Power unit with heated fuel rail

Abstract

The invention relates to a power unit comprising an internal combustion engine and a reservoir of pressurized gas used to boost said internal combustion engine, said power unit comprising an upstream distribution rail (1) for distributing gas to the combustion chambers of the engine, said rail (1) being inserted in a gas supply circuit connecting the gas reservoir and said combustion chambers. According to the invention, a pipe (10) through which a heat-transport fluid circulates, is in contact with the rail (1) in such a way as to vary the temperature of the gas flowing through said rail (1) before said gas is injected into the combustion chambers.

Description

Description Title of the invention: Powertrain equipped with a heated fuel rail

[0001] The present invention relates to a powertrain equipped with a heated fuel rail.

[0002] On internal combustion engines running on liquefied petroleum gas (or LPG), particularly those in motor vehicles, there is a risk of recondensation of the gas at the outlet of a vaporizer associated with the engine.

[0003] As is well known, LPG is stored in liquid form in a vehicle tank, then piped in liquid form to a solenoid valve located in the vehicle's engine compartment, which closes the LPG supply circuit if the engine is switched off. The still-liquid LPG then flows to the vaporizer / regulator, which serves both to vaporize the liquid LPG into gas and to regulate the gas pressure.

[0004] In the classic case of indirect multipoint injection, the gas from the vaporizer then enters the engine's fuel rail, or fuel distribution rail, which is equipped with multiple injectors opening into the intake manifolds of the engine's intake distributor. The gaseous LPG is introduced into the distributor's intake manifolds by the various injectors, where it mixes with outside air drawn into the distributor. The resulting air-fuel mixture is then drawn into the engine's combustion chambers to be burned.

[0005] Alternatively, in the case of direct injection, the gaseous fuel is injected directly into the engine's combustion chambers by the injectors.

[0006] The risk of re-condensation is present because the pressure drops from over 200 bar in a liquefied gas tank to just a few bar at the outlet of the pressure regulator and then in the fuel rail (in the aforementioned case of indirect injection). This sudden pressure drop means that the gas intended for injection into the engine's intake manifold, before being admitted into the engine's combustion chambers, will contain a liquid fraction. This liquid will be introduced into the intake manifold's inlet pipes along with the gaseous fraction and will tend to wet the manifold walls. The consequences of such a phenomenon of liquid accumulation on the walls of the distributor are that the quantity (mass flow rate) of gas injected into the combustion chambers is poorly controlled and that the mixture control then becomes random.

[0007] To avoid the re-condensation of LPG downstream of the vaporizer, more precisely in the fuel distribution rail, it is necessary to be positioned below the vaporization curve of the gas, which depends on the temperature, pressure and composition of the latter.

[0008] Publication US548393A discloses a fuel supply module for providing gaseous fuel to an internal combustion engine. The module includes a pressure regulator for reducing the gas pressure from a relatively high tank pressure to the relatively low pressure required for gas injection into the engine. The module also includes a heating chamber that at least partially surrounds the regulator. The fuel supply module only partially addresses the problem addressed by the invention.

[0009] Publication EP1934467B1 concerns an auxiliary cold-start system preferentially used in internal combustion engines that use alcohol as fuel, but so-called "flex-fuel" engines (alcohol, gasoline, CNG) are also included within the scope of the invention. This system uses resistors positioned at the injector inlets, resistors inside the injectors, or a single resistor for the entire injector nozzle support tubing. In addition, auxiliary injection nozzles, also equipped with resistors, are provided in the engine's intake manifold. Although fuel heating appears sufficient in this case, the need for multiple resistors will result in increased fuel consumption and significant additional costs.

[0010] A powertrain according to the invention is configured to prevent the formation of a liquid fraction downstream of the vaporizer and more specifically in the fuel distribution rail, while overcoming the disadvantages encountered in existing powertrains.

[0011] The invention relates to a powertrain comprising an internal combustion engine, a pressurized gas reservoir, and a vaporizer / regulator, said powertrain comprising an upstream gas distribution manifold towards the combustion chambers of the engine, said rail being inserted into a gas supply circuit connecting the gas tank and said combustion chambers.

