System for supplying gaseous fuel for an internal combustion engine

Abstract

The invention relates to a system for supplying a gaseous fuel for an internal combustion engine, which system is intended to be mounted in a vehicle in a predetermined orientation relative to the vertical. The system comprises a supply rail (2, 2', 2'') intended for receiving pressurised gaseous fuel in a main chamber (20), and a plurality of fuel injectors (10) connected to the supply rail (2, 2', 2''), wherein each injector is connected to a tap (22) of the rail, each tap (22) being delimited by an inner tap surface (220) connecting to an inner tubular surface (200) of the supply rail (2, 2', 2'') delimiting the main chamber (20). The inner tap surface (220) defines a flow channel with a continuous slope towards the injector from a low point in a section of the supply rail (2, 2', 2'') at the tap (22). A lubrication device (4) is provided in order to supply lubricant into the flow of gaseous fuel.

Description

[0001] Gaseous fuel supply system for an internal combustion engine

[0002] technical field

[0003] The present invention relates generally to the field of internal combustion engines operating with gaseous fuels such as hydrogen, and more particularly relates to a fuel system for such an engine.

[0004] Previous technique

[0005] For automotive applications, hydrogen engines are considered a promising alternative to gasoline or diesel engines since the emissions of a hydrogen engine consist mainly of water and hydrogen can be supplied via renewable energy sources.

[0006] Document GB2615326A shows a hydrogen-powered internal combustion engine. Hydrogen from a tank is first expanded through an expansion valve, then supplied to a fuel rail to which individual injectors are connected to deliver gaseous hydrogen to each of the combustion chambers.

[0007] However, the use of "dry" hydrogen, meaning without additional lubricant, can create a risk of wear on engine system components. While in liquid-fuel engines, components such as pressure regulators, injectors, etc., benefit from the lubrication and hydraulic damping effects of the fuel itself, this is not the case with gaseous-fuel engines. These components are therefore subject to increased wear, which can affect their lifespan and operational reliability. This lack of lubrication is even more problematic for fuel injectors used for direct fuel injection, as they face higher temperatures, leading to excessive wear, primarily at the needle / seat interface of the injector nozzle.

[0008] It has been proposed to integrate a lubrication system that releases liquid lubricant into the fuel supply system, for example, into the fuel rail. However, this lubricant release presents several challenges. Specifically, it is desirable to precisely control the amount of lubricant and avoid excessive lubrication of the injector, which could lead to sticking of the injector's moving components. It is also desirable that the lubricant be distributed homogeneously in the downstream circuit, meaning that similar amounts of lubricant reach each injector. Furthermore, there is a risk that the lubricant will condense on the walls, particularly those of the fuel rail, and then run off and accumulate at a low point.

[0009] Description of the invention

[0010] One objective of the invention is to provide a gaseous fuel supply system enabling lubrication of active components not exhibiting the observed defects.

[0011] With these objectives in mind, the invention relates to a gaseous fuel supply system for an internal combustion engine intended to be mounted in a vehicle in a predetermined orientation relative to the vertical, the supply system comprising a supply rail intended to receive pressurized gaseous fuel in a main chamber, and a plurality of fuel injectors connected to the supply rail, in which each injector is connected to a branch of the rail, each branch being delimited by an internal branching surface connecting to an internal tubular surface of the supply rail delimiting the main chamber, characterized in that the internal branching surface defines a sloping flow channel - preferably continuous - towards the injector from a low point in a section of the supply rail at the branch.

[0012] Thanks to this invention, when lubricant is injected into the fuel system, it no longer risks accumulating in the fuel rail. Indeed, if it were to deposit or condense on the walls (for example, of the main chamber), the lubricant will flow naturally by gravity along the flow channel to the injector, where it will perform its function, whether the injector is connected directly to the nozzle or via a supply tube. The important thing is that the flow channel has no obstruction that could prevent the lubricant from accumulating. This is achieved, for example, by ensuring that, once the fuel system is mounted on an engine and installed on a vehicle, the nozzles are angled downwards towards the injector and open at the lowest point of the internal tubular surface.This last condition is met, for example, if the internal surfaces are cylindrical and if the lowest generatrix of the internal tapping surface is tangent to the internal tubular surface. The term 'sloping' primarily refers to a slope angle that differs from the horizontal and vertical.

