Injection system with an injector for injecting a gaseous medium

Abstract

The present invention relates to an injection system with an injector (1) for injecting a gaseous medium, in particular a gaseous fuel, preferably hydrogen, into a combustion chamber (20) of an internal combustion engine. The injector (1) is arranged centrally, for example, in a cylinder head (15) with respect to a combustion chamber roof (16) or the combustion chamber (20). The injector (1) comprises, among other things, an axially movable valve closing element (5) for opening and closing at least one opening on a sealing seat (7), an actuator for actuating the valve closing element (5), and a flow-influencing geometry (10) arranged downstream of the sealing seat (7).According to the invention, the flow influencing geometry (10) is formed in an attachment body (8), wherein the attachment body (8) is cap-shaped and has a jacket region (21) and a base region (22), and the base region (22) is present as an annular circumferential edge of a through-opening (25), wherein the through-opening (25) has a plurality of circumferentially alternating segment regions (24, 24a, 24b) as a segment attachment nozzle, wherein the angles (U, U1, U2) of at least two segment regions (24, 24a, 24b) differ.

Description

State of the art

[0001] The present invention relates to an injection system with an injector for injecting a gaseous medium, in particular a gaseous fuel, into the combustion chamber of an internal combustion engine. Specifically, the invention relates to an injector with which hydrogen can be injected directly into the combustion chamber of a mixture-compressing, spark-ignition internal combustion engine.

[0002] Gas injectors are known from the state of the art in various designs. Due to cost advantages and improved environmental compatibility, gaseous fuels have recently become increasingly popular. Compared to injectors for liquid fuels, the injected gas volume occupies a much larger volume than an equivalent amount of liquid fuel. This results in an increased stroke requirement for a closing element, which is usually actuated by a magnetic actuator. Designing a magnetic circuit using standard materials is very difficult or sometimes impossible due to the limited installation space. Materials with higher magnetic force are very expensive and sometimes harmful to health (e.g., FeCo).

[0003] DE 10 2021 206 438 A1 already discloses a gas nozzle for a gas valve, which comprises a nozzle body that is at least partially hollow-cylindrical in shape and forms a sealing seat over which a gas flow path leads. Furthermore, the gas valve has a valve-closing element that is partially accommodated in the nozzle body and has an end section that is arranged outside the nozzle body and has a sealing contour that interacts with the sealing seat. Furthermore, the gas valve has a sleeve that surrounds the nozzle body and the end section of the valve-closing element and delimits the gas flow path downstream of the sealing seat. The gas flow path downstream of the sealing seat has a cross-sectional constriction to achieve the Venturi effect, in the region of which at least one intake channel opens. The sleeve is designed in the form of a blow cap that can be applied to the nozzle body.

[0004] Another injector for injecting a gaseous medium is also known from WO 2023 / 001384 A1. The blow cap, which can be placed on a nozzle body, has a sleeve-shaped base body with a circumferential surface that merges into a base region at the downstream end. The base region is designed such that at least one obliquely or asymmetrically discharging outlet opening is provided. Furthermore, a flow guide section directed inward toward the valve closing element, counter to the flow direction, is formed in the base region, which deflects the gas to be discharged. Disclosure of the invention

[0005] The injection system according to the invention with an injector for injecting a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine, with the features of claim 1 has the advantage that an optimized gas flow in the injector is made possible by geometric design of a flow influencing geometry arranged downstream of the sealing seat, so that the internal flow of the gaseous medium is designed to be as loss-free as possible via the inner contour of the cap-shaped attachment body, so that the back pressure located below, i.e. downstream of the valve closing element, is reduced and at the same time the injection jet can be introduced into the combustion chamber in a targeted manner.

[0006] This is achieved according to the invention in that the injector has a valve closing element for opening and closing at least one opening on a sealing seat. The valve closing element is preferably an axially movable valve needle with a plate-shaped end section. Furthermore, an actuator is provided for actuating the valve closing element. The actuator is preferably a magnetic actuator, but can also be, for example, a mechanically or (piezo-) electrically operated actuator. Further preferably, the actuator is configured to actively open the valve closing element by means of a lifting movement and to keep it open, while the valve closing element is closed by a spring force.

[0007] Advantageously, the flow influencing geometry is formed in an attachment body, wherein the attachment body has a jacket region and a base region and the base region is present as an annular circumferential edge of a through-opening, wherein the through-opening has a plurality of circumferentially alternating segment regions as a segment attachment nozzle, wherein the angles of at least two segment regions differ.

