Gas engine system

Abstract

To provide a gas engine system capable of suppressing abnormal combustion without using EGR.SOLUTION: A gas engine system 1 according to one embodiment includes: a reciprocal engine that uses gas obtained by vaporizing liquefied gas as fuel and to which air is supplied through an air supply passage; a liquid air production device 5 that produces liquid air by using cold when the liquefied gas is vaporized; and a nitrogen gas supply passage 71 for supplying nitrogen gas obtained by vaporizing liquid nitrogen in the liquid air to the air supply passage. For example, the liquefied gas is liquefied hydrogen.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to gas engine systems. [Background technology]

[0002] Conventionally, gas engine systems including reciprocating engines fueled by natural gas, hydrogen gas, etc. have been known. For example, Patent Document 1 discloses a gas engine system including a reciprocating engine fueled by hydrogen gas. In addition, in the gas engine system of Patent Document 1, in order to suppress the emission of NOx, a part of the exhaust gas is mixed with air by EGR (Exhaust Gas Recirculation) and supplied to the reciprocating engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-299890 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned EGR is effective not only in suppressing NOx emissions, but also in suppressing abnormal combustion such as pre-ignition, flashback, knocking, etc. However, EGR sometimes requires a dedicated blower or scrubber, which can pose problems in terms of space and cost.

[0005] Therefore, an object of the present disclosure is to provide a gas engine system that can suppress abnormal combustion without using EGR. [Means for solving the problem]

[0006] The present disclosure provides a gas engine system including a reciprocating engine that uses vaporized liquefied gas as fuel and is supplied with air through an air intake passage, a liquid air producing machine that produces liquid air by utilizing the cold heat generated when the liquefied gas vaporizes, and a nitrogen gas supply passage that supplies nitrogen gas formed by vaporizing liquid nitrogen in the liquid air to the air intake passage. Effect of the Invention

[0007] According to the present disclosure, a gas engine system is provided that can suppress abnormal combustion without using EGR. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a reciprocating engine and its surroundings in a gas engine system according to one embodiment. [Diagram 2] FIG. 2 is a schematic configuration diagram of a fuel supply machine and a liquid air production machine in the gas engine system. [Diagram 3] FIG. 11 is a schematic configuration diagram of a fuel supply device and a liquid air production device in a gas engine system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1 and 2 show a gas engine system 1 according to one embodiment. This gas engine system 1 includes a reciprocating engine 2 that uses vaporized liquefied gas as fuel, a fuel supplier 4 that supplies fuel to the reciprocating engine 2, and a liquid air producer 5 that produces liquid air by utilizing the cold generated when the liquefied gas is vaporized.

[0010] The liquefied gas is stored in the tank 15. In this embodiment, the liquefied gas is liquefied hydrogen, and the fuel is hydrogen gas. That is, the temperature of the liquefied gas in the tank 15 is −253° C. However, various liquefied gases other than liquefied hydrogen can be used as the liquefied gas that is the source of the fuel.

[0011] Air is supplied to the reciprocating engine 2 through an intake passage 11, and exhaust gas is discharged from the reciprocating engine 2 through an exhaust passage 12. In this embodiment, a compressor 31 and a turbine 32 of the turbocharger 3 are provided in the intake passage 11 and the exhaust passage 12, respectively. An air cooler 13 is also provided in the intake passage 11 downstream of the compressor 31. The air cooler 13 cools the intake air whose temperature has increased as a result of being compressed by the compressor 31. For example, the air cooler 13 is a heat exchanger that exchanges heat between the intake air and a heat medium such as the atmosphere or water.

[0012] In this embodiment, the reciprocating engine 2 is a four-stroke engine. However, the reciprocating engine 2 may be a two-stroke engine.

[0013] The reciprocating engine 2 includes a plurality of cylinders 21 (only one is shown in FIG. 1 as a representative) aligned in the axial direction of the crankshaft, and a cylinder head 22 attached to each cylinder 21. A piston 23 is disposed in each cylinder 21, and a combustion chamber 20 is formed between the piston 23 and the cylinder head 22.

[0014] An intake port 2a and an exhaust port 2b are formed in the cylinder head 22. The cylinder head 22 is also provided with an intake valve 24 that opens and closes the opening of the intake port 2a to the combustion chamber 20, and an exhaust valve 25 that opens and closes the opening of the exhaust port 2b to the combustion chamber 20.