[0013] The system includes at least one lubrication device to supply lubricant in the gaseous fuel stream, preferably on or upstream of the fuel rail. The lubrication device preferably supplies the lubricant by spraying so that it is carried by the gaseous stream to the components to be lubricated, in particular the injectors.

[0014] In this application, the term lubricant, or oil, refers to a lubricating fluid suitable for reducing friction and wear between moving parts, particularly at fuel injectors. Any type of lubricant / oil appropriate for the application may be used, taking into account the type of fuel, the fuel injector design, and the operating conditions (including ambient temperature). For example, a 5W-30 or 0W-30 engine oil may be used.

[0015] The present invention was developed in the context of the development of hydrogen combustion engines, but is applicable to gaseous fuels in general, particularly CNG (gas consisting mainly of methane) or Ammonia (consisting mainly of NH3), or any mixture of gaseous fuel comprising at least one of these gases.

[0016] Depending on the configuration, the lubrication device can be incorporated into the feed manifold, or placed upstream of it and connected via one or more tubes to the manifold.

[0017] According to a design feature, the fuel system includes an inlet tube opening into the fuel rail approximately halfway along its length (or at the main chamber) to supply fuel. A single lubrication device supplies lubricant to the inlet tube. This design minimizes the size and cost of the fuel system. The gaseous fuel is distributed through the fuel rail, splitting into two symmetrical streams.

[0018] According to one design, the fuel supply system includes a distribution piece for supplying fuel to the fuel rail. The distribution piece has an inlet tube and at least two distribution lines connected to the inlet tube at regular intervals. The fuel rail has as many pairs of outlets as the system has fuel lines, each distribution line opening into the fuel rail approximately midway between two adjacent outlets. The inlet tube has a single lubrication device. Here too, the lubrication device is single, but the flow is subdivided by the distribution piece, and then the flow is itself distributed into the fuel chamber between two outlets.

[0019] According to an improvement, the lubrication system generates jets of lubricant towards each of the distribution channels. This promotes a homogeneous distribution of the lubricant in the gas flow.

[0020] In one embodiment, the fuel rail comprises an inlet connector opening into a first channel extending parallel to a main chamber of the fuel rail. This first channel extends symmetrically on either side of the inlet connector and opens at its ends into the main chamber via two ports. Thus, the first channel is delimited by the body of the fuel rail, resulting in a compact design, as the channel is adjacent to the main chamber of the rail. This arrangement is suitable for a four-chamber internal combustion engine.

[0021] According to an improvement, each orifice is located approximately halfway between two adjacent connections. This allows for a homogeneous distribution between the connections.

[0022] In one embodiment, the feed ramp comprises an inlet connector opening into a first channel extending parallel to a main chamber of the feed ramp. This first channel extends symmetrically on either side of the inlet connector and opens at its ends in the middle of a second and a third channel, respectively, extending parallel to the main chamber. Each channel has two ends opening into the main chamber opposite one of the connections via ports. In this embodiment, the distribution is further subdivided for improved homogeneity and a more compact design.

[0023] According to one design, the lubrication device is an injection device comprising a solenoid capable of lifting a needle resting on a seat to open or close a lubricant passage. This type of injection device is of the same construction as an injector commonly used for gasoline injection. It is therefore a widely proven technology, suitable for the flow rates and pressure levels required to distribute this lubricant. According to another design, the supply system includes a lubricant source configured to provide pressurized lubricant to the lubrication device. A source type is, for example, an accumulator, in particular a bladder tank (or diaphragm accumulator). It allows for the passive supply of lubricant at sufficient pressure using simple means.

