Gas engine, control device, and control method

Abstract

A gas engine according to one embodiment of the present disclosure comprises a control device that executes a backfire suppression process for executing a backfire suppression process for injecting water from a water injector at such a timing that water spreads in a combustion chamber after an air supply valve opens an air supply port and that gas fuel spreads in the combustion chamber after water spreads in the combustion chamber.

Description

Gas engine, control device, and control method

[0001] The present disclosure relates to a gas engine, a control device, and a control method.

[0002] In Patent Document 1, in order to prevent the intake manifold from being excessively heated due to backfire, when the occurrence of backfire in the intake passage is detected, a hydrogen engine system that injects water into the intake manifold or the like is described.

[0003] Japanese Patent Application Laid-Open No. 2016-118109

[0004] As described above, the hydrogen engine system described in Patent Document 1 injects water when backfire occurs. However, if the occurrence of backfire itself can be suppressed, various problems caused by backfire will be reduced.

[0005] Therefore, an object of the present disclosure is to provide a gas engine capable of suppressing the occurrence of backfire.

[0006] A gas engine according to an aspect of the present disclosure includes a cylinder, a piston that reciprocates within the cylinder, an air supply port that supplies air to a combustion chamber defined by the cylinder and the piston, an exhaust port that discharges exhaust gas from the combustion chamber, an air supply valve that opens and closes the air supply port, an exhaust valve that opens and closes the exhaust port, a fuel injector that injects gas fuel into the air supply port, a water injector that injects water into the air supply port or the combustion chamber, and a control device capable of controlling the timing at which the water injector injects water. The control device performs a backfire suppression process of injecting water from the water injector at a timing such that after the air supply valve opens the air supply port, water spreads into the combustion chamber, and after the water spreads into the combustion chamber, gas fuel spreads into the combustion chamber.

[0007] According to the gas engine according to an aspect of the present disclosure, the occurrence of backfire can be suppressed.

[0008] Figure 1 is a schematic diagram of the mechanical system configuration of a gas engine. Figure 2 is a schematic diagram of the mechanical system configuration of a modified gas engine. Figure 3 is a block diagram of the control system configuration of a gas engine. Figure 4 is a flow chart of the backfire suppression program. Figure 5 is a diagram showing the timing of water injection by the water injector.

[0009] <Mechanical System Configuration of the Gas Engine> The embodiments will be described below. First, the configuration of the mechanical system of the gas engine 100 according to the embodiment will be described. Figure 1 is a schematic diagram of the configuration of the mechanical system of the gas engine 100. The gas engine 100 is an engine that uses gas fuel as fuel. The gas fuel in this embodiment contains hydrogen gas. The gas fuel containing hydrogen gas also includes hydrogen gas itself. Furthermore, the gas fuel is not limited to gas containing hydrogen gas, and may be a gas containing, for example, natural gas. As shown in Figure 1, the gas engine 100 includes a cylinder 11, a piston 12, an air intake port 13, an exhaust port 14, an air intake valve 15, an exhaust valve 16, a fuel injector 17, and a water injector 18.

[0010] The cylinder 11 is formed by a cylinder block 21 and a cylinder head 22. In other words, the cylinder block 21 forms the inner surface of the cylinder 11, and the cylinder head 22 forms the top surface of the cylinder 11. Figure 1 shows one cylinder 11, but the gas engine 100 according to this embodiment has multiple cylinders 11. Note that the vertical direction of the paper in Figure 1 is the axis direction of the central axis of the cylinder 11.

[0011] The piston 12 is a component that reciprocates within the cylinder 11 and is connected to the crankshaft via a connecting rod 23. Together with the cylinder 11, the piston 12 defines the combustion chamber 24 where gaseous fuel is burned. In particular, gaseous fuel containing hydrogen gas has good ignition properties, making it prone to backfire, where the flame flows back into the intake port 13. Possible causes of backfire include ignition due to contact with high-temperature substances such as already burned gas and deposits in the combustion chamber 24, as well as ignition by lubricating oil that is stirred up into the combustion chamber 24 and ignites on its own.

[0012] The air intake port 13 is a port that supplies air to the combustion chamber 24 and is formed in the cylinder head 22. In Figure 1, only one air intake port 13 is shown, but multiple air intake ports 13 may be formed for a single cylinder 11.

