Hydrogen engine system

Abstract

To reduce NOx emissions from hydrogen engines and to stabilize the combustion of a hydrogen-ammonia fuel mixture. [Solution] The hydrogen engine system 1 comprises a hydrogen engine 10, an NTA catalyst 13, an oxygen concentration sensor 41, and an ammonia water generation means 14 provided in the exhaust passage 12, an ammonia water circulation line 17, and a hydrogen injector 31 and an ammonia water injector 32 provided in the hydrogen engine 10. The control device 50 learns the difference between the air-fuel ratio obtained from the measured oxygen concentration and the stoichiometric pressure as an ammonia concentration learning value, and controls the ammonia water injector 32 based on the learned ammonia concentration learning value.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a hydrogen engine system equipped with a hydrogen engine that burns hydrogen as fuel.

Background Art

[0002] Conventionally, as this type of technology, an engine system described in Patent Document 1 is known. This system includes an engine that burns a mixed fuel of hydrogen and ammonia. By burning this mixed fuel, the engine improves the combustibility compared to the case where only ammonia is used as fuel and is used in a wide operating range. Compared to the case where only hydrogen is used as fuel, it appropriately controls the combustion efficiency, suppresses the occurrence of abnormal combustion, and aims to increase the output.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the engine system described in Patent Document 1, a problem is that a large amount of NOx is emitted when hydrogen burns in the engine, and suppressing NOx generation and purifying NOx become problems. In the above engine system, no NOx purification treatment is performed, and there is a concern that emissions will increase. Also, in the above engine system, although a mixed fuel of hydrogen and ammonia is burned, the combustion stabilization of the mixed fuel is not considered.

[0005] This disclosed technology has been made in view of the above circumstances, and its purpose is to provide a hydrogen engine system capable of reducing the amount of NOx emitted from a hydrogen engine and achieving combustion stabilization of a mixed fuel of hydrogen and ammonia. [Means for solving the problem]

[0006] To achieve the above objective, the technology described in claim 1 is a hydrogen engine system comprising: a hydrogen engine that burns hydrogen as fuel; an exhaust passage for discharging exhaust gas from the hydrogen engine after hydrogen has been burned in the hydrogen engine; a catalyst provided in the exhaust passage for converting nitrogen oxides and hydrogen contained in the exhaust gas discharged from the hydrogen engine into ammonia and water; an oxygen concentration measuring means provided in the exhaust passage for measuring the oxygen concentration after hydrogen has been burned in the hydrogen engine; an ammonia water generating means provided in the exhaust passage for generating ammonia water from ammonia and water; an ammonia water supply means for supplying the ammonia water generated by the ammonia water generating means to the hydrogen engine; and an ammonia water recirculation means for recirculating the ammonia water generated by the ammonia water generating means to the ammonia water supply means, wherein the system further comprises: an ammonia concentration learning means for learning the difference between the air-fuel ratio obtained from the measured oxygen concentration and the stoichiometric air-fuel ratio as an ammonia concentration learning value; and a control means for controlling the ammonia water supply means based on the learned ammonia concentration learning value.

[0007] According to the above technology configuration, exhaust gases from the hydrogen engine flow through a catalyst and an ammonia water generation means. The catalyst converts oxide nitrides (NOx) and hydrogen in the exhaust gas into ammonia and water. The ammonia water generation means produces ammonia water from ammonia and water. The produced ammonia water is recirculated by an ammonia water circulation means and supplied to the hydrogen engine by an ammonia water supply means. Therefore, NOx in the exhaust gases is converted to ammonia by the catalyst, produced and recovered as ammonia water by the ammonia water generation means, and supplied to the hydrogen engine by the ammonia water supply means for combustion together with hydrogen. The ammonia concentration learning means learns the difference between the air-fuel ratio obtained from the measured oxygen concentration and the stoichiometric air-fuel ratio as an ammonia concentration learning value, and the control means controls the ammonia water supply means based on the learned ammonia concentration learning value. Therefore, the amount of ammonia water supplied to the hydrogen engine is appropriately adjusted based on the ammonia concentration learning value.

[0008] To achieve the above objective, the technology described in claim 2 is intended to perform learning of the ammonia concentration after supplying a predetermined amount or less of ammonia water to the hydrogen engine using the ammonia water supply means, in the technology described in claim 1.

[0009] According to the configuration of the above technology, in addition to the operation of the technology described in claim 1, the ammonia concentration learning means performs ammonia concentration learning after a predetermined amount or less of ammonia water is supplied to the hydrogen engine. Therefore, ammonia concentration learning is performed after the air-fuel ratio of the hydrogen-ammonia mixed fuel has stabilized. [Effects of the Invention]

[0010] According to the technology described in claim 1, it is possible to reduce the amount of NOx emitted from a hydrogen engine and to stabilize the combustion of a mixed fuel of hydrogen and ammonia.