[0024] According to one embodiment, the fuel system is provided to supply hydrogen, CNG or ammonia.

[0025] According to another aspect, the invention relates to a vehicle equipped with an internal combustion engine comprising a gaseous fuel supply system as described herein, in which the supply rail is oriented so that the flow channel extends from the lower part of the main chamber and is inclined downwards relative to the horizontal.

[0026] Brief description of the figures

[0027] The invention will be better understood and other features and advantages will become apparent upon reading the following description, the description referring to the attached drawings, among which:

[0028] - Figure 1 is a perspective view of an engine comprising a power supply system according to a first embodiment of the invention;

[0029] - Figure 2 is a partial cross-sectional view of the engine power supply system of Figure 1;

[0030] - Figure 3 is a cross-sectional view along line III-III of Figure 2;

[0031] - Figure 4 is a cross-sectional view along line IV-IV of Figure 2;

[0032] - Figure 5 is a perspective view of an engine comprising a power supply system according to a second embodiment of the invention;

[0033] - Figure 6 is a top view of the power supply ramp in Figure 5;

[0034] - Figure 7 is a partial view of a cross-section of the feed system of Figure 5 in a longitudinal plane of the feed ramp;

[0035] - Figure 8 is a cross-sectional view along line VIII-VIII of Figure 7;

[0036] - Figure 9 is a transparent view of the power supply ramp in Figure 6;

[0037] - Figure 10 is a perspective view of a ramp for a feeding system according to a third embodiment of the invention; - Figure 11 is a longitudinal cross-sectional view of the ramp of Figure 10 (through the inlet fitting 40);

[0038] - Figure 12 is a schematic diagram of the membrane accumulator.

[0039] Detailed description

[0040] A cylinder head 1 of an internal combustion engine comprising a gaseous fuel supply system according to a first embodiment of the invention is shown in Figure 1. The engine is intended to be mounted in a vehicle in a predetermined orientation with respect to the vertical V. It is intended to be fueled by hydrogen in gaseous form. The fuel supply system comprises a fuel rail 2, shown in Figures 1 to 4 and intended to receive pressurized gaseous fuel in a main chamber 20, and a plurality of fuel injectors 10, in this case four, connected to the fuel rail 2. The injectors may be conventional gaseous fuel injectors, for example of the solenoid-operated direct-acting type (see e.g. WO 2023 / 052263).

[0041] The fuel rail 2 has a generally tubular shape extending along a principal direction P. It has tabs 21 by which it is fixed to the cylinder head 1. The injectors 10 deliver the gaseous fuel into four combustion chambers, not shown. Each injector 10 is connected to a fitting 22 on the fuel rail 2. The fittings 22 are typically designed as sockets forming an external protrusion of the tubular body of the rail 2. The fittings are designed to ensure a perfect seal and a secure connection between the rail and the injectors. The fittings may be integral with the tubular body or attached as separate pieces that are sealed (e.g., by brazing or welding). The entire rail assembly is typically made of metal, for example, stainless steel.

[0042] It will be appreciated that each branch 22 is delimited by an internal branch surface 220 connecting to an internal tubular surface 200 of the feed manifold 2 delimiting the main chamber 20. The internal branch surface 220 defines a sloping flow channel, here continuous, towards the injector from a low point in a section of the feed manifold 2 at the branch 22, as can be seen in detail in Figure 4. A pressure sensor 23 can be connected to the feed manifold 2 near one of the ends of the feed manifold 2. Thus, in operation, the feed system has a predetermined orientation, in that the injection manifold is oriented so that the flow channel 220 extends from the lower part of the main chamber 20 and is inclined downwards with respect to the horizontal H.More precisely, the inner tapping surface 220 meets the lowest point of the inner tubular surface 200. We can therefore say that the inner tapping surface 220, and the flow channel, is globally "tangential" to the body of the ramp (in comparison to conventional tappings which are radial).

