Fuel injector for a gas engine

Abstract

A fuel injector (1) for a gas engine, in particular a hydrogen engine, has a channel (4) for conveying gaseous fuel, into which a shaft (6) of a needle (5) is inserted, wherein a head (7) of the needle (5) is located at the end of the channel (4) and the inner diameter of the channel (4) widens in a funnel shape in the region of the head (7) to match the cross-sectional shape of the head (7). The corresponding region of the channel (4) is formed partly by an injector housing (2) and partly by an interchangeable end piece (9) attached to the injector housing (2), in particular by screwing it on.

Description

[0001] The invention relates to a fuel injector suitable for use in a gas engine, in particular a hydrogen engine, according to the preamble of claim 1.

[0002] A generic gas injector for injecting a gaseous fuel is known, for example, from DE 10 2014 224 344 A1. The known gas injector, i.e., fuel injector, has an outwardly opening valve closing element and a flow guide element for forming a gas jet.

[0003] EP 4 047 199 A1 discloses a fuel supply device for supplying fuel to an internal combustion engine. A primary fuel is stored, and a secondary fuel, particularly in the form of molecular hydrogen, is generated in the vehicle by means of on-board reforming. In the internal combustion engine, the primary fuel and the secondary fuel are combusted in the same way, with the secondary fuel being supplied, in particular, as a pilot fuel.

[0004] DE 10 2013 220 479 A1 relates to an internal combustion engine operable with liquid and gaseous fuel. In this case, direct injection is used to introduce gaseous fuel, while manifold injection is provided for introducing liquid fuel into the intake system of the internal combustion engine. Various injectors that enable both the injection of fuel and the injection of water into an internal combustion engine are known, for example, from documents DE 10 2017 005 162 A1 and DE 44 45 980 C2, AT 007 769 U1, EP 1 869 311 B1, and WO 2019 / 092 008 A1.

[0005] The invention is based on the object of specifying an injector which is further developed compared to the prior art and which is specifically designed for injecting gas into the intake tract or a combustion chamber of an internal combustion engine, in particular a hydrogen engine.

[0006] This object is achieved according to the invention by a fuel injector having the features of claim 1. The fuel injector, i.e. gas injector, has a channel provided for the passage of gaseous fuel, into which a needle is immersed. At the end of the channel there is a needle head which has an enlarged diameter compared to a shaft arranged concentrically in the channel. For the passage of the fuel, an area surrounding the shaft with an annular disk-shaped cross-section is thus available in the channel. Adapted to the contouring of the needle head, the inner diameter of the channel widens in a funnel shape in the region of the head, so that a free flow cross-section is maintained for the passage of the gaseous fuel.Furthermore, the section of the channel formed by the end piece opens at the front side of the end piece in the form of a Coanda geometry, wherein a tangent placed at a trumpet-like widening end section of the end piece forms an angle α of 45° ± 25° with a front plane touching the end piece.

[0007] According to claim 1, the funnel-shaped widening region of the channel is provided partly by a housing of the fuel injector and partly by an end piece attached to the housing, which, despite its shape being open on both sides, is also referred to as a cap or jet cap.

[0008] This design makes it possible, for example, to use a jet cap made of a different material than the injector housing. The channel into which the needle is immersed is formed by the housing, i.e., the injector housing. Because the contact point between the housing and the end piece lies in a widening section of the channel, the housing, like the end piece, can be contoured in such a way that the end piece does not exhibit a significant reduction in wall thickness in the contact area with the housing; in fact, the wall thickness of the end piece may even be increased in this area.

[0009] At the same time, an overlap between the end piece and the housing can exist in the housing section where the needle shaft is located, which means that the overlap area between the housing and the end piece is located in a channel section where the channel diameter is minimal. Accordingly, a large wall thickness of the housing is available in this section, so that the overlap with the end piece does not result in an excessive reduction in wall thickness, even if the outer diameter of the cylindrical housing in this area remains constant over the entire length of the channel and corresponds to the outer diameter of the end cap.

