In-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen and control method

Abstract

The invention discloses an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen and a control method, and belongs to the field of internal combustion engines. At present, an internal combustion engine technology taking pure hydrogen and pure oxygen as fuels still has many problems and defects. The invention relates to a fuel supply system, an internal combustion power system, a tail gas recovery system, a combustion control strategy, a knock control strategy and a tail gas recovery strategy of a pure hydrogen and pure oxygen direct injection internal combustion engine. The efficiency is improved, and the problem that a large amount of unburned hydrogen exists in tail gas is solved.

Description

Technical Field

[0001] The present invention provides an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen and a control method. The specific content involves the fuel supply system, internal combustion power system, exhaust gas recovery system of the in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen, as well as combustion control strategies, knock control strategies, and exhaust gas recovery strategies, belonging to the field of internal combustion engines. Background Art

[0002] With the proposal of the dual-carbon goal, the low-carbonization of internal combustion power has become a current research hotspot. Many low-carbon fuels can well address the fossil energy crisis, are more environmentally friendly, and have good development prospects. Among them, hydrogen, as a zero-carbon fuel, has only water as its combustion product. Compared with traditional fuel engines, hydrogen engines do not produce harmful substances such as nitrogen oxides and particulate matter during operation. At the same time, hydrogen is a fuel with relatively good combustion conditions, having a wide ignition limit and a high energy density, and is one of the fuels for achieving efficient combustion of internal combustion engines.

[0003] In the aerospace field, liquid hydrogen and liquid oxygen are widely used as propellants due to their extremely high specific impulse, high energy density which significantly improves the propulsion efficiency, and very high energy density. For problems such as liquid hydrogen leakage and hydrogen redundancy existing in the actual use of spacecraft, it can be used as fuel to supply the internal combustion engine, thereby reducing the types of fuels loaded on the spacecraft, and converting the redundant hydrogen combustion into mechanical energy through the internal combustion engine to improve the overall utilization efficiency of fuels in the aircraft. Driving a generator with internal combustion power can extend the flight time of the spacecraft and improve its overall power supply capacity, etc. And oxygen is currently the most widely used and efficient combustion oxidant.

[0004] According to different forms of hydrogen entering the cylinder, hydrogen internal combustion engines can be divided into intake port injection and in-cylinder direct injection hydrogen internal combustion engines, and some studies also attempt pre-chamber schemes. In the intake port injection mode, hydrogen is mixed with air in the intake port and then enters the cylinder. The low ignition energy of hydrogen makes the mixture extremely easy to be ignited by hot gas in the intake pipe, causing backfire, which has an adverse impact on the improvement of power performance, combustion stability, and safety. Adopting the structure of a pre-chamber can solve the problem of abnormal combustion, but it is limited by problems such as scavenging problems and low heat transfer efficiency, resulting in low efficiency. Compared with intake port injection and pre-chambers, in-cylinder direct injection has high efficiency while preventing abnormal combustion, and is the future of hydrogen internal combustion engines.

[0005] In summary, an internal combustion engine using pure hydrogen and pure oxygen as fuel and oxidant respectively has the advantages of zero carbon emissions and high efficiency. Especially in the aerospace field with pure hydrogen and pure oxygen conditions, it has more research and application value. Summary of the Invention

[0006] Currently, there are still many problems and deficiencies in the internal combustion engine technology using pure hydrogen and pure oxygen as fuels. When hydrogen and oxygen at the stoichiometric ratio are ignited, there will be extremely high pressure and temperature. Premixed hydrogen-oxygen fuel will increase the risk of engine backfire. The pre-chamber scheme can partially solve these problems, but the efficiency is lower than that of in-cylinder direct injection. And in-cylinder direct injection also faces the problems of intense combustion and a large amount of unburned hydrogen in the exhaust gas under rich hydrogen conditions. Therefore, the present invention provides an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen and a control method.

[0007] The present invention not only improves the efficiency but also solves the problem of a large amount of unburned hydrogen in the exhaust gas.

