Injector for injecting a gaseous medium

Abstract

The present invention relates to 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) 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 (21) 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) downstream of the sealing seat (7) is characterized by an inner contour (9) which, starting from an inner diameter (d) in the region of the valve closing element (5), decreases in the downstream direction over a small axial length to a diameter (D) which characterizes a central bore (23) which extends to an outlet (19), wherein the central bore (23) is flanked by at least one flow channel (24) located radially outwardly from it.

Description

Prior ArtThe present invention relates to 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 injector according to the invention for blowing 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 over the related art 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 as lossless as possible via the inner contour of the cap-shaped attachment body, so that the dynamic pressure located below, i.e. downstream of, the valve closing element is reduced and at the same time the jet can be introduced into the combustion chamber in a targeted manner.In addition, the forces acting on the valve closing element are reduced to a minimum in a particular manner. This reduces the magnetic force of an actuator, which must be selected to keep the injector open, and thus enables the use of cost-effective materials in the magnetic circuit of the actuator.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 flow influencing geometry, which is accommodated in particular in a cap-shaped attachment body, for short a blow cap, is distinguished according to the invention in that an inner contour is formed downstream of the sealing seat, which inner contour decreases from an inner diameter in the region of the valve closing element in the downstream direction to a diameter that characterizes a central bore that extends as far as an outlet, wherein the central bore is flanked by at least one flow channel located radially outwards from it.The advantages of such a concept can be seen in the fact that the greatest possible flexibility is made possible in the design of the beam pattern via the design of the attachment body. Overall, a more stable beam pattern can be generated by one or more supporting or flanking gas beams compared to known solutions. The gas flow can also be distributed uniformly throughout the combustion chamber, which is accompanied by improved mixture formation and a higher efficiency can be achieved.The dependent claims describe preferred developments of the invention.It can be particularly advantageous to arrange a plurality of flow channels in an unequally distributed manner over the circumference in order to form an asymmetric, one-sided jet pattern.A lateral deflection of the gas flow is thus possible without increasing the flow losses even when the central bore is configured vertically. Jet angles of any sizes can be generated in an advantageous manner, but particularly flows with a small jet angle. This design variant is advantageous in particular when the injector is installed laterally on the cylinder head. With the configuration according to the invention of the inner contour and a targeted beam deflection resulting therefrom, the risk of combustion anomalies can be minimized.The very variably configurable inner contour, due to a very different geometry configuration, in particular of the flow channels flanking the central bore, in turn allows a very flexible use of sleeves or attachment bodies on injectors in different combustion chamber geometries of internal combustion engines.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 injector for injecting a gaseous medium according to the prior art, FIG. 2 is a sectional view of a known cap-shaped attachment body for an injector according to FIG. 1 , FIG. 3 shows a schematic sectional view of a cap-shaped attachment body for an injector for injecting a gaseous medium according to a first exemplary embodiment, FIG. 4 shows a schematic sectional view of the cap-shaped attachment body from FIG. 3 rotated by 45° for an injector for blowing in a gaseous medium, FIG. 5 shows a bottom view of the attachment body according to FIG. 3 in a first embodiment variant of flow channels, FIG. 6 shows a bottom view of the attachment body according to FIG. 3 in a second embodiment variant of flow channels, FIG. 7 shows a schematic sectional view of a cap-shaped attachment body for an injector for blowing in a gaseous medium, analogous to FIG. 3, with a schematically indicated flow profile from a main flow and flanking secondary flows, FIG. 8 shows a bottom view of the attachment body according to FIG. 3 in a third embodiment variant of flow channels, FIG. 9 shows a bottom view of the attachment body according to FIG. 3 in a fourth embodiment variant of flow channels, FIG. 10 shows a bottom view of the attachment body according to FIG. 3 in a fifth embodiment variant of flow channels, and FIG. 11 shows a schematic sectional view of a cap-shaped attachment body for an injector for blowing in a gaseous medium, analogous to FIG. 3, with a schematically indicated flow profile from a main flow and at least one flanking secondary flow.Preferred Embodiments of the InventionTo better understand the invention, the basic structure of an injector for blowing in a gaseous medium and a known structure of a flow influencing geometry downstream of the valve seat in terms of flow technology are described below with reference to FIGS. 1 and 2.FIG. 1 schematically shows a sectional view of the known injector 1 for injecting a gaseous medium. Since the invention is directed to the flow influencing geometry 10 arranged downstream of the valve seat 3 in terms of flow, only this assembly is described in more detail here, even in the case of the known injector 1. For actuating the injector 1, a magnetic actuator 21 is provided, for example, so that the injector 1 can be controlled in a targeted manner by this means.The injector 1 also has a nozzle body 2 which, on the injection side, forms, on the end side, a valve seat 3, which is shaped, for example, conically, for a valve closing element 5 which opens outwards, that is to say opens in the direction of a combustion chamber 20. The valve closing element 5 is guided axially movably within the nozzle body 2 via a guide 18. In addition, the valve closing element 5 has an end section 6 in the form of a valve disk which, corresponding to the valve seat 3, forms a sealing seat 7. 