Device for introducing a fuel into a gas engine

Abstract

The present invention relates to a device for introducing a fuel into a gas engine, the device having a fuel tank which stores the fuel under a specific pressure, preferably at more than 5 bar, preferentially at more than 7 bar, a pressure control valve which is arranged downstream of the fuel tank and is designed to lower the fuel originating from the fuel tank to a constant, stationary pressure level, a first rail with at least one fuel injector for directly introducing the fuel into a combustion chamber of an engine cylinder, and a second rail with at least one fuel injector for introducing the fuel into an intake region of the engine cylinder. The device is characterized in that both the first rail and the second rail are arranged downstream of the pressure control valve and each draw their fuel that is to be output via their respective at least one fuel injector via the pressure control valve.

Description

[0001] Device for introducing a fuel into a gas engine

[0002] The present invention relates to a device for introducing fuel into a gas engine. Furthermore, the invention also encompasses a gas engine with such a device.

[0003] A gas engine is an internal combustion engine capable of burning a fuel that is gaseous at ambient pressure. In recent years, the market has been dominated by internal combustion engines powered by liquid fuels such as gasoline and diesel. There have been numerous experiments with internal combustion engines that use gaseous fuels such as compressed natural gas (CNG) or liquefied natural gas (LNG). For the series production of such internal combustion engines, the indirect multi-point injection system with spark ignition was used. This system injected the gas into the intake manifold leading to the combustion chamber, allowing the gas to be introduced into the intake manifold at a low pressure, typically less than 15 bar.

[0004] One of the main disadvantages of this type of gaseous fuel combustion technology is combustion stability, knocking, increased nitrogen emissions, and slow engine response. The inventors' research into gas-powered internal combustion engines (CNG, LNG, or H2), which aim to maximize engine performance while maintaining low NOx emissions, shows that direct injection technology for pilot injection (with spark ignition) combined with port fuel injection for actual power generation represents a highly promising solution for achieving stable and controlled combustion.

[0005] However, since the pilot injection and the main injection must take place at different pressure levels, this leads to the use of two independent, parallel injection systems, in which one system feeds the direct injection nozzles (LPDI; English for: liquefied petroleum direct injection) with a typical pressure between 20 and 60 bar and the other the intake manifold injection nozzles (PFI; English for: port fuel injection) with a typical pressure between 3 and 20 bar - depending on the engine load point.

[0006] This requires a complex pressure control solution, as two systems must be operated in parallel and controlled. For the same reason, the system is particularly complex due to the limited space available for the installation, which in turn negatively impacts costs.

[0007] The aim of this invention is to propose a device for introducing the fuel into the gas engine in order to ensure the correct pressure levels for the fuel nozzles injecting directly into the combustion chamber (i.e. the LPDI injectors) and, at the same time, for the fuel nozzles injecting into the intake manifold (i.e. the PFI injectors), while avoiding redundancy of components and reducing the space required on the engine.

[0008] A device according to the invention for introducing a fuel into a gas engine comprises a fuel tank which stores the fuel under a specific pressure, preferably more than 5 bar, more preferably more than 7 bar, a pressure control valve arranged downstream of the fuel tank which is designed to reduce the fuel originating from the fuel tank to a constant, stationary pressure level, a first rail with at least one fuel injector for directly introducing the fuel into a combustion chamber of an engine cylinder, and a second rail with at least one fuel injector for introducing the fuel into an intake region of the engine cylinder.The device is characterized in that both the first rail and the second rail are arranged downstream of the pressure control valve and each receive the fuel to be delivered via its respective at least one fuel injector via the pressure control valve.

[0009] The invention provides for the implementation of a single or shared fuel path that offers the possibility of ejecting the fuel in two stages with different and controlled pressure levels, as required for proper functionality.

[0010] This is advantageously possible because the injection pressure for direct injection is generally higher than the injection pressure for intake manifold injection. This enables combined and cascaded pressure control.

[0011] In contrast to the known state of the art, two separate fuel supply systems or fuel paths are no longer used, a first of which implements the fuel injectors for direct injection and a second of which implements the fuel injection for intake manifold injection.

[0012] Rather, the invention provides that at least one component is used jointly for the different fuel injections, as is shown, for example, by the joint use of the pressure control valve.

[0013] According to an optional development of the present invention, it can be provided that the first rail and the second rail are arranged in series with one another, so that the fuel must first flow through the first rail to reach the second rail.

[0014] The series arrangement of the two rails makes it possible to save connecting cables and further reduce the weight and manufacturing costs of the device.

