Power system with heated fuel rail

Abstract

The invention relates to a power system comprising an internal combustion engine and a pressurized gas container for pressurizing said internal combustion engine, said power system comprising an upstream distribution rail (1) for distributing gas into a combustion chamber of the engine, said rail (1) being inserted into a gas supply line connecting the gas container and said combustion chamber. According to the invention, a duct (10) through which the heat transfer fluid circulates is in contact with the rail (1) in such a way that the temperature of the gas flowing through the rail (1) is changed before the gas is injected into the combustion chamber.

Description

[0001] The present invention provides a power system having a heated fuel rail.

[0002] In internal combustion engines, in particular motor vehicle internal combustion engines, which are operated on liquefied petroleum gas (or LPG), there is a risk of recondensation of the gases at the outlet of the carburetor-regulator associated with the engine.

[0003] In a known manner, LPG is stored in the vehicle's tank in liquid phase and is then delivered in liquid phase to a solenoid valve located in the vehicle's engine compartment, which closes the LPG supply line when the engine is stopped. The LPG, still in liquid form, is then delivered to a carburetor-regulator, which serves both to vaporize the liquid LPG into gas and to ensure regulation of the gas pressure.

[0004] In the conventional case of indirect multi-point injection, the gas from the carburetor-regulator then enters the fuel rail or fuel distribution rail of the engine, which is provided with a plurality of injectors leading to the intake pipe of the distributor or intake manifold of the engine. The gaseous LPG is introduced into the intake pipe of the distributor through various injectors and mixed with the external air admitted to the distributor. The air-fuel mixture is then admitted to the combustion chamber of the engine to be burned therein.

[0005] Alternatively, in the case of direct injection, the gaseous fuel is injected directly into the combustion chamber of the engine via an injector.

[0006] If the pressure in the liquefied gas tank exceeds 200 bar, the pressure at the outlet of the carburetor-regulator and then in the fuel rail (in the case of indirect injection described above) is only a few bars, there is a risk of recondensation. This sudden drop in pressure means that the gas intended to be injected into the distributor of the engine, before being admitted to the combustion chamber of the engine, will include a liquid fraction, which will be introduced into the inlet duct of the distributor together with the gaseous fraction and tend to wet the walls of the distributor. The consequence of this phenomenon of liquid accumulation on the walls of the distributor is that the amount of gas injected into the combustion chamber (mass flow rate) is poorly controlled and the abundance control then becomes random.

[0007] In order to avoid recondensation of the LPG downstream of the vaporizer-regulator (more precisely in the fuel rail), it is necessary to position it below the evaporation curve of the gas, which depends on the temperature, pressure and composition of the latter.

[0008] US548393A discloses a fuel supply module for supplying gaseous fuel to an internal combustion engine, comprising: a pressure regulator for regulating the pressure of the gas from a relatively high tank pressure value to a relatively low value required for introducing the gas into the engine, and having a heating chamber at least partially surrounding the regulator. The fuel supply module only partially solves the problem of the present invention.

[0009] EP1934467B1 relates to a kind of auxiliary cold start system, it is preferably used for internal combustion engines using alcohol as fuel, but so-called "flex fuel" engines (alcohol, gasoline, NGV) are also included in the scope of the present invention (it is the subject of the present invention). The system uses a resistor positioned at the injector inlet, a resistor inside the injector or a resistor for the entire pipeline of the injector nozzle support (nozzle supports). In addition, an auxiliary injection nozzle placed in the intake manifold of the engine is provided, which also has a resistor. Although the fuel heating here seems to be sufficient, it is necessary to implement several resistors, which will lead to related excessive fuel consumption and huge additional costs.

[0010] The power system according to the invention is configured to prevent the formation of a liquid fraction downstream of the carburetor-regulator, more precisely in the fuel distribution rail, while overcoming the drawbacks encountered in prior art power systems.

[0011] The invention relates to a power system comprising an internal combustion engine, a pressurized gas tank and a carburetor-regulator, the power system comprising an upstream rail for distributing gas to the combustion chambers of the engine, the rail being inserted into a gas supply line connecting the gas tank and the combustion chambers.

