Fuel supply system for a reciprocating piston engine and method for supplying fuel to combustion chambers of an internal combustion engine

Abstract

The invention relates to a fuel supply system (1) for an internal combustion engine (10) designed as a reciprocating piston engine having a crankshaft and a plurality of combustion chambers (11, 12, 13, 14, 15, 16), in particular an internal combustion engine (10) operated with hydrogen, comprising a fuel rail (20, 24, 25) to which a plurality of fuel injectors (8) are connected via supply lines (22, 23, 28). At least one resonator valve (27, 30, 31), provided for actuation according to the crankshaft angle (a), is arranged between the fuel rail (20, 24, 25) and the fuel injectors (8).

Description

[0001] Fuel supply system for a reciprocating engine and method for supplying fuel to combustion chambers of an internal combustion engine

[0002] The invention relates to a fuel supply system designed according to the preamble of claim 1 for an internal combustion engine designed as a reciprocating piston engine with a crankshaft and several combustion chambers. The invention further relates to a method for supplying fuel, in particular gaseous fuel, to the combustion chambers of an internal combustion engine.

[0003] A fuel supply system of this type is known, for example, from DE 10 2021 213604 A1, which discloses an internal combustion engine for gaseous fuels. DE 10 2021 213604 A1 assumes that gaseous fuel, in particular hydrogen, is stored in a gas tank at an operating pressure and supplied to the combustion chambers via a supply line. A pressure relief line with a switchable drain valve branches off from the supply line, allowing gaseous fuel to be discharged from the supply line.According to the teaching of DE 102021 213604 A1, this is intended to ensure that after the internal combustion engine is switched off, only the ambient pressure or a pressure that does not deviate significantly from the ambient pressure prevails in the supply line, so that the supply line can be sealed with reasonable technical effort in order to prevent the escape of gaseous fuel to the outside even during longer periods of inactivity of the internal combustion engine.

[0004] EP 0 921 303 B1 relates to a common rail injection system for internal combustion engines. This injection system comprises a pump, an accumulator, and at least one injector per cylinder of the internal combustion engine. The accumulator is connected to the injectors via connecting elements, the connecting element being a clamp with an integrated bore bolted to the cylinder head of the internal combustion engine and a pressure pipe. A flow restrictor may be arranged between the clamp and the accumulator for each injector. DE 10 2009 020 867 B4 relates to an internal combustion engine with a fuel injector, the fuel injector being designed to inject fuel directly into a combustion chamber of the internal combustion engine. Possible fuels listed in DE 10 2009 020 867 B4 are gasoline, diesel, natural gas, and hydrogen.

[0005] Another device for supplying gaseous fuel to a combustion chamber of an internal combustion engine is disclosed in DE 10 2018 132 444 B4. In this case, a free end of a valve stem can serve as the rotor of an electromagnetic actuator.

[0006] German patent DE 10 2016 221 071 B4 discloses a further design possibility for an injector for an internal combustion engine powered by a gaseous fuel. In particular, it addresses the geometry of a nozzle seat. The injector according to DE 10 2016 221 071 B4 is intended to be suitable for hydrogen as a fuel.

[0007] Other fuel supply systems are known from GB 2 402 233 A, US 8 543 313 B2, JP H11 - 200 987 A, DE 102 17 592 A1 and DE 195 36458 A1.

[0008] The invention is based on the objective of further developing the supply of fuel, in particular gaseous fuel, to internal combustion engines, namely reciprocating engines, compared to the aforementioned prior art, whereby resonances within the power supply are to be taken into account in particular.

[0009] This problem is solved according to the invention by a fuel supply system designed for use in a reciprocating engine, comprising the features of claim 1. Likewise, the problem is solved by a method designed according to claim 7 for supplying fuel to a combustion chamber of an internal combustion engine. The embodiments and advantages of the invention explained below in connection with the fuel supply method also apply mutatis mutandis to the devices, i.e., the fuel supply system and the reciprocating engine equipped therewith, generally referred to as an internal combustion engine, and vice versa.

[0010] The fuel supply system is designed for a multi-cylinder reciprocating engine, i.e., an engine with a crankshaft and multiple combustion chambers, and comprises, in a basic concept known per se, a fuel rail I to which several fuel injectors are connected via supply lines. According to claim 1, at least one resonator valve, designed for actuation depending on the crankshaft angle, is arranged between the fuel rail I and the fuel injectors.

[0011] The reciprocating engine, equipped with the fuel supply system and intended for use in a passenger car or commercial vehicle, for example, can be designed to operate with a liquid fuel and / or a gaseous fuel, in particular hydrogen.