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, while the valve seat 3 on the nozzle body 2 has a conicity. However, other contours are also conceivable.The nozzle body 2 and the end section 6 of the valve closing element 5 are surrounded by a sleeve 8 for jet forming. In the following, in particular also with respect to the invention, reference is generally made to a flow influencing geometry 10 arranged downstream of the sealing seat 7 in terms of flow technology. This can be formed directly as one piece on the nozzle body 2, which however requires a high manufacturing effort, or integrated in an additional component, wherein this component is generally referred to as sleeve 8 in relation to the embodiments according to the prior art in FIGS. 1 and 2. The sleeve 8 has a large overlap length with the nozzle body 2 in order to be able to fasten the sleeve 8 securely and reliably. In principle, however, it is also possible to refer to a cap-shaped attachment body 8, which is also defined as a blow cap 8 with respect to the exemplary embodiments according to the invention.The sleeve 8 and the end section 6 of the valve closing element 5 together delimit a gas flow path 4, into which at least one intake duct 15 formed in the sleeve 8 opens. Air can be sucked from the environment into the gas flow path 4 via the one or more suction channels 15.If the valve closing element 5 is in an open position lifted from the valve seat 3, the gas flow path 4 then leads via the valve seat 3 into an interior space of the sleeve 8, which is characterized by a special shape with an inner contour 9. Starting from a cylindrical section 11 of the sleeve 8 following the valve closing element 5 in the flow direction, a reduction in cross section occurs at a large axial distance from the valve closing element 5 in a central cylindrical axial region 13 of the flow influencing geometry 10 of the sleeve 8, wherein the tapering is achieved via a conically extending section 12 in the inner contour 9 of the sleeve 8. The suction ducts 15 open exactly in the central axial region 13 into the inner contour 9 of the sleeve 8.The reduction in cross section within the gas flow path 4 provides the effect that, when the gas flows out via the gas flow path 4 in the direction of an outlet 19, air is drawn from the environment into the gas flow path 4 via the intake ducts 15 ("Venturi effect"). This means that air is added to the gas even before it reaches the outlet 19, so that the mixture preparation is improved in this way.The reduction in cross section is canceled again in that the central axial region 13 is again followed by a conically running section 14, but in this case widening conically in the direction of flow, this section 14 extending as far as the outlet 19. The cross-sectional reduction in the inner contour 9 of the sleeve 8 is provided in this respect for achieving the Venturi effect which is optimized together with the air admixture. Experience has shown that with such a solution or with other known geometries or inner contours of cap-shaped attachment bodies, sufficiently good results are not achieved with regard to the introduction of the jets into the combustion chamber 20 or their jet guidance and jet shaping for optimum combustion.Therefore, the object of the invention is to provide an inner contour 9 of a cap-shaped attachment body 8 with a flow influencing geometry 10 arranged downstream of the sealing seat 7 in terms of flow, with which optimum combustion results are achieved on the basis of the flow guidance according to the invention.Injection systems for the direct injection of a gaseous medium, in particular of hydrogen, but also CNG, methane, ammonia or mixtures of the aforementioned gases have the task of specifically controlling the metering and also the injection direction of the gas jet or the gas jets into the combustion chamber 20 via injection valves or generally injectors 1. For this purpose, corresponding sleeves or blow caps 8 can be used on the injector 1, as already explained above. Furthermore, injection systems for (hydrogen) direct injection have, on principle, a large lift requirement of the valve needle with the valve closing element 5. Materials with higher magnetic force and thus better B / H characteristics are very expensive and in part also harmful to health (e.g. FeCo). In this respect, a magnetic force reduction is also intended to be achieved by means of an improved beam guidance.The core of the invention consists in configuring the internal flow of the gaseous medium as free of losses as possible via the inner contour 9 of the cap-shaped attachment body 8 according to the invention, so that the dynamic pressure located below, i.e. downstream of, the plate-shaped end section 6 of the valve closing element 5 is reduced and at the same time the jet can be introduced into the combustion chamber 20 in a targeted manner. This defined inner contour 9 aims in particular at an improved