[0043] As seen in the variant in Fig. 4, the tapping surface 220 opens, at its end opposite the chamber 20, into an injector coupling passage 10, which leads to an adapter 7.1 defining a section 7.2 configured to receive a portion of the injector inlet. This is therefore a variant for direct coupling of the injector to the fuel rail.

[0044] The branch 22 thus forms a transverse extension of the fuel rail 2, which allows for injector coupling. By design, as can be seen from Fig. 4, the injector—represented by its axis I—is offset laterally relative to the fuel rail 2. The injector axis I is located at a distance D from the longitudinal axis C of the main chamber 20. The distance D (D>0) depends on the design. Furthermore, the injector axis I does not pass through the longitudinal axis C, and preferably does not pass through the main chamber 20.

[0045] The flow channel of the branch can be perpendicular or oblique to the longitudinal axis C.

[0046] The internal tapping surface 220 slopes downwards from the lowest point of the internal tubular surface 200 towards the passage 7, allowing oil to drain onto the walls. In the illustrated variant, the flow channel defined by the internal tapping surface 220 is generally tangential to the body of the manifold, but it will be understood that other angles are possible, as long as the flow channel slopes from the lowest point of the internal tubular surface 200. Considering the lowest generatrix of the internal tapping surface 220, the angle α between this generatrix and the horizontal (H) can be in the range 0 < α < 90° (the 90° angle is excluded here as it would correspond to a radial channel). For a design with a lateral tapping, in order to maintain a certain slope and sufficient offset, the intervals can be 10° < a < 80°, in particular 15° < a < 70°, or even 20° < a < 55°.The branch 22 therefore includes a branch piece forming a transverse protrusion of the supply ramp 2, in which the branch surface 220 and the passage 7 are made. The branch surface 220 extends from the lowest point of the main chamber 20 obliquely towards the passage 7, located lower down, the passage 7 being aligned along the axis I.

[0047] The fuel supply system according to the first embodiment includes a distribution piece 3 for supplying fuel to the fuel rail 2. The distribution piece 3 has a metal body (e.g., stainless steel) defining an inlet tube 31 and two distribution conduits 32 connected symmetrically to the inlet tube 31. Each distribution conduit 32 opens (here via an elbow 320) into the fuel rail 2 through two fittings 19. The fittings 19 open into the chamber 20 and have an external thread for connecting the conduits 32. It should be noted that the fittings 19 are positioned approximately midway between two adjacent ports 22. The inlet tube 31 includes a single lubrication device 4, carried in this case by the distribution piece 3, to supply lubricant to the gaseous fuel flow.The lubrication device 4 is for example arranged in a wall of the distribution part 3, with a portion of nozzle 43 positioned to discharge the lubricant into the gaseous fuel stream.

[0048] The fuel supply system includes a pressurized fuel tank supplying gaseous fuel to a regulator and then to a pipeline connected to the inlet tube 31, these elements not being shown.

[0049] The lubrication device 4, shown in simplified cross-section in Figure 7, is an injection device 4 comprising a solenoid 41 capable of lifting a needle 42 (typically attached to an armature) resting on a sealing seat to open or close a lubricant passage. The lubrication device 4 includes an outlet nozzle 43—which carries the sealing seat—through which two lubricant jets are generated, one directed respectively toward each of the two distribution channels 32. In particular, the outlet nozzle 43 has two orifices, each configured so that the respective lubricant jets are emitted along the axis of the associated distribution channel 32.

[0050] The supply system includes a lubricant source, for example, a diaphragm accumulator, to supply pressurized lubricant to the lubrication device 4. An embodiment of a diaphragm accumulator 70 is shown schematically in Fig. 12. The accumulator typically comprises a body 72, generally made of steel, defining a sealed inner chamber. This chamber is divided by a flexible and resistant elastomer diaphragm 74, often made of synthetic rubber. The lower part 76 typically contains the oil for lubricating the injectors 20. Above the diaphragm, in the upper part 77, is a gas, which may be nitrogen or air, and which constantly exerts pressure on the diaphragm and the oil below.This compressed gas pressure (which varies according to consumption) keeps the oil under pressure and ready to be released quickly when needed, via an outlet 78 (which also serves for filling). A valve 80 is located at the bottom to close the outlet 78 of the lower chamber. A valve 82 is located at the top, which controls a filling outlet of the upper chamber.

