Injector line for an injector for blowing in fuel

Description

[0001] The present invention relates to an injection line for an injector for injecting a fuel, preferably for injecting a gaseous fuel such as hydrogen into a combustion chamber of an internal combustion engine.

[0002] With increasingly stringent emissions limits worldwide and ambitious climate protection goals, the environmental requirements for internal combustion engines are constantly rising. The aim in the foreseeable future is low-emission or even emission-free drive technologies that meet even the strictest emissions limits and make a significant contribution to achieving climate protection goals. For combustion-based technologies, these goals are only achievable with the use of climate-neutral, regeneratively produced fuels that cause no emissions whatsoever along the entire value chain (so-called "zero-emission" fuels).

[0003] With current conventional gasoline, diesel and gas engines, the requirements for emission-free combustion are not achievable – even with the use of so-called e-fuels, e.g. a synthetically produced OME fuel, for the production of which only renewable energy is required – because the emission of harmful exhaust gases such as nitrogen oxides (NOx), unburned hydrocarbons (UHC) and soot cannot be completely reduced with current technologies.

[0004] Hydrogen combustion engines, which represent a promising alternative drive system, have therefore moved into focus. However, these currently exist almost exclusively in very small numbers or as demonstrators with a low level of development. Hydrogen produced using renewable energy would meet all the requirements of "zero emission" technology, as it can be combusted without producing emissions.

[0005] In passenger cars, for example, hydrogen engines with port fuel injection (PFI) are used, in which the fuel is thoroughly mixed with air for a sufficient amount of time before entering the combustion chamber. Hydrogen engines with direct injection of the fuel into the combustion chamber (direct injection, DI) play practically no role today, but compared to the PFI concept, they offer, among other things, higher efficiency, more stable combustion, and the elimination of the risk of backfire into the intake manifold.

[0006] In direct-injection hydrogen engines, a distinction is typically made regarding the maximum injection pressure in the injector (< 60 bar: low pressure, > 60 bar: high pressure), although the boundaries are not clearly defined and the transitions are gradual. Higher pressures offer the potential for a shorter injection duration in a later phase of compression at higher combustion chamber pressures, resulting in increased efficiency and improved combustion stability. However, overall efficiency decreases if prior compression of the hydrogen is necessary.

[0007] If the hydrogen is produced entirely from renewable energy sources, hydrogen combustion engines can operate almost climate-neutrally. Furthermore, numerous other advantages are offered: Use of established technologies with a high degree of maturity and existing production facilities; unlimited availability of hydrogen through water electrolysis; use of the existing filling station system possible (after appropriate conversion) with fast refueling times; (almost) emission-free conversion of hydrogen during combustion possible, as it is CO2-neutral, with only minimal CO, UHC, particulate and soot emissions (only caused by lubricants in the supply system, below the measurement limit) and only minimal NOx emissions through a suitable combustion process (possibly with exhaust gas recirculation, SCR catalyst); significantly lower requirements for hydrogen purity compared to fuel cell drives; no need for platinum in production as with fuel cells

[0008] In addition to these numerous advantages over other drive concepts, there are also several challenges that must be overcome in the development of hydrogen combustion engines: • low molecular weight of hydrogen, resulting in low density and consequently low volumetric energy density (but high mass-specific energy density); see Table 1 • provision of a correspondingly high volume flow rate during hydrogen injection • corresponding provision of large flow cross-sections in the injector and thus significantly larger actuator strokes required compared to conventional drive systems • mixture preparation in the combustion chamber / influencing the injection jet / ignition behavior during micro-injection Table 1: Mass- and volume-specific calorific value of diesel and hydrogen. A fuel injection device is known from DE 10 2018 131 831 A1, in which an injection line opens into a Venturi-shaped main channel. Gaseous fuel is introduced via this injection line, and at least one additional feed opening is provided through which a fluid, such as air or fuel, can be drawn into the injection line. The specific internal contour of the injection line, in particular the design of the outlet cross-section and flow-guiding structures, remains undefined. Diesel Wasserstoff (bei 25 °C) Heizwert in MJ / kg 43.0 120.0 Heizwert in MJ / m 3< 35'819 9.8 bei 1 bar 287.7 bei 30 bar 2464.4 bei 300 bar

[0009] The objective of the present invention is to overcome or mitigate the challenges and disadvantages partially outlined above and to provide a correspondingly improved injection line (also: injection cap) for an injector for injecting gases such as hydrogen. In particular, the injection line should ensure thorough mixing of fuel and air to enable the most homogeneous combustion possible in a combustion chamber. Furthermore, it is desirable for the injection line to contribute to better controllability of the mass flow introduced into the combustion chamber, as this allows for more precise and efficient combustion. Overall, the device according to the invention should enable an improved combustion process in a hydrogen combustion engine.

[0010] This is achieved with a blowing line that has all the features of claim 1.

[0011] The injection line according to the invention for an injector for injecting fuel, in particular gaseous fuel, preferably hydrogen, has at least one outlet opening through which the fuel to be injected flows and is characterized in that an inner contour of an outlet cross-section of the at least one outlet opening has at least one convex and at least one concave section.

[0012] It can be provided that the inner contour of the outlet cross-section has at least one convex and at least one concave section relative to a center point of the outlet cross-section. To define convex or concave sections in the outlet cross-section of the injection duct, it can be checked, for example, whether a straight connecting line between any two points of the outlet cross-section results in the actual inner contour lying on the side of the connecting line that is closer to the center of the contour (if yes: concave; if no: convex). The points defining the connecting line can be chosen arbitrarily along the inner contour.