[0015] Furthermore, according to the present invention, it can be provided that a flow control valve is arranged upstream of the second rail in order to enable a pressure variation of the fuel flowing into the second rail, preferably wherein the pressure control valve is arranged immediately upstream of the second rail.

[0016] If the two rails are arranged in series with each other, it can be provided that a flow control valve is provided upstream of the second rail, which is arranged between the first rail and the second rail in order to enable a pressure variation of the fuel flowing into the second rail.

[0017] This is particularly advantageous because the first rail, which has the injectors for direct injection, is supplied with a constant fuel pressure that is independent of the engine's operating point. The situation is different for the second rail, which has the injectors for intake manifold injection, because the target value of the fuel pressure depends on the engine load and the operating point of the engine to be supplied with fuel. It is therefore advantageous if a flow control valve, which can vary the fuel pressure, is arranged upstream of the second rail, preferably directly upstream of the second rail, so that the fuel pressure for the second rail can be adjusted depending on the required target pressure. Starting from the fuel tank, first the pressure control valve, then the first rail, then the flow control valve and finally the second rail are arranged in a row.This results in only one fuel supply path, which is significantly less susceptible to failure than an implementation with two parallel paths.

[0018] According to a further optional modification of the present invention, it can be provided that a flow control valve is provided upstream of the first rail, preferably wherein the flow control valve is arranged immediately upstream of the first rail.

[0019] A flow control valve is capable of variably adjusting the fuel pressure at the inlet to a setpoint. This setpoint is typically below the inlet pressure at the inlet of the flow control valve. Rapidly changing the pressure enables efficient fuel injection via the fuel injectors, thus initiating and executing the combustion process as optimally as possible.

[0020] A flow control valve is a component which, due to a corresponding control, is able to reduce the pressure level of the supplied fuel to a different pressure level in accordance with the control signals.

[0021] By providing a flow control valve upstream of the first rail, it is possible to also supply the first rail with a variable fuel pressure state.

[0022] According to an advantageous development of the present invention, a first flow control valve can be provided upstream of the first rail and a second flow control valve upstream of the second rail, wherein the first flow control valve is preferably arranged directly upstream of the first rail and the second flow control valve is arranged directly upstream of the second rail. As a result, the two rails, which can be connected in series, are independent of one another with regard to the desired fuel pressure in the respective rail. The fine adjustment of the desired fuel pressure is then carried out in the respective upstream flow control valve for the downstream rail.

[0023] The advantage here is that the first rail for supplying the injector units for direct injection requires a higher fuel pressure than the second rail, which supplies the injector units for intake manifold injection with fuel.

[0024] Furthermore, according to the invention, the fuel tank can be designed to deliver fuel at a variable pressure depending on the fuel fill level, preferably with the minimum pressure value of a fuel delivered from the fuel tank not falling below the constant, steady-state pressure level of the pressure control valve. Thus, as the fill level in the tank decreases, the discharge pressure of the fuel from the fuel tank can also decrease.

[0025] According to the invention, it can also be provided that it further comprises an engine control unit which is linked to an opening and closing mechanism for the fuel injectors of the first rail and the second rail for controlling them.

[0026] The engine control unit is therefore designed to coordinate and implement the opening and closing timing of the plurality of fuel injectors of the first rail and the second rail.

[0027] Preferably, it can also be provided that the engine control unit is linked to the at least one flow control valve in order to control the at least one flow control valve.

[0028] The engine control unit can therefore also control the flow control valve to vary the actual fuel pressure in the first rail and / or the second rail. However, the target fuel pressure also depends, in particular, on the timing of the operation of the fuel injectors of the first rail and / or the second rail.

[0029] Furthermore, according to an optional modification of the present invention, it can be provided that both the first rail and / or the second rail have a temperature sensor and / or a pressure sensor for detecting temperature and / or the pressure prevailing in the respective rail.

[0030] Preferably, the engine control unit is linked to the temperature sensor and / or the pressure sensor of the first rail and the second rail, respectively, in order to control the fuel injectors of the first rail and the second rail and / or the at least one flow control valve as a function thereof.

[0031] The information about the temperature and pressure value in the first rail and / or the second rail also serves to adjust the flow control valve or the timing in the operation of the fuel injectors in order to provide an optimal supply of fuel to the internal combustion engine.

[0032] The invention further relates to a gas engine, which is an embodiment of an internal combustion engine, with a device for supplying fuel to the gas engine according to one of the preceding variants.

[0033] Preferably, it can be provided that the gas engine is provided with a combustion chamber in which an ignition of a fuel introduced therein leads to a movement of a piston, and an intake region for introducing a fuel-air mixture into the combustion chamber.