[0051] In operation, the pressurized gas is supplied by the pipeline to the inlet tube 31 of the distribution piece 3 in which it receives in cycles a dose of lubricant supplied by the injection device 4. The gas with the lubricant charge passes through the distribution conduits 32 to arrive in the chamber 20 of the supply rail 2. It then passes through the connections 22 to the injectors 10 which thus benefit from the lubrication supplied by the lubricant-laden gas.

[0052] According to a second embodiment, shown in Figures 5 to 9, the supply rail 2' differs from that of the first embodiment in that, in addition to the distribution piece and distribution channels, it includes an inlet connector 23 opening into a first channel 24' extending parallel to a main chamber 20 of the supply rail 2'. The first channel 24' extends symmetrically on either side of the inlet connector 23 and opens at its ends through two ports 240 into the main chamber 20. Each port is located approximately midway between two adjacent ports 22. A support elbow is connected to the inlet connector 23 and receives the line from the pressure regulator to establish fluid communication with the supply rail 2'. The support elbow also receives the lubrication device 4, arranged to discharge lubricant into the fuel flow.The first channel 24, for example, is delimited by a channel piece 241 attached to the tubular part of the feed rail 2' and welded there in a watertight manner around its periphery. Note that in Figures 6 and 9 the input connector 23 is omitted, revealing the openings of the channels 24.

[0053] According to a third embodiment, shown in Figures 10 and 11, the 2" feed ramp comprises an input connector 40 opening into a first channel 24" extending parallel to the main chamber 20 of the 2" feed ramp, the first channel 24" extending symmetrically on either side of the input connector 40. The 2" feed ramp differs from that of the second embodiment in that the first channel 24" opens at its ends in the middle of a second and a third channel 25, 26 respectively, extending parallel to the main chamber 20, each of the channels 25, 26 among the second and third channels having two ends opening into the main chamber 20 opposite one of the ports 22 through ports 251, 252, 261, 262. The 2" feed ramp is mounted in the same way as that of the second embodiment.In this embodiment, a better distribution of the gas flow towards the 22 connections is ensured.

[0054] Since this variant is equipped with a simple inlet connector 40 (fitting type), the lubricant is added upstream of the rail, as in the first variant. A similar system can be used with a distribution piece 3 having an inlet tube 31, but only one distribution conduit 32 at the outlet, which connects to the connector 40. The lubrication device 4 is mounted on the distribution piece 3.

[0055] Alternatively, we could have a configuration similar to the second variant, where the inlet connector 40 would be of the type of connector 23 in Fig.7, and would therefore directly carry the lubrication device 4.

[0056] As shown in Figs. 5 to 11, the feed ramp comprises a tubular body whose inner surface 200 defines the main chamber 20, and the channels 24, 24”, 25 and 26 are arranged in strips (forming a superstructure) fixed to the outer wall of the tubular body. In the second variant, there is a strip 241 extending between the two orifices 240, defining channel 24. In the third variant, there are two superimposed strips: the strip 241, which defines channel 24, is placed on a longer strip 242, which defines two separate channels: channel 25 connecting orifices 251 and 252, and channel 26 connecting orifices 261 and 262.

[0057] The invention is not limited to the embodiments described by way of example. The engine could have a different number of injectors, for example, three or six. In the case of six injectors in the first embodiment, the connecting piece could have three supply lines.