[0008] The present invention adopts the following technical solutions:

[0009] An in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen, comprising: an oxygen supply system (P1), which sequentially includes an oxygen storage tank (1), an oxygen pressure reducing valve (2), a pressure stabilizing chamber (3), an oxygen flow controller (4), an oxygen flow sensor (5); a hydrogen supply system (P2), which sequentially includes a hydrogen storage tank (6), a hydrogen pressure reducing valve (7), a pressure stabilizing chamber (8), a hydrogen flow controller (9), a hydrogen flow sensor (10), an electronic throttle valve (11); an internal combustion power system (P3), which includes an intake pipe (12), an intake valve (13), a high-pressure oxygen nozzle (14), a cylinder pressure sensor (15), a spark plug (16), an exhaust valve (17), an exhaust pipe (18), a crankshaft position sensor (19), a rotational speed signal sensor (20), an internal combustion engine (21); an exhaust gas recovery system, which includes a condenser (22), a water storage tank (23), a suction pump (24); a control system (P5), a control unit ECU (25);

[0010] The control unit ECU (25) sends an oxygen flow controller opening signal a to the oxygen flow controller (3);

[0011] The control unit ECU sends a hydrogen flow controller opening signal b to the hydrogen flow controller (8);

[0012] The control unit ECU receives an oxygen flow signal c through the oxygen flow sensor (5);

[0013] The control unit ECU receives a hydrogen flow signal d through the hydrogen flow sensor (10);

[0014] The control unit ECU sends an electronic throttle valve opening signal e to the electronic throttle valve (11);

[0015] The control unit ECU receives a crankshaft position signal f through the crankshaft position sensor (19);

[0016] The control unit ECU sends an oxygen nozzle signal g to the high-pressure oxygen nozzle (14) to control the injection timing and injection pulse width of the oxygen nozzle;

[0017] The control unit ECU receives a cylinder pressure signal h through the cylinder pressure sensor (15);

[0018] The control unit ECU sends a spark plug ignition signal i through the spark plug (16) to control the electrode discharge of the spark plug;

[0019] The control unit ECU receives a rotational speed signal j through the rotational speed signal sensor (20);

[0020] The control unit ECU sends an exhaust gas extraction signal k to the exhaust gas extraction pump (24) to control the exhaust gas extraction pump.

[0021] A control method for an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen, specifically involving the fuel supply system, internal combustion power system, exhaust gas recovery system, combustion control strategy, knock control strategy, and exhaust gas recovery strategy of the pure hydrogen and pure oxygen in-cylinder direct injection internal combustion engine.

[0022] (1) Combustion control strategy

[0023] In the hydrogen supply system (P2), high-pressure hydrogen is stored in the hydrogen storage tank (6), and after passing through the hydrogen pressure reducing valve (7), hydrogen flow controller (8), pressure stabilizing chamber (9), hydrogen flow sensor (10), and electronic throttle valve (11), it enters the intake pipe (12); in the oxygen supply system (P1), the oxygen in the oxygen storage tank (1) passes through the oxygen pressure reducing valve (7), oxygen flow controller (3), pressure stabilizing chamber (4), oxygen flow sensor (5), and is injected into the cylinder through the high-pressure oxygen nozzle (14); according to the obtained hydrogen flow signal d and rotational speed signal j, the oxygen supply amount required to reach the desired equivalence ratio can be calculated. The hydrogen mass flow rate obtained through the hydrogen flow signal d is in kilograms per second (kg / s); the rotational speed obtained through the rotational speed signal j is n, in revolutions per minute (rpm); the crankshaft angle position Δθ passed by the intake valve opening and closing is in degrees of crankshaft angle (°CA); the mass of oxygen supplied can be calculated by the following formula, in kilograms (kg):

[0024]

[0025] Furthermore, calculate the high-pressure oxygen injection pulse width, and control the oxygen nozzle (14) through the oxygen nozzle signal g;

[0026] Igniting before top dead center can ensure that the fuel starts to burn when the piston reaches top dead center. Considering the flammability of hydrogen and oxygen, at 3 degrees of crankshaft rotation before top dead center, the control unit ECU (25) controls the spark plug (16) through the spark plug ignition signal i, making the electrodes of the spark plug (16) energized and generating a spark, providing the initial energy for igniting the hydrogen-oxygen mixture in the combustion chamber; the spark plug (16) controlled by the control unit ECU (25) works once in each cycle;