[0013] The same result is obtained, however, if one rolls the inner contour of the exit cross-section and then uses the mathematical prerequisites for the existence of a concave or convex function, whereby the course of the inner contour is considered the function.

[0014] The presence of concave and convex sections in the inner contour of the outlet cross-section can result in a diameter variation of the outlet cross-section and / or a sequence of convex and concave sections of the inner contour, leading to advantageous turbulence of the fluid (for example, fuel or fuel-air mixture). This turbulence is advantageous because thorough mixing of the fuel in a combustion chamber often requires sufficient turbulence and ensures efficient combustion of a fuel-air mixture. According to the invention, the injection line can further be designed to receive injected fuel and discharge it again via the outlet opening.

[0015] The injection line can typically be provided at the distal end of an injector and can either be located completely within a combustion chamber or extend at least into the combustion chamber with its outlet cross-section.

[0016] Thus, the injection line can be designed as the end piece or injection cap of an injector, from which the fuel or fuel-air mixture typically introduced into a combustion chamber originates. Accordingly, the fuel or fuel-air mixture is introduced into an inlet opening of the injection line and discharged from the outlet opening of the injection line.

[0017] According to the present invention, the inner contour of the injection line towards the outlet opening has at least one ramp arranged in the flow direction of the fuel to be injected, which is inclined towards or away from the outer circumferential side of the injection line, preferably extending to the outlet opening. Providing such a ramp, which either inclines towards the interior of the injection line or runs oppositely towards the exterior, can lead to a reduction or an acceleration of the velocity of a flow path flowing over such a ramp, so that vortices form in the boundary region with a flow whose velocity has not been changed or has been changed in the opposite direction. Vortices formed in this way also lead to turbulent mixing of the fluid flowing through the injection line, which again contributes to the effective combustion of a fuel flowing through the injection line.Fuel-air mixtures are advantageous.

[0018] According to the invention, a ramp of a contrary design is connected to the ramp in the circumferential direction perpendicular to the flow direction and / or a web is provided which continues the starting level of the ramp in the flow direction, preferably wherein the ramp is inclined away from the outer circumferential side.

[0019] If a bridge or a ramp with a contrasting design adjoins such a ramp laterally, a partition wall forms in the transition area between two ramps or between a ramp and a bridge. This partition wall runs along its length and at its end, for example at the outlet cross-section, creating areas of turbulence, as flow regions of different speeds meet here. This also ensures good mixing of the fluid flowing through the injection line.

[0020] According to a further development of the present invention, it can be provided that the outlet cross-section lies in a plane or is located in different, discretely or continuously distributed outlet planes along a main flow direction of the fuel to be injected.

[0021] According to the invention, it is therefore not necessary for the outlet cross-section to be arranged in a single cross-sectional plane, but it can also be located over several planes offset in the main flow direction.

[0022] According to the invention, it is also provided that at least one further opening, in particular a supply opening, is provided between the outlet opening and an inlet opening for introducing the fuel to be injected, in order to draw in or discharge a fluid, e.g. air and / or fuel, into the injection line, wherein preferably the at least one opening, in particular a supply opening, is oriented transversely to a main flow direction of the injection cap.

[0023] Furthermore, the injection line can be designed (for example, by a corresponding variation in the cross-sectional area in the main flow direction) such that, in combination with the at least one further supply opening, it forms a Venturi nozzle to draw in a fluid via the supply opening. If, for example, an injector is designed such that only pure fuel is introduced into the injection opening of the injection line, the mixing of air from the combustion chamber can occur via the at least one supply opening, so that the injection line then discharges a fuel-air mixture at its outlet opening. Naturally, the invention also encompasses the case where any fluid can be mixed in through the supply opening, for example, a fuel-air mixture already present in the combustion chamber.

[0024] According to an advantageous embodiment of the present invention, it can be provided that the at least one further opening, in particular a feed opening, is arranged upstream of the at least one ramp.

[0025] Since the ramp being positioned downstream of the at least one feed port has the effect of mixing the fluid flowing through the injection line, arranging the ramp downstream of the at least one feed port results in the supplied fluid being mixed with the fluid introduced into the injection port of the injection line. In particular, when fuel is introduced into the injection port of the injection line and air or the fluid predominant in a combustion chamber is introduced through the at least one feed port, the downstream ramp leads to good mixing of the fuel-air mixture.

[0026] According to a further optional modification of the present invention, it can be provided that the minimum cross-section of the injection line is formed by the outlet cross-section or an inlet cross-section, or lies along the injection line between the inlet cross-section and the outlet cross-section.

[0027] Furthermore, according to the invention, the injection line can be rotationally symmetrical, preferably rotationally symmetrical, about an axis of rotation parallel to its longitudinal direction. Thus, the injection line can be provided to essentially have the shape of a tube.

[0028] The invention may also include the fact that the injection line is not straight but curved.

[0029] According to a further development of the present invention, the inner contour of the outlet cross-section can be continuously differentiated. However, the inner contour can also be provided with abrupt changes, so that a discontinuous profile is also possible. A discontinuous profile is advantageous because particularly strong vortices are generated in the flow in the region of the discontinuous edges.

[0030] The invention further relates to an injector for injecting fuel with an injection line, preferably an injector according to one of the previously discussed variants, preferably wherein the injection line is the combustion chamber-side end piece of the injector. The injector can be designed to dispense a gaseous fuel, for example hydrogen.