Claims

Demands 1. Gaseous fuel supply system for an internal combustion engine intended to be mounted in a vehicle in a predetermined orientation with respect to the vertical, the supply system comprising a supply rail (2, 2', 2") for receiving pressurized gaseous fuel in a main chamber (20), and a plurality of fuel injectors (10) connected to the supply rail (2, 2', 2"), in which each injector is connected to a branch (22) of the rail, each branch (22) being delimited by an internal branching surface (220) connecting to an internal tubular surface (200) of the supply rail (2, 2', 2") delimiting the main chamber (20), characterized in that it comprises at least one lubrication device (4) for supplying lubricant in the gaseous fuel flow;and that the internal tapping surface (220) defines a sloping flow channel, preferably continuous, towards the injector from a low point in a section of the supply manifold (2, 2', 2") at the tapping point (22).; 2. Feeding system according to claim 1, characterized in that the branch is configured so that the longitudinal axis (I) of the injector is laterally offset with respect to the feed rail 2; and preferably the longitudinal axis (I) of the injector does not pass through the longitudinal axis (C) of the feed rail, and more preferably does not pass through the main chamber (20).

3. Feeding system according to claim 2, characterized in that the branch (22) comprises a branch piece (22.1) forming a transverse protrusion of the feed ramp (2), in which are formed the branch surface (220) and an injector coupling passage (7); the branch surface (220) extending from the lowest point of the main chamber (20) obliquely towards the injector coupling passage (7), located lower down.

4. Feeding system according to claim 1, 2 or 3, characterized in that the internal tubular surface (200) of the feed ramp and the internal tapping surfaces (220) are cylindrical; and in that for each tapping, the lowest generatrix of the internal tapping surface (220) is tangent to the internal tubular surface (200).

5. A feeding system according to any one of the preceding claims, characterized in that it comprises an inlet tube (31) opening into the ramp the supply is substantially at mid-length of the supply rail to provide the fuel, the lubrication device (4) being unique and supplying the lubricant to the inlet tube (31).

6. Fuel supply system according to any one of claims 1 to 4 characterized in that it comprises a distribution piece (3) for supplying fuel to the fuel rail (2), the distribution piece (3) comprising an inlet tube (31) and at least two distribution conduits (32) connected to the inlet tube (31), the fuel rail (2) comprising as many pairs of outlets (22) as the system has distribution conduits (32), each distribution conduit (32) opening into the fuel rail (2) substantially midway between two adjacent outlets (22), the inlet tube (31) comprising a single lubrication device (4).

7. Supply system according to claim 6, wherein the lubrication device (4) generates jets of lubricant towards each of the distribution conduits (32).

8. Power supply system according to any one of claims 1 to 4, wherein the power supply ramp (2') has an input connector (23) opening into a first channel (24) extending parallel to a main chamber (20) of the power supply ramp (2'), the first channel (24) extending symmetrically on either side of the input connector (23) and opening at its ends through two ports (240) into the main chamber (20).

9. Feeding system according to claim 8, in which each orifice (240) is located substantially midway between two adjacent spigots (22).

10. A power supply system according to any one of claims 1 to 4, wherein the power supply ramp (2") comprises an input connector (23") opening into a first channel (24") extending parallel to a main chamber (20) of the power supply ramp (2"), the first channel (24") extending symmetrically on either side of the input connector (23") and opening at its ends in the middle respectively of a second and a third channel (25, 26) extending parallel to the main chamber (20), each channel (25, 26) having two ends opening into the main chamber (20) opposite one of the taps (22) through ports (251, 252, 261, 262).

11. A feeding system according to any one of the preceding claims, wherein the lubrication device is an injection device (4) comprising a solenoid (41) capable of lifting a needle (42) resting on a seat to open or close a passage of lubricant.

12. Supply system according to any one of the preceding claims, characterized in that it comprises an accumulator for supplying pressurized lubricant to the lubrication device (4).

13. Fuel system according to any one of the preceding claims, characterized in that it is intended to supply hydrogen, CNG, or ammonia, or a gas comprising at least one of these.

14. Vehicle equipped with an internal combustion engine comprising a gaseous fuel supply system according to any one of the preceding claims, wherein the supply rail is oriented so that the flow channel extends from the lower part of the main chamber and is inclined downwards with respect to the horizontal.

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