[0008] In this way, numerous gas jet streamers can be advantageously generated in a hollow cone jet on radially spaced pitch circles. This is because the hollow cone jet is fanned out due to the geometry of the segmented areas. This increases the surface area of ​​the fuel gas jet to the combustion chamber air and improves the combustion chamber's permeation with fuel gas. This ensures better mixing of the fuel gas with the combustion chamber air. The thus better mixed fuel gas burns with fewer pollutants and ensures greater efficiency of the combustion engine.

[0009] Hydrogen combustion engines are typically operated lean (e.g., λ=2). Incomplete mixing of the fuel gas results in the disadvantage of richer gas mixtures in the combustion chamber. These richer regions then produce more harmful NOx during combustion, which is prevented by the measures according to the invention.

[0010] A further advantage of the segmented injection jet is that the gaps between the individual gas jet strands allow for pressure equalization between the outside and inside of the hollow cone jet. The segmented injection jet is less deflected, thus creating better penetration of the fuel gas into the combustion chamber air.

[0011] The injector according to the invention can generate a hollow-conical injection jet with a medium cone angle such that no Coanda effect occurs on the outside or inside of the injection jet. Sufficient space is provided on the inside and outside of the fuel gas cone for a compensating air flow to compensate for the entrained air.

[0012] The subclaims describe preferred developments of the invention.

[0013] This inner contour of the attachment body, defined according to the invention, with its special features in shape and design, can be advantageously accommodated in attachment bodies with reducible external dimensions. This, in turn, enables a very flexible use of sleeves or attachment bodies on injectors in various combustion chamber geometries of internal combustion engines.

[0014] Advantageously, the injector is arranged centrally in a cylinder head with respect to the combustion chamber roof or the combustion chamber.

[0015] The present invention is preferably used in injection systems that inject hydrogen directly into a combustion chamber. In particular, the injector is suitable for directly injecting hydrogen into a combustion chamber of an internal combustion engine. drawing

[0016] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings. Fig. 1 a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art, Fig. 2 a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art, Fig. 3 a schematic sectional view of the downstream valve end of an injector according to the invention for injecting a gaseous medium according to a first embodiment, Fig. 4 a schematic detailed view of the downstream valve end with a cap-shaped attachment body according to the first embodiment, Fig. 5 a symbolic and idealized representation of the distribution of gas jet strands that can be achieved by means of the cap-shaped attachment body and Fig. 6 an enlarged detailed view of the cap-shaped attachment body in a perspective view. Preferred embodiments of the invention

[0017] For a better understanding of the invention, the following is based on the Fig. 1 and Fig. 2 the basic structure of an injection system with at least one injector 1 for injecting a gaseous medium, in particular hydrogen, into a combustion chamber 20 of, for example, a mixture-compressing spark-ignition internal combustion engine is described.

[0018] In the Fig. 1 and Fig. 2, the known injector 1 for injecting a gaseous medium is shown schematically in section with its downstream valve end. The injector 1 has a valve seat 3, with which a valve closing element 5 cooperates to open and close a sealing seat 7. Since the invention is based on the flow-influencing geometry 10 ( Fig. 3 to 6), only the area around the sealing seat 7 is described in more detail here for the known injector 1. For actuating the injector 1, a magnetic actuator (not shown) is provided, for example, so that the injector 1 can be specifically controlled via this.

[0019] The injector 1 also has a nozzle body 2, which on the injection side forms the already mentioned, e.g. conically shaped valve seat 3 for the valve closing element 5, which opens outwards, i.e. in the direction of the combustion chamber 20. The valve closing element 5 is guided axially movably within the nozzle body 2, e.g. via a guide 18. In addition, the valve closing element 5 has an end section 6 in the form of a valve disk, which ultimately forms the sealing seat 7 corresponding to the valve seat 3. The two sealing seat partners, valve seat 3 and valve closing element 5, are each made of metal. The geometric and material design is such that sufficient tightness is guaranteed during operation of a hydrogen engine.In the event of a fault, a shut-off system (not shown here) installed upstream of the injector 1 for safety reasons would interrupt the supply of the gaseous medium, particularly the highly volatile hydrogen. The sealing contour of the end section 6 of the valve closing element 5 is, for example, rounded or conical, while the valve seat 3 on the nozzle body 2 has a conical shape. However, other contours are also conceivable.