[0013] The exhaust port 14 is a port for discharging exhaust gas from the combustion chamber 24 and is formed in the cylinder head 22. Although only one exhaust port 14 is shown in Figure 1, multiple exhaust ports 14 may be formed for a single cylinder 11.

[0014] The air supply valve 15 is a valve that opens and closes the air supply port 13. In this embodiment, the air supply valve 15 is configured to change the timing of opening and closing the air supply port 13 using a variable valve mechanism 32 (see Figure 3). However, the air supply valve 15 may also be configured so that the timing of opening and closing the air supply port 13 is constant.

[0015] The exhaust valve 16 is a valve that opens and closes the exhaust port 14. In this embodiment, the exhaust valve 16 is configured to change the timing of opening and closing the exhaust port 14 using a variable valve mechanism 32 (see Figure 3). However, the exhaust valve 16 may be configured so that the timing of opening and closing the exhaust port 14 is constant.

[0016] The fuel injector 17 is a device that injects gaseous fuel. In this embodiment, the fuel injector 17 is positioned to face the intake port 13 and injects gaseous fuel into the gaseous fuel injection section 25 of the intake port 13. As a result, a mixture of gaseous fuel and air is formed in the intake port 13, and the formed mixture is supplied to the combustion chamber 24. The mixture supplied to the combustion chamber 24 may be ignited by compression ignition or by using an ignition device. The ignition device may include a spark plug, as well as a device that injects pilot fuel, which is more easily ignited than the main fuel, and causes the pilot fuel to self-ignite for ignition.

[0017] The water injector 18 is a device that injects water. In this embodiment, the water injector 18 is positioned facing the air intake port 13 and injects water into the water injection section 26 of the air intake port 13. The water injection section 26 is located downstream of the gas fuel injection section 25, that is, closer to the combustion chamber 24 than the gas fuel injection section 25. Furthermore, the water injector 18 does not inject water constantly while the gas engine 100 is operating, but rather injects water when the control device 31, which will be described later, performs backfire suppression processing. As shown in Figure 2, the water injector 18 may also be positioned facing the combustion chamber 24 and inject water into the combustion chamber 24.

[0018] <Configuration of the gas engine control system> Next, the configuration of the control system of the gas engine 100 according to this embodiment will be described. Figure 3 is a block diagram of the configuration of the control system of the gas engine 100. As shown in Figure 3, the gas engine 100 according to this embodiment is equipped with a control device 31 that controls the gas engine 100.

[0019] The control device 31 includes a processor, volatile memory, non-volatile memory, and an I / O interface. The non-volatile memory of the control device 31 stores a backfire suppression program, which will be described later, and the processor performs calculations using the volatile memory based on each program.

[0020] As shown in Figure 3, the control device 31 is electrically connected to the variable valve mechanism 32, and by transmitting a control signal to the variable valve mechanism 32, it can control the timing of when the intake valve 15 opens and closes the intake port 13, and when the exhaust valve 16 opens and closes the exhaust port 14. The control device 31 is also electrically connected to the fuel injector 17, and by transmitting a control signal to the fuel injector 17, it can control the timing of when the fuel injector 17 injects gaseous fuel. Furthermore, the control device 31 is electrically connected to the water injector 18, and by transmitting a control signal to the water injector 18, it can control the timing of when the water injector 18 injects water.

[0021] Furthermore, the control device 31 is electrically connected to an in-cylinder pressure sensor 41, an intake pressure sensor 42, an exhaust pressure sensor 43, a crank angle sensor 44, a hydrogen gas flow meter 45, and a torque meter 46. By receiving measurement signals from these devices, the control device can acquire in-cylinder pressure, intake pressure, exhaust pressure, crank angle, hydrogen gas flow rate, and engine torque.

[0022] <Backfire Suppression Program> Next, the backfire suppression program executed by the control device 31 will be described. Figure 4 is a flowchart of the backfire suppression program. As shown in Figure 4, when the backfire suppression program is started, the control device 31 first acquires various measured values ​​(step S1). Specifically, the control device 31 acquires in-cylinder pressure, intake pressure, exhaust pressure, crank angle, hydrogen gas flow rate, and engine torque by receiving measurement signals from the in-cylinder pressure sensor 41, intake pressure sensor 42, exhaust pressure sensor 43, crank angle sensor 44, hydrogen gas flow meter 45, and torque meter 46.