[0031] Since a sound transition from subsonic to supersonic speeds occurs along the flow path of the injection line during the dispensing of fuel or a fuel-air mixture, it is possible to decouple the mass flow from the combustion chamber back pressure. It is clear to those skilled in the art that achieving this sound transition from subsonic to supersonic speeds depends on a multitude of factors, such as the exact geometry of the injection line, the pressures in the injector and combustion chamber, and the fluid temperature in the injector. Furthermore, the combustion chamber pressure can vary during an injection phase, as the piston may, for example, already be moving towards the top dead center of the cylinder to perform compression.

[0032] When injecting fuel, the injector performs an opening phase, a subsequent plateau phase, and a closing phase, wherein the amount of fuel to be injected initially rises, remains at a high level, and then falls again, and the injector introduces the fuel to be injected into the injection line during the plateau phase at such a pressure that for more than two-thirds of the plateau phase duration, preferably for the entire duration of the plateau phase, the fuel flow in the injection cap and / or at its inlet cross-section / its outlet cross-section undergoes a sound transition from subsonic to supersonic, wherein preferably the sound transition already occurs in parts of the opening phase and / or the closing phase.

[0033] Maintaining sound transmission over a longer injection period ensures that improved mass flow control persists. It is particularly advantageous if sound transmission occurs during the injector's opening or closing phase, when the maximum amount of fuel is not yet or no longer being dispensed. This ensures decoupling from engine backpressure, and thus improved mass flow control, at least during the plateau phase when a large portion of the fuel is dispensed.

[0034] The injector is operated in such a way that the fuel flow through the injector is supersonic at the at least one outlet of the injection line. In combination with convex and concave sections in the inner contour of the outlet, this results in particularly good turbulence / mixing of the fluid discharged through the injection line.

[0035] Furthermore, it can be provided that an injection line has at least one ramp, in which the at least one ramp arranged in the flow direction of the fuel to be injected extends from the outer circumferential side of the injection line towards the interior, and the injector is operated in such a way that the fuel flow at the beginning of the at least one ramp is supersonic and forms a compression shock at the beginning of the ramp due to the ramp sloping towards the interior, and / or the at least one ramp arranged in the flow direction of the fuel to be injected extends from the outer circumferential side of the injection line outwards, away from the interior, and the injector is operated in such a way that the fuel flow at the end of the at least one ramp is supersonic and forms a compression shock due to a surface at the end of the ramp that no longer slopes and preferably then runs parallel to the main flow direction.

[0036] In fluid mechanics, a compression shock describes a discontinuous change in the flow state, in which a supersonic flow encounters an obstacle and must move away from it. Since information about the pressure disturbances propagates at the speed of sound, no upstream transmission of this information into the supersonic range occurs, resulting in a sudden adjustment of the flow state during the compression shock. This abrupt change of state is used in the injection line to mix several fluids, such as fuel and air, so that a subsequent combustion process of the fuel-air mixture proceeds with high effectiveness and efficiency.

[0037] The invention may also relate to an internal combustion engine with gas direct injection, in particular hydrogen direct injection, comprising an injector according to one of the above variants.

[0038] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1: a longitudinal sectional view through an injector according to the invention, Fig. 2: a representation of different states of components and pressures in an injector, Fig. 3: a graphical representation of the mass flow exiting an injector over an opening cycle, Fig. 4: a representation of an equivalent circuit diagram of a flow path realized by a series connection of at least one throttling point, Fig. 5: several representations for arranging a narrowest cross-sectional area in the injection line together with a resulting flow velocity, Fig. 6: views of differently shaped injection lines according to the present invention, Fig. 7: views of differently shaped injection lines according to the present invention with an outlet opening of one or more planes, Fig.Fig. 8: Several illustrations of an injection line according to the invention with a further opening arranged between the injection opening and the outlet opening for supplying a fluid into the injection line or releasing a fluid flowing in the injection line, Fig. 9: Several illustrations of an injection line according to the invention with one or more outlet openings, Fig. 10: Several illustrations of an inner contour of the outlet opening of the injection line according to the invention to illustrate a convex and a concave section in the inner contour, Fig. 11: Several illustrations of an inner contour of the outlet opening of the injection line according to the invention to illustrate a convex and a concave section in the inner contour, Fig. 12: A detailed view of an injection line according to the invention with alternatingly arranged webs and ramps in the concave section, Fig.Fig. 13: Several detailed views of different variants of webs and ramps in the inner contour area of ​​the outlet opening of an injection line according to the invention; Fig. 14: A further detailed view in the area of ​​an inner contour of the injection line according to the invention, wherein the outlet cross-section lies in different planes; Fig. 15: A further detailed view in the area of ​​an inner contour of the injection line according to the invention, wherein adjacent ramps are offset from each other in the main flow direction and / or provided with different inclinations; and Fig. 16: Several detailed views in the area of ​​an inner contour of the injection line according to the invention, wherein, at a flow velocity in the supersonic range, the compression shocks forming in the area of ​​ramps are graphically highlighted.

[0039] The following detailed character description of Fig. 1 refers to an injector for injecting hydrogen, but it is clear to the person skilled in the art that the invention also includes an injector for injecting gas or another fuel.

[0040] Fig. 1 Figure 1 shows a longitudinal section of the injector 1 according to the invention for injecting hydrogen into a combustion chamber 16. The injector 1 has an injector housing 2 in which various components of the injector 1 are located. A gas connection 11 is provided on the connection side for introducing hydrogen into the injector 1. First, the hydrogen or another combustible fluid is guided through a bore in a cover 29 running approximately centrally in the injector housing 2, and subsequently through a fluid channel in an armature counterpart 27, a through-opening 10 in the armature 5, and the hollow interior 12 of a hollow needle 3 to the end of the hollow needle 3 furthest from the connection side 11.