[0012] According to the invention, a heat transfer fluid circulation pipe is in contact with the fuel rail so as to vary the temperature of the gas passing through said rail before it is injected into the engine's combustion chambers. In this way, depending on the temperature of the heat transfer fluid circulating in the pipe, the temperature of the gas at the tank outlet can either be increased or decreased. Preferably, the temperature of the heat transfer fluid circulating in the pipe is raised in order to increase the temperature of the gases circulating in the fuel rail and thus prevent the formation of liquid droplets that could be carried to the distributor, where they would stagnate at least partially, and therefore not all of which would be admitted into the combustion chambers, with all the problems that this could cause.Advantageously, the heat transfer fluid is a liquid, preferably water. The fluid can be part of either a circuit specifically designed for heating the gases circulating in the intake manifold, or an existing circuit such as the engine cooling system. Advantageously, the powertrain uses indirect injection, meaning the gas is not injected directly into the combustion chambers but upstream of intake valves opening into these chambers, via the intake manifolds of a distributor. The gas can be, for example, natural gas, town gas, or liquefied petroleum gas (LPG).The fuel rail can be considered an intake plenum, meaning a volume with a single inlet from the pressure regulator and multiple outlets containing injector ports. Each injector opens into a combustion chamber of the engine, specifically into an intake manifold of the distributor which leads to a combustion chamber. Heat transfer between the coolant circulation line and the fuel rail occurs primarily through thermal conduction.

[0013] According to one possible feature of the invention, the gas is injected from the rail into intake pipes of an engine distributor serving the combustion chambers.

[0014] According to one possible feature of the invention, the distribution rail is metallic, and the heat transfer fluid circulation pipe is also metallic and brazed to said rail. In this way, heat exchange between the fluid circulation pipe and the rail occurs primarily by thermal conduction. The fluid circulation pipe can be attached directly to the rail, and the assembly consisting of said pipe and rail is then installed in the vehicle. Alternatively, the rail can be installed after it has already been mounted in the vehicle. In this latter case, the fluid circulation pipe can be attached to the rail at the last minute, according to the user's requirements.

[0015] According to one possible feature of the invention, the distribution manifold is elongated, with the heat transfer fluid circulation pipe wrapped around said manifold. In this configuration, since the heat transfer fluid circulation pipe surrounds the manifold, the temperature change of the gases circulating in said manifold will be homogeneous and complete, without risk of creating a temperature gradient within said gases.

[0016] According to one possible feature of the invention, the heat transfer fluid circulation pipe is helical in shape, said pipe having at least two continuous loops extending along the entire length of the distribution manifold. In this way, the temperature change of the gases circulating in the manifold will be effective along its entire length. Preferably, the pipe comprises four loops extending along the entire length of the distribution manifold. Advantageously, each loop completely encircles the manifold by extending over a portion of its length.

[0017] According to one possible feature of the invention, the distribution manifold has a parallelepiped shape and a square cross-section, said distribution manifold being delimited by an inlet face into which a cylindrical nozzle opens. Preferably, this nozzle extends perpendicularly to the inlet face. This nozzle is designed to receive a conduit from a vaporizer located at the outlet of the gas tank, and constitutes an inlet to the manifold for the gases coming from the tank.

[0018] According to one possible feature of the invention, the nozzle is straight and opens into a central area of ​​the inlet face such that an axis of revolution of said nozzle is in continuity with a longitudinal and central axis of the distribution ramp. The nozzle is arranged on the ramp so as to be in perfect extension of said ramp and so as to increase the length of said ramp.

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

[0020] According to one possible feature of the invention, the gas distribution manifold has a sensor for measuring the temperature and pressure of the gases circulating inside said distribution manifold.

[0021] The invention also relates to an assembly of a gas distribution ramp and a heat transfer fluid circulation tube for the realization of a powertrain according to the invention.

[0022] According to the invention, the heat transfer fluid circulation pipe is metallic and the distribution manifold is metallic, the fluid circulation pipe being brazed to the distribution manifold. Preferably, the heat transfer fluid circulation pipe snakes around the manifold.

[0023] The invention also relates to a vehicle comprising a powertrain according to the invention.

[0024] According to the invention, the heat transfer fluid circulation pipe is part of an engine cooling circuit.

