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 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) widens conically and has an angle (U) and thereby continues a conicity of the valve seat (3) with a seat angle (S) and S > U applies.

Description

Prior ArtThe present invention relates to an injection system having an injector for injecting a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine. The invention relates in particular to an injector with which hydrogen can be injected directly into the combustion chamber of a mixture-compressing, spark-ignited internal combustion engine.Gas injectors are known from the prior art in different configurations. Because of cost advantages and improved environmental compatibility, gaseous fuels have become more popular recently. It is problematic here, in comparison with injectors for liquid fuels, that the quantity of gas to be injected takes up a much larger volume than an equivalent quantity of liquid fuel. This results in an increased stroke requirement of a closing element, which is usually actuated by a magnetic actuator. The design of the magnetic circuit using standard materials is very difficult or in some cases impossible because of the limited installation space. Materials with higher magnetic force are very expensive and in some cases harmful to health (e.g. FeCo).DE 10 2021 206 438 A1 already discloses a gas nozzle for a gas valve, which nozzle nozzle comprises a nozzle body which is at least partially hollow-cylindrical and forms a sealing seat via which a gas flow path leads. In addition, the gas valve has a valve closing element which is held in sections in the nozzle body and can move in a stroke manner, with an end section which is arranged outside the nozzle body and has a sealing contour which interacts with the sealing seat. In addition, the gas valve has a sleeve surrounding the nozzle body and the end section of the valve closing element, which sleeve delimits the gas flow path downstream of the sealing seat, wherein the gas flow path downstream of the sealing seat has a cross-sectional constriction for achieving the Venturi effect, in the region of which at least one intake duct opens. The sleeve is designed in the form of a blow cap which can be applied to the nozzle body.A further injector for blowing in a gaseous medium is likewise 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 lateral surface which merges at the downstream end into a base region. The base region is designed in such a way that at least one obliquely or asymmetrically blowing-off outlet opening is provided, wherein a flow guide section directed inwards towards the valve closing element counter to the flow direction is furthermore formed in the base region, said flow guide section carrying out a flow deflection of the gas to be blown out.Disclosure of the InventionThe injection system according to the invention having an injector for injecting a gaseous medium, in particular a gaseous fuel, into a combustion chamber of an internal combustion engine, having 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, such that the internal flow of the gaseous medium is designed as free of losses as possible via the inner contour of the cap-shaped attachment body, such that the dynamic pressure located below, that is to say 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.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 and keep open the valve closing element by a stroke movement, while the valve closing element is closed by a spring force.The injector is advantageously arranged centrally in a cylinder head with respect to the combustion chamber roof or the combustion chamber. The flow influencing geometry is formed in a top body, wherein the top body has a jacket region and a base region and the base region is present as an annularly encircling edge of a passage opening, wherein the passage opening extends in a conically widening manner and has an angle and in the process continues a conicity of the valve seat with a seat angle, wherein the angle of the passage opening is smaller than the seat angle.The injector according to the invention can generate a hollow-cone injection jet with a injection cone angle such that no Coanda effect occurs on the outside and on the inside of the injection jet. On the inside and on the outside, there is sufficient space on the combustion gas blow cone for a compensating air flow which compensates for the entrained air.The dependent claims describe preferred developments of the invention.This inner contour of the attachment body defined according to the invention can be advantageously accommodated with its special features in shape and design in attachment bodies with reducible external dimensions. This in turn allows a very flexible use of sleeves or attachment bodies on injectors in different combustion chamber geometries of internal combustion engines.In combustion chamber roofs which have a continuous course of varying roof angles as viewed over the circumference, it can be of great advantage that adequately for this purpose the angle of the through-opening in the base region of the attachment body also varies in a continuous course.The present invention is preferably used in injection systems directly injecting a combustion chamber. In particular, the injector is suitable for the direct injection of hydrogen into a combustion chamber of an internal combustion engine.DRAWINGPreferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art, FIG. 2 shows a schematic sectional view of an injection system with an injector for injecting a gaseous medium according to the prior art, FIG. 3 shows a schematic sectional view of an injection system with an injector according to the invention for injecting a gaseous medium according to a first exemplary embodiment, FIG. 4 shows a schematic detailed view of an outflow-side valve end with a cap-shaped attachment body according to the first exemplary embodiment, FIG. 5 shows a schematic detailed view of an outflow-side valve end with a cap-shaped attachment body according to a second exemplary embodiment, FIG. 6 shows a schematic sectional view of an injection system with an injector according to the invention for injecting a gaseous medium according to a third exemplary embodiment, and FIG. 7 is a schematic sectional view of a section along the line VII-VII through the injection system in FIG. 6.Preferred Embodiments of the InventionTo better understand 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-ignited internal combustion engine, for example, is described below with reference to FIGS. 1 and 2.FIGS. 1 and 2 schematically show the known injector 1 for injecting a gaseous medium in section with its downstream valve end. The injector 1 has a valve seat 3 with which a valve closing element 5 cooperates for opening and closing a sealing seat 7. Since the invention is directed to the flow influencing geometry 10 (FIGS. 3 to 7 ) arranged downstream of the valve seat 3 in terms of flow, only the region around the sealing seat 7 is described in more detail here, even in the case of the known injector 1. For the actuation of the injector 1, a magnetic actuator, not shown, is provided, for example, so that the injector 1 can be controlled in a targeted manner by this.The injector 1 also has a nozzle body 2 which, on the injection side, forms on the end side the already mentioned, for example conically shaped, valve seat 3 for the valve closing element 5 which opens outwards, that is to say opens in the direction of the combustion chamber 20. The valve closing element 5 is guided axially movably within the nozzle body 2, for example, 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 in a manner corresponding to the valve seat 3. The two sealing seat partners valve seat 3 and valve closing element 5 are each metallic. The geometric and material design is effected in such a way that sufficient tightness is ensured during operation of a hydrogen engine. In the event of a fault, a shut-off system, which is fluidically connected upstream of the injector 1 for safety reasons and is not shown here, would ensure an interruption of the supply of the gaseous medium, in particular of the readily 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 conicity. However, other contours are also conceivable.The injection jet of an injector 1 for injecting fuel gas into the combustion chamber 20 of an internal combustion engine should be designed such that the fuel gas mixes in the best possible