[0027] (2) Knock control strategy

[0028] To quantify the severity of the pressure rise in the internal combustion engine and prevent knock from occurring, the in-cylinder pressure rise rate dp / dθ is defined, where p is the pressure in megapascals (MPa), obtained through the cylinder pressure signal h connected between the control unit ECU (25) and the cylinder pressure sensor (15), and θ is the crankshaft position in degrees of crankshaft rotation (°CA), obtained through the crankshaft position signal f connected between the control unit ECU (25) and the crankshaft position sensor (19). The control unit ECU (25) obtains the in-cylinder pressure and crankshaft angle in real time and calculates the pressure rise rate dp / dθ in real time. When the internal combustion engine runs to a certain cycle, if the highest pressure rise rate calculated in real time exceeds 150% of the calibrated highest pressure rise rate under normal combustion conditions of this internal combustion engine, it is determined that the engine has knocked. According to experimental calibration, the reference value of the highest pressure rise rate under the condition of stable normal combustion at a speed of 1500 rpm for a direct injection internal combustion engine with pure hydrogen and pure oxygen in the cylinder is given: 0.8 MPa / °CA. That is, for this experimental direct injection internal combustion engine with pure hydrogen and pure oxygen in the cylinder, under the condition of a speed of 1500 rpm, when the highest pressure rise rate of a certain cycle exceeds 1.2 MPa / °CA, it is determined that the engine has knocked;

[0029] When engine knocking occurs, the knocking is first controlled by delaying the ignition angle. In the next cycle, the spark plug ignition signal i sent by the control unit ECU (25) to the spark plug (16) is delayed by 3 degrees of crankshaft rotation angle. Because in the combustion strategy, the ignition is defaulted to occur 3 degrees of crankshaft rotation angle before top dead center. When knocking occurs, the first ignition angle delay can make the engine ignite at top dead center, ensuring that the hydrogen-oxygen fuel burns during the downward stroke of the piston. If the maximum pressure rise rate in this cycle still exceeds 150% of the above-mentioned normal combustion maximum pressure rise rate, the spark plug ignition signal i is repeatedly delayed by 3 degrees of crankshaft rotation angle until the error between the maximum pressure rise rate in a certain cycle and the above-mentioned normal combustion maximum pressure rise rate does not exceed 10%; if after repeating the delay step 5 times, the maximum pressure rise rate still exceeds 150% of the above-mentioned normal combustion maximum pressure rise rate, the knocking is controlled by reducing the oxygen injection amount. In the next cycle, the injection pulse width of the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) is reduced by 10% until the error between the maximum pressure rise rate in a certain cycle and the above-mentioned normal combustion maximum pressure rise rate does not exceed 10%; when the injection pulse width of the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) is reduced to 50% of the initial injection pulse width in a certain cycle and the engine still knocks, in the next cycle, the cycle control unit ECU (25) controls the oxygen control valve (3) and the hydrogen control valve (8) through signal a and signal b, cuts off the supply of hydrogen and oxygen, and at the same time controls the closing of the throttle valve through the throttle signal e, and no longer sends the spark plug ignition signal i to the spark plug (16), completing the shutdown to avoid damaging the engine cylinder block.

[0030] (3) Exhaust gas recovery strategy

[0031] The control unit ECU (25) is connected to the crankshaft position sensor (19) and obtains the crankshaft position signal f; when the crankshaft position signal f is at 20 degrees before bottom dead center, the exhaust valve (17) opens, the exhaust valve (17) moves downward, and the in-cylinder combustion exhaust gas enters the exhaust pipe (18) due to the pressure difference and is discharged from the internal combustion engine cylinder (21). When the crankshaft position signal f is at 20 degrees after top dead center, the exhaust valve (17) closes, the exhaust valve (17) moves upward, and the exhaust ends. The exhaust valve (17) opens and closes once every 720 degrees of crankshaft rotation angle;

[0032] After the exhaust valve (17) opens, the in-cylinder combustion exhaust gas entering the exhaust pipe (18) enters the condenser (22). The main components of the exhaust gas are water vapor and excess hydrogen. Among them, the water vapor becomes liquid water after passing through the condenser (22) and enters the water storage tank (23); the control unit ECU (25) is connected to the air extraction pump (24) and controls the air extraction pump (24) through the exhaust gas extraction signal k. At the same crankshaft angle when the exhaust valve is closed, the control unit ECU (25) sends an opening signal k to the air extraction pump (24), so that the excess hydrogen discharged through the exhaust pipe (18) and condensed by the condenser (22) is pumped into the hydrogen storage tank (6) through the air extraction pump (24) and enters the hydrogen supply system (P2) to participate in subsequent combustion as fuel. When the crankshaft turns 60 degrees after the exhaust valve (17) is closed, that is, 80 degrees after top dead center, the control unit ECU (25) sends a closing signal k to the air extraction pump (24). Description of the Drawings