[0015] Furthermore, the cylinder head 22 is provided with a fuel injection valve 26 that injects fuel into the intake port 2a or into the combustion chamber 20, and an ignition device 27 that ignites the mixture of intake air and fuel in the combustion chamber 20. Note that the fuel injection valve 26 does not necessarily have to be provided in the cylinder head 22, and may be provided in the intake passage 11.

[0016] The ignition device 27 may be an ignition plug, or may be an auxiliary chamber type ignition device including an auxiliary chamber communicating with the combustion chamber 20 via a nozzle hole. Alternatively, the ignition device 27 may be a device that injects pilot oil into the combustion chamber 20 to self-ignite the pilot oil.

[0017] The fuel supplier 4 includes a fuel supply passage 41 that connects the tank 15 and the fuel injection valve 26. The fuel supply passage 41 is provided with a flow rate control valve 42, a main heat exchanger 61, a sub-heat exchanger 43, a buffer tank 44, and a flow rate control valve 45 in this order from the upstream side.

[0018] The flow rate control valve 42 adjusts the flow rate of the liquefied gas (liquefied hydrogen in this embodiment) flowing from the tank 15 into the main heat exchanger 61. The main heat exchanger 61 vaporizes the liquefied gas by exchanging heat between the liquefied gas and air. The auxiliary heat exchanger 43 heats the vaporized gas (hydrogen gas in this embodiment) flowing out from the main heat exchanger 61 to a required temperature of the reciprocating engine 2. For example, the auxiliary heat exchanger 43 is a heat exchanger that exchanges heat between the vaporized gas and a heat medium such as air or water. The heat medium cooled by the auxiliary heat exchanger 43 may be used as a cold source in the above-mentioned air cooler 13, or the auxiliary heat exchanger 43 itself may be used as the air cooler 13. The buffer tank 44 temporarily stores the vaporized gas. The flow rate control valve 45 adjusts the flow rate of the vaporized gas supplied from the buffer tank 44 to the fuel injection valve 26.

[0019] The liquid air production machine 5 includes an air passage 51 having one end opening in the atmosphere and the other end connected to a rectification tower 62. In the air passage 51, a filter 52, a blower 53, a moisture / carbon dioxide separator 54, a first auxiliary heat exchanger 55, a second auxiliary heat exchanger 56, a main heat exchanger 61, and a pump 57 are provided in this order from the upstream side. That is, the main heat exchanger 61 is shared by the fuel supplier 4 and the liquid air production machine 5.

[0020] The blower 53 is a means for sending air from one end of the air passage 51 to the main heat exchanger 61, and the filter 52 removes foreign matter in the air taken in from the atmosphere. The moisture / carbon dioxide separator 54 removes moisture and carbon dioxide from the air that has passed through the filter 52. The air from which moisture and carbon dioxide have been removed is preliminarily cooled in the first auxiliary heat exchanger 55 and the second auxiliary heat exchanger 56, and then heat-exchanged with a liquefied gas (liquefied hydrogen in this embodiment) in the main heat exchanger 61, whereby the air is liquefied at a temperature lower than the boiling point of nitrogen. The liquefied air flowing out of the main heat exchanger 61 is supplied to the fractionator 62 by the pump 57.

[0021] In the distillation tower 62, the vapor rising inside the tower comes into contact with the reflux liquid flowing down inside the tower. As a result, liquid oxygen is extracted from the lower part of the distillation tower 62, nitrogen gas is extracted from the upper part of the distillation tower 62, and liquid argon is extracted from the middle part of the distillation tower 62. It is also possible to extract liquid nitrogen from the middle part of the distillation tower 62.

[0022] The liquid oxygen taken out from the bottom of the rectification column 62 is guided through an oxygen supply passage 81 to the above-mentioned first auxiliary heat exchanger 55, and is used as a cold heat source for cooling air upstream of the main heat exchanger 61. The oxygen gas vaporized in the first auxiliary heat exchanger 55 is released into the atmosphere. The oxygen supply passage 81 is provided with a flow rate regulating valve 82 for regulating the amount of liquid oxygen taken out.

[0023] The nitrogen gas extracted from the top of the distillation column 62, in other words, the nitrogen gas formed by vaporizing the liquid nitrogen in the liquid air produced by the liquid air production machine 5, is supplied to the air intake passage 11 through a nitrogen gas supply passage 71. In this embodiment, the nitrogen gas supply passage 71 merges with the air intake passage 11 upstream of the compressor 31. However, the nitrogen gas supply passage 71 may also merge with the air intake passage 11 downstream of the compressor 31.