[0012] The invention is based on the consideration that resonances in a fuel supply system for an internal combustion engine can play a role with both gaseous and liquid fuels. To ensure uniform operating conditions in all combustion chambers of the engine, for example, the lines to the individual injectors can be made of the same length, despite differing distances from a fuel rail. Similarly, it is conceivable to supply groups of cylinders via separate fuel supply systems, thereby limiting the length of the lines leading to the individual injectors.

[0013] The device and method described in the application depart from such approaches and establish a connection between the angular position of the crankshaft and the state of a resonator valve in the fuel supply system. This connection can be expressed in various ways: On the one hand, it is possible to selectively amplify resonances by actuating the resonator valve. Alternatively, resonances can be suppressed by actuating the resonator valve. This applies to any type of reciprocating engine, for example, inline, V-, or boxer engines.

[0014] According to a first group of embodiments, the resonator valve is arranged between a first cylinder group and a second cylinder group of the reciprocating engine. In many cases, the individual cylinder groups comprise several cylinders, for example, two, three, or four. In the extreme case of a two-cylinder engine, even a single cylinder constitutes a cylinder group. Generally, the different cylinder groups do not necessarily comprise the same number of cylinders. For example, a deliberate asymmetry is created by grouping two combustion chambers of a six-cylinder engine into a first cylinder group and the remaining four combustion chambers into a second cylinder group. Similarly, in the case of a four-cylinder engine, a three-one split of the combustion chambers is possible.In such a case, the resonator valve is installed in a line that connects a single injector line, i.e., a line that leads via an injector into a combustion chamber, with an injector arrangement that includes three further injectors and associated lines.

[0015] Another group of embodiments provides that each fuel injector is assigned a separate resonator valve. The resonator valve can, in particular, be connected to a Helmholtz resonator. Optionally, a shut-off valve is arranged between the resonator valve and the fuel injector, which can be used individually or in conjunction with the resonator valve to influence resonances.

[0016] The patented method for supplying fuel to a combustion chamber of an internal combustion engine, which has a crankshaft and several combustion chambers, is generally characterized by the fact that, depending on the angular position of the crankshaft, at least one resonator valve, which is arranged between a fuel rail and a fuel injector intended for injecting fuel into a combustion chamber, is actuated out of phase with the actuation of the fuel injector. With the aid of the resonator valve, resonances can be selectively amplified or suppressed in individual cases.

[0017] In both cases, it may be possible to switch the fuel flow from the fuel injector into the combustion chamber of the internal combustion engine in at least one direction by actuating the resonator valve. This switch can be performed between a Coanda flow, which is in contact with a combustion chamber wall, and a jet flow detached from the combustion chamber wall. Such a switch can occur once or multiple times within a single power stroke of the internal combustion engine.

[0018] The fuel supply system can be designed specifically as a hydrogen injection system. Alternatively, the fuel supply system can be designed for operation with other gaseous fuels, such as methane, propane, and / or butane. The engine equipped with the fuel supply system can be a vehicle engine, i.e., a rail-bound or non-rail-bound vehicle, an aircraft, or a watercraft, or a stationary engine.

[0019] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. The drawing shows:

[0020] Fig. 1 shows a first embodiment of a fuel supply system for an internal combustion engine,

[0021] Fig. 2 shows a second embodiment of a fuel supply system,

[0022] Fig. 3 shows a jet flow exiting a fuel injector of a fuel supply system, Fig. 4 shows a Coanda flow exiting the fuel injector of a fuel supply system,

[0023] Fig. 5 shows an internal combustion engine designed as a reciprocating piston engine with a power supply system enabling switching between jet flow and Coanda flow,

[0024] Fig. 6 shows in a diagram the course of an injector pressure in a fuel supply system as a function of the diameter of a supply line for gaseous fuel,

[0025] Fig. 7 shows a partial representation of an internal combustion engine with a fuel supply system that offers switching options regarding the type of fuel flow, based on a representation similar to Fig. 5.

[0026] Fig. 8 shows a diagram illustrating possible pressure and mass flow profiles in the fuel supply system according to Fig. 7 in a first operating mode.

[0027] Fig. 9 shows in a further diagram the curves of pressures and mass flow in a second actuation mode of the fuel supply system according to Fig. 7.

