Gas engine system

Abstract

A gas engine system (1) according to one embodiment of the present invention comprises: a reciprocating engine for supplying air through an air supply path using gas obtained by gasifying liquefied gas as a fuel; a liquid air generator (5) that generates liquid air by means of cooling when the liquefied gas is gasified; and a nitrogen gas supply path (71) for supplying nitrogen gas obtained by vaporizing liquid nitrogen in the liquid air to the gas supply path. For example, the liquefied gas is liquefied hydrogen.

Description

Technical Field

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

[0002] In the past, there is a known gas engine system including a reciprocating engine using natural gas, hydrogen, etc. as fuel. For example, Patent Document 1 discloses a gas engine system including a reciprocating engine using hydrogen as fuel. In addition, in the gas engine system of Patent Document 1, in order to suppress the No x The exhaust gas is discharged, and part of the exhaust gas is mixed with air through EGR (Exhaust Gas Recirculation) and supplied to the reciprocating engine.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-299890 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The above-mentioned EGR is not only effective for No x It is effective for suppressing the emission of EGR and also for suppressing abnormal combustion such as premature ignition, backfire, and knocking. However, a dedicated blower, scrubber, etc. are sometimes used in EGR, and there are cases where space and cost become problems.

[0008] Therefore, an object of the present disclosure is to provide a gas engine system capable of suppressing abnormal combustion without using EGR.

[0009] Means for solving problems

[0010] The present disclosure provides a gas engine system, which comprises: a reciprocating engine, which uses gas obtained by vaporizing liquefied gas as fuel and supplies air through an air supply path; a liquid air making machine, which uses refrigeration during the vaporization of the liquefied gas to make liquid air; and a nitrogen supply path, which supplies nitrogen gas obtained by vaporizing liquid nitrogen in the liquid air to the air supply path.

[0011] Effects of the Invention

[0012] According to the present disclosure, a gas engine system capable of suppressing abnormal combustion without using EGR is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic structural diagram of the periphery of a reciprocating engine in a gas engine system according to one embodiment.

[0014] Figure 2 This is a schematic structural diagram of the fuel supply machine and the liquid air making machine in the above-mentioned gas engine system.

[0015] Figure 3 This is a schematic structural diagram of the fuel supply machine and the liquid air making machine and their surroundings in a gas engine system of a modified example. DETAILED DESCRIPTION

[0016] Figure 1 and Figure 2 A gas engine system 1 according to one embodiment is shown. The gas engine system 1 includes a reciprocating engine 2 using gas obtained by vaporizing liquefied gas as fuel, a fuel supply machine 4 for supplying fuel to the reciprocating engine 2, and a liquid air production machine 5 for producing liquid air by utilizing refrigeration during vaporization of the liquefied gas.

[0017] The liquefied gas is stored in the tank 15. In the present 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 as the source of the fuel.

[0018] Air is supplied to the reciprocating engine 2 through the air supply path 11, and exhaust gas is discharged from the reciprocating engine 2 through the exhaust path 12. In the present embodiment, the compressor 31 and the turbine 32 of the supercharger 3 are respectively provided on the air supply path 11 and the exhaust path 12. In addition, in the air supply path 11, an air cooler 13 is provided on the downstream side of the compressor 31. The air cooler 13 cools the supply air that has been compressed by the compressor 31 and has increased in temperature. For example, the air cooler 13 is a heat exchanger that performs heat exchange between the supply air and a heat medium such as the atmosphere or water.

[0019] In the present embodiment, the reciprocating engine 2 is a four-stroke engine, but the reciprocating engine 2 may be a two-stroke engine.

[0020] The reciprocating engine 2 includes a plurality of (in Figure 1 2 and 3. In the figure, only one is shown as a representative) cylinder 21 and cylinder head 22 installed in each cylinder 21. A piston 23 is arranged in each cylinder 21, and a combustion chamber 20 is formed between the piston 23 and the cylinder head 22.

[0021] The cylinder head 22 is provided with an air supply port 2a and an exhaust port 2b. The cylinder head 22 is also provided with an air supply valve 24 for opening and closing the opening of the air supply port 2a relative to the combustion chamber 20 and an exhaust valve 25 for opening and closing the opening of the exhaust port 2b relative to the combustion chamber 20.