[0033] Figure 1 . Schematic diagram of an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen

[0034] In the figure: oxygen supply system (P1), which successively includes an oxygen storage tank (1), an oxygen pressure reducing valve (2), an oxygen flow controller (3), a pressure stabilizing chamber (4), an oxygen flow sensor (5); hydrogen supply system (P2), which successively includes a hydrogen storage tank (6), a hydrogen pressure reducing valve (7), a hydrogen flow controller (8), a pressure stabilizing chamber (9), a hydrogen flow sensor (10), an electronic throttle valve (11); internal combustion power system (P3), which includes an intake pipe (12), an intake valve (13), a high-pressure oxygen nozzle (14), a cylinder pressure sensor (15), a spark plug (16), an exhaust valve (17), an exhaust pipe (18), a crankshaft position sensor (19), a rotational speed signal sensor (20), an internal combustion engine (21); exhaust gas recovery system, which includes a condenser (22), a water storage tank (23), an air extraction pump (24); control system (P5), control unit ECU (25);

[0035] Signals: oxygen control signal a, hydrogen control signal b, oxygen flow signal c, hydrogen flow signal d, throttle signal e, crankshaft position signal f, oxygen injection signal h, cylinder pressure signal i, spark plug ignition signal j, rotational speed signal l, exhaust gas extraction signal m. Detailed Embodiment

[0036] The following combines Figure 1 and the detailed embodiment to further illustrate the present invention:

[0037] (1) Combustion control strategy

[0038] In the hydrogen supply system (P2), high-pressure hydrogen is stored in the hydrogen storage tank (6) and enters the intake pipe (12) through the hydrogen pressure reducing valve (7), hydrogen flow controller (8), pressure stabilizing chamber (9), hydrogen flow sensor (10), and electronic throttle valve (11); in the oxygen supply system (P1), oxygen in the oxygen storage tank (1) passes through the oxygen pressure reducing valve (7), oxygen flow controller (3), pressure stabilizing chamber (4), oxygen flow sensor (5), and is sprayed into the cylinder through the high-pressure oxygen nozzle (14); according to the obtained hydrogen flow signal d and rotational speed signal j, the oxygen supply amount required to reach the desired equivalence ratio can be calculated. The hydrogen mass flow rate obtained through the hydrogen flow signal d is in kilograms per second (kg / s); the rotational speed obtained through the rotational speed signal j is n, in revolutions per minute (rpm); the crankshaft angle Δθ passed through by the opening and closing of the intake valve, in degrees of crankshaft rotation (°CA); the mass of oxygen supplied can be calculated by the following formula, in kilograms (kg):

[0039]

[0040] Furthermore, the high-pressure oxygen injection pulse width is calculated, and the oxygen nozzle (14) is controlled through the oxygen nozzle signal g.

[0041] Ignition before top dead center can ensure that the fuel starts to burn when the piston reaches top dead center. Considering the flammability of hydrogen and oxygen, at 3 degrees of crankshaft rotation before top dead center, the control unit ECU (25) controls the spark plug (16) through the spark plug ignition signal i, making the electrodes of the spark plug (16) energized and generating a spark, providing the initial energy for igniting the hydrogen-oxygen mixture in the combustion chamber; the spark plug (16) controlled by the control unit ECU (25) works once in each cycle.

