Injector system comprising injector for injecting a gaseous medium

Abstract

The invention relates to an injector system comprising 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 centrally located in a cylinder head (15) with respect to the combustion chamber roof (16) or to the combustion chamber (20). The injector (1) comprises, inter alia, 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) positioned downstream of the sealing seat (7) in terms of flow. According to the invention, the flow-influencing geometry (10) is formed in an attachment body (8), the attachment body (8) is cap-shaped and has a lateral region (21) and a base region (22), and the base region (22) is provided as a peripheral annular edge of a through-opening (25). The through-opening (25) expands conically, has an angle (U), and in the process continues the conicity of the valve seat (3) with a seat angle (S), wherein S > U.

Description

[0001] Description

[0002] title for blowing in a

[0003] Medium

[0004] State of the art

[0005] 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.

[0006] 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).A gas nozzle for a gas valve is already known from DE 10 2021 206 438 A1, 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.

[0007] 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, comprises 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.

[0008] Disclosure of the invention

[0009] 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.

[0010] This is achieved according to the invention in that the injector has a valve closing element for opening and closing at least one opening at 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.

[0011] Advantageously, the injector is arranged centrally in a cylinder head with respect to the combustion chamber roof or the combustion chamber. 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 peripheral edge of a through-opening, wherein the through-opening extends conically and has an angle and thereby continues a conicity of the valve seat with a seat angle, wherein the angle of the through-opening is smaller than the seat angle. The injector according to the invention can generate a hollow conical injection jet with a blow cone angle such that

[0012] No Coanda effect occurs in the injection jet. There is sufficient space inside and outside the fuel gas blow cone for a compensating air flow to balance the entrained air.

[0013] The subclaims describe preferred developments of the invention.

[0014] 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 very flexible use of sleeves or attachment bodies on injectors in various combustion chamber geometries of internal combustion engines.

[0015] In the case of combustion chamber roofs which have a continuously varying roof angle over the circumference, it can be of great advantage if the angle of the passage opening in the base area of ​​the attachment body also varies in a continuous manner.

[0016] 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 the combustion chamber of an internal combustion engine.

[0017] drawing

[0018] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings. Figure 1 shows a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art.

[0019] Figure 2 is a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art,

[0020] Figure 3 is a schematic sectional view of an injection system with an injector according to the invention for injecting a gaseous medium according to a first embodiment,

[0021] Figure 4 is a schematic detailed view of a downstream valve end with a cap-shaped attachment body according to the first embodiment,

[0022] Figure 5 is a schematic detailed view of a downstream valve end with a cap-shaped attachment body according to a second embodiment,

[0023] Figure 6 is a schematic sectional view of an injection system with an injector according to the invention for injecting a gaseous medium according to a third embodiment and

[0024] Figure 7 is a schematic sectional view of a section along the line VII - VII through the injection system in Figure 6.

[0025] Preferred embodiments of the invention For a better understanding of the invention, 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 a mixture-compressing spark-ignition internal combustion engine, for example, is described below with reference to Figures 1 and 2.

[0026] Figures 1 and 2 show a schematic section of the known injector 1 for injecting a gaseous medium, 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 directed to the flow-influencing geometry 10 (Figures 3 to 7) arranged downstream of the valve seat 3 in terms of flow technology, only the area around the sealing seat 7 is described in more detail here for the known injector 1. For actuating the injector 1, for example, a magnetic actuator (not shown) is provided, so that the injector 1 can be controlled in a targeted manner.

[0027] 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.

[0028] The injection jet of an injector 1 for injecting fuel gas into the combustion chamber 20 of an internal combustion engine should be designed so that the fuel gas mixes optimally 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 inlet 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.

[0029] In known injectors 1 according to Figures 1 and 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 and inner surfaces of the hollow cone-shaped jet. On the outer gas jet surface, a flow develops 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 develops.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 symbolized by a in Figure 1. The injection jet 17 penetrates the combustion chamber 20 in a largely cylindrical manner and mixes poorly with the surrounding air. Subsequent combustion may therefore be incomplete. This may result in more harmful exhaust gases, particularly NOx, and the internal combustion engine will experience lower efficiency.

[0030] The injector 1 according to Figure 2, for example, has an unfavorably large blowing angle. Here, too, air is entrained both inside and out by the injection jet 17. The large blowing angle creates a compensating air flow inside. This compensating air flow does not exist 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 outside, which is marked with . 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, more harmful exhaust gases and poor engine running.

[0031] 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.

[0032] Figures 3 to 7 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.

[0033] The injector 1 according to the invention, as shown in Figures 3 and 4, can generate a hollow-conical injection jet 17 with a blow cone angle B such that no Coanda effect occurs on the outside or inside. Sufficient space is provided on the inside and outside of 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 direction of flow.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 with 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 peripheral edge of a through opening 25.