manner with the air in the combustion chamber 20. In the figures, therefore, in addition to the injector 1, the combustion chamber 20 is also indicated schematically. In addition, two gas exchange valves 11, 12 are shown symbolically, while the illustration of a spark plug is omitted. The gas exchange valves 11, 12 are arranged as inlet or outlet valves in a cylinder head 15, the closure plates of the gas exchange valves 11, 12 having their sealing seat in a combustion chamber roof 16 of the cylinder head 15.In known injectors 1 according to FIGS. 1 and 2 without any measures influencing the flow downstream of the sealing seat 7, unfavorably 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 of known injectors 1 with a valve closing element 5 opening to the outside when the nozzle is designed in a conical manner. The injection jet 17 entrains the surrounding air at the outer surface and inner surface of the hollow-cone-shaped jet. On the outer gas jet surface, a flow occurs in the space between combustion chamber roof 16, cylinder wall 19 and 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 balancing air flow occurs. Therefore, a negative pressure is generated 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 FIG. 1. The injection jet 17 penetrates largely cylindrically into the combustion chamber 20 and mixes poorly with the surrounding air. The subsequent combustion may thus take place incompletely. More harmful exhaust gas, in particular NOx, can be produced, and the internal combustion engine has a poorer efficiency.The injector 1 according to FIG. 2 has, for example, an unfavorable large blow angle. Here, air is also entrained on the outside and on the inside of the injection jet 17. The large blow angle produces a compensating air flow on the inside. On the outside, there is no balancing air flow, since the space between the injection jet 17 and the combustion chamber roof 16 is too small. In this case, a negative pressure is generated externally, which is marked "-". Due to this effect, the injection jet 17 receives an even greater blow angle than when it exits at the sealing seat 7 of the injector 1. This injection jet also takes up only a small part of the air in the combustion chamber 20, and thus there is insufficient mixing and more harmful exhaust gas and poor engine running even in such a case.Therefore, the object of the invention is to provide a flow influencing geometry 10 which is fluidically arranged downstream of the sealing seat 7 and with which optimum combustion results are achieved on the basis of the flow guidance according to the invention.FIGS. 3 to 7 show embodiments according to the invention of injection systems or injectors 1, with which advantageous gas jet angles can be achieved and the above-described negative effects are omitted. Here, an air flow is produced on the outside and on the inside of the hollow cone jet, which compensates for the air entrained by the combustion gas blow louver. The jet angle remains approximately the same near the injector and away from the injector. The fuel gas mixes well with the air and the combustion heat is converted well into piston work. The internal combustion engine produces little harmful exhaust gas and has good efficiency.The injector 1 according to the invention according to FIGS. 3 and 4 can generate a hollow-cone injection jet 17 with a blow cone angle B such that no Coanda effect occurs on the outside and on the inside. On the inside and on the outside, there is sufficient space on the combustion gas blow cone for a compensating air flow which compensates for the entrained air. The injector 1 now advantageously has an attachment body 8 which is of sleeve-shaped design and is securely and fixedly attached to the nozzle body 2 at the outflow-side valve end. The attachment body 8 can also be referred to as a "blow cap" and has a flow influencing geometry 10, which is distinguished in particular by a conicity which continues a conicity present on the nozzle body 2 by the valve seat 3 in a manner widening in the flow direction. The attachment body 8 has a jacket region 21 and a base region 22, which extend substantially perpendicularly to one another, wherein the fixed connection to the nozzle body 2 takes place in the jacket region 21, and the base region 22 defines the flow influencing geometry 10 only as an annularly encircling edge of a passage opening 25.The combustion 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, which angle B or U is approximately half as large as the roof angle of the combustion chamber roof 16 of the internal combustion engine delimiting the combustion chamber 20. In the exemplary embodiment shown, there are approximately the following values: 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 inventive blow cone angle B or the angle U of the attachment body 8, respectively. For a relatively large seat angle S, the desired large gas cross section on the valve seat 3 responds in the case of an injector 1 opening with a specific stroke, which results in a high desired gas throughput.The attachment body 8 is firmly connected to the nozzle body 2 e.g. by means of welding, adhesive bonding, pressing or screwing. The attachment body 8 is made of metal or of ceramic. A ceramic material has the advantage that the heat input from the combustion phase into the seat region is lower, since ceramics have poorer heat conduction than metallic materials. The edge angle K on the flow influencing geometry 10 in the base region 22 of the attachment body 8 shown in FIG. 4 can be formed to be acute, rectangular, but also obtuse and can lie in the range of 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 into it with a slight axial overlap. Alternatively, the injector 1 can also be installed in the receiving bore for the injector 1 in a slightly retracted manner 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 bottom region 22 of the sleeve- or cap-shaped attachment body 8 has an axial height which corresponds to about 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 height of the end face of the valve closing element 5 or slightly above or below.Normally, sealing seats 7 on gas injectors are not perfectly tight in the closed state. There is a slight leakage of fuel gas. However, if the valve seat 3 is well ventilated, the exhausted fuel gas distributes and narrows well in the combustion chamber 20. This early combustion, before top dead center, effectively brakes piston motion. In addition to the unnecessarily burnt combustion gas, the pre-ignition means a very strong or damaging load of the piston, connecting rod and crankshaft.FIG. 5 shows a second exemplary embodiment of the invention. In contrast to the embodiment shown in FIGS. 3 and 4, the plate-shaped end section 6 of the valve closing element 5 has a layer 24 of an insulating material, such as ceramic or a ceramic composite material, toward the combustion chamber 20. As a result, the combustion-induced heat input to the valve seat 3 via the valve closing element 5 is reduced. The plate-shaped end section 6 of the valve closing element 5 has on the outer contour a conical bevel which has an angle Z which corresponds approximately 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.FIGS. 6 and 7 show a further exemplary embodiment which is distinguished in that the roof angle D of the combustion chamber roof 16 is not constant all around 360° and varies in this respect. FIG. 7 shows a schematic sectional illustration of a section along the line VII-VII in FIG. 6, it being evident that, viewed in different directions over the circumference, different large roof angles D are present, which are denoted by D 1 and D 2 by way of example. In reality, due to the continuous course of the combustion chamber roof 16, there are an integral number of different angles D, wherein D 1 denotes the smallest roof angle and D 2 denotes the largest roof angle. The varying roof angles D are, for example, between 150° and 180°. Corresponding to 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, wherein the angle U also varies over the circumference, e.g. adequately with respect to the roof angle D (U 1, U 2). The through-opening 25 in the base region 22 of the attachment body 8 will advantageously also continuously change its angle U. Segmenting of the through-opening 25 is also conceivable.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 of the combustion chamber roof 16.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 206 438 A1