[0042] (2) Knock control strategy

[0043] In order to quantify the severity of the pressure rise in an internal combustion engine to prevent knocking, the in-cylinder pressure rise rate dp / dθ is defined, where p is the pressure in megapascals (MPa), obtained from the cylinder pressure signal h connected by the control unit ECU (25) and the cylinder pressure sensor (15), θ is the crankshaft position in degrees of crankshaft rotation (°CA), obtained from the crankshaft position signal f connected by the control unit ECU (25) and the crankshaft position sensor (19). The control unit ECU (25) obtains the in-cylinder pressure and crankshaft angle in real time and calculates the pressure rise rate dp / dθ in real time. When the internal combustion engine runs to a certain cycle, if the highest pressure rise rate calculated in real time exceeds 150% of the calibrated highest pressure rise rate under normal combustion conditions of this internal combustion engine, it is determined that knocking occurs in the engine. According to experimental calibration, the reference value of the highest pressure rise rate under the condition of stable normal combustion of a direct injection internal combustion engine with pure hydrogen and pure oxygen at a speed of 1500 rpm is given: 0.8 MPa / °CA. That is, for this experimental direct injection internal combustion engine with pure hydrogen and pure oxygen, at a speed of 1500 rpm, when the highest pressure rise rate of a certain cycle exceeds 1.2 MPa / °CA, it is determined that knocking occurs in the engine;

[0044] When knocking occurs in the engine, first, the knocking is controlled by delaying the ignition angle. In the next cycle, the spark plug ignition signal i sent by the control unit ECU (25) to the spark plug (16) is delayed by 3 degrees of crankshaft rotation. Because in the combustion strategy, it is default to ignite 3 degrees of crankshaft rotation before top dead center. When knocking occurs, the first ignition angle delay can make the engine ignite at top dead center, ensuring that the hydrogen-oxygen fuel burns during the piston downward stroke. If the highest pressure rise rate in this cycle still exceeds 150% of the above normal combustion highest pressure rise rate, then repeat delaying the spark plug ignition signal i by 3 degrees of crankshaft rotation until the error between the highest pressure rise rate of a certain cycle and the above normal combustion highest pressure rise rate does not exceed 10%; If after repeating the delay step 5 times, the highest pressure rise rate still exceeds 150% of the above normal combustion highest pressure rise rate, then the knocking is controlled by reducing the oxygen injection amount. In the next cycle, the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) has its injection pulse width reduced by 10% until the error between the highest pressure rise rate of a certain cycle and the above normal combustion highest pressure rise rate does not exceed 10%; When the injection pulse width of the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) is reduced to 50% of the initial injection pulse width in a certain cycle and the engine still has knocking, then in the next cycle, the cycle control unit ECU (25) controls the oxygen control valve (3) and the hydrogen control valve (8) through signal a and signal b, cuts off the supply of hydrogen and oxygen, and at the same time controls the closing of the throttle through the throttle signal e and no longer sends the spark plug ignition signal i to the spark plug (16) to complete shutdown and avoid damaging the engine cylinder block.

[0045] (3) Exhaust gas recovery strategy

[0046] The control unit ECU (25) is connected to the crankshaft position sensor (19) and obtains the crankshaft position signal f; when the crankshaft position signal f is at 20 degrees before the bottom dead center, the exhaust valve (17) opens, the exhaust valve (17) moves downward, and the in-cylinder combustion exhaust gas enters the exhaust pipe (18) due to the pressure difference and is discharged from the internal combustion engine cylinder (21). When the crankshaft position signal f is at 20 degrees after the top dead center, the exhaust valve (17) closes, the exhaust valve (17) moves upward, and the exhaust ends. The exhaust valve (17) opens and closes once every 720 degrees of crankshaft rotation;

[0047] After the exhaust valve (17) opens, the in-cylinder combustion exhaust gas entering the exhaust pipe (18) enters the condenser (22). The main components of the exhaust gas are water vapor and excess hydrogen. Among them, the water vapor becomes liquid water after passing through the condenser (22) and enters the water storage tank (23); the control unit ECU (25) is connected to the air extraction pump (24) and controls the air extraction pump (24) through the exhaust gas extraction signal k. At the same crankshaft rotation angle when the exhaust valve closes, the control unit ECU (25) sends an opening signal k to the air extraction pump (24), so that the excess hydrogen discharged from the exhaust pipe (18) and condensed by the condenser (22) is pumped into the hydrogen storage tank (6) through the air extraction pump (24) and enters the hydrogen supply system (P2) as fuel to participate in subsequent combustion. When the crankshaft rotation angle is 60 degrees after the exhaust valve (17) closes, that is, at 80 degrees after the top dead center, the control unit ECU (25) sends a closing signal k to the air extraction pump (24).