[0020] The injection jet of an injector 1 for injecting fuel gas into the combustion chamber 20 of an internal combustion engine should be designed to ensure optimal mixing of the fuel gas with the air in the combustion chamber 20. Therefore, in the figures, in addition to the injector 1, the combustion chamber 20 is also schematically indicated. Furthermore, two gas exchange valves 11, 12 are symbolically represented, while a spark plug is omitted. The gas exchange valves 11, 12 are arranged as intake and exhaust valves in a cylinder head 15, with the closing plates of the gas exchange valves 11, 12 having their sealing seat in a combustion chamber roof 16 of the cylinder head 15.

[0021] For known injectors 1 according to the Fig. 1 and Fig. 2 Without any measures to influence the flow downstream of the sealing seat 7, unfavorable small or large blow angles at the injector 1 can characterize the injection jet 17. The injection jet 17, indicated by arrows, has the shape of a hollow cone, which is typical for known injectors 1 with an outward-opening valve closing element 5 and a conical nozzle design. The injection jet 17 entrains the surrounding air on the outer surface and inner surface of the hollow cone-shaped jet. On the outer gas jet surface, a flow is created in the space between the combustion chamber roof 16, the cylinder wall 19, and the injection jet 17, which compensates for the entrained air. Air is also entrained on the inner surface of the gas jet. Due to the small jet angle and small diameter of the inner surface, no compensating air flow is created.This creates a negative pressure inside the injection jet 17, which draws the injection jet 17 radially inward into an almost cylindrical shape. The negative pressure is indicated by a "-" in the . Fig. 1. The injection jet 17 penetrates the combustion chamber 20 in a largely cylindrical manner and mixes poorly with the surrounding air. As a result, subsequent combustion may be incomplete. This may result in increased harmful exhaust gases, particularly NOx, and the internal combustion engine will experience reduced efficiency.

[0022] The injector 1 according to Fig. 2, for example, has an unfavorably large blowing angle. Here, too, air is entrained on the outside and inside by the injection jet 17. The large blowing angle creates a compensating air flow on the inside. This compensating air flow does not exist on the outside because the space between the injection jet 17 and the combustion chamber roof 16 is too small. In this case, a negative pressure is created on the outside, which is marked with a "-". Due to this effect, the injection jet 17 has an even larger blowing angle than when it exits at the sealing seat 7 of the injector 1. This behavior of the injection jet is called the Coanda effect. This injection jet also only captures a small portion of the air in the combustion chamber 20. In this case, too, there is insufficient mixing and more harmful exhaust gases and poor engine running.

[0023] Therefore, the object of the invention is to provide a flow influencing geometry 10 which is arranged downstream of the sealing seat 7 in terms of flow technology and with which optimal combustion results are achieved due to the flow guidance according to the invention.

[0024] Fig. Figures 3 to 6 show inventive designs of injection systems or injectors 1, with which advantageous gas jet angles can be achieved and the previously described negative effects are avoided. Here, an air flow is created on the outside and inside of the hollow cone jet, which compensates for the air entrained by the fuel gas blowing vane. The jet angle remains approximately the same near and far from the injector. The fuel gas mixes well with the air, and the combustion heat is effectively converted into piston work. The internal combustion engine produces little harmful exhaust gas and is highly efficient.

[0025] The injector 1 according to the invention according to Fig. 3 and Fig. 4 can generate a hollow conical injection jet 17 in such a way that no Coanda effect occurs outside or inside. The injection jet 17 has a plurality of gas jet strands, which are Fig. 5. Sufficient space is provided inside and outside the fuel gas blow cone for a compensating air flow to compensate for the entrained air. Advantageously, the injector 1 now has a sleeve-shaped attachment body 8 that is securely and firmly attached to the downstream valve end of the nozzle body 2. The attachment body 8 can also be referred to as a "blower cap" and has a flow-influencing geometry 10 that is characterized in particular by a conicity that continues a conicity present on the nozzle body 2 due to the valve seat 3 in a manner that widens in the flow direction. Furthermore, the attachment body 8 is characterized in particular by the fact that it represents a segmented attachment nozzle for generating gas jet streamers.The attachment body 8 has a jacket region 21 and a base region 22, which extend largely perpendicular to each other, wherein the fixed connection to the nozzle body 2 takes place in the jacket region 21 and the base region 22 only defines the flow influencing geometry 10 as an annular circumferential edge of a through opening 25.