jet formation by a specific deflection of the gas flow radially inward in the downstream direction to a central bore with a main flow, wherein at least one flow channel is additionally provided, which enables a flanking secondary flow. Due to the very variable contouring of the inner contour 9, a very flexible use of sleeves or attachment bodies 8 on injectors 1 in different combustion chamber geometries of internal combustion engines is made possible.Below, with reference to FIGS. 3 to 11, injectors 1 with flow influencing geometries 10 according to the invention, which are fluidically arranged downstream of the valve seat 3, are described in detail according to preferred exemplary embodiments of the invention. As already mentioned above, these flow influencing geometries 10 can be formed directly as one part on the nozzle body 2 or, as shown in all the figures, can be integrated in an additional component which can be referred to as a cap-shaped attachment body 8 (blow cap 8 for short). The attachment body 8 will usually have a significantly shorter overlap length with the nozzle body 2 than shown in FIG. 1. What is important is merely a secure and reliable fastening to the nozzle body 2, which enables a perfect and axis-parallel alignment with respect to the injector 1. Known joining methods such as pressing, welding, soldering, adhesive bonding or combinations thereof can be used.FIG. 3 shows a first exemplary embodiment of a flow influencing geometry 10 arranged downstream of the valve seat 3 in terms of flow in a cap-shaped attachment body 8 and produced via an internal cover 9 according to the invention. The valve closing element 5 with its plate-shaped end section 6 is only shown schematically and simplified. However, the end section 6 can also have bevels or rounded-off areas on its outer contour.The flow influencing geometry 10 produced with the inner contour 9 according to the invention has an essential geometry specification which generates above all a deflection of the gas flow radially inward in the downstream direction. The flow deflection is to take place in the downstream direction directly downstream of the valve closing element 5. In the region of the end section 6 of the valve closing element 5, the inner contour 9 of the attachment body 8 has an inner diameter d. This is intended to reduce over a short axial length to a diameter D, which then characterizes a central bore 23 which extends, for example, substantially cylindrically as far as the outlet 19. The following should apply to the ratio D / d: 0.2<D / d<0.5. A main flow 23' of the gas flow should be blown off via the central bore 23.The core of the invention is in this respect the deflection of the gas flow through the inner geometry of the attachment body 8. The attachment body 8 contains in this case, in addition to the central bore 23, at least one, but preferably a plurality of further flow channels 24 which direct the central gas flow emerging from the central bore 23 in the desired direction.The advantages of such a concept can be seen in the fact that the greatest possible flexibility is made possible in the design of the beam pattern via the design of the attachment body 8. Overall, a more stable beam pattern can be generated by one or more supporting or flanking gas beams compared to known solutions. The gas flow can also be distributed uniformly in the entire combustion chamber 20, which is associated with improved mixture formation and a higher efficiency can be achieved.FIG. 4 shows a schematic sectional view of the cap-shaped attachment body 8 from FIG. 3 rotated by 45° for an injector 1 for blowing in a gaseous medium. In this view, the flow channels 24 are recognizable. These flow channels 24 are situated in a defined manner between the inner contour 9 running toward the central bore 23, and these flow channels 24 are designed such that they run much steeper with their walls of the channel bases in the axial direction, so that a much less strong radial component is impressed on the flow directed along said channel bases. Viewed over the total length I from the end section 6 of the valve closing element 5 to the outlet 19, the axial subsection I' of the central bore 23 should be at least 30%. Generally, 0.3<I' / I<0.75 is to be considered.FIG. 5 shows a bottom view of the attachment body 8 according to FIG. 3 in a first embodiment variant of flow channels 24, while FIG. 6 shows a bottom view of the attachment body 8 according to FIG. 3 in a second embodiment variant of flow channels 24.In the embodiment according to FIG. 5, for example, four flow channels 24 are provided, which are each arranged uniformly around the central bore 23 in a manner offset by 90° from one another and have a rectangular cross section. In particular, between two and eight such flow channels 24 are conceivable.In the embodiment according to FIG. 6, for example, four flow channels 24 are provided, which are each arranged uniformly around the central bore 23 offset by 90° from one another and have a crescent-shaped or generally concavely arched cross section. In particular, between two and eight such flow channels 24 are conceivable.FIG. 7 shows a schematic sectional view of a cap-shaped attachment body 8 for an injector 1 for blowing in a gaseous medium, analogous to FIG. 3, with a schematically indicated flow profile from a main flow 23' which exits through the central bore 23 and, for example, four flanking secondary flows 24' which exit from the flow channels 24, as shown by way of example in FIGS. 5 and 6.FIGS. 8 to 11 are intended to indicate the particularly suitable possibility of generating a beam image which exits the attachment body 8 asymmetrically or on one side. In this case, FIG. 8 shows a bottom view of the attachment body 8 according