[0025] A powertrain according to the invention has the advantage of being able to safely and reliably maintain a sufficiently high temperature of the gases passing through the intake manifold to prevent the formation of liquid droplets that could be injected into the combustion chambers. Furthermore, it has the advantage of being able to perform this additional function without requiring extensive structural modifications and without being larger in size.

[0026] A detailed description of a preferred embodiment of a powertrain according to the invention is given below, with reference to the following figures:

[0027] [Fig. 1] Figure 1 is a perspective view of a ramp and a circulation pipe for a heat transfer fluid of a powertrain according to the invention.

[0028] The principle of a powertrain according to the invention is to include a heated distribution rail 1, designed to heat a gas at the outlet of a vaporizer that vaporizes the gas from a storage tank, before it is injected into the combustion chambers of an internal combustion engine, in particular into the intake manifolds of an engine air distributor supplying the combustion chambers in the case of indirect injection, or alternatively directly into the combustion chambers. Such a heated rail 1 can be integrated into a powertrain having an internal combustion engine with a fuel to be heated by indirect injection, such as natural gas, town gas, or LPG.

[0029] A powertrain according to the invention comprises an internal combustion engine, a liquid-phase gas storage tank, which could, for example, contain LPG essentially composed of a mixture of butane and propane, and a vaporizer for vaporizing the gas from the tank. In such powertrains, there is a risk of gas recondensation at the outlet of the vaporizer, and more specifically in a fuel distribution rail located at the outlet of said vaporizer, to which the gas, theoretically in a purely gaseous phase, is routed. In this case, a gaseous mixture containing a liquid fraction is injected into the engine's combustion chambers, particularly into the intake manifolds of an engine distributor serving said combustion chambers. This mixture will wet the walls of the distributor's intake manifolds and at least partially prevent the liquid from entering said chambers.The consequence of such an injection is that the quantity of gas injected is not well controlled and the fuel mixture control becomes random.

[0030] To prevent the formation of this liquid fraction, a powertrain according to the invention implements a heated gas distribution rail 1, said rail 1 being placed on the gas circuit between the vaporizer located at the outlet of the gas tank, and the combustion chambers of the engine, and more specifically in the case of indirect injection, between the vaporizer and a distributor upstream of the combustion chambers. This heated rail 1 is designed to warm the gases passing through it, thus preventing the formation of liquid droplets upstream of the engine's combustion chambers. Such a rail therefore allows for the injection of only gases, towards the chambers, specifically into an engine distributor in the case of indirect injection.

[0031] Referring to Figure 1, the heating element 1 has an elongated, parallelepiped-shaped hollow body 2, said body 2 having a square cross-section. This hollow body 2 is delimited by an inlet face 3 and an outlet face, each square, said two faces 3 representing the two ends of said hollow body 2 considered along a longitudinal axis thereof. The heating element 1 has a straight, cylindrical end 4 opening into a central area of ​​the inlet face 3 of the hollow body 2. In this way, the axis of revolution of this end 4 coincides with a longitudinal and central axis of the hollow body 2. The end 4 extends the hollow body 2 to increase its length. This end 4 has a collar 5 in the form of an annular ridge that locally increases the outer diameter of said end 4.This fitting 4 is designed to receive a cylindrical conduit from a vaporizer located at the outlet of a gas reservoir, said conduit being press-fitted around this straight fitting 4. This manifold 1 advantageously has three gas outlet channels 6, 7, 8, said channels being parallel to each other and extending perpendicularly to a longitudinal axis of the hollow body 2 of the manifold 1. Each of these outlet channels 6, 7, 8 has a housing 9 opening into said outlet channel 6, 7, 8, and intended to house 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 rail 1, and a third channel 7 is located centrally on said hollow body 2, equidistant from the other two outlet channels 6, 8. A pressure and temperature sensor 9 is placed on the hollow body 2 of the rail 1, said sensor 9 opening into the hollow body 2 to measure the pressure and temperature of the gases flowing through the rail 1. It should be noted that the rail 1 is made of metal.

