Pressure regulator for hydrogen internal combustion engine

Abstract

A pressure regulator for an internal combustion engine gas injection system comprises a regulator body 12 with a gas passage 14 therein. A control section 22 defines a valve seat 28 surrounding the ga

Description

Technical field The present invention generally relates to a pressure regulator for a hydrogen internal combustion engine, in particular to a pressure regulator of a fuel supply system of a combustion engine. Background Art Many stationary and mobile internal combustion engines (ICE) utilize a compressed gas as a gaseous fuel which, when mixed with air provides the energy to power the engine. The gaseous fuel, e.g. compressed natural gas (CNG) or hydrogen, is generally stored in a tank under high pressure which pressure may be, for example, in the order of about 700 bar. Such high pressure is not generally compatible with the operation of an internal combustion engine. Accordingly, the gas pressure must be reduced to a level acceptable for introduction into the ICE. The pressure level of the CNG for introduction into the ICE may be in the range of 2 bar to 10 bar and up to 40 bar for hydrogen ICE. A pressure regulator is therefore installed between the fuel tank G and the fuel rail / injectors to provide the desired reduction in pressure of the gaseous fuel. Many pressure regulator applications have heretofore utilized a mechanical pressure regulator to provide the reduction in gas pressure by utilization of a combination of valves, diaphragms and / or pistons, springs and other mechanical devices to provide the reduction in the gas pressure. Also known are electronically controlled gas pressure regulator. However most electronic gas pressure regulators known for CNG applications can only operate at pressure up to 16 bar, making them unsuitable for hydrogen engines which operate at higher pressures, typically between 40 and 20 bar. A further drawback of the conventional pressure regulators for gaseous fuels is linked to the interface design. The valve member typically has a conical shape that cooperates with a conical valve seat; and the pressure regulation is achieved by controlling the axial position of the valve member relative to the valve seat. Depending on the configuration, it may be difficult to maintain a minimum flow crosssection. Technical problem It is an object of the present invention to provide a pressure regulator of improved design. This object is achieved by a pressure regulator valve as claimed in claim 1. General Description of the Invention According to the present invention, a pressure regulator for a gas injection system of an internal combustion engine comprises: a regulator body with a gas passage extending between an inlet section for receiving gaseous fuel at a high pressure and an outlet section; a control section defining a valve seat surrounding the gas passage and cooperating with a valve member, the valve member being moveable axially between a closed position in which the valve member is applied onto the valve seat preventing flow of gaseous fuel therethrough, and one or more open positions off the valve seat; wherein the control section comprises a straight cylindrical section opening on a diverging section defining the valve seat; wherein the valve member comprises a cylindrical portion axially protruding from a tapered portion; wherein in a closed position of the valve member the cylindrical portion thereof is clearance fitted in the cylindrical section and the tapered portion rests against the diverging section; wherein the pressure regulator is selectively operable: in a first mode, in which the valve member is off the valve seat, the cylindrical portion being partially engaged inside the cylindrical section, whereby the flow cross-section is defined by an annular gap between the cylindrical section and the cylindrical portion; in a throttling mode, in which the valve member is axially positioned such that the flow cross-section is defined by the annular gap between the front end of the cylindrical portion and the diverging section, said flow cross section being however smaller than the cross section of the cylindrical section; and in an open mode, in which the valve member is axially positioned such that the flow cross-section, defined by the annular gap between the front end of the cylindrical portion and the diverging section, is larger than the cross section of the cylindrical section. It will be appreciated that the present comprises a pressure regulator (or pressure regulator unit) including a valve member and control section that are configured to provide three (at least) different flow control modes. In practice, the skilled person may dimension the cooperating diameters in the different modes to obtain desirable flow rates through the regulator. The first mode corresponds to minimum flow, e.g. for idling. The first mode can be stably maintained since it is available over a range of axial positions, depending on the dimension of the cylindrical protrusion. The second and third modes offer two throttling ranges at intermediate or full flow. In embodiments, the diverging section comprises a first sub-section connecting on one side the cylindrical section and one the opposite side a second sub-section. The second sub-section has a wider opening than the first sub-section and defines the valve seat. In the throttling mode, the valve member is axially positioned such that the flow cross-section is defined by the annular gap between the front end of the cylindrical portion and the first sub-section or the second sub-section. Preferably, the first and second sub-sections are conical, the second sub-section having a broader aperture angle than the first sub-section. In embodiments, an annular sealing element is arranged between the cylindrical portion and the tapered section, the sealing element engaging the diverging section, resp. second sub-section, in closed position. The sealing element may be configured such that in closed position, it overlaps the first and second sections. The element may have a peripheral shape that generally follows the slope angle of the tapered portion and preferably radially protrudes relative to the tapered portion. In