[0022] The cylinder head 22 is provided with a fuel injection valve 26 for injecting fuel into the air supply port 2a or the combustion chamber 20 and an ignition device 27 for igniting the mixture of the air supply and the fuel in the combustion chamber 20. The fuel injection valve 26 need not necessarily be provided in the cylinder head 22, but may also be provided in the air supply passage 11.

[0023] Ignition device 27 may be a spark plug or a sub-chamber type ignition device including a sub-chamber communicating with combustion chamber 20 via an injection hole. Alternatively, ignition device 27 may be an ignition device that injects pilot oil into combustion chamber 20 to cause the pilot oil to self-ignite.

[0024] The fuel supplier 4 includes a fuel supply path 41 connecting the tank 15 and the fuel injection valve 26. The fuel supply path 41 includes a flow regulating valve 42, a main heat exchanger 61, a sub-heat exchanger 43, a buffer tank 44, and a flow regulating valve 45 in order from the upstream side.

[0025] The flow regulating valve 42 regulates the flow of the liquefied gas (liquefied hydrogen in the present 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 the air. The auxiliary heat exchanger 43 heats the gasified gas (hydrogen in the present embodiment) flowing out of the main heat exchanger 61 to the required temperature of the reciprocating engine 2. For example, the auxiliary heat exchanger 43 is a heat exchanger that exchanges heat between the gasified gas and a heat medium such as the atmosphere or water. The heat medium cooled by the auxiliary heat exchanger 43 can be used as a cooling source in the above-mentioned air cooler 13, and the auxiliary heat exchanger 43 itself can also be used as an air cooler 13. The buffer tank 44 temporarily stores the gasified gas. The flow regulating valve 45 regulates the flow of the gasified gas supplied from the buffer tank 44 to the fuel injection valve 26.

[0026] The liquid air generator 5 includes an air passage 51 having one end open to the atmosphere and the other end connected to the distillation tower 62. In the air passage 51, a filter 52, a blower 53, a water / 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 order from the upstream side. That is, the main heat exchanger 61 is shared by the fuel supply machine 4 and the liquid air generator 5.

[0027] The blower 53 is a unit that sends air from one end of the air path 51 to the main heat exchanger 61, and the filter 52 removes foreign matter in the air sucked from the atmosphere. The moisture and carbon dioxide separator 54 removes moisture and carbon dioxide from the air that has passed through the filter 52. After the air from which moisture and carbon dioxide have been removed is preliminarily cooled by the first sub-heat exchanger 55 and the second sub-heat exchanger 56, it exchanges heat with liquefied gas (liquefied hydrogen in this embodiment) in the main heat exchanger 61, thereby becoming 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 distillation tower 62 by the pump 57.

[0028] In the distillation tower 62, the vapor rising in the tower contacts the reflux liquid flowing down in the tower. Therefore, liquid oxygen is taken out from the lower part of the distillation tower 62, nitrogen is taken out from the upper part of the distillation tower 62, and liquid argon is taken out from the middle part of the distillation tower 62. Alternatively, liquid nitrogen may be taken out from the middle part of the distillation tower 62.

[0029] The liquid oxygen taken out from the lower part of the distillation tower 62 is guided to the first secondary heat exchanger 55 through the oxygen supply line 81, and is used as a cooling source for cooling the air on the upstream side of the main heat exchanger 61. The oxygen gasified in the first secondary heat exchanger 55 is released into the atmosphere. In addition, a flow rate regulating valve 82 for adjusting the amount of liquid oxygen taken out is provided in the oxygen supply line 81.

[0030] The nitrogen gas taken out from the upper part of the distillation tower 62, in other words, the nitrogen gas obtained by gasifying the liquid nitrogen in the liquid air produced by the liquid air production machine 5, is supplied to the gas supply path 11 through the nitrogen supply path 71. In the present embodiment, the nitrogen supply path 71 merges with the gas supply path 11 on the upstream side of the compressor 31, but the nitrogen supply path 71 may also merge with the gas supply path 11 on the downstream side of the compressor 31.

[0031] In the nitrogen supply path 71, a flow regulating valve 72, a heat exchanger 73, a buffer tank 74 and a flow regulating valve 75 are provided in order from the upstream side. The flow regulating valve 72 regulates the flow of nitrogen taken out from the upper part of the distillation tower 62. The heat exchanger 73 heats the nitrogen to about the atmospheric temperature. For example, the heat exchanger 73 is a heat exchanger that performs heat exchange between nitrogen and a heat medium such as the atmosphere or water. The heat medium cooled by the heat exchanger 73 can be used as a cooling source in the above-mentioned air cooler 13, and the heat exchanger 73 itself can also be used as the air cooler 13. The buffer tank 74 temporarily stores nitrogen. The flow regulating valve 75 regulates the flow of nitrogen supplied from the buffer tank 74 to the gas supply path 11.

