein said conveying duct (<NUM>) is provided with at least an adjustment mean (<NUM>) suitable to regulate the flow rate of the exchanger fluid that laps the body (<NUM>) of the pressure reducer (<NUM>), so as to bring the body (<NUM>) of the pressure reducer (<NUM>) to a temperature higher than a predetermined minimum value,
characterised in that said at least one conveying duct (<NUM>) comprises a ventilation duct of an air conditioning system of the vehicle (<NUM>).