[0012] According to the invention, the pipe for circulating a heat transfer fluid is in contact with the track so as to change the temperature of the gas passing through the track before the gas is injected into the combustion chamber of the engine. In this way, the temperature of the gas at the outlet of the tank can be increased or decreased according to the temperature of the heat transfer fluid circulating in the pipe. Preferably, the temperature of the heat transfer fluid circulating in the track is high to increase the temperature of the gas circulating in the track, thereby preventing the formation of droplets that may be delivered to the distributor, the droplets will at least partially stagnate and therefore the droplets will not all be admitted to the combustion chamber, which may cause many inconveniences. Advantageously, the heat transfer fluid is a liquid, and preferably, this liquid is water. The fluid can be part of a circuit designed specifically for the function of heating the gas circulating in the track, or it can be part of an already existing circuit (for example, an engine cooling circuit). Advantageously, the power system is indirectly injected, which means that the gas is not injected directly into the combustion chamber, but injected into the intake pipe of the distributor upstream of the intake valve leading to the chamber. The gas can be, for example, natural gas, city gas or liquefied petroleum gas (LPG). The distribution rail is similar to an intake plenum, i.e. a volume with a single inlet from the carburetor-regulator and a plurality of outlets including the housings of the injectors, each of which opens into the combustion chambers of the engine, i.e. an intake pipe leading to the distributor, which opens into the combustion chambers. The heat transfer between the heat transfer fluid circulation duct and the rail is mainly carried out by heat conduction.

[0013] According to a possible characteristic of the invention, the gases are injected from the rail into the intake duct of the distributor of the engine serving the combustion chambers.

[0014] According to a possible feature of the invention, the distribution rail is metal and the coolant circulation conduit is metal and brazed to the rail. In this way, the heat exchange between the fluid circulation conduit and the rail is mainly carried out by heat conduction. The fluid circulation conduit can be fixed directly to the rail, and the assembly consisting of the fluid circulation conduit and the rail is installed in the vehicle. It can also be done when the rail is already installed on the vehicle. In the latter case, the fluid circulation conduit can be fixed to the rail at the last moment according to the needs of the user.

[0015] According to a possible feature of the invention, the distribution track is elongated and the coolant circulation pipe is wound around the track. With this configuration, since the coolant circulation pipe surrounds the track, the temperature variation of the gas circulating in the track will be uniform and complete without the risk of seeing the generation of temperature gradients in the gas.

[0016] According to a possible characteristic of the invention, the heat transfer fluid circulation duct is spiral, said duct having at least two consecutive loops extending over the entire length of the distribution track. In this way, the temperature variation of the gas circulating in the track will be effective over the entire length of said track. Preferably, the duct comprises four loops extending over the entire length of the distribution track. Advantageously, each loop completely surrounds the track by extending over part of the length of said track.

[0017] According to a possible characteristic of the invention, the distribution track has a parallelepiped shape and has a square cross section, said distribution track being defined by an inlet face into which a cylindrical end piece opens. Preferably, the end piece extends perpendicularly to the inlet face. The end piece is intended to receive a conduit coming from a steam expander placed at the outlet of the gas tank and to form an inlet to the track for the gas coming from the tank.

[0018] According to a possible characteristic of the invention, the end piece is rectilinear and opens into a central area of ​​the inlet face so that the axis of rotation of the end piece is continuous with the longitudinal and central axis of the distribution track. The end piece is arranged on the track so as to perfectly extend the track and so as to increase the length of the track.

[0019] According to a possible characteristic of the invention, the distribution rail comprises a plurality of outlet channels, each outlet channel having a housing for receiving an injector. Advantageously, these outlet channels are parallel to each other and extend perpendicularly to the longitudinal axis of the rail.

[0020] According to a possible characteristic of the invention, the gas distribution rail has sensors for measuring the temperature and the pressure of the gas circulating inside said distribution rail.

[0021] Another object of the invention is an assembly of a gas distribution rail and of pipes for circulating a heat transfer fluid, for producing a power system according to the invention.

[0022] According to the present invention, the coolant circulation pipe is metal, the distribution rail is metal, and the fluid circulation pipe is brazed to the distribution rail. Preferably, the coolant circulation pipe is wound on the rail.

[0023] Another object of the invention is a vehicle comprising a power system according to the invention.

[0024] According to the invention, the coolant circulation conduit is part of the engine cooling circuit.