[0034] In other words, the at least one fuel injector of the first rail is arranged such that it is designed to deliver fuel directly into the combustion chamber of the gas engine. The at least one fuel injector of the second rail, however, is arranged at a different location on the gas engine and delivers fuel into an intake area of ​​the combustion chamber. Thus, fuel is already delivered via the at least one fuel injector of the second rail during air intake (during the intake stroke of the gas engine), so that the delivered fuel mixes with air in the intake area and is then drawn into the combustion chamber by the intake movement.

[0035] Since, for example, the air-fuel mixture drawn in this way is not flammable with the desired quality (e.g., because the mixture is too lean), direct fuel injection into the combustion chamber can occur during the compression phase or shortly thereafter via the fuel injector of the first rail. This fuel is much more flammable (possibly only locally in the combustion chamber) than the air-fuel mixture previously drawn in via the intake area. By igniting the much richer mixture obtained through direct injection, a uniform flame front can develop, leading to efficient combustion of the fuel introduced into the combustion chamber.

[0036] The invention also includes the fact that the fuel which is introduced into the combustion chamber via direct injection is introduced into a pre-chamber of the gas engine.

[0037] According to a further advantageous development of the present invention, it can be provided that the at least one fuel injector of the first rail and the at least one fuel injector of the second rail are each designed to deliver fuel during operation of the engine, in particular during a working cycle of the engine comprising several engine strokes, preferably in such a way that fuel is introduced directly into the combustion chamber of the engine via the at least one fuel injector of the first rail, so that a fuel can be introduced directly into the combustion chamber of the engine, and an injection of fuel into the intake region takes place via the at least one fuel injector of the second rail, so that a fuel-air mixture can be introduced into the combustion chamber during the intake stroke of the engine.According to the invention, it can also be provided that the engine control unit is designed to introduce fuel via the at least one fuel injector of the first rail during a compression stroke of the engine and / or to introduce fuel via the at least one fuel injector of the second rail during an intake stroke of the engine.

[0038] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show:

[0039] Fig. 1 : a structural representation of a device for introducing a fuel into a gas engine according to the prior art,

[0040] Fig. 2: a structural representation of a device for introducing a

[0041] Fuel in a gas engine according to the invention,

[0042] Fig. 3: a structural representation of a device for introducing a

[0043] Fuel into a gas engine according to another embodiment,

[0044] Fig. 4: a structural representation of a device for introducing a

[0045] fuel into a gas engine according to another embodiment, and

[0046] Fig. 5: a structural representation of a device for introducing a

[0047] Fuel into a gas engine according to another embodiment.

[0048] Fig. 1 shows a structural representation of a device for introducing a fuel into a gas engine according to the prior art.

[0049] It can be seen that both the first rail 4 and the second rail 5 each have a separate fuel supply path, each of which leads separately to the fuel tank 2. This results in significant disadvantages, particularly with regard to the need for multiple components, since the installation space required by the multiple components must also be dimensioned to be large.

[0050] Fig. 2 shows a structural diagram of a device for introducing a fuel into a gas engine according to the present invention.

[0051] It can be seen that significantly fewer components are required compared to the prior art shown in Fig. 1, since the first rail 4 and the second rail 5 are connected in series.

[0052] The fuel stored in a fuel tank 2, which assumes a gaseous state at ambient pressure (e.g., LNG, CNG, or H2), is thus fed to both the first rail 4 and the second rail 5 via the same pressure control valve 3. In the embodiment shown in Fig. 2, the output pressure at the outlet of the pressure control valve 3 corresponds to the target pressure for the first rail 4, which is used for direct injection into a combustion chamber of a gas engine. Thus, several fuel injectors 6 are provided on the first rail 4, which, via control commands from an engine control unit 10, inject the fuel directly into a combustion chamber of an internal combustion engine at a specific time and for a specific duration.

[0053] According to the invention, a pre-chamber which is fluidically connected to a main combustion chamber of the gas engine can also be regarded as a combustion chamber

[0054] The second rail 5 is arranged further downstream in series, so that fuel introduced into the second rail 5 has already flowed through the pressure control valve 3 and the first rail 4. The fuel injectors 7 arranged on the second rail 5 serve to introduce fuel into an intake area (e.g., an intake manifold of a combustion chamber of a gas engine) so that the fuel can mix with intake air upstream of a combustion chamber before the air-fuel mixture is drawn into the combustion chamber, preferably during an intake stroke of the engine. In order to be able to achieve a pressure in the second rail 5 that varies depending on the pressure control valve 3, a flow control valve 8 is provided between the first rail 4 and the second rail 5, which flow control valve can be controlled by the engine control unit 10 to set a corresponding target pressure value for the fuel flowing into the second rail 5.As a rule, the second rail 5, which is used for intake manifold injection, requires a fuel with a lower pressure than the first rail 5, which is used for direct injection into the combustion chamber of a gas engine.