[0028] Unless otherwise stated, the following explanations apply to all embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0029] A fuel supply system 1 for a gaseous fuel, in particular hydrogen, is used in the exemplary embodiments in an internal combustion engine 10, which is designed as a multi-cylinder reciprocating engine. The design of the reciprocating engine 10 shown in Fig. 5 is the same in all exemplary embodiments. The crankshaft, designated 2, is coupled to a piston 4 via a connecting rod 3. The crankshaft angle is designated a. Depending on the crankshaft angle a, the intake and exhaust valves of the reciprocating engine 10 are controlled in a manner known per se (not shown). The crankshaft angle a is detected by means of a sensor 5. The sensor 5 is linked to a control unit 6, which can be centrally or decentrally designed and is also linked to the fuel supply system 1. Electrical lines are designated 7 in Fig. 5. The only component of the fuel supply system 1 shown in Fig.5. A fuel injector 8 is shown. A spark plug 9 is also indicated.

[0030] Fig. 1 shows a first embodiment of the fuel supply system 1, as it can be used in the reciprocating engine 10 according to Fig. 5. In the case of Fig. 1, the internal combustion engine 10 is a six-cylinder, in-line reciprocating engine whose combustion chambers are designated 11, 12, 13, 14, 15, 16. Alternatively, the internal combustion engine 10 can be configured as a V-engine or as a boxer engine. In each case, three combustion chambers 11, 12, 13 belong to a first cylinder group 17 and three further combustion chambers 14, 15, 16 to a second cylinder group 18. All cylinders of the internal combustion engine 10 are located in a single engine block 19, indicated in Fig. 5.

[0031] Combustion chambers 11, 12, 13, 14, 15, 16 are supplied with fuel, i.e., hydrogen, via a single fuel rail 20, with a supply valve 21 upstream of the fuel rail 20. Supply lines 22, 23 extend from the fuel rail 20, supplying fuel to the first cylinder group 17 and the second cylinder group 18, respectively. These supply lines 22, 23 terminate in secondary fuel rails 24, 25, which are also assigned to the respective cylinder groups 17, 18. Thus, each secondary fuel rail 24, 25 is responsible for supplying fuel to the three combustion chambers 11, 12, 13 of the first cylinder group 17 and to the three combustion chambers 14, 15, 16 of the second cylinder group 18, respectively. The two secondary fuel rails 24, 25 are directly connected to each other via an intermediate line 26. A resonator valve 27 is installed in the intermediate line 26.Six supply lines 28 extend from the fuel rails 24, 25, each leading into a fuel injector 8, which is depicted as a valve in Fig. 1, as well as in Fig. 2. The lengths of all six supply lines 28 are coordinated. In the embodiment shown in Fig. 1, all supply lines 28 have a uniform length. The fuel flow KS exiting the fuel injectors 8 can be influenced by switching the resonator valve 27, as will be explained in more detail below.

[0032] In the embodiment shown in Fig. 2, each combustion chamber 11, 12, 13, 14, 15, 16 is supplied with pressurized hydrogen via a separate supply line 22 leading from the fuel rail 20. In contrast to the embodiment shown in Fig. 1, the internal combustion engine 10 shown in Fig. 2 can also be designed as a reciprocating piston engine with a different number of cylinders, for example as a four-cylinder engine, particularly in the form of an inline engine.

[0033] In the case of Fig. 2, a Helmholtz resonator 29 is connected to the supply line 22, with a resonator valve 30 being connected between the supply line 22 and the Helmholtz resonator 29. Furthermore, in the embodiment according to Fig. 2, a shut-off valve 31 exists, which is located between the branch from the supply line 22 to the Helmholtz resonator 29 and the fuel injector 8. By switching the resonator valve 30 and / or the shut-off valve 31, resonances in the fuel supply system 1 can be selectively influenced. In this way, the fuel injectors 8 assigned to the individual combustion chambers 11, 12, 13, 14 can be controlled either uniformly or differently from one another.The latter option is particularly relevant when resonances occur not only in the fuel supply but also in the optionally pre-compressed air supplied to the combustion chambers 11, 12, 13, 14 and / or in the exhaust system, and these resonances are to be influenced on a cylinder-specific basis. This also applies to the embodiment shown in Fig. 1. Figures 3 and 4 show various flow conditions in the combustion chambers 11, 12, 13, 14, 15, 16, which can be selectively adjusted by actuating the resonator valve 27 (Fig. 1) or the two valves 30, 31 (Fig. 2). A fuel flow is generally designated KS. In the case of Fig. 3, the fuel flow KS is designed as a jet flow JS, which is directed from the injector 8 towards the center of the combustion chamber.The jet flow JS is a detached flow that arises due to a large pressure difference between the fuel exiting the fuel injector 8 and the pressure prevailing in the combustion chamber 11, 12, 13, 14, 15, 16.