Claims

1. An in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen, characterized in that Comprising: An oxygen supply system (P1), which successively includes an oxygen storage tank (1), an oxygen pressure reducing valve (2), a pressure stabilizing chamber (3), an oxygen flow controller (4), and an oxygen flow sensor (5); a hydrogen supply system (P2), which successively includes a hydrogen storage tank (6), a hydrogen pressure reducing valve (7), a pressure stabilizing chamber (8), a hydrogen flow controller (9), a hydrogen flow sensor (10), and an electronic throttle valve (11); an internal combustion power system (P3), which includes an intake pipe (12), an intake valve (13), a high-pressure oxygen nozzle (14), a cylinder pressure sensor (15), a spark plug (16), an exhaust valve (17), an exhaust pipe (18), a crankshaft position sensor (19), a rotational speed signal sensor (20), and an internal combustion engine (21); an exhaust gas recovery system, which includes a condenser (22), a water storage tank (23), and a suction pump (24); a control system (P5), a control unit ECU (25); The control unit ECU (25) sends an oxygen flow controller opening signal a to the oxygen flow controller (3); The control unit ECU sends a hydrogen flow controller opening signal b to the hydrogen flow controller (8); The control unit ECU receives an oxygen flow signal c through the oxygen flow sensor (5); The control unit ECU receives a hydrogen flow signal d through the hydrogen flow sensor (10); The control unit ECU sends an electronic throttle valve opening signal e to the electronic throttle valve (11); The control unit ECU receives a crankshaft position signal f through the crankshaft position sensor (19); The control unit ECU sends an oxygen nozzle signal g to the high-pressure oxygen nozzle (14) to control the injection timing and injection pulse width of the oxygen nozzle; The control unit ECU receives a cylinder pressure signal h through the cylinder pressure sensor (15); The control unit ECU sends a spark plug ignition signal i through the spark plug (16) to control the electrode discharge of the spark plug; The control unit ECU receives a rotational speed signal j through the rotational speed signal sensor (20); The control unit ECU sends an exhaust gas suction signal k to the suction pump (24) to control the suction pump.