[0034] The fuel gas blow cone angle B corresponds to the angle U of the through-opening 25 in the base region 22 of the attachment body 8. This angle B or U is approximately half the size of the roof angle of the combustion chamber roof 16 of the internal combustion engine, which delimits the combustion chamber 20. In the exemplary embodiment shown, the following values ​​apply: average roof angle D: 160°, angle U on the attachment body 8: 0.3 x D to 0.75 x D, here 50° to 120°, preferably approximately 80°, blow cone angle B: 0.3 x D to 0.75 x D, here 50° to 120°, preferably approximately 80°. The seat angle S of the valve seat 3 on the nozzle body 2 is greater than the blow cone angle B according to the invention or the angle U of the attachment body 8. The desired large gas cross-section at the valve seat 3 in an injector 1 opening with a certain stroke speaks in favor of a relatively large seat angle S, which results in a high desired gas throughput.

[0035] 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. The edge angle K shown in Figure 4 on the flow influencing geometry 10 in the base area 22 of the attachment body 8 can be acute, right-angled, or blunt and can be in the range from 30° to 120°, preferably between 75° and 105°. 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 mounting bore for the injector 1 in order to transfer as little heat as possible to the injector tip.In this way, a robust and wear-resistant valve seat 3 can be created. The base region 22 of the sleeve- or cap-shaped attachment body 8 has an axial height corresponding 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 level with the end face of the valve closing element 5, or slightly above or below it.

[0036] 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.

[0037] A second embodiment of the invention is shown in Figure 5. In contrast to the embodiment shown in Figures 3 and 4, the plate-shaped end section 6 of the valve closing element 5 has a layer 24 made of an insulating material such as ceramic or a

[0038] Ceramic composite material. This reduces the combustion-related heat input to the valve seat 3 via the valve closing element 5. The plate-shaped end section 6 of the valve closing element 5 has a conical bevel on its outer contour, which has an angle Z that approximately corresponds to the blow cone angle B or the angle U of the through opening 25 in the base region 22 of the attachment body 8.

[0039] Figures 6 and 7 show a further exemplary embodiment which is characterized in that the roof angle D of the combustion chamber roof 16 is not constant over 360° and therefore varies. Figure 7 shows a schematic sectional view of a section along the line VII - VII in Figure 6. It can be seen that, viewed in different directions over the circumference, there are different roof angles D which are designated by D1 and D2 as an example. In reality, due to the continuous course of the combustion chamber roof 16, there are innumerable different angles D, where D1 denotes the smallest roof angle and D2 the largest roof angle. The varying roof angles D are, for example, between 150° and 180°. In accordance with this variability, the angle U of the through-opening 25 in the base region 22 of the attachment body 8 can also vary over the circumference, where the angle U, for example,appropriately to the roof angle D, the angle U varies along the circumference (U1, U2). The through-opening 25 in the base region 22 of the attachment body 8 will advantageously also continuously change its angle U. Segmentation of the through-opening 25 is also conceivable.

[0040] 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.

Claims

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) is arranged in a cylinder head (15) with respect to the combustion chamber roof (16) orof the combustion chamber (20) is arranged centrally, and 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) in terms of flow technology, characterized in 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) widens conically and has an angle (U) and in this case continues a conicity of the valve seat (3) with a seat angle (S) and S > U applies.

2. Injection system according to claim 1, characterized in that with the injector (1) a hollow conical injection jet (17) with a blow cone angle (B) can be injected into the combustion chamber (20).

3. Injection system according to claim 2, characterized in that the blowing cone angle (B) corresponds to the angle (U) of the through opening (25) in the bottom region (22) of the attachment body (8).

4. Injection system according to claim 2 or 3, characterized in that the combustion chamber roof (16) of the cylinder head (15) has a mean roof angle (D) and the following applies to the relationship between roof angle (D) and angle (U) on the attachment body (8): 0.3 x D < U < 0.75 x D.

5. Injection system according to claim 4, characterized in that the angle (U) of the through opening (25) in the bottom region (22) of the attachment body (8) has a size of 50° to 120°, preferably approximately 80°.

6. Injection system according to claim 4 or 5, characterized in that the roof angle (D) of the combustion chamber roof (16) is between 150° and 180°.

7. Injection system according to one of claims 4 to 6, characterized in that, viewed over the circumference, the combustion chamber roof (16) has a constant roof angle (D) or there is a continuous course of changing roof angles (D).

8. Injection system according to one of the preceding claims, characterized in that, viewed over the circumference, the angle (U) of the through-opening (25) in the bottom region (22) of the attachment body (8) is constant or there is a continuous course of changing angles (U).

9. Injection system according to one of the preceding claims, characterized in that the valve closing element (5) has a conical bevel at a plate-shaped end section (6) on the outer contour with an angle (Z) which preferably corresponds to the angle (U) of the through opening (25) in the bottom region (22) of the attachment body (8).

10. Injection system according to one of the preceding claims, characterized in 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).

11. Injection system according to one of the preceding claims, characterized in 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.

12. Injection system according to claim 11, characterized in that the valve closing element (5) has a layer (24) made of an insulating material such as ceramic or a ceramic composite material at its end section (6) towards the combustion chamber (20).

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