[0034] In contrast to the jet flow JS, a Coanda flow CS, visible in Fig. 4, is present at the combustion chamber wall designated 32. As long as the fuel flow KS is configured as a Coanda flow CS, a rich mixture, compared to the filling of the rest of the combustion chamber 11, 12, 13, 14, 15, 16, reaches the spark plug 9, which is located on the combustion chamber roof next to the fuel injector 8. The fuel flow KS can be switched between a Coanda flow CS at the combustion chamber wall 32 and a jet flow JS within one and the same stroke of the internal combustion engine 10.

[0035] Figure 6 shows pressure profiles in various fuel supply systems 1 suitable for both the internal combustion engine 10 according to Figure 1 and the internal combustion engine 10 according to Figure 2, which differ in the diameter of a supply line 22, 23, 28. In the cases considered, the supply lines 22, 23, 28 have diameters of 5 mm, 7.5 mm, and 10 mm, respectively. As can be seen from Figure 6, the pressure fluctuations are greater the smaller the diameter of the supply line 22, 23, 28. In each case, an inlet valve of the internal combustion engine 10 is opened at time 0 ms and closed at 4.5 ms. By appropriately controlling the at least one resonator valve 27, 30, and optionally also the additional valve 31, which is also referred to as a shut-off valve and also functions as a resonator valve, pressure fluctuations after the aforementioned times zero ms and 4.5 ms can be specifically influenced.In particular, it is possible to reduce a pressure drop occurring after time zero, which is especially pronounced with small pipe diameters, by generating a resonance in the fuel supply system 1. Conversely, targeted suppression of resonances, which is also achieved by actuating the valves 27, 30, 31 in a manner dependent on the crankshaft angle α, prevents an excessive pressure increase after the intake valve of the internal combustion engine 10 closes.

[0036] In the embodiment shown in Figures 7 to 9, a resonator valve 31, designed as a shut-off valve and comparable to the embodiment shown in Figure 2, is arranged upstream of the fuel injector 8 in the direction of fuel flow. A nozzle needle, which is part of the fuel injector 8, is designated 33 in Figure 7.

[0037] In a first operating mode of the fuel supply system 1 according to Fig. 7, shown in Fig. 8, the valve 31, which is provided to the fuel injector 8 for supplying hydrogen to the combustion chamber 11, is permanently open during fuel supply. The instantaneous mass flow rate Mm and the cumulative mass flow rate Mk are shown as a function of the crankshaft angle α. In general, the mass flow rate, i.e., the flow of fuel, is denoted by M. Furthermore, also as a function of the crankshaft angle α, the curves of various pressures p are shown, namely a pressure psa at the injector inlet, a nozzle pressure psb, a cylinder pressure pn, and a pressure p33 at the outlet side of the nozzle needle 33.

[0038] As can be seen in Fig. 8, the pressure psb and, to a lesser extent, the pressure p33 drop significantly during fuel supply. This is due to flow losses in the fuel injector 8. The instantaneous mass flow Mm increases approximately linearly after the fuel injector 8 opens, reaching a plateau. With the cessation of fuel supply, i.e., when the fuel injector 8 closes, the instantaneous mass flow Mm also drops approximately linearly back to zero. Only during the opening and closing phases does a Coanda flow CS, as shown in Fig. 4, develop, which is designated in Fig. 8 as the initial Coanda phase Ca and the final Coanda phase Ce, respectively. The two Coanda phases Ca and Ce result from altered geometric expansion conditions compared to the period when the fuel injector 8 is fully open.

[0039] The operating mode according to Fig. 9 differs from the operating mode according to Fig. 8 in that the resonator valve 33, i.e. switching valve, is initially closed at the start of fuel injection and only opens with a delay after the fuel injector 8 has opened.

