GB2634220A

GB2634220A - Gaseous fuel delivery system for an internal combustion engine

Info

Publication number: GB2634220A
Application number: GB2315067.5A
Authority: GB
Inventors: Dratch Rodolphe
Original assignee: Phinia Delphi Luxembourg SARL
Current assignee: Phinia Delphi Luxembourg SARL
Priority date: 2023-10-02
Filing date: 2023-10-02
Publication date: 2025-04-09
Also published as: WO2025073761A1; GB202315067D0

Abstract

The invention provides a gaseous fuel delivery system 10 for an internal combustion engine, comprising a source of pressurized gas 12, a gas delivery pipe 18, and a gas rail 14 coupled to at least one gas injector 16, wherein the source of pressurized gas 12 is fluidly coupled to the gas rail 14 via the gas delivery pipe 18, characterized by at least one pressure damping chamber 20 serially connected in the gas delivery pipe 18 between an outlet of the pressure source 12 and an inlet of the gas rail 14, wherein the pressure damping chamber 20 has an internal diameter greater DC than an internal diameter DL of the gas delivery pipe 18. The invention aims to damp pressure oscillations with a fuel rail of a hydrogen internal combustion engine.

Description

GASEOUS FUEL DELIVERY SYSTEM FOR AN INTERNAL COMBUSTION

ENGINE

Technical field

The present invention generally relates to gaseous fuel delivery systems for internal combustion engines, more specifically to gaseous fuel delivery systems for hydrogen internal combustion engines (H2-ICE) in automotive vehicles.

Background Art

Fuel injection systems are widely used in the automotive industry to deliver timely and precise quantities of pressurized fuel to an engine. Conventional Diesel or Gasoline fuel injection systems typically follow the "common rail system" architecture, which comprises a high-pressure pump, a fuel rail, a plurality of injector and a fuel delivery pipe to fluidly couple the high-pressure pump and fuel rail.

The quantity of fuel delivered by an injector is directly related to the duration of the injection (injector open time) and the pressure within the rail during the injection. To ensure the correct quantity of fuel is delivered to the engine, it is thus necessary to control of the pressure within the rail. However, the fuel pressure within the system is known to erratically oscillate, e.g. due to the noise generated by the high-pressure pump or injector actuation. These pressure oscillations inevitably lead to inconsistencies in amounts of fuel delivered by the injector, which are of course to be avoided.

To damp pressure oscillations within the fuel rail, orifices are typically arranged at the inlet and outlets of the fuel rail. Orifices are generally defined as devices for partially restricting flow by decreasing the cross-sectional area of the flow path, thereby locally converting flow pressure to flow velocity. Downstream of the orifice, the flow is allowed to expand, thereby converting flow velocity back to flow pressure.

This process decreases the amplitude of the pressure oscillations, leading to more stable and predictable amounts of fuel delivered.

Unfortunately, the inventors have found that whilst these orifices are an effective way to damp pressure variations for Diesel or Gasoline fuel delivery systems, they present serious drawbacks when gaseous fuel is used. Indeed, using orifices in gaseous fuel injection systems causes a severe pressure drop, decreasing the total pressure at the gaseous fuel injectors and leading to excessive injection rate decay.

An alternative way to damp pressure oscillation would be to increase the inner volume of the gaseous fuel rail. However, this solution is also far from ideal, as regulations require completely emptying the gaseous fuel delivery system upon engine shut off.

Technical problem It is an object of the present invention to provide a gaseous fuel delivery system comprising means to damp pressure oscillation without the aforementioned 10 drawbacks.

This object is achieved by a gaseous fuel delivery system as claimed in claim 1. General Description of the Invention To achieve this object, the invention provides a gaseous fuel delivery system for an internal combustion engine. The gaseous fuel delivery system comprises a source of pressurized gas, a gas delivery pipe, and a gas rail coupled to at least one gas injector, the source of pressurized gas being fluidly coupled to the gas rail via the gas delivery pipe.

According to the invention, the gaseous fuel delivery system comprises at least one pressure damping chamber serially connected in the gas delivery pipe between an outlet of the pressure source and an inlet of the gas rail, with the pressure damping chamber having an internal diameter greater than an internal diameter of the gas delivery pipe.

As pressurized gas flows along the gas delivery pipe from the source of pressurized gas towards the gas rail, the cross-sectional area of the flow varies due to the difference between the internal diameter of the pressure damping chamber (or plurality thereof) and the internal diameter of the gas delivery pipe. Hence, when gas flow enters the pressure damping chamber, it expands due to the increase in cross-sectional area, thereby decreasing its velocity and increasing its pressure. Conversely, when the flow leaves the pressure damping chamber, its velocity increases as its pressure decreases. This back-and-forth conversions between static and dynamic pressure damps pressure oscillations, increasing the stability of the pressure downstream of the pressure damping chamber and within the gas rail. The gaseous fuel delivery system according to the invention thus ensure stable pressure in the gas rail with little to no total pressure drop.