[0025] The power system according to the invention has the advantage of being able to ensure in a safe and reliable manner that the gas passing through the distribution rail has a sufficiently high temperature to prevent the formation of droplets that can be injected into the combustion chamber. It also has the advantage of being able to provide this additional function without having to make structural changes in depth and without having to be more complicated.

[0026] A detailed description of a preferred embodiment of the power system according to the present invention is given below with reference to the following drawings:

[0027] [ Figure 1 ] Figure 1 is a perspective view of tracks and pipes for circulating a heat transfer fluid in a power system according to the present invention.

[0028] The principle of the power system according to the invention consists in comprising a heating distribution rail 1 for heating the gas at the outlet of the carburetor-regulator which vaporizes the gas from the tank before the gas is injected into the combustion chamber of the internal combustion engine, in particular in the case of indirect injection into the intake duct of the engine air distributor supplying the combustion chamber, or alternatively directly into the combustion chamber. Such a heating rail 1 can be integrated into a power system with an internal combustion engine with a fuel heated by indirect injection, for example natural gas, city gas or LPG.

[0029] The power system according to the invention comprises: an internal combustion engine; a tank for storing gas in liquid phase (which may be, for example, LPG essentially comprising a mixture of butane and propane); and a carburetor-regulator for vaporizing the gas coming from the tank. On such a power system, there is a risk of recondensation of the gas at the outlet of the carburetor-regulator (more precisely, on a fuel distribution rail situated at the outlet of said carburetor-regulator, to which theoretically only gas in gas phase is delivered). In this case, a gas mixture comprising a liquid portion (which will wet the intake duct wall of the manifold and at least partially prevent the introduction of liquid into said chamber) is injected towards the combustion chamber of the engine, in particular into the intake duct of the manifold of the engine serving said combustion chamber. The consequence of such an injection is that the amount of injected gas is not well controlled and the abundance control becomes random.

[0030] In order to prevent the formation of such liquid fractions, the power system according to the invention uses a heated gas distribution rail 1, which is located on the gas line between the carburetor-regulator placed at the outlet of the gas tank and the combustion chamber of the engine, more precisely, in the case of indirect injection, between the carburetor-regulator and the distributor upstream of said combustion chamber. The purpose of this heating rail 1 is to heat the gas passing through it, thus preventing the formation of liquid drops upstream of the combustion chamber of the engine. This rail thus allows the gas to be injected only into said chamber, in particular into the distributor of the engine in the case of indirect injection.

[0031] Reference Figure 1, the heating track 1 has an elongated hollow body 2 of parallelepiped shape, which has a square cross-sectional shape. The hollow body 2 is defined by an inlet face 3 and an outlet face, both of which are square, the two faces 3 materializing the two ends of the hollow body 2 considered along its longitudinal axis. The track 1 has a cylindrical rectilinear end piece 4, which leads to the central area of ​​the inlet face 3 of the hollow body 2. In this way, the axis of rotation of the end piece 4 is merged with the longitudinal and central axis of the hollow body 2. The end piece 4 extends the hollow body 2 so as to increase its length. The end piece 4 has a flange 5 in the form of an annular bead, which locally increases the outer diameter of the end piece 4. The end piece 4 is used to receive a cylindrical conduit from a steam expander placed at the outlet of the gas tank, which is press-fitted around the rectilinear end piece 4. The track 1 advantageously has three gas outlet channels 6, 7, 8, which extend parallel to each other and perpendicular to the longitudinal axis of the hollow body 2 of the track 1. Each of these outlet channels 6, 7, 8 has a housing 9 which opens into said outlet channels 6, 7, 8 and is used to accommodate an injector (not visible in the figure). Of the three outlet channels 6, 7, 8, two channels 6, 8 are located near the two end faces 3 of the hollow body 2 of the track 1, and the third channel 7 is located in the center of the hollow body 2, equidistant from the other two outlet channels 7, 8. A pressure and temperature sensor 9 is placed on the hollow body 2 of the track 1, the sensor 9 opening into the interior of the hollow body 2 to measure the pressure and temperature of the gas passing through the track 1. It should be noted that the track 1 is made of metal.