[0010] The combination of housing and end piece according to the application represents a suitable basis for combining housings of uniform dimensions with end pieces of different shapes, if necessary. End pieces of different shapes can, for example, have different outlet cross-sections. Likewise, the designs of curved contours on the open end face, which is not to be connected to the housing, can vary from end piece to end piece. Such contours, in particular, adjoin a cylindrical inner wall of the end piece and can terminate at the end face of the end piece with a sharp edge or a rounded edge. The angle at which the contour of the end piece opens in a trumpet-like manner towards its end face is referred to as the Coanda angle and is, for example, 45° ± 25°, whereby different end pieces can fill the entire specified angular range in stages.

[0011] The Coanda effect, the extent of which in this case depends particularly on the shape of the injector's end piece, generally states that a flowing liquid or gas tends to flow along a curved surface. A nozzle designed using the Coanda effect is known in principle, for example, from DE 10 2018 109 858 B4.

[0012] In various configurations, the head of the needle of the gas injector can have a cylindrical surface section arranged concentrically within a likewise cylindrical section of the inner wall of the end piece. The cylindrical surface section of the head extends, for example, to a flat end face of the head.

[0013] The connection between the end piece and the housing, in particular a housing attachment, is made, for example, in the form of a screw connection. In this case, a section of the housing is provided with an external thread and a section of the end piece with a corresponding internal thread. Stop surfaces, at which contact is established between the housing and the end piece when the end piece is screwed on, can have a conical shape. The conical contact surfaces extend from a first linear, circular contact area located in the wall of the channel to a likewise circular linear area of ​​larger diameter, which simultaneously represents one end of a cylindrical area provided with the aforementioned screw connection.

[0014] At the second end of this cylindrical section, for example, opposing annular disc-shaped surfaces of the housing and the end piece can be present. Optionally, a seal is inserted between the housing and the end piece at this point.

[0015] The injector needle can be displaced, for example, by means of an electromagnetic actuator or a piezoelectric actuator. The fuel injector can be designed either as an injector for intake manifold injection or for direct injection of gaseous fuel into a combustion chamber of an internal combustion engine, in particular a reciprocating piston engine.

[0016] An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. In the drawing: Fig. 1 a fuel injector of a gas engine in a sectional view.

[0017] A fuel injector, designated overall by reference numeral 1, is intended for use in a hydrogen-powered gas engine (not shown). In this case, the gas engine is a reciprocating piston engine of a motor vehicle. Alternatively, it could be a stationary gas engine in a combined heat and power plant.

[0018] The fuel injector 1, i.e. gas injector, has a Fig. 1 has a housing 2 that is only partially visible. The housing 2, i.e., the injector housing, includes a tubular housing extension 3, through which a channel 4 is formed through which hydrogen can flow. Any means upstream of the channel 4 for reducing the pressure of the hydrogen to be burned in the gas engine are not shown.

[0019] Located in channel 4 is a shaft 6 of a needle 5, i.e., a valve needle. Means for moving the needle 5 are also not shown. The shaft 6 has a diameter d6. The diameter of channel 4 in the section surrounding the shaft 6 is designated d4.

[0020] A head 7 of the needle 5 is connected to the shaft 6. The diameter of the head 7, designated d7, is more than three times the diameter d6 of the shaft 6 in the illustrated embodiment. The head 7 is arranged in an end piece 9, which is also referred to as a cap or jet cap and is firmly connected to the housing extension 3 by means of a screw connection 10. In the area of ​​the screw connection 10 there is an area generally referred to as the overlap area, in which the end piece 9 concentrically encloses the housing extension 3. The outer diameter of the essentially tubular end piece 9, designated d9a, corresponds to the outer diameter of the housing extension 3.

[0021] A plane located on the outlet side of the gas injector 3 at the end face of the end piece 9 represents a front plane 14. A distance a7_9 exists between this front plane 14 and the end face of the head 7, designated 13. The plane defined by the end face 13 intersects a cylindrical central section 16 of the end piece 9. The inner diameter of the end piece 9, measured in the region of the central section 16, is designated d9i and is significantly larger than the diameter d7 of the head 7, so that a free, annular disk-shaped flow cross-section remains for the gas flowing through the fuel injector 1 to be supplied to a combustion chamber of the internal combustion engine.