[0032] In addition, in the present embodiment, the bypass passage 76 is connected to the nitrogen supply passage 71 in a manner bypassing the heat exchanger 73. More specifically, in the present embodiment, the flow rate regulating valve 72 is a three-way valve, and the upstream end of the bypass passage 76 is connected to the flow rate regulating valve 72. The downstream end of the bypass passage 76 is connected to the nitrogen supply passage 71 on the downstream side of the heat exchanger 73.

[0033] The bypass passage 76 passes through the second sub-heat exchanger 56 of the liquid air making machine 5, and the flow regulating valve 72 also plays a role in switching which of the heat exchanger 73 and the second sub-heat exchanger 56 the nitrogen gas taken out from the distillation tower 62 is guided to. When the nitrogen gas is guided to the second sub-heat exchanger 56, it is used as a cooling source for cooling the air on the upstream side of the main heat exchanger 61.

[0034] The flow control valves 42, 45, 72, 75, 82 are controlled by the controller 9. Figure 1 and Figure 2 In order to simplify the drawings, some signal lines are omitted.

[0035] Regarding the controller 9, the functions of the elements disclosed in this specification can be performed using a circuit or processing circuit that includes a general-purpose processor, a special-purpose processor, an integrated circuit, an ASIC (Application Specific Integrated Circuits), an existing circuit, and / or a combination thereof that is constructed or programmed to perform the disclosed functions. The processor includes transistors and other circuits and is therefore considered to be a processing circuit or circuit. In the present disclosure, a circuit, unit, or component is hardware that performs the listed functions, or hardware that is programmed to perform the listed functions. The hardware may be the hardware disclosed in this specification, or it may be other known hardware that is programmed or constructed to perform the listed functions. In the case where the hardware is a processor that is considered to be a type of circuit, the circuit, component, or unit is a combination of hardware and software, and the software is used to construct the hardware and / or processor.

[0036] In particular, regarding the control of the flow rate regulating valve 45 , the controller 9 controls the flow rate regulating valve 45 based on the rotation angle of the crankshaft and the required output of the reciprocating engine 2 .

[0037] In addition, the controller 9 is electrically connected to an oxygen concentration meter 91 and a pressure sensor 92. The oxygen concentration meter 91 detects the oxygen concentration on the downstream side of the confluence point of the nitrogen supply path 71 in the air supply path 11, and the pressure sensor 92 detects the pressure in the combustion chamber 20. The controller 9 controls the flow regulating valve 75 based on 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 regulating valve 75 so that the oxygen concentration detected by the oxygen concentration meter 91 becomes the target oxygen concentration. In addition, the controller 9 determines whether abnormal combustion such as premature ignition, backfire, and knocking occurs based on the pressure detected by the pressure sensor 92, and increases the opening of the flow regulating valve 75 when abnormal combustion occurs.

[0038] In the gas engine system 1 of the structure described above, since the nitrogen concentration in the mixture of the supply air and the fuel increases, the minimum ignition energy, that is, the minimum ignition energy, required to generate flame propagation in the mixture becomes larger. Therefore, abnormal combustion such as premature ignition and backfire is suppressed. In addition, due to the increase in the nitrogen concentration in the mixture, the time from maintaining the mixture at a certain temperature to ignition, that is, the ignition delay, becomes longer, so knocking is also suppressed. Therefore, abnormal combustion can be suppressed without using EGR. In addition, since the nitrogen concentration in the mixture increases and the adiabatic flame temperature decreases, NO can also be suppressed. x Furthermore, since nitrogen is generated by utilizing refrigeration during gasification of liquefied gas, which is the source of fuel, not much energy is required to generate nitrogen.

[0039] In particular, when the fuel is hydrogen as in the present embodiment, hydrogen has not only a shorter ignition delay but also a smaller minimum ignition energy than methane, and therefore it is highly important to increase the nitrogen concentration in the air-fuel mixture from the viewpoint of suppressing premature ignition.

[0040] (Variation Example)

[0041] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present disclosure.