2. A method for controlling an in-cylinder direct injection internal combustion engine based on pure hydrogen and pure oxygen as claimed in claim 1, characterized in that Including one or a combination of a combustion control strategy, a knock control strategy, and an exhaust gas recovery strategy; (1) Combustion control strategy In the hydrogen supply system (P2), high-pressure hydrogen is stored in the hydrogen storage tank (6) and enters the intake pipe (12) through the hydrogen pressure reducing valve (7), hydrogen flow controller (8), pressure stabilizing chamber (9), hydrogen flow sensor (10), and electronic throttle valve (11); in the oxygen supply system (P1), oxygen in the oxygen storage tank (1) passes through the oxygen pressure reducing valve (7), oxygen flow controller (3), pressure stabilizing chamber (4), oxygen flow sensor (5), and is sprayed into the cylinder through the high-pressure oxygen nozzle (14); according to the obtained hydrogen flow signal d and rotational speed signal j, the oxygen supply amount to reach the required equivalence ratio can be calculated. The hydrogen mass flow rate obtained through the hydrogen flow signal d is in kilograms per second (kg / s); the rotational speed obtained through the rotational speed signal j is n, in revolutions per minute (rpm); the crankshaft angle passed by the intake valve opening and closing is Δθ, in degrees of crankshaft rotation (°CA); the mass of oxygen supplied can be calculated by the following formula, in kilograms (kg): Furthermore, calculate the high-pressure oxygen injection pulse width, and control the oxygen nozzle (14) through the oxygen nozzle signal g; Igniting before top dead center can ensure that the fuel starts to burn when the piston reaches top dead center. Considering the flammability of hydrogen and oxygen, 3 degrees of crankshaft rotation before top dead center, the control unit ECU (25) controls the spark plug (16) through the spark plug ignition signal i, so that the electrodes of the spark plug (16) are energized and generate sparks, providing initial energy for igniting the hydrogen-oxygen mixture in the combustion chamber; the spark plug (16) controlled by the control unit ECU (25) works once in each cycle; (2) Knock control strategy To quantify the severity of pressure rise in an internal combustion engine to prevent knocking, the in-cylinder pressure rise rate dp / dθ is defined, where p is the pressure in megapascals (MPa), obtained from the cylinder pressure signal h connected by the control unit ECU (25) and the cylinder pressure sensor (15), θ is the crankshaft position in degrees of crankshaft rotation (°CA), obtained from the crankshaft position signal f connected by the control unit ECU (25) and the crankshaft position sensor (19). The control unit ECU (25) obtains the in-cylinder pressure and crankshaft angle in real time and calculates the pressure rise rate dp / dθ in real time. When the internal combustion engine runs to a certain cycle, if the highest pressure rise rate calculated in real time exceeds 150% of the calibrated highest pressure rise rate under normal combustion conditions of this internal combustion engine, it is determined that knocking occurs in the engine. According to experimental calibration, the reference value of the highest pressure rise rate under the condition of stable operation of normal combustion of a direct injection internal combustion engine with pure hydrogen and pure oxygen at a speed of 1500 rpm is given: 0.8 MPa / °CA. That is, for this experimental direct injection internal combustion engine with pure hydrogen and pure oxygen, at a speed of 1500 rpm, when the highest pressure rise rate of a certain cycle exceeds 1.2 MPa / °CA, it is determined that knocking occurs in the engine; When knocking occurs in the engine, first, the knocking is controlled by delaying the ignition angle. In the next cycle, the spark plug ignition signal i sent by the control unit ECU (25) to the spark plug (16) is delayed by 3 degrees of crankshaft rotation. Because in the combustion strategy, it is default to ignite 3 degrees of crankshaft rotation before top dead center. When knocking occurs and the ignition angle is delayed for the first time, it can make the engine ignite at top dead center, ensuring that the hydrogen-oxygen fuel burns during the downward stroke of the piston. If the highest pressure rise rate in this cycle still exceeds 150% of the above-mentioned normal combustion highest pressure rise rate, the spark plug ignition signal i is repeatedly delayed by 3 degrees of crankshaft rotation until the error between the highest pressure rise rate of a certain cycle and the above-mentioned normal combustion highest pressure rise rate does not exceed 10%; if after repeating the delay step 5 times, the highest pressure rise rate still exceeds 150% of the above-mentioned normal combustion highest pressure rise rate, the knocking is controlled by reducing the oxygen injection amount. In the next cycle, the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) has its injection pulse width reduced by 10% until the error between the highest pressure rise rate of a certain cycle and the above-mentioned normal combustion highest pressure rise rate does not exceed 10%; when the injection pulse width of the oxygen nozzle signal g sent by the control unit ECU (25) to the high-pressure oxygen nozzle (14) is reduced to 50% of the initial injection pulse width in a certain cycle and knocking still occurs in the engine, in the next cycle, the cycle control unit ECU (25) controls the oxygen control valve (3) and the hydrogen control valve (8) through signal a and signal b, cuts off the supply of hydrogen and oxygen, and at the same time controls the closing of the throttle valve through the throttle signal e and no longer sends the spark plug ignition signal i to the spark plug (16) to complete the shutdown and avoid damaging the engine block; (3) Exhaust gas recovery strategy The control unit ECU (25) is connected to the crankshaft position sensor (19) and obtains the crankshaft position signal f. When the crankshaft position signal f is at 20 degrees before bottom dead center, the exhaust valve (17) opens and moves downward. The combustion exhaust gas in the cylinder enters the exhaust pipe (18) due to the pressure difference and is discharged from the internal combustion engine cylinder (21). When the crankshaft position signal f is at 20 degrees after top dead center, the exhaust valve (17) closes and moves upward, ending the exhaust process. The exhaust valve (17) opens and closes once every 720 degrees of crankshaft rotation. After the exhaust valve (17) opens, the combustion exhaust gas in the cylinder that enters the exhaust pipe (18) enters the condenser (22). The exhaust gas includes water vapor and hydrogen. Among them, the water vapor becomes liquid water after passing through the condenser (22) and enters the water storage tank (23). The control unit ECU (25) is connected to the air extraction pump (24) and controls the air extraction pump (24) through the exhaust gas extraction signal k. At the same crankshaft rotation angle when the exhaust valve closes, the control unit ECU (25) sends an opening signal k to the air extraction pump (24), so that the excess hydrogen condensed by the condenser (22) and discharged through the exhaust pipe (18) is pumped into the hydrogen storage tank (6) by the air extraction pump (24) and enters the hydrogen supply system (P2) to participate in subsequent combustion as fuel. When the crankshaft rotation angle is 60 degrees after the exhaust valve (17) closes, that is, at 80 degrees after top dead center, the control unit ECU (25) sends a closing signal k to the air extraction pump (24).

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