[0041] Depending on the position of the hollow needle 3 relative to the valve plate 9, the injection openings 4 penetrating the valve plate 9 are either closed or open. In the Fig. 1 In the depicted state, the injection ports 4 are closed by pressing the hollow needle 3 against the valve plate 9, as the end face of the hollow needle 3 covers the opening contours of the injection ports 4. To improve the seal, sealing elements 30 can be provided that extend around the opening contours of the injection ports 4 and, in a sealing state, contact the end face of the hollow needle 3. If the injection ports 4 are closed by the end face of the hollow needle 3, the fluid flow of hydrogen at this point in the injector 1 is stopped, and no downstream flow of hydrogen occurs beyond the valve plate 9.

[0042] If, however, the injection ports 4 are opened, which is effected by lifting the hollow needle 3 away from the valve plate 9, the hydrogen introduced into the injector 1 at a certain pressure flows out of the interior 12 of the hollow needle 3 and exits through the multiple injection ports 4 on the side of the valve plate 9 spaced away from the hollow needle 3. After passing through a check valve 20, 21, 23, which may be provided in the injector 1, the pressurized hydrogen flows through the injection line 50 (sometimes also called the injection cap), which has at least one outlet port 51. After passing through this injection line 50, the hydrogen delivered by the injector 1 is typically located outside the injector 1 in a combustion chamber 16. Air can be added there or through feed ports 54 provided in the injection line.In addition, compression of the hydrogen-air mixture takes place in combustion chamber 16, which then ignites or is ignited.

[0043] The check valve 20, 21, 23, located on the side of the valve plate 9 facing away from the hollow needle 3, serves to keep the very high pressure prevailing in the combustion chamber away from the at least one injection opening 4. Otherwise, the very high pressure prevailing in the combustion chamber 16 could act on the end face of the hollow needle 3 closing the injection opening 4 via the at least one injection opening 4, moving it from its position. In a subsequent operating step of the injector 1, the hydrogen required for combustion would then no longer be introduced into the combustion chamber 16, but rather a mixture that is already at least partially combusted, which could lead to an interruption of the combustion process or, at best, to reduced combustion efficiency.

[0044] The check valve 20, 21, 23 comprises a valve tappet 20, a valve guide 21, and a valve spring 23, which forces the valve tappet in a closing direction. Hydrogen may only escape through the opening contour 19 of the check valve 20, 21, 23 if the pressure on the side of the check valve 20, 21, 23 facing the valve plate 9 is at least greater than the pressure on the side facing away from the check valve 20, 21, 23 (facing the valve plate 9) by the restoring force exerted on the valve tappet 20 by the valve spring 23. This prevents fluid from flowing in from the side of the check valve 20, 21, 23, which is arranged in the injection tube 22, facing the combustion chamber 16.

[0045] The valve needle 3, designed as a hollow needle 3, is movable back and forth in the longitudinal direction of the injector 1. The movement of the valve needle 3 is controlled by a valve 5, 6, which in the present illustration of the Fig. 1 This is a solenoid valve. The hollow needle 3 is rigidly connected to an armature element 5, which in turn reacts to the magnetic force generated by a coil 6. The coil 6 can optionally be energized such that the resulting magnetic force moves the armature element 5 towards the gas connection 11. This movement also moves the hollow needle 3, which is rigidly connected to the armature element 5, causing it to rise relative to the valve plate 9. This opens the injection ports 4 in the valve plate 9, allowing hydrogen to flow through the valve plate 9. Possible methods for attaching the hollow needle 3 to the armature element 5 include crimping, screwing into the armature element 5, gluing, or other suitable fastening options.

[0046] For precise guidance of the hollow needle 3 along the longitudinal axis or axis of rotation X of the injector or of the hollow needle 3 itself, a needle guide 14 is provided, which circumferentially encloses one outer surface of the hollow needle 3. Sliding friction occurs in the contact area between the needle guide 14 and the outer surface of the hollow needle 3, so it can be advantageous if one or both of the contact surfaces have a special coating, in particular a carbon coating. It has been shown that such a carbon-containing coating is advantageous with regard to the tribological requirements of the two sliding components.

[0047] The needle guide 14 can be designed such that it extends from the valve plate 9 and cantilevers inwards at a certain distance from it, only coming into contact with the outer surface of the hollow needle 3 at this distance. Regardless of the specific design of the needle guide 14, the hollow needle 3 penetrates the needle guide 14 in such a way that the end of the needle 3 facing the valve plate 9 remains completely guided through the needle guide 14 even when lifted from the valve plate 9. The needle guide, like the anchor element 5 and the hollow needle 3, can be designed to be rotationally symmetrical or rotationally symmetrical with respect to the axis of rotation X of the injector 1.

[0048] At the end of the hollow needle 3 facing the valve plate 9, a flange-like projection is provided, which facilitates covering the at least one injection opening 4 in the valve plate 9. Furthermore, the hollow needle 3 can also have additional flow channels 7 extending obliquely or perpendicularly to its longitudinal direction, through which hydrogen introduced into the hollow needle 3 can flow out. The advantage of this is that the side of the hollow needle 3 facing the injection openings 4 is surrounded on both sides, i.e., from the inside and the outside, by the hydrogen introduced into the injector 1. Thus, the stroke of the valve needle 3 or the armature element 5 can be minimized while still achieving the required hydrogen flow rate. This is because the flow can split into an external flow and an internal flow through the outlet hole of the hollow needle 3 facing the valve plate 9. The flange-like projection 8, also called the plate, is therefore surrounded on both sides by the flow.