[0040] At the moment the fuel injector 8 opens, it still contains a reserve quantity of fuel, so the injection process initially resembles the process shown in Fig. 8. However, the plateau of the instantaneous mass flow Mm that occurs in the process shown in Fig. 8 is not reached. Rather, after the completion of the initial Coanda phase Ca, i.e., the transition to the jet flow JS, as shown in Fig. 3, there is indeed a brief further increase in the instantaneous mass flow Mm, but this increase quickly transitions into a local maximum. To allow the further supply of fuel, the switching valve 33 is opened. A phase that includes an interim drop and immediately subsequent renewed increase in the instantaneous mass flow Mm ensures a Coanda flow and is designated as the mean Coanda phase Cm in the diagram according to Fig. 9. In total, there are in the operating mode according to Fig.9 during the injection of fuel, thus three temporally separated phases Ca, Cm, C. e , in which the fuel flow is configured as a Coanda flow. These phases Ca, Cm, Ce are separated from each other by two phases in which the fuel, i.e., hydrogen, flows into the combustion chamber 11 in the form of a jet flow JS. Overall, a defined distribution of the fuel in the combustion chamber 11 is achieved in this way, whereby, if necessary, depending in particular on the load and speed of the internal combustion engine 10, and possibly also on the mixture ratio of different fuels, switching between the operating modes according to Figures 8 and 9 is possible at any time. Reference numeral list

[0041] Fuel supply system

[0042] crankshaft

[0043] connecting rod

[0044] Pistons

[0045] sensor

[0046] control unit electrical line

[0047] Fuel injector

[0048] spark plug

[0049] Internal combustion engine, reciprocating engine

[0050] combustion chamber

[0051] combustion chamber

[0052] combustion chamber

[0053] combustion chamber

[0054] combustion chamber

[0055] Combustion chamber first cylinder group second cylinder group

[0056] Engine block

[0057] fuel rail

[0058] Supply valve

[0059] Supply line

[0060] Supply line

[0061] Second order fuel rail

[0062] Second order fuel rail

[0063] Intermediate line

[0064] Resonator valve

[0065] Supply line

[0066] Helmholtz resonator

[0067] Resonator valve 31 Shut-off valve, resonator valve

[0068] 32 Combustion chamber wall

[0069] 33 Jet needle a Crankshaft angle

[0070] Ca, C e , Cm Coanda phases

[0071] CS Coanda Current

[0072] JS Jet Flow

[0073] KS fuel flow

[0074] M Mass flow, general

[0075] Mk mass flow, cumulative

[0076] Mm mass flow, instantaneous p pressure, psa pressure, injector inlet pressure, psb pressure, nozzle pii cylinder pressure

[0077] P33 Pressure, Outlet Needle

Claims

Patent claims 1. Fuel supply system (1) for an internal combustion engine (10) designed as a reciprocating piston engine with a crankshaft and several combustion chambers (11, 12, 13, 14, 15, 16), with a fuel rail (20, 24, 25) to which several fuel injectors (8) are connected via supply lines (22, 23, 28), characterized in that at least one resonator valve (27, 30, 31) is arranged between the fuel rail (20, 24, 25) and the fuel injectors (8) for actuation depending on the crankshaft angle (a).

2. Fuel supply system (1) according to claim 1, characterized in that the resonator valve (27) is arranged between a first cylinder group (17) and a second cylinder group (18).

3. Fuel supply system (1 ) according to claim 1 , characterized in that each fuel injector (8) is assigned a separate resonator valve (30).

4. Fuel supply system (1 ) according to claim 3, characterized in that the resonator valve (30) is connected to a Helmholtz resonator (29).

5. Fuel supply system (1 ) according to claim 3 or 4, characterized by a shut-off valve (31) arranged between the resonator valve (30) and the fuel injector (8).

6. Fuel supply system (1 ) according to one of claims 1 to 5, characterized in that it is designed as an injection system for a gaseous fuel, in particular hydrogen.

7. Method for supplying fuel to a combustion chamber (11, 12, 13, 14, 15, 16) of an internal combustion engine (10), which has a crankshaft (2) and several combustion chambers (11, 12, 13, 14, 15, 16), wherein, depending on the angular position of the crankshaft (2), at least one resonator valve (27, 30, 31), which is arranged between a fuel rail (20, 24, 25) and a fuel injector (8) provided for injecting fuel into a combustion chamber (11, 12, 13, 14, 15, 16), is actuated out of phase with the actuation of the fuel injector (8).

8. Method according to claim 7, characterized in that resonances are amplified by actuating the resonator valve (27, 30, 31).

9. Method according to claim 7 or 8, characterized in that resonances are suppressed by actuating the resonator valve (27, 30, 31).

10. Method according to one of claims 7 to 9, characterized in that the actuation of the resonator valve (27, 30, 31) causes a switching of a fuel flow directed from the fuel injector (8) into the combustion chamber (11, 12, 13, 14, 15, 16) in at least one switching direction between a Coanda flow (CS) adjacent to a combustion chamber wall (32) and a jet flow (JS) detached from the combustion chamber wall (32).

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