[0024] The nitrogen gas supply passage 71 is provided with a flow rate control valve 72, a heat exchanger 73, a buffer tank 74, and a flow rate control valve 75 in this order from the upstream side. The flow rate control valve 72 controls the flow rate of the nitrogen gas taken out from the top of the distillation column 62. The heat exchanger 73 heats the nitrogen gas to about atmospheric temperature. For example, the heat exchanger 73 is a heat exchanger that exchanges heat between the nitrogen gas and a heat medium such as the atmosphere or water. The heat medium cooled by the heat exchanger 73 may be used as a cold source in the above-mentioned air cooler 13, or the heat exchanger 73 itself may be used as the air cooler 13. The buffer tank 74 temporarily stores the nitrogen gas. The flow rate control valve 75 controls the flow rate of the nitrogen gas supplied from the buffer tank 74 to the air supply passage 11.

[0025] Furthermore, in this embodiment, a bypass path 76 is connected to the nitrogen gas supply path 71 so as to bypass the heat exchanger 73. More specifically, in this embodiment, the flow rate control valve 72 is a three-way valve, and the upstream end of the bypass path 76 is connected to this flow rate control valve 72. The downstream end of the bypass path 76 is connected to the nitrogen gas supply path 71 on the downstream side of the heat exchanger 73.

[0026] The bypass passage 76 passes through the second auxiliary heat exchanger 56 of the liquid air production machine 5, and the flow rate control valve 72 also plays a role in switching whether the nitrogen gas extracted from the rectification tower 62 is guided to the heat exchanger 73 or the second auxiliary heat exchanger 56. When the nitrogen gas is guided to the second auxiliary heat exchanger 56, it is used as a cold source for cooling air upstream of the main heat exchanger 61.

[0027] The above-mentioned flow rate adjustment valves 42, 45, 72, 75, and 82 are controlled by a controller 9. Note that in Figures 1 and 2, some signal lines are omitted from the drawings in order to simplify the drawings.

[0028] With respect to the controller 9, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, Application Specific Integrated Circuits (ASICs), 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 recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. In the case where the hardware is a processor, which is considered a type of circuit, 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.

[0029] In particular, with regard to the control of the flow rate adjustment valve 45 , the controller 9 controls the flow rate adjustment valve 45 based on the rotation angle of the crankshaft and the required output for the reciprocating engine 2 .

[0030] The controller 9 is also electrically connected to an oxygen concentration meter 91 and a pressure sensor 92. The oxygen concentration meter 91 detects the oxygen concentration downstream of the junction of the nitrogen gas supply passage 71 in the air intake passage 11, and the pressure sensor 92 detects the pressure in the combustion chamber 20. The controller 9 controls the flow rate control valve 75 in accordance with the oxygen concentration detected by the oxygen concentration meter 91 and the pressure detected by the pressure sensor 92. For example, the controller 9 controls the flow rate control valve 75 so that the oxygen concentration detected by the oxygen concentration meter 91 becomes a target oxygen concentration. The controller 9 also determines whether or not abnormal combustion such as pre-ignition, flashback, or knocking has occurred based on the pressure detected by the pressure sensor 92, and increases the opening of the flow rate control valve 75 when abnormal combustion has occurred.

[0031] In the gas engine system 1 having the above-described configuration, the nitrogen concentration in the mixture of the intake air and the fuel increases, so that the minimum ignition energy, which is the minimum ignition energy required to generate flame propagation in the mixture, increases. This suppresses abnormal combustion such as pre-ignition and backfire. Furthermore, the increase in the nitrogen concentration in the mixture lengthens the ignition delay, which is the time from when the mixture is held at a certain temperature until it ignites, so that knocking is also suppressed. Therefore, abnormal combustion can be suppressed without using EGR. In addition, the increase in the nitrogen concentration in the mixture reduces the adiabatic flame temperature, so that NOx can also be suppressed. Moreover, since nitrogen gas is generated by utilizing the cold energy generated when the liquefied gas that is the source of the fuel vaporizes, the generation of nitrogen gas does not require a large amount of energy.

[0032] In particular, when the fuel is hydrogen gas as in this embodiment, hydrogen not only has a shorter ignition delay but also a smaller minimum ignition energy than methane, so it is important to increase the nitrogen concentration in the mixture from the standpoint of suppressing pre-ignition.

[0033] (Modification) The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0034] 3, the liquefied gas stored in the tank 15 may be LNG, and natural gas vaporized from the LNG may be the fuel for the reciprocating engine 2. In this case, the temperature of the liquefied gas in the tank 15 is −162° C.