In the context of the invention, the term "diameter" should be interpreted as "generalized diameter", i.e. the cross-section of the pressure damping chamber and of the gas delivery pipe is not restricted to circular geometries and may be e.g. square or hexagonal.

The gas delivery pipe thus typically forms a pipe in which one or more pressure damping chambers are integrated. The pressure damping chambers may be typically formed by hollow components connected in series in the pipe. Where there is a plurality of pressure damping chambers, the gas delivery pipe is thus a pipe where pipe sections are interrupted by serially connected pressure damping chambers, which have a comparatively greater diameter than the pipe sections.

The gas delivery pipe is arranged between the source of pressurized and the gas rail, being coupled to the latter to supply pressurized gas. The gas delivery pipe can be directly connected at one end to the source of pressurized gas and/or directly connected at the other end to the gas rail. Indirect connection is also possible, where an intermediate pipe, duct or hose is arranged between and end of the gas delivery pipe and the source of pressurized gas, respectively the gas rail. Preferably, the gas delivery pipe is directly connected to the gas rail.

The pressure damping chambers are integrated in the gas delivery pipe in a gas-sealed manner, to form a gas tight passage. Any appropriate attachment means can be employed, using welding, joints, or other.

In embodiments, the gas delivery pipe and the pressure damping chamber (or chambers) are made as a single piece, preferably from metal, in particular stainless steel compatible with hydrogen to limit the embrittlement, e.g. austenitic stainless steel. The pressure damping chamber(s) is/are preferably welded to adjacent pipe section of the gas delivery pipe.

In embodiments, the pressure damping chamber has a length greater than or equal to the internal diameter of the gas delivery pipe.

In embodiments, the pressure damping chamber has a length greater than or equal to its own internal diameter.

In embodiments, the gas delivery pipe comprises at least two, preferably three, pressure damping chambers serially integrated therein. First test have shown that the damping effect can be optimized by varying the dimensions of the pressure damping chambers. In particular, the diameter of the pressure damping chambers can be decreased when augmenting the number of pressure damping chambers.

In embodiments, the internal diameter of the gas delivery pipe is constant. In other words, the internal diameter of the portions of the gas delivery pipe separating the 10 pressure damping chambers is constant.

In embodiments, the gas rail comprises a pressure sensor configured to monitor the pressure within the gas rail.

In embodiments, the pressure damping chamber is cylindrical. Preferably, the pressure damping chamber has a longitudinal cylinder axis parallel to the gas flow direction. A plurality of pressure damping chambers may be arranged coaxially.

In embodiments, the internal diameter of the gas delivery pipe is comprised between 8 and 15 mm.

In embodiments, the internal diameter of the pressure damping chamber is comprised between 9 and 25 mm, preferably between 10 and 20 mm.

In embodiments, the pressure damping chamber has a length comprised between 50 and 150 mm.

In embodiments, the gas delivery pipe has a length comprised between 1 and 7 m, for example the length may be between 1 and 2, 3, 4, 5, or 6 m.

In embodiments, the pressure damping chamber(s) are located proximally to the gas rail, preferably within 1 m from the inlet of the gas rail.

In embodiments, the gas rail is coupled to a plurality of gas injectors, preferably at least 3 and/or at most 6 gas injectors.

Brief Description of the Drawings

A preferred embodiment will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a schematic view of an embodiment of the gaseous fuel delivery system according to the invention; Fig. 2 is a graphical representation of the rail pressure plotted against engine speed for gaseous fuel delivery systems with and without pressure damping chambers; Fig. 3 is a graphical representation of the rail pressure plotted against engine speed for prior art gaseous fuel delivery systems having different orifice configurations.

Description of Preferred Embodiments

Figure 1 shows a schematic view of a gaseous fuel delivery system 10 according to an embodiment of the invention. The gaseous fuel delivery system 10 comprises a source of pressurized gaseous fuel 12 (or simply 'gas), a gas rail 14, a plurality of gas injectors 16 connected thereto, and a gas delivery pipe 18. The present system 10 is designed for supplying gaseous fuel, such as e.g. hydrogen, to an internal combustion engine (H2-ICE), to be combusted therein upon introduction in combustion chamber(s) thereof. The gaseous fuel delivery system 10 with the H2-ICE may equip vehicles such as e.g. cars, trucks, buses, etc. The term "gaseous fuel" generally includes combustible fluids (e.g. H2 or CH4) which are in their gaseous state when exposed to nominal operating conditions of the injector and the engine, e.g. pressure and temperature. Regarding more specifically hydrogen as gaseous fuel for an ICE, it typically consists of a gas with at least 90% hydrogen (H2), preferably pure hydrogen with no more than 2% impurities The source of pressurized gas 12 may typically comprise at least one gas tank designed to receive gaseous fuel at high-pressures, typically of several hundred bar, e.g. 350 or 700 bar. The gas tank may be a cryogenic tank. The source of pressurized gas 12 may include a pressure regulator to deliver the gaseous fuel at controlled pressure, e.g. up to 50 or 40 bar, as well as a shut-off valve to isolate the source 12 from the downstream components of the delivery system 10. The source of pressurized gas 12 may further comprise an adaptor configured to enable fluid coupling with the gas delivery pipe 18.