[0011] According to the technology described in claim 2, in addition to the effects of the technology described in claim 1, it is possible to perform appropriate ammonia concentration learning. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram showing a hydrogen engine system according to one embodiment. [Figure 2] A flowchart illustrating an example of ammonia water supply control according to one embodiment. [Modes for carrying out the invention]

[0013] The following describes in detail, with reference to the drawings, one embodiment of the hydrogen engine system implemented as a system mounted on an automobile.

[0014] [Overview of the hydrogen engine system] Figure 1 shows a schematic diagram of the hydrogen engine system 1. The hydrogen engine system 1 comprises a hydrogen engine 10, an intake passage 11, an exhaust passage 12, a NOx to Ammonia (NTA) catalyst 13, and an ammonia water generation means 14.

[0015] The hydrogen engine 10 has a combustion chamber 10a for burning fuel. The intake passage 11 introduces air (intake) into the combustion chamber 10a. The exhaust passage 12 discharges the exhaust after combustion in the combustion chamber 10a. An oxygen concentration sensor 41 is provided in the exhaust passage 12 between the hydrogen engine 10 and the NTA catalyst 13 to measure the oxygen concentration Ox in the exhaust after combustion in the hydrogen engine 10. The oxygen concentration sensor 41 is an example of the "oxygen concentration measuring means" in this disclosed technology. The NTA catalyst 13 provided in the exhaust passage 12 converts NOx and hydrogen contained in the exhaust into ammonia and water.

[0016] In this embodiment, the ammonia water generation means 14 provided in the exhaust passage 12 generates ammonia water from ammonia and water. The ammonia water generation means 14 includes a heat exchanger 21 and an exhaust muffler 22. The heat exchanger 21 lowers the temperature of the exhaust gas flowing from the NTA catalyst 13, thereby liquefying the vapor. The heat exchanger 21 is provided integrally with the exhaust manifold (not shown).

[0017] The hydrogen engine 10 includes a hydrogen supply means 15 and an ammonia water supply means 16. The hydrogen supply means 15 consists of a hydrogen injector 31 that injects hydrogen into the combustion chamber 10a. The ammonia water supply means 16 consists of an ammonia water injector 32 that injects ammonia water into the combustion chamber 10a.

[0018] The hydrogen engine system 1 further includes an aqueous ammonia circulation line 17. The aqueous ammonia circulation line 17 circulates the aqueous ammonia generated by the aqueous ammonia generation means 14 to the aqueous ammonia injector 32. An aqueous ammonia secondary tank 36 and an electric pump 37 are provided in the aqueous ammonia circulation line 17. The aqueous ammonia secondary tank 36 secondarily stores the aqueous ammonia flowing out from the exhaust muffler 22. The electric pump 37 pumps the aqueous ammonia to the aqueous ammonia injector 32. The aqueous ammonia circulation line 17, the aqueous ammonia secondary tank 36, and the electric pump 37 constitute an example of the "aqueous ammonia circulation means" of this disclosed technology.

[0019] The NTA catalyst 13 is provided with a reducing agent supply means 19 for supplying a reducing agent for reducing ammonia. Hydrogen is used as the reducing agent, and another hydrogen injector 33 is provided as the reducing agent supply means 19. Hydrogen is supplied to this hydrogen injector 33, similar to the hydrogen injector 31.

[0020] [Regarding the control of the hydrogen engine system] The hydrogen engine system 1 further includes a control device 50 that controls it. The control device 50 controls each injector 31 to 33 in order to control the hydrogen engine 10. The control device 50 executes control to supply aqueous ammonia as fuel to the hydrogen engine 10. Here, the description of the control for supplying hydrogen as fuel to the hydrogen engine 10 is omitted. The control device 50 corresponds to an example of the "ammonia concentration learning means" and the "control means" of this disclosed technology.

[0021] FIG. 2 shows an example of the content of "aqueous ammonia supply control" by a flowchart. In this flowchart, in step 100, the control device 50 determines whether ammonia concentration learning (described later) is completed. If this determination is affirmative, the control device 50 executes normal injection control in step 110. That is, it controls each injector 31 to 33 to inject and supply hydrogen and aqueous ammonia to the hydrogen engine 10. Then, the control device 50 once terminates the process.

[0022] On the other hand, if the determination in step 100 is negative, the control device 50 determines in step 120 whether it is in the ammonia learning execution area. The determination of the learning execution area is based on the condition of the stable operation of the hydrogen engine 10. For example, the conditions are when the intake air amount is stable or after the engine warm-up is completed. If the determination by the control device 50 is negative, the process proceeds to step 110.

[0023] On the other hand, if the determination in step 120 is affirmative, the control device 50 controls the ammonia water injection by the ammonia water injector 32 to be temporarily below "1.5 mg / st" in step 130.

[0024] Next, in step 140, the control device 50 calculates the air-fuel ratio from the measured oxygen concentration Ox.