[0049] An air gap 24 is provided between the needle guide 14 and the armature element 5, allowing a certain degree of movement of the needle guide in the longitudinal direction of the injector 1. The needle guide 14 fulfills its primary function regardless of its exact position, so even the slight longitudinal play of the injector 1 does not alter this. In particular, this air gap 24 serves as a reserve when the injector housing 2 is compressed, for example, by mounting the injector 1 to an engine or by thermal expansion and contraction. This allows changes in the length of the injector housing 2 in the longitudinal direction to be compensated without exerting a force on the needle guide 14. On the side of the armature element 5 facing away from the hollow needle 3, a counterpart 27 is provided, in which an elastic spring element 13 in the form of a coil spring is arranged, which pushes the armature element 5 towards the valve plate 9.Without actuating valve 5, 6, the hollow needle 3 is forced towards valve plate 9 and closes the at least one injection opening 4. Similar to the anchor element 5, the anchor counterpart 27 also has a through-hole, the center of which can be located on the longitudinal center axis X of the injector 1. A simple way to introduce the elastic spring element 13 into the anchor counterpart 27 is to change the diameter of the through-hole of the anchor counterpart 27. The resulting step is used as a stop surface for the elastic spring element 13, so that no further design modifications are necessary. The through-hole through the anchor counterpart 27 can be created by two bores of different diameters that have the same bore center axis. Alternatively, the bore center axis can be identical to the center axis of the anchor element 5.

[0050] To improve the magnetic flux when the valve 5, 6 is used as a solenoid valve, the coil 6 can be surrounded on its outer surface by an iron backing 25, in which the magnetic field can propagate particularly well. The same applies to the housing components directly surrounding the armature element 5 and the armature counterpart 27, which are also preferably made of a magnetizable material. Thus, it can be advantageous if the pole tube 28, which is a component of the injector housing 2, is also made of iron or another ferromagnetic material. The same applies to the armature counterpart 27, which is also advantageously made of a magnetizable material.

[0051] A visual representation of the magnetic field lines is illustrated by reference symbol 15. These have a direction which, when considering the Fig. 1 The rotation is counterclockwise. This pulls the anchor element 5 towards the anchor counterpart 27 and lifts the hollow needle 3 from the valve plate 9 or from the injection openings 4 that penetrate the valve plate 9, allowing hydrogen to flow towards the check valve, from where hydrogen is finally introduced into the combustion chamber 16 via the injection cap 18.

[0052] Fig. 2 This shows the basic behavior of injector 1 during injection. Initial position at time... tAt bottom dead center (BDC) of the cylinder piston, the pre-tensioned needle spring 13 and valve spring 23, respectively, press the valve needle 3 and valve tappet 20 into their respective stops on the sealing element of the valve plate 30 and in the seat of the valve guide 21, respectively, thus closing the throttle ports 4 and 19, which connect the needle chamber to the valve chamber and the valve chamber to the injection chamber when the needle needle 3 and valve tappet 20 are open. The pressure in the injector 1 corresponds to the pressure in the supply line, while the pressure in the combustion chamber 16 and in the injection chamber corresponds to the boost pressure during the intake phase of the cylinder piston, in which fresh air is drawn into the combustion chamber 16 via the intake valves. The pressure in the valve chamber corresponds approximately to the combustion chamber pressure and depends, among other things, on the valve spring 23, the pressure in the combustion chamber 16 during the phase of expelling the hot combustion gases via the exhaust valves of the combustion chamber 16 and, if applicable, on prior injections.The following is a simplified representation of the function, without taking into account the charge exchange through the opening and closing of the intake and exhaust valves of the combustion chamber 16.

[0053] At the time t 1. The control unit applies a voltage signal via the electrical contacts to the coil 26 of the actuator, causing the current F1 in the electrical circuit to rise to a defined final level. The current-carrying coil 26 induces a magnetic field in the actuator, the magnetic field lines 15 of which spread out around the coil in a torus shape (see Fig. 1 The magnetic field generates a magnetic force F2 in the air gap between the armature 5 and the armature counterpart 27, resulting in at time tThe armature 5 is attracted to the counterpart 27 as soon as the magnetic force F2 exceeds the closing force (sum of the preload force of the needle spring 13 and the pressure forces on the needle 3 and the armature 5). The build-up of the magnetic field, and thus the magnetic force F2, is delayed by eddy currents in the iron parts of the magnetic circuit. The armature 5 is fixedly connected to the valve needle 3 or is a one-piece armature-valve needle assembly, so that the valve needle 3 moves uniformly with the armature 5 along a needle stroke F3. As soon as the previously compressed, elastic sealing element 30 on the sealing plate 9 at time tWhen the needle 3 is no longer in contact with the face of the valve needle 3, the connection between the needle chamber and the valve chamber is released, allowing fuel to flow from the needle chamber into the valve chamber. This increases the pressure in the valve chamber. As soon as the pressure difference between the valve chamber and the injection chamber corresponds to a force difference on the valve tappet 20 equal to the preload force of the valve spring 23, the passive valve opens, i.e., the valve tappet 20 moves away from the seat along one tappet stroke F4 and releases the connection between the valve chamber and the injection chamber, allowing fuel to flow from the valve chamber into the injection chamber. This results in a pressure increase in the injection chamber (see F8 Pressure in the injection chamber). The fuel then flows downstream through the opening(s) 51 in the injection line 50 into the combustion chamber 16. The injection line 50 (orThe injection cap is designed such that the flow is introduced into the combustion chamber 16 in a defined state (jet orientation, inlet pulse, jet pattern, etc.). The open state of needle 3 and valve tappet 20 is maintained throughout the entire remaining injection phase. The flow level can be reduced (e.g., by a PWM voltage signal) as soon as valve needle 3 is fully open and any potential rebound does not cause valve needle 3 to close. During injection, the engine cylinder is in the compression phase, so the combustion chamber pressure F5 rises steadily.

