Hydrogen engine system

Abstract

To provide a hydrogen engine system suppressed in complication and enlargement while securing energy efficiency.SOLUTION: A hydrogen engine system comprising: a hydrogen engine that uses gaseous hydrogen as fuel; a tank that stores liquid hydrogen; a pump that pumps the liquid hydrogen toward the hydrogen engine; a vaporizer that converts the liquid hydrogen pumped from the tank into gaseous hydrogen by heating and supplies the gaseous hydrogen to the hydrogen engine; a boil-off gas supply passage that supplies boil-off gas in the tank to the vaporizer; and an oxygen supplier that supplies oxygen to the vaporizer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen engine system. [Background technology]

[0002] There is a hydrogen engine system that includes a hydrogen engine that uses gaseous hydrogen as fuel, a tank that stores liquid hydrogen, a pump that pressure-feeds the liquid hydrogen to the hydrogen engine, and a vaporizer that heats the liquid hydrogen pressure-feed from the tank to convert it to gaseous hydrogen and supplies it to the hydrogen engine. For example, in the hydrogen engine system described in Patent Document 1, boil-off gas in the tank is used to generate electricity, and hot water produced during power generation is supplied to the vaporizer as a heat source. In this way, energy efficiency is ensured by effectively utilizing the boil-off gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-112236 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned hydrogen engine system requires a power generating device that generates electricity using boil-off gas, which makes the system complicated and large in size.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hydrogen engine system that ensures energy efficiency while preventing the system from becoming too complicated and large in size. [Means for solving the problem]

[0006] The above object can be achieved by a hydrogen engine system comprising: a hydrogen engine fueled by gaseous hydrogen; a tank for storing liquid hydrogen; a pump for pressure-feeding the liquid hydrogen toward the hydrogen engine; a vaporizer for converting the liquid hydrogen pressure-feeded from the tank into gaseous hydrogen by heating and supplying the gaseous hydrogen to the hydrogen engine; a boil-off gas supply passage for supplying boil-off gas in the tank to the vaporizer; and an oxygen supplier for supplying oxygen to the vaporizer, wherein the vaporizer uses the heat of reaction between the boil-off gas supplied to the vaporizer and the oxygen as a heat source for heating the liquid hydrogen. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hydrogen engine system that ensures energy efficiency while suppressing complexity and size increases. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram of a hydrogen engine system. DETAILED DESCRIPTION OF THE INVENTION

[0009] FIG. 1 is a configuration diagram of a hydrogen engine system 1. In this embodiment, the hydrogen engine system 1 is mounted on a vehicle and includes a tank 10, a pump 20, a carburetor 30, a hydrogen engine 40, three-way valves 51, 52, 53, and 54, air compressors 61 and 62, a muffler 70, an ECU (Electronic Control Unit) 100, and drive wheels 110. The power of the hydrogen engine 40 is transmitted to the drive wheels 110 via a transmission, causing the vehicle to run. The vehicle may be, for example, a hydrogen engine vehicle equipped with only the hydrogen engine 40 as a power source, or a hybrid vehicle equipped with both the hydrogen engine 40 and a motor as a power source. The hydrogen engine 40 is powered by burning gaseous hydrogen as fuel.

[0010] One end of pipe 81 is connected to pump 20, and the other end is connected to one end of heat exchanger 32 in vaporizer 30. One end of pipe 82 is connected to the other end of heat exchanger 32 in vaporizer 30, and the other end is connected to three-way valve 53. One end of pipe 83 is connected to three-way valve 53, and the other end is connected to hydrogen engine 40. One end of pipe 84 is connected to an upper part of tank 10, and the other end is connected to three-way valve 51. One end of pipe 85 is connected to three-way valve 51, and the other end is connected to three-way valve 52. One end of pipe 86 is connected to three-way valve 52, and the other end is connected to a lower part of vaporizer 30. One end of pipe 87 is connected to three-way valve 52, and the other end is connected to three-way valve 53. One end of pipe 88 is connected to three-way valve 51, and the other end is connected to muffler 70. One end of pipe 91 is connected to hydrogen engine 40, and the other end is connected to three-way valve 54. One end of the pipe 92 is connected to the three-way valve 54, and the other end is connected to the muffler 70. One end of the pipe 93 is connected to the three-way valve 54, and the other end is connected to the inside of the carburetor 30.

[0011] The ECU 100 is mainly composed of a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 100 executes various control processes related to the hydrogen engine system 1 by running programs installed in the memory on the CPU. The ECU 100 controls the pump 20, three-way valves 51, 52, 53, and 54, and air compressors 61 and 62 according to the warm-up state and operating state of the hydrogen engine 40.

[0012] Tank 10 stores hydrogen in a liquid state. Pump 20 pumps liquid hydrogen (LH2) stored in tank 10 toward hydrogen engine 40. Vaporizer 30 heats the liquid hydrogen pumped by pump 20 through pipe 81, converts it into gaseous hydrogen (GH2), and supplies it to hydrogen engine 40 through pipes 82 and 83. As the liquid hydrogen flows through heat exchanger 32, the liquid hydrogen is heated and converted into gaseous hydrogen, as will be described in detail later. ECU 100 controls three-way valve 53, so that gaseous hydrogen is supplied to hydrogen engine 40 through pipes 82 and 83.