embodiments, the annular sealing element has a circular or trapezoidal crosssection; and / or is mounted to, or overmolded on, the tapered portion. In embodiments, the cylindrical portion has an axial length of between 0.25 and 1 mm. Advantageously, a conical tip protrudes from the front end of the cylindrical portion. This provides for a pre-guiding function relative to the cylindrical section of the gas passage. In embodiments, an actuator is associated with the valve member to axially move the latter. The actuator may be axially arranged with respect to the regulator body on the side of the outlet section. The invention also relates to a gas delivery system for a hydrogen internal combustion engine powered with gaseous fuel (e.g. H2 or other). The gas delivery system comprises a fuel rail, a set of gas injectors and a pressure regulator according to any of the preceding claims. A control unit is configured to selectively move the valve member to achieve a desired downstream gas pressure, the control unit receiving a downstream gas pressure signal from a pressure sensor. Brief Description of the Drawings Further details and advantages of the present invention will be apparent from the following detailed description of several not limiting embodiments with reference to the attached drawings, wherein: Fig. 1 is a cross sectional view through a pressure regulator according to a first embodiment of the invention, in closed position; Fig. 2 is a view of the pintle of Fig. 1; Fig. 3 is a cross sectional view of the body of Fig. 1; Figs. 4 to 7 are a cross sectional views through the pressure regulator of Fig.1, in the first, second and third regulating modes; Fig. 8: is a cross sectional view through a second embodiment of the present pressure regulator. Description of Preferred Embodiments Embodiments of the inventive pressure regulator unit 10, or simply pressure regulator, for pressurized gaseous fuel is described below. The present pressure regulator unit 10 has been developed for hydrogen engines, CNG engines or fuel cell gas. A first embodiment is represented in Figs 1 to XX. The pressure regulator unit 10 comprises a body 12 with a gas passage 14 extending between an inlet section 16 for receiving the gaseous fuel at a high pressure and an outlet section 18 from which the gaseous fuel is discharged. The gas inlet 16 is in communication with a high-pressure fuel tank system (not shown) and the gaseous fuel is discharged through the outlet section 18 towards a fuel rail assembly (not shown) e.g. at around 3 to 40 bar, and up to 60 bar, depending on the application. The body 12 is made of metal, e.g. stainless steel, and may have any appropriate outer shape. In the embodiment the body 12 has a generally cylindrical shape extending along an axis A, whereby the body 12 has a first end 12.1, a second end 12.2 and a side 12.3. The inlet section 16 is located at the first end 12.1 of the body 12, from which the passage 14 defines a high-pressure section or chamber 20, followed by a control section 22, and then the outlet section 18. As will be explained in detail, the control section 22 is designed, in cooperation with a valve member 30, to perform the pressure regulator function, namely by moving the valve member 30 axially relative to control section 22. The control section 22 is a part of the passage 14 and is configured to define several (here three) contiguous sections, namely a cylindrical section 24, an intermediate section 26 and a sealing section 28, through which gas may flow from the inlet section 16 to the outlet section 18. In the embodiment, the cylindrical section 24 is a straight cylinder with circular crosssection, i.e. its diameter D1 is constant along axis A. The annular sealing section 28 surrounds the cylindrical section 24 and is axially separated from the cylindrical section 24 by the intermediate section 26. The sealing section 28 and intermediate section 26 are both designed as conical section, the sealing section having an aperture angle As which is greater than the aperture angle Ai of the intermediate section 24, i.e. As>Ai. For example, Ai may lie between 40 and 60°; As may lie between 30 and 80°; where As>Ai. In other words, on the side of the valve member 30, the cylindrical section 24 opens in a diverging intermediate section 26, and further axially on a wider sealing section 28. Hence, the control section 22 has a structured cross-section along axis A. The valve member 30 exhibits, in turn, a structured profile designed to cooperate with the control section 22 to define a plurality of regulating configurations or modes, which allow different throttling possibilities. The valve member 30 is here formed by the end of a pintle 29 (shown in part), which is reciprocally moveable along axis A and associated with an actuator (not shown). Valve member 30 comprises a cylindrical tip portion 32 surrounded at its base by a tapered (or flared) section 34 connecting pintle 29. The tip portion 32 is provided for pre-guiding. In this embodiment, the flared section 34 has a base diameter that corresponds to the pintle outer diameter, and tapers down axially towards cylindrical tip portion 32. The flared section 34 is preferably frustoconical with an aperture angle A3, but could be cylindrical. The cylindrical tip portion 32 has a circular cross-section with diameter D2 (e.g. about 2 to 5 mm). Diameter D2 corresponds to diameter D1, with a controlled annular clearance, e.g. in the order of 1 to 50 pm in diameter, in particular less than 20 pm or less than 15 urn. At its end face the cylindrical tip portion 32 is provided with an end cone 36. The axially most distal part of the cylindrical tip portion 32, with regard to the flared section 34, is referred to as front edge 38. An annular sealing element 40 is provided in the flared section 34. The annular sealing element 40 is engaged into an annular groove (not shown) and has an outer peripheral shape that generally follows the slope angle of the flared section 34. The annular sealing element 40 is made of polymer, e.g. PTFE EPDM. In general polymer is selected for material compatibility with the gas. In Fig.1 the valve member 30 is in the closed position, i.e. gas cannot flow from the inlet section 16 to the