[0022] A cylindrical surface section 12 of the head 7 adjoins the end face 13 of the head 7. Thus, two cylindrical surfaces, namely the surface section 12 and the central section 16, which represents a section of the inner surface of the end piece 9, are concentrically opposite each other. A rounded transition in the form of a curved surface section 11 is formed between the cylindrical surface section 12 and the shaft 6. A radius of curvature given in this section 11 is designated R11.

[0023] Opposite the curved surface section 11 of the head 7 are a likewise curved inner section 17 of the end piece 9 and a likewise curved end section 18 of the housing extension 3. The inner section 17 of the end piece 9 merges seamlessly into the cylindrical central section 16 in the direction of the end plane 14. The end section 18 adjoins the straight, cylindrical section of the channel 4. The two curved sections 17, 18 abut one another, so that, viewed from the interior of the channel 4, which widens in this area, an annular, circumferential joint can be seen between the housing extension 3 and the end piece 9. This joint is the end of a frustoconical contact area between the housing 2 and the end piece 9, which is formed by a conical contact surface 19 of the housing extension 3 and a conical contact surface 20 of the end piece 20.The centering of the end piece 9 relative to the housing extension 3 results from the design of the contact surfaces 19, 20.

[0024] In the area of ​​the transition between the housing extension 3 and the end piece 9, that is to say in the area of ​​the said joint, the inner contour of the assembly comprising the housing extension 3 and the end piece 9, which delimits the channel 4, has a radius of curvature R17 which is slightly larger than the radius R11, so that an at least approximately uniform gap width, that is to say height of the channel 4, results in its widening area.

[0025] The conical contact surfaces 19, 20 extend to the essentially cylindrical outer and inner surfaces of the housing extension 3 and the end piece 9, on which the aforementioned screw connection 10 is formed. At the end of the screw connection 10 facing away from the conical contact surfaces 19, 20, there is a flat stop surface 21 of the housing extension 3 and a likewise flat stop surface 22 of the end piece 9, i.e. the jet cap to be screwed onto the housing extension 3. In order to avoid geometric overdetermination, a narrow, Fig. 1, a gap may be provided, which may optionally accommodate a seal (also not shown). It is also possible to connect the end piece 9 in the area of ​​the stop surfaces 21, 22 with a material bond, in particular by welding, to the housing extension 3. Furthermore, instead of a screw connection, pressing the end piece 9 onto the housing extension 3 is also possible.

[0026] As far as the shape of the end piece 9 is concerned, there are many design options, which in any case allow a combination with the Fig. 1. The shape of the end piece 9 may depend in particular on the shape of existing surrounding components, on the cylinder internal flow concept selected in the individual case, on the placement of the spark plug, on the valve timing, and on the boost pressure.

[0027] In the illustrated embodiment, the end piece 9 describes a so-called Coanda geometry in its area bordering the front plane 14. Here, the inner surface of the end piece 9 runs out in the form of a curved end section 15, which takes on a conical shape towards the front plane 14, i.e. Fig. 1 has a constant slope. The angle α between a tangent drawn in the section plane shown, i.e. in the longitudinal section of the channel 4, to the conical contour of the end section 15 and the front plane 14 is 45° ± 25°. In the case of angles not shown, which are opposite to the Fig. 1 visible end piece 9 of the replaceable jet caps, angles α of the Coanda contour may differ from the example shown, which in particular also lie within the stated range of 20° to 70°. Furthermore, such designs of caps 9 for the gas injector 1 (not shown) may have an inner diameter d9i, which differs from the one shown in Fig. 1 illustrated embodiment.