[0023] Next, the control device 31 calculates the mean effective pressure, which is the effective work done in one cycle, the power ratio, which is the ratio of engine output to the rated output of the gas engine 100, the hydrogen gas mixture ratio, which is the proportion of hydrogen gas in the gas fuel, and the intake and exhaust pressure difference, which is the difference between the intake pressure and the exhaust pressure, based on the various measurements obtained in step S1 (step S2). Of these, the mean effective pressure can be calculated based on the in-cylinder pressure and the crank angle. The engine output used to calculate the power ratio can be calculated based on the crank angle and the engine torque. Furthermore, the hydrogen gas mixture ratio can be calculated based on the hydrogen gas flow rate.

[0024] Next, the control device 31 determines whether or not the backfire conditions are met (step S3). For example, if at least one of the following conditions is met, such as the average effective pressure being equal to or greater than a predetermined reference effective pressure, the output ratio being equal to or greater than a predetermined reference output ratio, the mixing ratio being equal to or greater than a predetermined reference mixing ratio, and the intake / exhaust pressure difference being equal to or less than a predetermined reference pressure difference, then it is determined that the backfire conditions are met. If the above backfire conditions are met, there is a high probability that backfire will occur in the gas engine 100.

[0025] When the control device 31 determines that the backfire conditions are met (YES in step S3), that is, when it determines that there is a high probability of backfire occurring in the gas engine 100, it performs backfire suppression processing (step S4). The backfire suppression processing is a process in which, after the intake valve 15 opens the intake port 13, water is injected from the water injector 18 at a timing such that the water injected from the water injector 18 spreads in the combustion chamber 24 before the gas fuel injected from the fuel injector 17.

[0026] Figure 5 shows the timing of water injection from the water injector 18 during the backfire suppression process in step S4. More specifically, Figure 5 is a diagram showing the lift curves of the intake valve 15 and exhaust valve 16, with the timing of gas fuel injection from the fuel injector 17 and water injection from the water injector 18 added. The horizontal axis of Figure 5 is the crank angle, and the vertical axis is the lift amount. The solid line represents the lift curve of the intake valve 15, and the dashed line represents the lift curve of the exhaust valve 16. In other words, Figure 5 shows the operating status of each device during the transition period from the exhaust stroke to the intake stroke.

[0027] As shown in Figure 5, in the backfire suppression process, the control device 31 injects gaseous fuel from the fuel injector 17 and water from the water injector 18 before the intake valve 15 begins to open the intake port 13. Furthermore, in this embodiment, the control device 31 injects water from the water injector 18 before injecting gaseous fuel from the fuel injector 17. As a result, after the intake valve 15 opens the intake port 13, the water injected from the water injector 18 spreads throughout the combustion chamber 24. Then, after the water injected from the water injector 18 has spread throughout the combustion chamber 24, the gaseous fuel injected from the fuel injector 17 spreads throughout the combustion chamber 24.

[0028] Thus, in the backfire suppression process of this embodiment, water spreads into the combustion chamber 24 before the gaseous fuel. Therefore, before the gaseous fuel spreads into the combustion chamber 24, the already burned gas and high-temperature substances such as deposits in the combustion chamber 24 are cooled, and the autoignition of lubricating oil stirred up into the combustion chamber 24 is also suppressed. As a result, the occurrence of backfire can be suppressed.

[0029] Furthermore, if water spreads into the combustion chamber 24 before gas fuel after the intake valve 15 opens the intake port 13, it is not necessary to inject water from the water injector 18 before injecting gas fuel from the fuel injector 17. For example, as in this embodiment, if the water injector 18 injects water into a water injection unit 26 located downstream of the gas fuel injection unit 25 of the intake port 13, water may be injected from the water injector 18 at the same time as the gas fuel is injected from the fuel injector 17. Even in this case, when the intake valve 15 opens the intake port 13, water spreads into the combustion chamber 24 before gas fuel after the intake valve 15 opens the intake port 13. Therefore, the occurrence of backfire can be suppressed.