[0054] To end the injection process, the control unit terminates the power supply, so that the current F1 through coil 26 is reduced to zero (time ). t4) Due to the eddy currents, the magnetic force F2 also decreases with a time delay. As soon as the magnetic force F2 is less than the sum of the closing force of the needle spring 13 and the hydraulic forces on the needle 3 and the armature 5, the needle 3 and the armature 5 begin to close uniformly (time point t 5 ); see also F3, F4. When the end face of the needle 3 meets the sealing element 30 of the valve plate 9, the connection between the needle chamber and the valve chamber is severed and the fuel flow from the needle chamber to the valve chamber is interrupted (time t6). This causes the pressure in valve chamber F7 to drop. When the pressure difference between valve chamber F7 and injection chamber F8 corresponds to a force difference on the valve tappet 20 equal to the valve spring force, the valve tappet 20 moves back to its closed position on the valve seat 21 and is pressed against the seat 21 by the increasing pressure F5 in combustion chamber 16 and thus in the injection chamber, so that the fuel connection between the valve chamber and the injection chamber is interrupted (possibly after a period of the tappet bouncing against the valve seat 21) (time points). t 6 - t 7) . The injection process is now complete. During the further compression phase of combustion chamber 16 until top dead center (TDC) within the period t 7 - t 8. The air-fuel mixture is compressed in the injection chamber, while it expands during the subsequent expansion phase (period). t 8 - t 9) ,The further interim increase in combustion chamber pressure F5 due to combustion is not shown here for the sake of simplicity. If the pressure in combustion chamber 16 drops to such an extent that the difference between the pressure forces on the valve tappet 20 corresponds to the preload force of the valve spring 23 (time ) t 9), the valve tappet 20 opens briefly again, allowing some of the fuel present in the valve chamber to escape into the combustion chamber 16. This process depends on the spring force and can occur repeatedly (period t 9 - t 10) .

[0055] The respective mass flow of the fuel via the injection openings 4, the opening contour 19 and the at least one outlet opening 51 is indicated by F9, F10 or F11 respectively.

[0056] Fig. 3 Figure 1 shows a simplified graphical representation of an opening cycle of injector 1, where time is plotted on the abscissa and the mass flow rate discharged by injector 1 is plotted on the ordinate. It can be seen that the opening cycle of injector 1 can be divided into three distinct phases. The opening phase begins with the mass flow rate rising from zero to its maximum level. During the plateau phase, this maximum level is maintained for a certain period before the closing of injector 1 in the closing phase leads to a sharp drop in the mass flow rate to zero.

[0057] With short injection durations (for example, pre- or post-injection), the plateau phase can be omitted or kept very short.

[0058] Fig. 4 is a schematic representation of a substitute image for a flow path along a streamline from injector 1 to combustion chamber 16. Such a substitute image can be viewed as a series connection of n (n ≥ 1) throttle points.

[0059] In Fig. 4 Two throttle points connected in series (throttle point 1 and throttle point n) are shown as examples, where a sound transition from subsonic to supersonic speeds occurs along the flow path during the plateau phase. To better visualize this, a velocity profile graph is provided for each throttle point, showing that the sound transition from subsonic to supersonic speeds takes place in the region of the smallest flow cross-section.

[0060] The sound transmission decouples the mass flow from the combustion chamber back pressure. Whether sound transmission occurs along the flow path during injector operation or while using the injection line depends on the cross-sections of the throttles, their exact geometry, the pressures prevailing in the injector and combustion chamber, and the fluid temperature in the injector. The pressure in combustion chamber 16 varies during the intake phase depending on the movement of the cylinder piston during compression (see...). Fig. 2 ).

[0061] It is advantageous if the narrowest cross-section along the flow path during injector operation is dimensioned such that at least one sound transmission along the flow path is achieved for at least two-thirds of the entire plateau phase, preferably for the entire plateau phase, up to the maximum engine backpressure during the injection phase. Between the individual throttling points, the flow may be adapted from supersonic to subsonic via compression strokes.

[0062] Fig. 5 This shows several possibilities for arranging the narrowest cross-section of the injection line at different locations. Fig. 5(a) shows the narrowest cross-section of the injection pipe in an area between the inlet and outlet openings, Fig. 5 (b) shows the narrowest cross-section of the injection pipe at the level of the outlet opening and Fig. 5 (c) shows the narrowest cross-section of the injection line at the level of the inlet opening.

[0063] Overall, it is advantageous for the injection line or injector if the n throttles arranged in series, which define the flow path along a streamline from the injector to the combustion chamber, are coordinated and positioned in such a way that a supersonic flow exists at the outlet of the injection line (at least during a plateau phase of the injector). This is beneficial with regard to shock-induced turbulence or mixing of fuel and air.

[0064] Fig. 6 shows two differently shaped versions of a 50 mm blowing line. Fig. 6 (a) Figure 50 shows an injection line 50, which essentially has the form of a straight pipe. The black arrow symbolizes the flow direction of the fluid carried through the injection line 50, which is discharged at the outlet opening 51.