[0028] In the curved area of ​​the end section 15, i.e., between the front plane 14 and the cylindrical central section 16, a radius of curvature R15 exists. In this case, this radius R15 deviates from each of the previously mentioned radii R11, R17 by no more than 50% upwards or downwards. This contributes significantly to ensuring that the flow of the gas flowing through the injector 1, i.e., hydrogen, adheres to the inner surface of the end piece 9 over the entire length of the end piece, even beyond the head 7.

[0029] For the longitudinal adjustment of the needle 5 and head 7, an actuator (not shown) is provided, which operates particularly electromagnetically or piezoelectrically, but can also be mechanically driven. In the case of electromagnetic actuation, the shaft 5 can be rigidly connected to an armature of an actuator. Alternatively, it is possible to arrange the needle 5 rigidly in the housing 2, including the housing extension 3, and to provide means for releasing and blocking the gas flow at another location on the fuel injector 1. List of reference symbols 1 fuel injector, gas injector 2 Housing, injector housing 3 Housing attachment 4 channel 5 Needle, valve needle 6 shaft 7 heads 8 Exit area 9 End piece, cap, jet cap 10 screw connection 11 curved surface section of the head 12 cylindrical surface section of the head 13 Frontal surface of the head 14 Frontal plane of the cap 15 curved end section of the cap, bordering the frontal plane 14 16 cylindrical central section of the cap, inner surface 17 curved inner section of the cap 18 curved end section of the housing attachment 19 conical contact surface of the housing attachment 20 conical contact surface of the cap 21 flat stop surface of the housing attachment 22 flat stop surface of the cap α angle a7_9 Distance between the frontal surface of the head and the frontal plane of the cap d4 Diameter of the channel d6 Diameter of the shaft d7 Diameter of the head d9a Outer diameter of the cap d9i inner diameter of the central section of the cap R11 Radius of the curved surface section of the head R15 Radius of the end section of the cap R17 Radius of the inner section of the cap, adjacent to the housing neck

Claims

[1] Fuel injector (1) for a gas engine, with a channel (4) provided for the passage of gaseous fuel, into which a shaft (6) of a needle (5) is immersed, wherein a head (7) of the needle (5) is located at the end of the channel (4) and the inner diameter of the channel (4) widens in a funnel shape in the region of the head (7) in adaptation to the cross-sectional shape of the head (7), characterized by that the funnel-shaped widening region of the channel (4) is formed partly by an injector housing (2) and partly by an end piece (9) attached to the injector housing (2), and that the section of the channel (4) formed by the end piece (9) opens at the front side of the end piece (9) in the form of a Coanda geometry, wherein a tangent laid to a trumpet-like widening end section (18) of the end piece (9) encloses an angle (α) of 45° ± 25° with a front plane (14) touching the end piece (9). [2] Fuel injector (1) according to claim 1, characterized by that the end piece (9) is screwed to the housing (2), i.e. injector housing. [3] Fuel injector (1) according to claim 1, characterized by that the end piece (9) is connected to the housing (2) by a press connection. [4] Fuel injector (1) according to one of claims 1 to 3, characterized by that the end piece (9) has the same outer diameter (d9a) as that section of the housing (2) in which the channel (4) is formed. [5] Fuel injector (1) according to one of claims 1 to 4, characterized by that a surface contact is established between the housing (2) and the end piece (9) on conical contact surfaces (19, 20) of the housing (2) and the end piece (9). [6] Fuel injector (1) according to claim 5, characterized by that the conical contact surfaces (19, 20) describe a truncated cone tapering in the direction from the shaft (6) to the head (7). [7] Fuel injector (1) according to claim 6, characterized by that the conical contact surfaces (19, 20) adjoin an overlap region in which the housing (2) is connected to the end piece (9), the overlap region enclosing the channel (4) and the shaft (6) in a ring shape. [8] Fuel injector (1) according to one of claims 1 to 7, characterized by that the head (7) of the needle (5) has a cylindrical surface portion (12) which is arranged concentrically within a cylindrical central portion (16) of the end piece (9). [9] Use of a fuel injector (1) according to claim 1 in a hydrogen-powered internal combustion engine.

Images