[0055] The pressure at the outlet of the fuel tank 2, which varies depending on the fill level of the fuel tank 2, is regulated to a constant pressure value via the pressure control valve 3, for example, using a mechanical pressure control unit. This constant pressure value is sufficiently high for the fuel injectors 6 on the first rail 4 to perform their task of directly injecting the fuel. A pilot quantity, ignited by an ignition spark, is injected directly into the combustion chamber. Both the pilot quantity of fuel to be injected and the required pressure of the fuel to be injected are essentially constant and independent of the workload of the gas engine being supplied with fuel.

[0056] For reasons of clarity, any safety and servo valves are not shown in any of the figures. However, those skilled in the art will be aware that these can be advantageously provided to ensure safe operation.

[0057] The fuel not injected by the first rail 4 but passed on is then converted into a variable-pressure fuel by means of a flow control valve 8, which is provided at a different pressure depending on requirements. The injection quantity, like the target fuel pressure, can be varied over time. This depends, among other things, on the current workload and the desired engine power of the gas engine to be supplied with fuel. The flow control valve 8 adjusts the fuel pressure to the desired target value, should this deviate from the target value. Since the required pressure for the fuel injectors 7 of the second rail 5 is generally lower than for the fuel injectors 6 of the first rail 4, the flow control valve 8 is a variable pressure reducer.The flow control valve 8 is also controlled via the engine control unit 10, which also controls the fuel injectors 7 of the second rail 5 with regard to the amount of fuel to be dispensed and the timing of the injection.

[0058] Fig. 3 shows a further modification of the basic inventive concept, in which, in contrast to Fig. 2, the first rail 4 also has an upstream flow control valve 9. This also makes it possible to vary the pressure of the fuel in the first rail 4, so that direct injection can also take place at different pressure ratios of the fuel to be injected.

[0059] Fig. 4 shows a further variant of the present invention in which the first rail 4 and the second rail 5 are no longer connected in series, but instead jointly use only the pressure control valve 3. Downstream of the pressure control valve 3, the path for guiding the fuel splits and then runs either to the first rail 4 or to the second rail 5. Before the fuel reaches a respective rail 4, 5, however, it flows through a respective flow control valve 8, 9, which enables a variation of the fuel pressure on the subsequently arranged rail 4, 5. Each of the flow control valves 8, 9 is controlled by the engine control unit 10. The parallel arrangement of the first rail 4 and the second rail 5 is advantageous over the prior art due to the joint use of the pressure control valve 3.In addition, line sections downstream of the pressure control valve 3 are also used jointly, so that here too an advantageous effect in terms of costs and the space required can be achieved. Fig. 5 shows a further variant of the system according to the invention, the basic structure of which is based on the previous Fig. 4. In deviation from this, the second rail 5, which is used for the intake manifold injection, is subjected to a constant fuel pressure, namely with a fuel pressure as provided by the pressure control valve 3, which can be a mechanical pressure control valve. The first rail 5, on the other hand, has a flow control valve which is arranged upstream of the first rail 4 but is not arranged in a common fuel path through which both the first rail 4 and the second rail 5 are supplied with fuel.

[0060] The advantages of the present invention are better cost efficiency, lower packing density, improved safety structure, higher reliability and improved responsiveness.

[0061] It will be clear to those skilled in the art that the presented concept is applicable to all internal combustion engines that utilize both port and direct injection, which can be based on different pressure levels. Examples include heavy-duty engines for mobile machinery, which have high power density and high dynamic requirements. Furthermore, the present invention would also be ideally suited for large engines typically used in mining.