to FIG. 3 in a third embodiment variant of flow channels 24, FIG. 9 shows a bottom view of the attachment body 8 according to FIG. 3 in a fourth embodiment variant of flow channels 24, and FIG. 10 shows a bottom view of the attachment body 8 according to FIG. 3 in a fifth embodiment variant of flow channels 24. Whereas three flow channels 24 are provided over an angular range of approximately 180° in the embodiments according to FIGS. 8 and 9, the embodiment according to FIG. 10 is reduced to a single flow channel 24, which covers only an angular range of a maximum of 90° depending on the width.FIG. 11 shows a schematic sectional view of a cap-shaped attachment body 8 for an injector 1 for blowing in a gaseous medium, analogous to FIG. 3, with a schematically indicated flow profile comprising a main flow 23' and at least one flanking secondary flow 24', which ensures a deflected gas jet despite a central bore 23.A lateral deflection of the gas flow is thus possible even with a vertical configuration of the central bore 23 without increasing the flow losses. Jet angles of any sizes can be generated in an advantageous manner, but particularly flows with a small jet angle. This design variant is advantageous in particular when the injector 1 is installed laterally on the cylinder head. In the lateral installation position of the injector 1, care should be taken above all to ensure that the gas jet is not directed in the direction of the inlet duct or directly in the direction of locally hot spots in order to avoid combustion anomalies, such as a back ignition in the inlet duct or an early pre-ignition by hot spots. With the configuration according to the invention of the inner contour 9 and a targeted beam deflection resulting therefrom, this risk can be minimized.By varying the steepness of the inner contour 9 in the region of the obliquely running flow channels 24, a correspondingly great range of variations can be produced on beam images with different beam angles. The flow channels 24 are generally shaped in such a way that they end in the region of the outlet 19 on a larger diameter than the diameter D of the central bore 23, so that the walls of the channel bottoms of the flow channels 24 run out at a radial distance x (FIG. 4 ) from the central bore 23. The flow channels 24 can run on one and the same attachment body 8 with identical, but also with different angles inclined at an angle. Contour angles of up to 60° are conceivable, for example.The circumferential widths of the flow channels 24 are ideally between 20° and 70° and can also vary on one and the same attachment body 8.The concept according to the invention allows a particularly great flexibility in the design of the beam image. The gas flow can be distributed very uniformly in the entire combustion chamber 20, which improves the mixture formation and increases the efficiency.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

Injector (1) for blowing a gaseous medium, in particular a gaseous fuel, preferably hydrogen, into a combustion chamber (20) of an internal combustion engine, comprising an axially movable valve closing element (5) for opening and closing at least one opening at a sealing seat (7), an actuator (21) for actuating the valve closing element (5), and a flow influencing geometry (10), which is fluidically arranged downstream of the sealing seat (7), characterized in that the flow influencing geometry (10) downstream of the sealing seat (7) is characterized by an inner contour (9) which, starting from an inner diameter (d) in the region of the valve closing element (5) in the downstream direction, decreases in the direction of small axial length to a diameter (D) which characterizes a central bore (23) which extends as far as an outlet (19), wherein the central bore (23) is flanked by at least one flow channel (24) located radially outwards from it.Injector according to Claim 1, characterized in that the following applies to the ratio D / d: 0.2 < D / d < 0.5.Injector according to Claim 1 or 2, characterized in that, viewed over the total length (I) from the valve closing element (5) to the outlet (19), an axial subsection (I') of the central bore (23) is at least 30%.Injector according to one of the preceding claims, characterized in that preferably between two and eight flow channels (24) are arranged distributed over the circumference.Injector according to Claim 4, characterized in that a plurality of flow channels (24) are arranged uniformly distributed over the circumference at equal distances from one another.Injector according to Claim 4, characterized in that a plurality of flow channels (24) are arranged distributed unequally over the circumference in order to form an asymmetric, one-sided jet pattern.Injector according to one of the preceding claims, characterized in that the at least one flow channel (24) is shaped in such a way that it ends in the region of the outlet (19) on a larger diameter than the diameter (D) of the central bore (23), so that the wall of the channel base of the flow channel (24) terminates at a radial distance (x) from the central bore (23).Injector according to one of the preceding claims, characterized in that the flow channels (24) are formed with rectangular or sickle-shaped or generally concavely arched cross sections.Injector according to one of the preceding claims, characterized in that the flow influencing geometry (10), which is fluidically arranged downstream of the sealing seat (7), is realized in a cap-shaped attachment body (8), in particular a blow cap.Injector according to Claim 9, 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).Injector 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 in the form of a disk.

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