[0026] The base region 22 of the attachment body 8 is designed with multiple segments, i.e. segment regions 24 of the through-opening 25 in the base region 22 of the attachment body 8 have angles U of different sizes alternating over the circumference. In the illustrated embodiment, twenty-four segment regions 24 are provided, with twelve segment regions 24a having an angle U1 and twelve segment regions 24b having an angle U2 in the through-opening 25. These alternate regularly around the circumference with the same size and with constant angles U1, U2. In the present case, two partial circles result for the segment regions 24, with the radially outer segment regions 24a having the angle U1 and the radially inner segment regions 24b having the angle U2 and U1 > U2. The angles U of the segment regions 24, 24a, 24b of the through-opening 25 in the base region 22 of the attachment body 8 have a size of 50° to 120°.

[0027] The attachment body 8, as a segmented nozzle, can ideally have between four and forty segment regions 24, preferably between seven and twenty segment regions 24. It is also conceivable to represent not only two different angles U across the segment regions 24 of the through-opening 25 in the base region 22 of the attachment body 8, but also angles U3, U4, etc. Furthermore, depending on the desired particular strand geometry and spread, the segment regions 24 do not have to be of constant size or at the same distance from one another. However, each pitch circle of the differently angled segment regions 24 should have a conically widening contour. Theoretically, radially inner segment regions 24 can also run without an angle, i.e., parallel to the longitudinal valve axis.

[0028] The mean blow cone angle largely corresponds to the mean size of the various angles U1, U2,... of the through-opening 25 in the base region 22 of the attachment body 8. The seat angle S of the valve seat 3 on the nozzle body 2 is greater than the mean blow cone angle or the size of the largest angle U1 of the attachment body 8 according to the invention, so that S > U1 applies. The desired large gas cross-section at the valve seat 3 with an injector 1 opening with a specific stroke speaks in favor of a relatively large seat angle S, which results in a high desired gas throughput.

[0029] The attachment body 8 is firmly connected to the nozzle body 2, e.g., by welding, gluing, pressing, or screwing. The attachment body 8 is made of metal or ceramic. A ceramic material has the advantage that the heat input from the combustion phase into the seat area is lower, since ceramics have poorer thermal conductivity than metallic materials.

[0030] The valve closing element 5 can have, at its end section 6 towards the combustion chamber 20, a layer (not shown in detail) made of an insulating material such as ceramic or a ceramic composite material.

[0031] The valve end of the injector 1 with the attachment body 8 does not protrude into the combustion chamber 20 or protrudes with a slight axial overlap. Alternatively, the injector 1 can also be installed slightly retracted in the receiving bore for the injector 1 in order to transfer as little heat as possible to the injector tip. In this way, a robust and low-wear valve seat 3 can be created. The base region 22 of the sleeve- or cap-shaped attachment body 8 has an axial height that corresponds to approximately 5% to 70% of the diameter of the valve seat 3 for good ventilation. Thus, the axial end face of the attachment body 8 is approximately at the level of the end face of the valve closing element 5 or slightly above or below.

[0032] Typically, the sealing seats 7 on gas injectors are not perfectly sealed when closed. This results in a slight fuel gas leakage. However, if the valve seat 3 is well ventilated, the escaping fuel gas is distributed and diluted effectively in the combustion chamber 20. Axially longer attachment bodies 8 or flow control geometries 10 can have the disadvantage that the fuel gas continues to burn for a longer time after the combustion phase, resulting in undesirable early combustion during the subsequent injection. This early combustion, before top dead center, essentially slows down the piston movement. In addition to the unnecessarily burned fuel gas, pre-ignition places a very heavy and damaging load on the piston, connecting rod, and crankshaft.

[0033] Fig. Figure 5 shows a symbolic and idealized representation of the distribution of gas jet strands 27 in an imaginary horizontal section through the combustion chamber 20, which can be achieved by means of the cap-shaped attachment body 8 and, in the specific example, lie on two radially spaced partial circles. The radially outer gas jet strands 27a are generated by the segment regions 24a of the through-opening 25 in the base region 22 of the attachment body 8 at the angle U1, while the orientation of the radially inner gas jet strands 27b results from the contouring of the segment regions 24b of the through-opening 25 in the base region 22 of the attachment body 8 at the angle U2.