The source of pressurized gas 12 is fluidly coupled to gas rail 14 by means of the gas delivery pipe 18, thereby enabling transport of pressurized gas from the source of pressurized gas 12 to the plurality of gas injectors 16. More specifically, the gas delivery pipe 18 defines a gas delivery line (or channel) in its inner volume, the gas delivery line operatively connecting the source of pressurized gas 12 to an inlet valve of the gas rail 14. Preferably, the gas delivery pipe 18 comprises only two openings (i.e. for connection to the source of pressurized gas 12 and to an inlet valve of the gas rail 14).

The gas rail 14 is conventionally a tubular member that defines a plenum chamber between its inlet and its multiple outlets distributed along the length of the rail, each outlet being coupled to a gas injector 16. The gas rail 14 is typically made of metal, preferably stainless steel compatible with hydrogen to limit the embrittlement, and is made as a single piece with a length selected based on the engine size (e.g. around 200 mm for a 4 cylinders and up to 800 mm for a 6 cylinders engine). A pressure sensor (not shown) is arranged on the gas rail 14 and is configured to send pressure data to an Engine Control Unit of the vehicle.

Each gas injector 16 may typically comprises a solenoid-actuated pintle configured to selectively enable or prevent flow of pressurized gaseous fuel through a nozzle of the injector into a combustion chamber of the engine. Operation of the gas injectors 16 is controlled by the Engine Control Unit.

The source of pressurized gas 12, gas rail 14 and gas injector 16 operate based on known principles and may be of any appropriate design; since they are not the focus of the invention they will not be further described.

The gas delivery pipe 18 comprises a plurality of hollow pressure damping chambers 20 serially connected with each other along the gas delivery pipe 18 between the source of pressurized gas 12 and the gas rail 14. The pressure damping chamber are hollow, i.e. solely define a passage for gas flow and do not comprise any valve member or other component therein. In the shown embodiment, these pressure damping chambers 20 are arranged coaxially, parallel to the direction of gas flow within the gas delivery pipe 18. The pressure damping chambers 20 have an internal diameter Dc greater than an internal diameter DL of the gas delivery pipe 18, and a length Lc greater than this internal diameter Dc. Pressure damping chambers 20 are separated from one another by a portion 22 of the gas delivery pipe 18 which may have a length Ls smaller than the length Lc of a pressure damping chamber. Advantageously, the internal diameter DL of the gas delivery pipe 18 is constant. In other words, the diameter of the portions 22 separating the pressure damping chambers 20 is constant. The gas delivery pipe and the pressure damping chamber made from metal, e.g. stainless steel, compatible with hydrogen to limit the embrittlement, as a single piece having a length of e.g. 1 to 7m. Advantageously, the pressure chambers may be located proximally to the gas rail, e.g. within lm from the inlet of the gas rail.

As pressurized gas flows along the gas delivery pipe 18 from the source of pressurized gas 12 towards the gas rail 14, the cross-sectional area of the flow varies due to the difference between the internal diameter Dc of the pressure damping chambers 20 and the internal diameter DL of the gas delivery pipe 18. Hence, when gas flow enters a pressure damping chamber 20, it expands due to the increase in cross-sectional area, thereby decreasing its velocity and increasing its pressure. Conversely, when the flow leaves a pressure damping chamber 20, its velocity increases as its pressure decreases. Each of these back-and-forth conversions between static and dynamic pressure damps pressure oscillations, increasing the stability of the pressure downstream of the pressure damping chambers 20 and within the gas rail 14. As previously mentioned, stable pressure in the gas rail 14 is critical to ensure precision and consistency in the amount of gas delivered by the gas injectors 16.

This increase in pressure stability is illustrated on figure 2, which shows graphical representations of the rail pressure plotted against engine speed for two different gaseous fuel delivery systems. Specifically, plot P1 represents the rail pressure for a classical gas delivery system having no pressure damping chamber, whilst plot P2 represents the rail pressure for a gas delivery system 10 according to the invention. As it can be seen, plot P2, which is comprised between 41 ± 1 bar, is thrice as stable as plot P1, which is comprised between 41 ± 3 bar.