[0065] Fig. 6 (b) Figure 1, however, shows a curved design of the injection line 50, which allows the injection angle of the fluid jet exiting the outlet opening 51 to be influenced. As a rule, the geometric outlet angle does not correspond to the outlet angle of the flow, especially if the length of the injection line is relatively short and the flow direction of the jet can therefore only be influenced to a limited extent.

[0066] Fig. 7 shows different representations of injection lines whose outlet cross-section lies in a plane ( Fig. 7 (a) ) or in different, discretely or continuously distributed exit levels (see Fig. 7 (b) bis (d) ).

[0067] The representations at Fig. 7 (a) Each has an exit cross-section that is arranged in a single plane.

[0068] Fig. 7 (b) In contrast, it shows an outlet opening 51 that does not lie in a plane but extends along the direction of flow.

[0069] Fig. 7 (c) und Fig. 7 (d) This shows another possibility for an outlet opening 51 that is not arranged in a single plane. As an example, the inner contour 52 of the injection line 50 is provided with rectangular protrusions in the flow direction of the fluid to be discharged, which extend circumferentially around the injection line 50. Here, too, different outlet planes result for the flow passing through the injection line 50, which are arranged offset from each other in the flow direction. Fig. 7 (d) This shows the outlet from the injection line 50 in a rolled-up form. Here, the rectangular crenellations that define the multiple outlet levels are particularly easy to see.

[0070] Fig. 8 shows further advantageous modifications of the injection line 50, in which at least one further opening 56 is provided in the area between the inlet opening and the outlet opening 51, which can be used to supply a fluid into the injection line and / or to discharge a fluid from the injection line 50.

[0071] Fig. 8 (a) Figure 50 shows an injection line 50, the outlet opening 51 of which is located in a combustion chamber 16 and into whose inlet opening fuel is supplied by the injector 1. The injection line 50 has several supply openings 56 in the area between the inlet opening and the outlet opening 51 to draw air from the combustion chamber 16 into the interior of the injection line 50. This allows fuel and air to mix, resulting in a fuel-air mixture being discharged through the outlet opening 51 into the combustion chamber 16. To facilitate the intake of combustion chamber air along the main flow direction through the injection line 50, at least one additional supply opening 56 can be designed as a Venturi nozzle. In this process, changes in cross-section along the main flow direction of the injection line 50 are used to create a suction effect through the at least one feed opening 56.

[0072] Fig. 8 (b) Figure 1, however, shows the use of the opening 56, located between the inlet and outlet openings 51, for dispensing fuel flowing in the injection line 50. Here, at least one additional opening 56 is used to discharge the fuel to be delivered to the combustion chamber 16 via the injection line 50. Thus, fuel is dispensed not only via the outlet opening 51 at the end of the injection line 50, but also via at least one additional opening 56. By appropriately dimensioning the cross-sectional profile along the main flow direction of the injection line 50, fuel can exit the injection line 50 through at least one additional opening 56.

[0073] Fig. 9 Figure 50 shows differently designed injection lines 50, where it is evident that an injection line 50 can also have several outlet openings 51. Figure 50 shows, for example, that the injection line 50 can have several outlet openings 51. Fig. 9 (a) an injection line 50 with only one outlet opening 51, whereas Fig. 9 (b) Figure 51 shows several outlet openings which (as shown) can lie in a common plane.

[0074] Fig. 10 shows different representations of the inner contours 52 of the injection line 50, in which it can be seen that these each have at least one convex and at least one concave section in the inner contour 52.

[0075] Fig. 10 (a) Figure 1 shows a blowing line in a perspective view, in which the specific design of the inner contour 52 in the outlet opening 51 can already be seen. The section plane AA is in Fig. 10 (b) shown, so that the inner contour 52 of the exit opening 51 is also shown.

[0076] In the Fig. 10 (b) The inner contours 52 can be seen, which are designed with alternating convex and concave sections.

[0077] Fig. 10 (c) The figure shows internal contours 52 that are purely convex and have no concave sections. Thus, the circular or elliptical internal contour shown as an example is a purely convex internal contour 52 that has no concave sections and therefore results in less effective mixing when the fluid conveyed through the injection line 50 exits.

[0078] Fig. 10 (d) shows three different internal contours 52 of the outlet opening 51 according to the invention.

[0079] In this configuration, there are crenellated elements extending towards the center along the circumference, contributing to the formation of the convex sections. Thus, in this cross-sectional view, the wall thickness is not constant in the circumferential direction but can change continuously or abruptly, so that when a fluid is passed through the inlet line 50 and discharged from the outlet opening 51, the specific shape of the inner contours 52 contributes to good mixing due to the turbulence that occurs.

[0080] Fig. 11 This shows one way to determine convex and / or concave inner contour sections. Convex areas are marked with an x ​​and concave areas with a v.

[0081] If an arbitrarily positionable connecting line of the inner contour 52 is considered, the connecting line passes through a convex section if the actual course of the inner contour 52 runs on the side of the connecting line facing away from the center of the exit opening 51 and a concave section if the actual course of the inner contours 52 runs on the side of the connecting line facing towards the center of the exit opening.

[0082] Fig. 11 (a) This shows a purely convex inner contour, whereas Fig. 11 (b) und Fig. 11 (c) Each shows an inner contour 52 that has both concave and convex sections. It may be provided that the inner contour at the outlet opening 51 is continuously differentiable or has kinks.