[0042] For example, you can also Figure 3 As in the gas engine system 1A of the illustrated modification, the liquefied gas stored in the tank 15 is LNG, and the natural gas obtained by gasification of the LNG is used as the fuel of the reciprocating engine 2. In this case, the temperature of the liquefied gas in the tank 15 is -162°C.

[0043] In this gas engine system 1A, compared with the liquid air manufacturing machine 5 of the above-mentioned embodiment, a liquid air manufacturing machine 5A is adopted in which the position of the main heat exchanger 61 is changed to between the water and carbon dioxide separator 54 and the first sub-heat exchanger 55, and a compressor 58 and an expansion turbine 59 are used instead of the blower 53 and the pump 57. The air flowing in the air path 51 is gas until 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 fractionator 62.

[0044] like Figure 3 As shown, when the liquefied gas is LNG, since the temperature of LNG under atmospheric pressure is higher than the boiling point of nitrogen, air compression power is required when producing liquid air. On the other hand, if the liquefied gas is liquefied hydrogen as in the above embodiment, the temperature of liquefied hydrogen under atmospheric pressure is lower than the boiling point of nitrogen, so such compression power is not required.

[0045] In the gas engine system 1A, a blower 77 as a nitrogen gas delivery means is provided on the nitrogen gas supply path 71 between the fractionator 62 and the flow rate regulating valve 72 .

[0046] (Summarize)

[0047] As a first embodiment, the present disclosure provides a gas engine system comprising: a reciprocating engine that uses gas obtained by vaporizing liquefied gas as fuel and supplies air through an air supply path; a liquid air manufacturing machine that utilizes refrigeration during the vaporization of the liquefied gas to manufacture liquid air; and a nitrogen supply path that supplies nitrogen gas obtained by vaporizing liquid nitrogen in the liquid air to the air supply path.

[0048] According to the above structure, since the nitrogen concentration in the mixture of the supply air and the fuel increases, the minimum ignition energy required to make the mixture produce flame propagation, that is, the minimum ignition energy, becomes larger. Therefore, abnormal combustion such as premature ignition and flashback is suppressed. In addition, due to the increase in the nitrogen concentration in the mixture, the time from keeping the mixture at a certain temperature to ignition, that is, the ignition delay, becomes longer, so knocking is also suppressed. Therefore, abnormal combustion can be suppressed without using EGR. In addition, since the nitrogen concentration in the mixture increases and the adiabatic flame temperature decreases, NO can also be suppressed. x Furthermore, since nitrogen is generated by utilizing refrigeration during gasification of liquefied gas, which is the source of fuel, not much energy is required to generate nitrogen.

[0049] As a second aspect, according to the first aspect, the liquefied gas may be liquefied hydrogen. When the liquefied gas is LNG, since the temperature of LNG under atmospheric pressure is higher than the boiling point of nitrogen, compression power for air is required when producing liquid air. On the other hand, if the liquefied gas is liquefied hydrogen, since the temperature of liquefied hydrogen under atmospheric pressure is lower than the boiling point of nitrogen, such compression power is not required.

[0050] As a third aspect, according to the first or second aspect, for example, the liquid air generator may include a heat exchanger that performs heat exchange between the air from which moisture and carbon dioxide have been removed and the liquefied gas.

[0051] As a fourth embodiment, it may be that, according to any of the first to third embodiments, for example, the above-mentioned gas engine system further comprises: a flow regulating valve, which is arranged in the nitrogen supply path; and a controller, which controls the flow regulating valve according to the oxygen concentration in the gas supply path on the downstream side of the confluence point of the nitrogen supply path.

Claims

1. A gas engine system comprising: A reciprocating engine uses gas from liquefied gas as fuel and supplies air through an air supply line; a liquid air generator that produces liquid air by utilizing refrigeration during the gasification of the liquefied gas; and A nitrogen gas supply path supplies nitrogen gas obtained by gasifying liquid nitrogen in the liquid air to the gas supply path.

2. The gas engine system according to claim 1, wherein: The liquefied gas is liquefied hydrogen.

3. The gas engine system according to claim 1 or 2, wherein: The liquid air generator includes a heat exchanger for performing heat exchange between the air from which moisture and carbon dioxide have been removed and the liquefied gas.

4. The gas engine according to claim 1 or 2, wherein: The gas engine system also has: a flow rate regulating valve provided in the nitrogen supply passage; and A controller controls the flow rate regulating valve according to the oxygen concentration in the gas supply passage on the downstream side of a junction point of the nitrogen gas supply passage.

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