[0025] Next, in step 150, the control device 50 calculates the deviation between the calculated air-fuel ratio and the theoretical air-fuel ratio (stoichiometry) and determines whether the value is below "20%". If the determination by the control device 50 is affirmative, in step 160, the ammonia concentration learning is completed and the process proceeds to step 110.

[0026] [[ID=1,7]]On the other hand, if the determination in step 150 is negative, the control device 50 converts the deviation of the air-fuel ratio into an ammonia concentration in step 170, learns it as the ammonia concentration learning value, and returns the process to step 130.

[0027] [Regarding the operation and effect of the hydrogen engine system] According to the configuration of the hydrogen engine system 1 of this embodiment described above, the exhaust gas discharged from the hydrogen engine 10 flows through the NTA catalyst 13 and the ammonia water generation means 14. In the NTA catalyst 13, nitride oxides (NOx) and hydrogen in the exhaust gas are converted into ammonia and water. In the ammonia water generation means 14, ammonia water is produced from ammonia and water. The produced ammonia water is recirculated through the ammonia water recirculation line 17 and injected into the hydrogen engine 10 by the ammonia water injector 32. Therefore, NOx in the exhaust gas is converted into ammonia by the NTA catalyst 13, produced and recovered as ammonia water in the ammonia water generation means 14, and supplied to the hydrogen engine 10 by the ammonia water injector 32 for combustion together with hydrogen. The control device 50 learns the difference between the air-fuel ratio obtained from the measured oxygen concentration Ox and the stoichiometric pressure as an ammonia concentration learning value. The control device 50 controls the ammonia water injector 32 based on the ammonia concentration learning value. Therefore, the amount of ammonia water supplied to the hydrogen engine 10 is appropriately adjusted based on the ammonia concentration learning value. Therefore, it is possible to reduce NOx emissions from the hydrogen engine 10 and stabilize the combustion of the hydrogen-ammonia fuel mixture.

[0028] According to the configuration of this embodiment, the control device 50 performs ammonia concentration learning only after ammonia water at a concentration of 1.5 mg / st or less is supplied to the hydrogen engine 10. Therefore, it is possible to perform ammonia concentration learning only after the air-fuel ratio of the hydrogen-ammonia fuel mixture has stabilized. As a result, appropriate ammonia concentration learning can be performed.

[0029] <Another embodiment> Furthermore, this disclosed technology is not limited to the embodiments described above, and it can be implemented by appropriately modifying a part of the configuration without departing from the spirit of the disclosed technology.

[0030] (1) In the above embodiment, the ammonia water generation means 14 is composed of a heat exchanger 21 and an exhaust muffler 22, but the ammonia water generation means can also be composed of a heat exchanger alone.

[0031] (2) In the above embodiment, the hydrogen engine system 1 was implemented in an automobile, but the hydrogen engine system can be implemented in a mobile body other than an automobile. [Industrial applicability]

[0032] This disclosed technology can be applied to vehicles equipped with hydrogen engines, etc. [Explanation of Symbols]

[0033] 1. Hydrogen engine system 10 Hydrogen engine 12 Exhaust passage 13 NTA catalyst (catalyst) 14 Ammonia water generating means 16 Ammonia water supply means 17. Ammonia-water recirculation line (ammonia-water recirculation means) 32 Ammonia water injector 41. Oxygen concentration sensor (means for measuring oxygen concentration) 50 Control device (ammonia concentration learning means, control means)

Claims

1. A hydrogen engine that burns hydrogen as fuel, An exhaust passage for discharging exhaust gas from the hydrogen engine after the hydrogen has been burned in the hydrogen engine, A catalyst is provided in the exhaust passage for converting nitrogen oxides contained in the exhaust gas discharged from the hydrogen engine and the hydrogen into ammonia and water, An oxygen concentration measuring means provided in the exhaust passage for measuring the oxygen concentration after the hydrogen has been burned in the hydrogen engine, The exhaust passage is provided with an ammonia water generating means for generating ammonia water from the ammonia and the water, Ammonia water supply means for supplying the ammonia water produced by the ammonia water generating means to the hydrogen engine, Ammonia water recirculation means for recirculating the ammonia water generated by the ammonia water generating means to the ammonia water supply means, In a hydrogen engine system equipped with, An ammonia concentration learning means learns the difference between the air-fuel ratio obtained from the measured oxygen concentration and the stoichiometric air-fuel ratio as an ammonia concentration learning value, A control means that controls the ammonia water supply means based on the learned ammonia concentration learned value. A hydrogen engine system characterized by being equipped with the following features.

2. In the hydrogen engine system according to claim 1, The ammonia concentration learning means performs learning of the ammonia concentration after supplying a predetermined amount or less of the ammonia water to the hydrogen engine using the ammonia water supply means. A hydrogen engine system characterized by the following features.

Images