[0083] Fig. 12 Figure 1 shows a further detailed view of a (rolled-out) inner contour of the outlet opening 51. The inner contour may be provided with webs 55 and ramps 54 along the flow direction. The arrangement of ramps 54 and webs 55 leads to strong velocity differences between the adjacent flow paths and in the boundary layer at the walls of the webs 55, which are Fig. 12 are represented by arrows of varying brightness. Strong vortices form at the edges of the inner contour 52 and at the outlet of the injection line 50, resulting in good turbulent mixing of fuel and air. This mixing is in the Fig. 12 represented by the arrows running around the dashed lines.

[0084] Fig. 13 This shows a representation of three differently designed inner contours, each of which is provided with webs 55 and ramps 54 in the area of ​​the outlet opening or outlet cross-section 53.

[0085] Fig. 13 (a) This shows several ramps 54 sloping away from the interior, between each of which a web 55 is arranged, representing a consistent continuation of the inner contour. In the outlet cross-section 53, this results in a crenellated design, with the rectangular crenellations directed towards the interior of the injection pipe.

[0086] Fig. 13 (b) Figure 1 shows a different embodiment in the area of ​​the outlet opening, in which ramps 54 are provided that slope towards the interior of the injection pipe. The ramps 54 are each separated from one another by a straight web 55, so that the outlet cross-section 53 also has a crenellated design, with the crenellations pointing towards the interior of the injection pipe.

[0087] Fig. 13 (c) Figure 54 shows another embodiment in which ramps 54 inclined in different directions are arranged alternately. Again, it can be seen that the darker arrows flow at a higher speed than the lighter arrows, so that turbulence is created between the different fast flows and at the outlet, leading to good mixing.

[0088] The invention is of course not limited to the combinations of ramps 54 and walkways 55 shown in the figures, since only particularly advantageous embodiments are considered in more detail therein.

[0089] Fig. 14 Figure 54 shows another variant of ramps 54 and ribs 55 in the area of ​​the outlet opening of the injection line 50, in which the outlets (with or without ramps) are located on staggered planes. Furthermore, it is possible for the ramps 54 to begin at different positions along the flow direction and to have different gradients.

[0090] Fig. 15 This shows ramps 54, all of which slope away from the interior of the injection pipe, but can have different gradients. This shows that the in Fig. 15 The centrally located ramp 54 has a steeper incline than the adjacent ramps 54. Furthermore, the ramps 54 are also offset from each other in the direction of flow.

[0091] Fig. 16 Figure 1 shows two detailed views of the injection line in the area of ​​the outlet opening, where ramps 54 and webs 55 are provided and the prevailing flow is supersonic (Ma>1). If the injection line is operated such that the flow at the beginning and end of ramps 54 is supersonic, a compression shock occurs at the points where the flow is deflected from the outside towards the center of the flow, extending towards the center of the flow. The formation of this compression shock creates shock-induced vortices, which lead to improved mixing of fuel and air.

[0092] Overall, the invention allows for a better mixing of fuel and air in the measured injection line, and in the case of operation of the injection line with a supersonic flow, decoupling of the mass flow from the engine back pressure is also possible.

Claims

1. Injection conduit (50) for an injector (1) for injection of fuel, in particular gaseous fuel, preferably hydrogen, comprising: at least one outlet opening (51) through which the injectable fuel can flow, wherein an inner contour (52) of an outlet cross-section (53) of the at least one outlet opening (51) has both at least one convex (x) and at least one concave (v) section, at least one feed opening (56) is provided between the outlet opening (51) and an inlet opening for introducing the fuel to be injected in order to draw a fluid, e.g. air and / or fuel, into the injection conduit (50), the inner contour (52) of the injection conduit (50) towards the outlet opening (51) has at least one ramp (54) arranged in the direction of flow of the fuel to be injected and is inclined towards or away from the outer circumferential side, wherein the ramp (54) preferably extends as far as the outlet opening (51), and the at least one feed opening (56) is arranged upstream of the at least one ramp (54), characterised in that the ramp (54) is adjoined by a ramp (54) of contrasting design in the circumferential direction extending perpendicular to the direction of flow, and / or a web (55) is provided that continues the initial level of the ramp (54) in the direction of flow, preferably wherein the ramp (54) is inclined away from the outer circumferential side.

2. Injection conduit (50) according to the preceding claim 1, wherein the injection conduit (50) is designed to receive a fuel to be injected and to discharge it again via the outlet opening (51).

3. Injection conduit (50) according to one of the preceding claims, wherein the ramp (54) extends to the outlet opening (51).

4. Injection conduit (50) according to one of the preceding claims, wherein the outlet cross-section (53) lies in one plane or is located in different, discretely or continuously distributed outlet planes along a main flow direction of the fuel to be injected.

5. Injection conduit (50) according to one of the preceding claims, wherein the at least one feed opening (56) is oriented transversely to a main flow direction of the injection cap.

6. Injection conduit (50) according to one of the preceding claims, wherein the minimum cross-section of the injection conduit (50) is provided by the outlet cross-section (53) or an inlet cross-section or along the injection conduit (50) between the inlet cross-section and the outlet cross-section (53).

7. Injection conduit (50) according to one of the preceding claims, wherein the injection conduit (50) is torsionally symmetrical, preferably rotationally symmetrical, with respect to an axis of rotation extending parallel to its longitudinal direction.

8. Injection conduit (50) according to one of the preceding claims, wherein the inner contour (52) of the outlet cross-section (53) is continuously differentiable.

9. Injector (1) for injection fuel with an injection conduit (50) according to one of the preceding claims, preferably wherein the injection conduit (50) is the end piece of the injector (1) on the combustion chamber side.