[0032] A pipe 10 made of metal for circulating a heat transfer fluid is brazed to the hollow body 2 of the track 1 in order to heat the gases coming from the tank before they are redirected to the combustion chamber of the engine via the outlet channels 6, 7, 8 of said track 1. This pipe 10 is preferably cylindrical and has a constant internal diameter. Advantageously, this pipe 10 is spiral and winds around the hollow body 2 of the track 1. For example, it can have four loops 11, 12, 13, 14 extending over the entire length of the hollow body 2 of the track 1 in a row. In other words, each loop extending over a part of the length of the track 1 completely surrounds the hollow body 2 of the track 1. In this way, by surrounding the hollow body 2 of the track 1, the heat transfer fluid circulation pipe 10 will uniformly and completely heat the gases circulating in the track 1, thereby avoiding the establishment of temperature gradients in said gases. The heat transfer fluid can be, for example, water from the cooling circuit of the engine, in which case the pipe 10 will be an integral part of said cooling circuit. For example, the temperature of the water circulating in the pipe 10 can be between 30°C and 80°C.

[0033] Thus, thanks to the presence of the water circulation duct 10 fixed around the hollow body of the track 1, the gas circulating in said track 1 will be sufficiently heated to prevent the formation of droplets that could penetrate the intake duct of the engine manifold and accumulate on its walls (called "wall wetting"). Thanks to the presence of this heated track 1, only gas without droplets will enter the intake duct of the distributor and then the combustion chamber as a whole. The injection system of the power system according to the invention is indirect. The heating of the gas is very fast, in the order of a few seconds.

[0034] It should be noted that the water circulation conduit 10 may have various shapes, but the key is that it is in contact with the hollow body 2 of the track 1 so as to heat the gas circulating in said track 1 substantially by heat conduction.

Claims

1. A power system comprising an internal combustion engine, a pressurized gas tank and a carburetor-regulator, the power system comprising an upstream rail (1) for distributing gas to a combustion chamber of the engine, the rail (1) being inserted into a gas supply line connecting the gas tank and the combustion chamber, It is characterized in that A duct (10) for circulating a heat transfer fluid is in contact with the track (1) in order to modify the temperature of the gas passing through the track (1) before the gas is injected into the combustion chamber of the engine.

2. The power system according to claim 1, It is characterized in that The gas is injected from the rail (1) into the intake duct of the engine distributor serving the combustion chamber.

3. The power system according to claim 1 or 2, It is characterized in that The distribution rail (1) is metallic and the heat transfer fluid circulation pipe (10) is metallic and brazed to the rail (1).

4. The power system according to any one of claims 1 to 3, It is characterized in that The distribution rail (1) is elongated, and the coolant circulation pipe (10) is wound around the rail (1).

5. The power system according to claim 4, It is characterized in that The heat transfer fluid circulation duct (10) is spiral-shaped and has at least two continuous loops (11, 12, 13, 14) extending over the entire length of the distribution track (1).

6. The power system according to any one of claims 1 to 5, It is characterized in that The distribution track (1) has a parallelepiped shape and has a square cross section and is defined by an inlet face (3) into which a cylindrical end piece (4) opens.

7. The power system according to claim 6, It is characterized in that The end piece (4) is rectilinear and opens into a central region of the inlet face (3) such that the axis of rotation of the end piece (4) is continuous with the longitudinal and central axis of the distribution rail (1).

8. The power system according to any one of claims 1 to 7, It is characterized in that The distribution rail (1) comprises a plurality of outlet channels (6, 7, 8), each of the outlet channels (6, 7, 8) having a housing (9) for receiving an injector.

9. The power system according to any one of claims 1 to 8, It is characterized in that The gas distribution rail (1) has a sensor (9) for measuring the temperature and pressure of the gas circulating inside the distribution rail (1).

10. An assembly of a gas distribution rail (1) and a heat transfer fluid circulation pipe (10) for producing a power system according to any one of claims 3 to 9, It is characterized in that The heat transfer fluid circulation conduit (10) is made of metal, and the distribution rail (1) is made of metal, and the heat transfer fluid circulation conduit (10) is brazed to the distribution rail (1).

11. A vehicle comprising a power system according to any one of claims 1 to 9, It is characterized in that The coolant circulation conduit (10) forms a part of the engine cooling circuit.

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