[0032] A metal heat transfer fluid circulation tube 10 is brazed to the hollow body 2 of the rail 1 to preheat the gases from the reservoir before they are redirected to the engine's combustion chambers via the outlet channels 6, 7, 8 of said rail 1. This tube 10 is preferably cylindrical and has a constant internal diameter. Advantageously, this tube 10 is helical in shape and winds around the hollow body 2 of the rail 1. It may, for example, have four continuous loops 11, 12, 13, 14, extending along the entire length of the hollow body 2 of the rail 1. In other words, each loop completely surrounds the hollow body 2 of the rail 1, extending over a portion of the rail 1's length.In this way, by surrounding the hollow body 2 of the rail 1, the heat transfer fluid circulation tube 10 will heat the gases circulating in the rail 1 homogeneously and completely, preventing the establishment of a temperature gradient in said gases. The heat transfer fluid could, for example, be water, which would come from an engine cooling circuit, in which case the tube 10 would be an integral part of said cooling circuit. The temperature of the water circulating in the tube 10 could, for example, be between 30°C and 80°C.

[0033] Thus, thanks to the presence of the water circulation tube 10 fixed around the hollow body of the fuel rail 1, the gases circulating in said fuel rail 1 will be sufficiently heated to prevent the formation of liquid droplets, which could penetrate the intake manifolds of an engine distributor and accumulate on their walls (this is referred to as "wall wetting"). Only gases free of liquid droplets will enter the intake manifolds, and then entirely into the combustion chambers, thanks to the presence of this heated fuel rail 1. The injection system of a powertrain according to the invention is indirect. The heating of the gases is very rapid, on the order of a few seconds.

[0034] It should be noted that the water circulation tube 10 can take on a variety of forms, the essential thing being that it is in contact with the hollow body 2 of the ramp 1 in order to heat essentially by thermal conduction the gases circulating in said ramp 1.

Claims

Demands

1. Powertrain comprising an internal combustion engine, a pressurized gas tank and a vapor-reducer, said powertrain comprising an upstream gas distribution rail (1) to the combustion chambers of the engine, said rail (1) being inserted into a gas supply circuit connecting the gas tank and said combustion chambers, characterized in that a heat transfer fluid circulation tube (10) is in contact with the rail (1) so as to vary the temperature of the gas passing through said rail (1) before said gas is injected to the combustion chambers of the engine.

2. Powertrain according to claim 1, characterized in that the gas is injected from the rail (1) into intake pipes of an engine distributor serving the combustion chambers.

3. Powertrain according to claim 1 or 2, characterized in that the distribution ramp (1) is metallic, and in that the heat transfer fluid circulation pipe (10) is metallic and is brazed to said ramp (1).

4. Powertrain according to any one of claims 1 to 3, characterized in that the distribution ramp (1) is elongated, and in that the heat transfer fluid circulation tube (10) is wound around said ramp (1).

5. Powertrain according to claim 4, characterized in that the heat transfer fluid circulation tube (10) is helical in shape, and in that it has at least two continuous loops (11, 12, 13, 14) extending over the entire length of the distribution ramp (1).

6. Powertrain according to any one of claims 1 to 5, characterized in that the distribution ramp (1) has a parallelepiped shape and a square cross-section, and in that said distribution ramp (1) is delimited by an inlet face (3) into which a cylindrical nozzle (4) opens.

7. Powertrain according to claim 6, characterized in that the nozzle (4) is straight and opens into a central area of ​​the face inlet (3) so that an axis of revolution of said nozzle (4) is in continuity with a longitudinal and central axis of the distribution ramp (1).

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

9. Powertrain according to any one of claims 1 to 8, characterized in that the gas distribution rail (1) has a sensor (9) for measuring the temperature and pressure of the gases circulating inside said distribution rail (1).

10. Assembly of a gas distribution ramp (1) and a heat transfer fluid circulation pipe (10) for the realization of a powertrain according to any one of claims 3 to 9, characterized in that the heat transfer fluid circulation pipe (10) is metallic and the distribution ramp (1) is metallic, and in that the heat transfer fluid circulation pipe (10) is brazed to the distribution ramp (1).

11. Vehicle comprising a powertrain according to any one of claims 1 to 9, characterized in that the heat transfer fluid circulation pipe (10) is part of an engine cooling circuit.

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