[0003] WO 2023 / 001384 A1

[0004]

Claims

Injection system having 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 centrally in a cylinder head (15) with respect to the combustion chamber roof (16) or the combustion chamber (20), 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, characterized in that the flow influencing geometry (10) is formed in a top body (8), wherein the attachment body (8) is designed in the form of a cap and has a casing region (21) and a base region (22), and the base region (22) is present as an annularly encircling edge of a passage opening (25), wherein the passage opening (25) extends in a conically widening manner and has an angle (U) and in the process a conicity of the valve seat (3) continues with a seat angle (S) and S>U applies.Injection system according to Claim 1, characterized in that a hollow-cone injection jet (17) can be injected into the combustion chamber (20) with a blow cone angle (B) by means of the injector (1).Injection installation according to Claim 2, characterized in that the angle (B) of the blow cone corresponds to the angle (U) of the through-opening (25) in the base region (22) of the attachment body (8).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 of roof angle (D) to angle (U) on the attachment body (8): 0.3 x D < U < 0.75 x D.Injection installation according to Claim 4, characterized in that the angle (U) of the through-opening (25) in the base region (22) of the attachment body (8) has a size of 50° to 120°, preferably approximately 80°.Injection installation according to Claim 4 or 5, characterized in that the roof angle (D) of the combustion chamber roof (16) is between 150° and 180°.Injection installation 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).Injection installation according to one of the preceding claims, characterized in that, viewed over the circumference, the angle (U) of the through-opening (25) in the base region (22) of the attachment body (8) is constant or there is a continuous course of changing angle (U).Injection system according to one of the preceding claims, characterized in that the valve closing element (5) has, on a plate-shaped end section (6) on the outer contour, a conical chamfer with an angle (Z) which preferably corresponds to the angle (U) of the through-opening (25) in the base region (22) of the attachment body (8).Injection system according to one of the preceding claims, characterized in that the cap-shaped attachment body (8) can be attached to an injection-side end of the injector (1), in particular to a nozzle body (2).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.Injection system according to Claim 11, characterized in that the valve closing element (5) has, at its end section (6) towards the combustion chamber (20), a layer (24) made of an insulating material, such as, for example, ceramic or a ceramic composite material.

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