It should further be noted that with the inventive design, the flow velocity advantageously reaches a minimum value within the pressure damping chambers 20 (since the internal diameter Dc of the latter is greater than the internal diameter DL of the gas delivery pipe 18). Conversely, the flow velocity reaches a maximum value within the gas delivery pipe 18. In other words, the maximum flow velocity within the gas delivery pipe 18 is defined by its own internal diameter. This is in direct contrast to prior art designs comprising orifices, wherein the maximum flow velocity within the gas delivery pipe 18 is defined by the minimum diameter of the orifice.

The inventors have found that orifices in gas delivery systems cause a severe pressure drop when gaseous fuel is used. Indeed, when gaseous fuel reaches the orifice, the sharp increase in flow velocity due to the decrease in cross-sectional area leads to excessive friction loss and pressure drop. This pressure drop is shown on figure 3, which is a graphical representation of the rail pressure plotted against engine speed for gaseous fuel delivery systems having different orifice configurations. Specifically, plot GO represents the rail pressure for a gas delivery system with no orifice, G1 represents the rail pressure for one with an orifice having a diameter of 4 mm, G2 represents the rail pressure for one with an orifice of 3 mm, G3 represents the rail pressure for one with an orifice of 2 mm, and G4 represents the rail pressure for one with an orifice of 1.5 mm. All five configurations have the same original pressure, i.e. the pressure generated by the source of pressurized gas at the upstream end of the gas delivery pipe 18. As it can be seen, orifices of smaller diameter lead to lower rail pressure. Indeed, smaller orifices lead to higher maximum flow velocity, higher friction loss and thus higher pressure drop. However, smaller orifices also lead to improved pressure damping and rail pressure stability, as smaller orifices locally converts more flow pressure to flow velocity and vice versa. Hence, when using orifices, the skilled person is forced to compromise between decreasing the pressure drop and improving the rail pressure stability. In contrast, the inventive method enables pressure oscillation damping without increasing the maximum flow velocity, thereby leading to improved rail pressure stability with no pressure drop.

Claims

Claims 1. Gaseous fuel delivery system (10) for an internal combustion engine, comprising a source of pressurized gas (12), a gas delivery pipe (18), and a gas rail (14) coupled to at least one gas injector (16), wherein the source of pressurized gas (12) is fluidly coupled to the gas rail (14) via the gas delivery pipe (18), characterized by at least one pressure damping chamber (20) serially connected in the gas delivery pipe (18) between an outlet of the pressure source (12) and an inlet of the gas rail (14), wherein the pressure damping chamber (20) has an internal diameter greater (Dc) than an internal diameter (DL) of the gas delivery pipe (18).
2. Gaseous fuel delivery system (10) according to claim 1, wherein the pressure damping chamber (20) has a length (Lc) greater than or equal to the internal diameter (DO) of the gas delivery pipe (18).
3. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the pressure damping chamber (20) has a length (Lc) greater than or equal to its own internal diameter (Dc).
4. Gaseous fuel delivery system (10) according to any of the preceding claims, comprising at least two, preferably three, pressure damping chambers (20).
5. Gaseous fuel delivery system (10) according to claim 4, wherein the pressure damping chambers (20) are serially connected to each other along the gas delivery pipe (18).
6. Gas delivery system according to claim 5, wherein the pressure damping chambers are separated from each other by a portion of the gas delivery pipe having a length smaller than or equal to the length of a pressure damping chamber.
7. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the internal diameter (DO) of the gas delivery pipe (18) is constant.
8. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the gas rail (14) comprises a pressure sensor configured to monitor the pressure within the gas rail (14).
9. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the pressure damping chamber (20) is cylindrical.
10. Gaseous fuel delivery system (10) according to claim 9, wherein the pressure damping chamber (20) has a longitudinal cylinder axis parallel to the gas flow direction.
11. Gaseous fuel delivery system (10) according to claim 9 or 10, comprising a plurality of pressure damping chambers (20) arranged coaxially.
12. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the gas delivery pipe (18) and the pressure damping chamber (20) are made as a single piece, preferably from metal, in particular stainless steel.
13. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the internal diameter (DO) of the gas delivery pipe (18) is comprised between 8 and 15 mm.
14. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the internal diameter (Dc) of the pressure damping chamber (20) is comprised between 9 and 25 mm, preferably between 10 and 20 mm.
15. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the pressure damping chamber (20) has a length (Lc) comprised between 50 and 150 mm.
16. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the gas delivery pipe (18) has a length comprised between 1 and 7 m.
17. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the pressure damping chamber(s) (20) are located proximally to the gas rail (14), preferably within 1 m from the inlet of the gas rail (14).
18. Gaseous fuel delivery system (10) according to any of the preceding claims, wherein the gas rail (14) is coupled to a plurality of gas injectors (16), preferably at least 3 and/or at most 6 gas injectors.