[0034] In the Fig. 6 shows an enlarged detailed view of the cap-shaped attachment body 8 in a perspective view to illustrate the segment regions 24a, 24b with at least two different angles U1, U2 of the through opening 25 of the attachment body 8.

[0035] By means of the attachment body 8, the hollow cone jet is fanned out into individual gas jet strands 27, whereby the surface area of ​​the fuel gas jet relative to the combustion chamber air is increased and the combustion chamber 20 is better permeated with fuel gas. This ensures better mixing of the fuel gas with the combustion chamber air. The thus better mixed fuel gas burns with fewer pollutants and ensures better efficiency of the combustion engine. Hydrogen combustion engines are usually operated lean (e.g., λ=2). Incomplete mixing of the fuel gas disadvantageously creates areas in the combustion chamber 20 with richer gas mixture ratios. These richer areas then generate more harmful NOx during combustion, which is avoided by the measures according to the invention.

[0036] A further advantage of the segmented injection jet 17 is that the gaps between the gas jet strands 27 allow for pressure equalization between the outside and inside of the hollow cone jet. The segmented injection jet 17 is less deflected, thus resulting in better penetration of the combustion gas into the combustion chamber air.

[0037] The invention is particularly suitable for a central installation position of the injector 1 in the cylinder head 15 and with respect to the orientation of the combustion chamber 20 or the combustion chamber roof 16. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 206 438 A1

[0003] WO 2023 / 001384 A1

[0004]

Claims

[1] Injection system with an injector (1) for injecting a gaseous medium, in particular a gaseous fuel, preferably hydrogen, into a combustion chamber (20) of an internal combustion engine delimited by a combustion chamber roof (16), wherein the injector (1) comprises an axially movable valve closing element (5) for opening and closing at least one opening on a valve seat (3), an actuator for actuating the valve closing element (5) and a flow influencing geometry (10) arranged downstream of the valve seat (3), characterized byin that the flow influencing geometry (10) is formed in an attachment body (8), wherein the attachment body (8) is cap-shaped and has a jacket region (21) and a base region (22), and the base region (22) is present as an annular circumferential edge of a through-opening (25), wherein the through-opening (25) has, as a segment attachment nozzle, a plurality of circumferentially alternating segment regions (24, 24a, 24b), wherein the angles (U, U1, U2) of at least two segment regions (24, 24a, 24b) differ. [2] Injection system according to claim 1, characterized by that the through opening (25) of the attachment body (8) extends conically widening overall and continues a conicity of the valve seat (3) with a seat angle (S) and S > U1 applies, where U1 is the largest angle of the segment areas (24a). [3] Injection system according to claim 1 or 2, characterized bythat a hollow conical injection jet (17) with a medium blow cone angle can be injected into the combustion chamber (20) using the injector (1). [4] Injection system according to one of the preceding claims, characterized by that gas jet strands (17) can be generated with the attachment body (8) of the injector (1) on at least two radially spaced partial circles. [5] Injection system according to one of the preceding claims, characterized by that the segment areas (24, 24a, 24b) of the through opening (25) alternate regularly in the same size and with constant angles (U1, U2) around the circumference. [6] Injection system according to one of the preceding claims, characterized by that the attachment body (8) has between four and forty segment regions (24, 24a, 24b) with at least two different angles (U, U1, U2) at the through opening (25). [7] Injection system according to claim 4, characterized bythat the angles (U, U1, U2) of the segment regions (24, 24a, 24b) of the through opening (25) in the base region (22) of the attachment body (8) have a size of 50° to 120°. [8] Injection system according to one of the preceding claims, characterized by that the cap-shaped attachment body (8) can be attached to a spray-side end of the injector (1), in particular to a nozzle body (2). [9] Injection system according to one of the preceding claims, characterized by that the valve closing element (5) is part of an axially movable valve needle, wherein the valve closing element (5) has an end section (6) which is largely plate-shaped. [10] Injection system according to claim 9, characterized by that the valve closing element (5) has a layer of an insulating material such as ceramic or a ceramic composite material at its end section (6) towards the combustion chamber (20). [11] Injection system according to one of the preceding claims, characterized by that the injector (1) is arranged centrally in a cylinder head (15) with respect to the combustion chamber roof (16) or the combustion chamber (20).

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