[0035] In this gas engine system 1A, compared to the liquid air production machine 5 of the above embodiment, the position of the main heat exchanger 61 is changed to between the moisture / carbon dioxide separator 54 and the first sub-heat exchanger 55, and a liquid air production machine 5A is adopted in which a compressor 58 and an expansion turbine 59 are used instead of the blower 53 and the pump 57. The air flowing through the air passage 51 is in a gaseous state up to the expansion turbine 59, and is liquefied by being expanded by the expansion turbine 59. That is, liquefied air (for example, -200°C) containing liquefied oxygen and liquefied nitrogen is supplied from the expansion turbine 59 to the rectification column 62.

[0036] As shown in Fig. 3, when the liquefied gas is LNG, the temperature of LNG at atmospheric pressure is higher than the boiling point of nitrogen, so that compression power for air is required when producing liquid air. In contrast, when the liquefied gas is liquefied hydrogen as in the above embodiment, the temperature of liquefied hydrogen at atmospheric pressure is lower than the boiling point of nitrogen, so that compression power is not required.

[0037] In the gas engine system 1A, a blower 77 is provided in the nitrogen gas supply passage 71 between the rectification column 62 and the flow rate control valve 72 as a means for sending out nitrogen gas.

[0038] (summary) In a first aspect, the present disclosure provides a gas engine system comprising: a reciprocating engine that uses vaporized liquefied gas as fuel and is supplied with air through an air intake passage; a liquid air producing machine that produces liquid air by utilizing the cold heat generated when the liquefied gas vaporizes; and a nitrogen gas supply passage that supplies nitrogen gas formed by vaporizing liquid nitrogen in the liquid air to the air intake passage.

[0039] According to the above configuration, the nitrogen concentration in the mixture of the intake air and the fuel increases, so that the minimum ignition energy, which is the minimum ignition energy required to generate flame propagation in the mixture, increases. This suppresses abnormal combustion such as pre-ignition and backfire. Furthermore, the increase in the nitrogen concentration in the mixture lengthens the ignition delay, which is the time from when the mixture is held at a certain temperature until it ignites, so that knocking is also suppressed. Therefore, abnormal combustion can be suppressed without using EGR. In addition, the increase in the nitrogen concentration in the mixture reduces the adiabatic flame temperature, so that NOx can also be suppressed. Moreover, since nitrogen gas is generated by utilizing the cold energy generated when the liquefied gas that is the source of the fuel vaporizes, a large amount of energy is not required to generate the nitrogen gas.

[0040] As a second aspect, in the first aspect, the liquefied gas may be liquefied hydrogen. When the liquefied gas is LNG, the temperature of LNG at atmospheric pressure is higher than the boiling point of nitrogen, so that compression power for air is required when producing liquid air. On the other hand, when the liquefied gas is liquefied hydrogen, the temperature of liquefied hydrogen at atmospheric pressure is lower than the boiling point of nitrogen, so that such compression power is not required.

[0041] As a third aspect, in the first or second aspect, for example, the liquid air producing machine may include a heat exchanger that performs heat exchange between air from which moisture and carbon dioxide have been removed and the liquefied gas.

[0042] As a fourth aspect, in any of the first to third aspects, for example, the above gas engine system may further include a flow control valve provided in the nitrogen gas supply passage, and a controller that controls the flow control valve in accordance with the oxygen concentration in the air intake passage downstream of the confluence of the nitrogen gas supply passage. [Explanation of symbols]

[0043] 1,1A Gas Engine System 11 Air supply path 2 Reciprocating engine 4 Fuel supply machine 5. Liquid air generator 61 Main heat exchanger 71 Nitrogen gas supply line 75 Flow Control Valve 9. Controller

Claims

1. A reciprocating engine that uses vaporized liquefied gas as fuel and receives air through an air intake; a liquid air producing device which produces liquid air by utilizing the cold generated when the liquefied gas is vaporized; a nitrogen gas supply passage for supplying nitrogen gas generated by vaporizing liquid nitrogen in the liquid air to the air supply passage; A gas engine system comprising:

2. The gas engine system of claim 1 , wherein the liquefied gas is liquefied hydrogen.

3. 3. The gas engine system according to claim 1, wherein the liquid air generator includes a heat exchanger that performs heat exchange between air from which moisture and carbon dioxide have been removed and the liquefied gas.

4. a flow rate regulating valve provided in the nitrogen gas supply line; 3. The gas engine according to claim 1, further comprising: a controller that controls the flow rate regulating valve in accordance with an oxygen concentration in the air supply passage downstream of a junction with the nitrogen gas supply passage.

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