[0013] Although the tank 10 is vacuum insulated, the stored liquid hydrogen will naturally evaporate over time due to heat input. The boil-off gas (BOG-H2), which is hydrogen gas generated by natural evaporation, accumulates in the upper part of the tank 10. The boil-off gas increases the pressure inside the tank. Therefore, when the hydrogen engine 40 is stopped, the ECU 100 controls the three-way valve 51 to release the boil-off gas through pipes 84 and 88 to the muffler 70, and then dilutes it with the air compressor 61 before releasing it into the atmosphere.

[0014] During warm-up after starting the hydrogen engine 40, the ECU 100 controls the three-way valves 51 and 52 to introduce boil-off gas into the vaporizer 30 via pipes 84, 85, and 86. The pipes 84, 85, and 86 are an example of a boil-off gas supply passage. The ECU 100 also supplies oxygen into the vaporizer 30 by blowing air into the vaporizer 30 using the air compressor 62. The air compressor 62 is an example of an oxygen supplier. As a result, oxygen (O2) in the air and hydrogen (H2) in the boil-off gas are mixed in the vaporizer 30, and the hydrogen and oxygen react to produce water and generate reaction heat as shown in the following formula: 2H2+O2=2H2O+286kJ

[0015] The liquid hydrogen in the heat exchanger 32 is heated by the heat of the reaction described above, and changes into gaseous hydrogen. In this way, the boil-off gas is effectively used, ensuring energy efficiency. Furthermore, because the liquid hydrogen is heated by the heat of reaction between oxygen in the air and the hydrogen in the boil-off gas, there is no need for a power generator to generate electricity to change the state of the liquid hydrogen into gaseous hydrogen. This prevents the hydrogen engine system 1 from becoming too complicated and large.

[0016] Furthermore, a thermocouple 31 is provided inside the vaporizer 30. The ECU 100 heats the gas inside the vaporizer 30 using the thermocouple 31. This further promotes the reaction between hydrogen and oxygen. The generated reaction heat turns the produced water into high-temperature steam. This promotes the state change from liquid hydrogen to gaseous hydrogen inside the heat exchanger 32. The reaction between hydrogen and oxygen is further promoted by using copper as a catalyst. For this reason, the power consumption of the thermocouple 31 is reduced by using copper wire for the thermocouple 31.

[0017] When boil-off gas is not required for the carburetor 30, the ECU 100 controls the three-way valves 51, 52, and 53 to supply the boil-off gas to the hydrogen engine 40 via pipes 84, 85, 87, and 83. This improves fuel efficiency. Furthermore, when the boil-off gas is to be released to the atmosphere after the hydrogen engine 40 has started, the ECU 100 controls the three-way valve 54 to dilute the boil-off gas released to the muffler 70 with the exhaust gas of the hydrogen engine 40 discharged to the muffler 70 via pipes 91 and 92. This allows the boil-off gas to be diluted and released to the atmosphere while the air compressor 61 is stopped, reducing power consumption.

[0018] Furthermore, after the hydrogen engine 40 has been sufficiently warmed up, the ECU 100 controls the three-way valve 54 to introduce the exhaust gas from the hydrogen engine 40 into the carburetor 30 via pipes 91 and 93. In this way, the heat of the exhaust gas can promote the change of state from liquid hydrogen to gaseous hydrogen, thereby improving fuel efficiency.

[0019] As described above, energy efficiency is ensured by using the heat of reaction between oxygen in the air and hydrogen in the boil-off gas to change the state of liquid hydrogen to gaseous hydrogen. Furthermore, since a power generation device to generate the electricity required to promote this state change is not required, the system is kept small and complex. Furthermore, the use of copper wire for the thermocouple 31, the supply of boil-off gas to the hydrogen engine 40, the dilution of the boil-off gas with exhaust gas, and the use of exhaust gas to change the state of liquid hydrogen to gaseous hydrogen all contribute to reduced power consumption and improved fuel efficiency.

[0020] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0021] 1 Hydrogen engine system 10 Tank 20 Pump 30 Vaporizer 40 Hydrogen Engine 62 Air compressor (oxygen supply machine) 84, 85, 86 Piping (boil-off gas supply passage)

Claims

[Claim 1] a hydrogen engine fueled by gaseous hydrogen; A tank storing liquid hydrogen, a pump that pumps the liquid hydrogen toward the hydrogen engine; a vaporizer that converts the liquid hydrogen pressure-fed from the tank into gaseous hydrogen by heating and supplies the gaseous hydrogen to the hydrogen engine; a boil-off gas supply passage that supplies the boil-off gas in the tank to the vaporizer; an oxygen supplier that supplies oxygen to the vaporizer; a hydrogen engine system, wherein the vaporizer uses the heat of reaction between the boil-off gas supplied to the vaporizer and the oxygen as a heat source for heating the liquid hydrogen;

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