[0030] According to the lift curve shown in Figure 5, the intake valve 15 begins to open the intake port 13 before top dead center, while the exhaust valve 16 finishes closing the exhaust port 14 after top dead center. In other words, valve overlap occurs near top dead center. However, the opening and closing timing of the intake valve 15 and exhaust valve 16 is not limited to the timing shown in Figure 5, and valve overlap does not necessarily have to occur. Also, for example, the intake valve 15 may be configured to begin opening the intake port 13 after top dead center.

[0031] Returning to Figure 4, when the control device 31 determines that the backfire occurrence conditions are not met (NO in step S3), that is, when it determines that there is not a high probability of backfire occurring in the gas engine 100, it stops the backfire suppression process (step S5). In other words, in this embodiment, if there is not a high probability of backfire occurring in the gas engine 100, water is not injected from the water injector 18 during the backfire suppression process. Therefore, unnecessary water injection can be prevented, and water consumption can be reduced.

[0032] Next, after going through steps S4 and S5, the process returns to step S1 and repeats each step. Note that "performing backfire suppression processing" in step S4 includes both starting backfire suppression processing and continuing backfire suppression processing. Also, "stopping backfire suppression processing" in step S5 includes both stopping the backfire suppression processing that was being performed and continuing to stop backfire suppression processing.

[0033] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0034] <Summary> The first item disclosed in this specification is a gas engine comprising a cylinder, a piston that reciprocates within the cylinder, an air intake port that supplies air to a combustion chamber separated by the cylinder and the piston, an exhaust port that discharges exhaust gas from the combustion chamber, an air intake valve that opens and closes the air intake port, an exhaust valve that opens and closes the exhaust port, a fuel injector that injects gaseous fuel containing hydrogen gas into the air intake port, a water injector that injects water into the air intake port or the combustion chamber, and a control device that can control the timing at which the water injector injects water, wherein the control device performs a backfire suppression process by injecting water from the water injector at a timing such that water spreads into the combustion chamber after the air intake valve opens the air intake port, and gaseous fuel spreads into the combustion chamber after the water has spread.

[0035] This configuration can suppress the occurrence of backfire.

[0036] A second item disclosed herein is the gas engine described in the first item, wherein the fuel injector injects gaseous fuel before the intake valve opens the intake port, and the control device in the backfire suppression process injects water from the water injector before the fuel injector injects gaseous fuel.

[0037] This configuration allows for easy implementation of backfire suppression.

[0038] A third item disclosed herein is a gas engine according to the first or second item, wherein the fuel injector injects gas fuel into a gas fuel injection section of the air intake port, and the water injector injects water into a water injection section located downstream of the gas fuel injection section of the air intake port.

[0039] This configuration allows for more reliable implementation of backfire suppression.

[0040] The fourth item disclosed herein is a gas engine according to any one of the first to third items, wherein the control device performs the backfire suppression process when at least one of the backfire occurrence conditions is met, namely the mean effective pressure being equal to or greater than a predetermined reference effective pressure, the output ratio being equal to or greater than a predetermined reference output ratio, the mixing ratio being equal to or greater than a predetermined reference mixing ratio, and the intake / exhaust pressure difference being equal to or less than a predetermined reference pressure difference, and stops the backfire suppression process when the backfire occurrence conditions are not met.

[0041] This configuration can reduce water consumption.

[0042] The fifth item disclosed herein is a gas engine according to any one of the first to fourth items, wherein the gas fuel is a gas containing hydrogen gas.

[0043] Gas fuels containing hydrogen gas are more prone to backfire than other gas fuels. Therefore, the above configuration can effectively suppress the occurrence of backfire.

[0044] Item 5 disclosed in this specification is a gas engine comprising a cylinder, a piston reciprocating within the cylinder, an air supply port for supplying air to a combustion chamber defined by the cylinder and the piston, an exhaust port for discharging exhaust gas from the combustion chamber, an air supply valve for opening and closing the air supply port, an exhaust valve for opening and closing the exhaust port, a fuel injector for injecting gas fuel containing hydrogen gas into the air supply port, and a water injector for injecting water into the air supply port or the combustion chamber. The water injector is a control device capable of controlling the timing of water injection, and the control device injects water from the water injector at a timing such that after the air supply valve opens the air supply port, water spreads into the combustion chamber, and after the water spreads into the combustion chamber, gas fuel spreads into the combustion chamber.