[0062] List of reference symbols:

[0063] 1 Device for introducing a fuel into a gas engine

[0064] 2 Fuel tank 3 Pressure control valve

[0065] 4 first rail for direct injection

[0066] 5 second rail for intake manifold injection

[0067] 6 Fuel injector of the first rail

[0068] 7 Second rail fuel injector 8 Flow control valve

[0069] 9 Flow control valve

[0070] 10 Engine control unit

[0071] 11 Temperature sensor

[0072] 12 Pressure sensor

Claims

Claims 1. Device (1) for introducing a fuel into a gas engine, comprising: a fuel tank (2) which stores the fuel under a specific pressure, preferably at more than 5 bar, more preferably at more than 7 bar, a pressure control valve (3) arranged downstream of the fuel tank (2) which is designed to reduce the fuel originating from the fuel tank (2) to a constant, stationary pressure level, a first rail (4) with at least one fuel injector (6) for directly introducing the fuel into a combustion chamber of an engine cylinder, and a second rail (5) with at least one fuel injector (7) for introducing the fuel into an intake region of the engine cylinder, characterized in that both the first rail (4) and the second rail (5) are arranged downstream of the pressure control valve (3) and each have their respective at least one fuel injector (6,7) to be dispensed via the pressure control valve (3).

2. Device (1) according to claim 1, wherein the first rail (4) and the second rail (5) are arranged in series with one another, so that the fuel must first flow through the first rail (4) to reach the second rail (5).

3. Device (1) according to one of the preceding claims, wherein a flow control valve (8; 9) is arranged upstream of the second rail (5) in order to enable a pressure variation of the fuel flowing into the second rail (5), preferably wherein the flow control valve (8) is arranged immediately upstream of the second rail (5).

4. Device (1) according to claim 2, wherein a flow control valve (8) is provided upstream of the second rail (5), which is arranged between the first rail (4) and the second rail (5) in order to enable a pressure variation of the fuel flowing into the second rail (5).

5. Device (1) according to one of the preceding claims, wherein a flow control valve (9) is provided upstream of the first rail (4), preferably wherein the flow control valve (9) is arranged immediately upstream of the first rail (4).

6. Device (1) according to one of the preceding claims, wherein a first flow control valve (9) is provided upstream of the first rail (4) and a second flow control valve (8) is provided upstream of the second rail (5), wherein preferably the first flow control valve (9) is arranged immediately upstream of the first rail (4) and the second flow control valve (8) is arranged immediately upstream of the second rail (5).

7. Device (1) according to one of the preceding claims, wherein the fuel tank (2) is designed to deliver fuel at a variable pressure depending on a fuel fill level, preferably wherein the minimum pressure value of a fuel delivered from the fuel tank (2) does not fall below the constant, stationary pressure level of the pressure control valve (3).

8. Device (1) according to one of the preceding claims, further comprising a motor control unit (10) provided with an opening or closing mechanism for the fuel injectors (6) of the first rail (4) and the second rail (5) are linked for their control.

9. Device (1) according to claim 8, further developed with the features of claim 3, 4, 5 and / or 6, wherein the engine control unit (10) is linked to the at least one flow control valve (8; 9) in order to control the at least one flow control valve (8; 9).

10. Device (1) according to one of the preceding claims, wherein both the first rail (4) and / or the second rail (5) have a temperature sensor (11) and / or a pressure sensor (12) for detecting temperature and / or the pressure prevailing in the respective rail (4, 5).

11. Device (1) according to claim 8 or 9, further developed with the features of claim 10, wherein the engine control unit (10) is linked to the temperature sensor (11) and / or the pressure sensor (12) of the first rail (4) or the second rail (5) in order to control the fuel injectors (6) of the first rail (4) and the second rail (5) and / or the at least one flow control valve (8; 9) as a function thereof.

12. Gas engine with a device (1) for supplying fuel to the gas engine according to one of the preceding claims.

13. Gas engine according to the preceding claim 12, with a combustion chamber in which ignition of a fuel introduced therein leads to movement of a piston, and an intake region for introducing a fuel-air mixture into the combustion chamber.

14. Gas engine according to one of the preceding claims 12 or 13, wherein the at least one fuel injector (6) of the first rail (4) and the at least one fuel injector (7) of the second rail (5) are each designed to, during operation of the engine, in particular during a cycle comprising several engine cycles Working cycle of the engine, to deliver fuel, preferably in such a way that fuel is introduced directly into the combustion chamber of the engine via the at least one fuel injector (6) of the first rail (4), so that a fuel can be introduced directly into the combustion chamber of the engine, and an injection of fuel into the intake region takes place via the at least one fuel injector (7) of the second rail (5), so that a fuel-air mixture can be introduced into the combustion chamber during the intake stroke of the engine.

15. Gas engine according to the preceding claim 14, further developed with the features of claim 8, wherein the engine control unit (10) is designed to introduce fuel via the at least one fuel injector (6) of the first rail (4) during a compression stroke of the engine and to introduce fuel via the at least one fuel injector (7) of the second rail (5) during an intake stroke of the engine.

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