outlet section 18. The cylindrical tip portion 32 is engaged in the cylindrical section 24. The flared section 34 and sealing element 40 are in contact with the sealing section 28, thereby closing the valve seat regulator in gastight manner. Advantageously, the annular sealing element 40 is configured to be compressible and so that at least part thereof slightly protrudes relative to the flared section. Accordingly, in the closed position, the annular sealing element 34 is pressed against the sealing section 28. Preferably, the sealing element 40 is arranged such that in the closed position, it overlaps the sealing section 28 and intermediate section 26. As can be seen in Fig. 1, in the closed position the sealing element 40 is axially positioned to bridge from the sealing section 28 over to the intermediate section 26. In the embodiment, the sealing element 40 is approximately centered on the edge junction between the intermediate and sealing sections 26, 28, corresponding to position L2. It will be appreciated that the design of the present pressure regulator 10 provides for three regulation modes, defined by the axial position of the valve member 30. Axial positions are indicated in the drawings: - L0: closed position; - L1: edge junction between cylindrical section 24 and intermediate section 26; - L2: edge junction between intermediate section 26 and sealing section 28; - L3: end of sealing section 28 in lift off direction. The first regulation mode corresponds to a minimal flow. When the valve member 30 lifts off from the closed position (pintle position L0), the flared section 34 and sealing element 40 will separate from the sealing section 28, hence enabling flow through the control section 22. It should be noted that during this first part of the opening stroke, the flow cross-section is defined by the annular clearance Go existing between the cylindrical portion 32 and the cylindrical section 24. Therefore, the cylindrical portion 32 is configured to have a predetermined length. This minimum flow exists as the valve member 30 is moved axially in opening direction (to the left in the figures) from L0 up to position L1 (Figs.5 is the end position of this first mode). The second regulation mode starts when the front edge 38 of the valve member 30 passes beyond the edge junction between the cylindrical section 24 and intermediate section 26 at L1. From there, the flow cross section is defined by the distance / gap Gi between the front edge 38 of the valve member 30 and the intermediate section 26, see Fig.6.. The third regulation mode then enters into play when the front edge 38 of the valve member passes beyond the edge junction between the intermediate section 26 and the sealing section 28 at L2. From there, the flow cross section is defined by the gap / distance G2 between the front edge 38 and the sealing section 28. A fourth regulation mode is entered when the valve member 30 is moved axially to the point where the gap G2 between the front edge 38 and passage 14 is such that the defined flow cross section is greater than the cross-section area of section 24 (diameter Di). This is the configuration allowing maximum flow rate. To recap, the inventive regulator 10 provides for four regulating modes that depend on the axial position of the valve member 30 relative to the control section 22: Mode 1 : a constant, minimum flow exists as the valve member front edge 38 is located between axial positions L1 and L0 (excluding the closed position). Mode 2 - intermediate flow: flow cross-section is determined by axial position along intermediate section 26, i.e. between L1 and L2; Mode 3 - second intermediate flow: flow cross-section is determined by axial position along sealing section 28, i.e. beyond L2 in opening direction. Mode 4 - full flow: valve member position is moved to a position where the distance with respect to sealing section 28 (or passage 14) defines a greater flow area than cylindrical section 24. This is the full flow and may occur between L2 and L3, or even beyond L3, depending on the geometry. In operation, the axial position of the valve member 30 is adjusted relative to the valve cross-section to achieve a desired flow rate. The valve member 30 is thus moved to define a certain flow-cross section. An advantage of the present design is that a stable minimum flow cross-section exists over a certain axial distance in the vicinity of the closed position; this is mode 1. The axial extent of mode 1 corresponds to the distance L0-L1 and hence to the axial length of the cylindrical portion 32. In practice, the cylindrical portion 32 may e.g. have an axial length of between 0.25 and 1 mm, although other dimensions can be adopted by those skilled in the art. The actuator is typically arranged on the outlet side (left side in the figures), i.e. on the downstream side. The actuator is configured to selectively move the valve element 30 along axis A to achieve a desired downstream gas pressure. In practice, the actuator is operated by means of a control unit, which receives a pressure signal from a pressure sensor arranged to measure the pressure downstream of the control section. The pressure sensor may be arranged in the outlet section 18 or in a component downstream of the pressure regulator 10. Although not shown, a spring is typically arranged around the pintle 29 to bias the valve member 30 in closing position. Fig. 8 represents another embodiment similar to that of Figs. 1 to 7, however the cylindrical section opens directly on a frustoconical sealing section 28’ with unique aperture angle. One could also say that this corresponds to a configuration of the first embodiment where As=Ai. In this case, there is only three regulation modes: Mode 1 : a constant, minimum flow exists as the valve member front edge 38 is located between axial positions L1 and L0 (excluding the closed position). Mode 2 - intermediate flow: flow cross-section is determined by axial position along sealing section 28, i.e. Gap Gi between L1 and L2’. Mode 3 - full flow: valve member position is moved to a position beyond L2’, where the gap Gi with respect to sealing section 28 (or passage 14) defines a greater flow cross-section than cylindrical section 24. This is the full flow.