[0045] According to this configuration, the occurrence of backfire can be suppressed.

[0046] Item 6 disclosed in this specification is a control method for controlling the timing of water injection by a water injector in a gas engine comprising a cylinder, a piston reciprocating within the cylinder, an air supply port for supplying air to a combustion chamber defined by the cylinder and the piston, an exhaust port for discharging exhaust gas from the combustion chamber, an air supply valve for opening and closing the air supply port, an exhaust valve for opening and closing the exhaust port, a fuel injector for injecting gas fuel into the air supply port, and a water injector for injecting water into the air supply port or the combustion chamber. The control method injects water from the water injector at a timing such that after the air supply valve opens the air supply port, water spreads into the combustion chamber, and after the water spreads into the combustion chamber, gas fuel spreads into the combustion chamber.

[0047] According to this method, the occurrence of backfire can be suppressed.

[0048] 11 Cylinder 12 Piston 13 Air supply port 14 Exhaust port 15 Air supply valve 16 Exhaust valve 17 Fuel injector 18 Water injector 24 Combustion chamber 25 Gas fuel injection part 26 Water injection part 31 Control device 100 Gas engine

Claims

1. A gas engine comprising: a cylinder; a piston that reciprocates within the cylinder; an air intake port that supplies air to a combustion chamber separated by the cylinder and the piston; an exhaust port that discharges exhaust gas from the combustion chamber; an air intake valve that opens and closes the air intake port; an exhaust valve that opens and closes the exhaust port; a fuel injector that injects gaseous fuel into the air intake port; a water injector that injects water into the air intake port or the combustion chamber; and a control device capable of controlling the timing at which the water injector injects water, wherein the control device performs a backfire suppression process by injecting water from the water injector at a timing such that water spreads into the combustion chamber after the air intake valve opens the air intake port, and gaseous fuel spreads into the combustion chamber after the water has spread into the combustion chamber.

2. The gas engine according to claim 1, wherein the fuel injector injects gas fuel before the intake valve opens the intake port, and the control device injects water from the water injector before the fuel injector injects gas fuel in the backfire suppression process.

3. The gas engine according to claim 1, wherein the fuel injector injects gas fuel into the gas fuel injection section of the air intake port, and the water injector injects water into a water injection section located downstream of the gas fuel injection section of the air intake port.

4. The gas engine according to claim 1, wherein the control device performs the backfire suppression process when at least one of the following backfire occurrence conditions is met: the mean effective pressure is equal to or greater than a predetermined reference effective pressure; the output ratio is equal to or greater than a predetermined reference output ratio; the mixing ratio is equal to or greater than a predetermined reference mixing ratio; and the intake / exhaust pressure difference is equal to or less than a predetermined reference pressure difference; and stops the backfire suppression process when the backfire occurrence conditions are not met.

5. The gas engine according to claim 1, wherein the gas fuel is a gas containing hydrogen gas.

6. A gas engine comprising: a cylinder; a piston that reciprocates within the cylinder; an air intake port for supplying air to a combustion chamber separated by the cylinder and the piston; an exhaust port for discharging exhaust gas from the combustion chamber; an air intake valve for opening and closing the air intake port; an exhaust valve for opening and closing the exhaust port; a fuel injector for injecting gaseous fuel into the air intake port; and a water injector for injecting water into the air intake port or the combustion chamber, wherein the control device is capable of controlling the timing at which the water injector injects water, and the control device injects water from the water injector at a timing such that water spreads into the combustion chamber after the air intake valve opens the air intake port, and gaseous fuel spreads into the combustion chamber after the water has spread into the combustion chamber.

7. A control method for controlling the timing of water injection by the water injector in a gas engine comprising: a cylinder; a piston that reciprocates within the cylinder; an air intake port for supplying air to a combustion chamber separated by the cylinder and the piston; an exhaust port for discharging exhaust gas from the combustion chamber; an air intake valve for opening and closing the air intake port; an exhaust valve for opening and closing the exhaust port; a fuel injector for injecting gaseous fuel into the air intake port; and a water injector for injecting water into the air intake port or the combustion chamber, wherein the water injector injects water at a timing such that water spreads into the combustion chamber after the air intake valve opens the air intake port, and gaseous fuel spreads into the combustion chamber after the water has spread.

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