Claims

1. A pressure regulator for a gas injection system of an internal combustion engine comprisinga regulator body (12) with a gas passage (14) extending between an inlet section (16) for receiving gaseous fuel at a high pressure and an outlet section (18);a control section (22) in the gas passage, the control section including a valve seat (28) surrounding said gas passage and cooperating with a valve member (30), said valve member being moveable axially between a closed position in which said valve member is applied onto said valve seat preventing flow of gaseous fuel therethrough, and one or more open positions off said valve seat;characterized in thatsaid control section comprises a straight cylindrical section (24) opening on a diverging section defining said valve seat (28);said valve member comprises a cylindrical portion (32) axially protruding from a tapered portion (34);wherein in a closed position of said valve member the cylindrical portion (32) thereof is clearance fitted in said cylindrical section (24) and the tapered portion (34) rests against said diverging section (28);wherein the pressure regulator is selectively operable:in a first mode, in which said valve member is off said valve seat, the cylindrical portion being partially engaged inside the cylindrical section, whereby the flow cross-section is defined by an annular gap (Go) between the cylindrical section and the cylindrical portion;in a throttling mode, in which the valve member is axially positioned such that the flow cross-section is defined by an annular gap (Gi) between the front end of the cylindrical portion and the diverging section, said flow cross section being however smaller than the cross section of the cylindrical section (24); andin an open mode, in which the valve member is axially positioned such that the flow cross-section, defined by the annular gap (G2) between the front end of thecylindrical portion and the diverging section, is larger than the cross section of the cylindrical section (24).

2. The pressure regulator as claimed in claim 1, whereinsaid diverging section comprises a first sub-section(26) connecting on one side the cylindrical section and one the opposite side a second sub-section (28),wherein the second sub-section (28) has a wider opening than the first subsection (26) and defines said valve seat;wherein in said throttling mode the valve member is axially positioned such that the flow cross-section is defined by the annular gap (G2) between the front end of the cylindrical portion and the first sub-section or the second sub-section.

3. The pressure regulator as claimed in claim 1 or 2, wherein an annular sealing element (40) is arranged between the cylindrical portion and the tapered section, said sealing element engaging the diverging section, resp. second sub-section, in closed position.

4. The pressure regulator as claimed in claim 2, wherein the sealing element is configured such that in closed position, it overlaps the first and second subsections.

5. The pressure regulator as claimed in claim 2, 3 or 4, wherein said sealing element has a peripheral shape that generally follows the slope angle of the tapered portion and preferably radially protrudes relative to the tapered portion.

6. The pressure regulator as claimed in any of claims 2 to 5, wherein said annular sealing element has a circular or trapezoidal cross-section; and / or is mounted to, or overmolded on, the tapered portion.

7. The pressure regulator as claimed in any of claims 2 to 6, wherein the first and second sub-sections are conical, the second sub-section having a broader aperture angle than the first sub-section.

8. The pressure regulator as claimed in any of the preceding claims, wherein the cylindrical portion has an axial length of between 0.25 and 1 mm.

9. The pressure regulator as claimed in any of the preceding claims, wherein a conical tip (36) protrudes from the front end of the cylindrical portion.

10. The pressure regulator as claimed in any of the preceding claims, comprising an actuator associated with the valve member to axially move the latter.

11. The pressure regulator as claimed in claim 10, wherein the actuator is axially arranged with respect to the regulator body on the side of the outlet section.

12. A gas delivery system for an internal combustion engine powered with gaseous fuel, the gas delivery system comprising a fuel rail, a set of injectors and a pressure regulator according to any of the preceding claims; and a control unit configured to selectively move the valve member to achieve a desired downstream pressure, the control unit receiving a downstream gas pressure signal from a pressure sensor.

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