Composite injection hydrogen internal combustion engine and injection control method thereof

Abstract

The invention relates to a composite injection hydrogen internal combustion engine and an injection control method thereof, and the composite injection hydrogen internal combustion engine comprises an air inlet system, a low-pressure air inlet channel hydrogen supply system, a high-pressure in-cylinder direct injection hydrogen supply system, an ignition system and a control system, the control system dynamically adjusts the ratio of low-pressure gas inlet channel hydrogen injection to high-pressure cylinder internal direct injection hydrogen by correspondingly controlling the working states of the gas inlet system, the low-pressure gas inlet channel hydrogen supply system and the high-pressure cylinder internal direct injection hydrogen supply system, and specifically, the ratio of low-pressure gas inlet channel hydrogen injection to high-pressure cylinder internal direct injection hydrogen injection is adjusted according to the rotating speed and target power of an engine. The proportion of air inlet channel injection and in-cylinder direct injection is dynamically adjusted. Compared with the prior art, a composite double-injection mode is introduced, more accurate combustion control can be achieved, higher flexibility and adaptability are provided, the performance and combustion efficiency of the hydrogen internal combustion engine can be optimized within a wider working condition range, and the combustion stability and fuel economy of the engine are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen internal combustion engines, and in particular to a compound injection hydrogen internal combustion engine and an injection control method thereof. Background Art

[0002] In the context of the increasingly serious global warming problem, in order to reduce carbon emissions, current automotive industry researchers and engineers are urgently seeking low-carbon or carbon-free automotive power solutions. Hydrogen, as a clean, zero-carbon energy source with abundant sources, has the characteristics of low quality, high calorific value, rapid combustion and good anti-explosion performance. Therefore, it is considered to be one of the most promising zero-carbon emission energy sources for automotive power systems in the 21st century. Hydrogen internal combustion engines have relatively low requirements for hydrogen fuel purity, and are similar to traditional internal combustion engines in structure and have strong compatibility. They retain the main structure and system of traditional internal combustion engines and are no different from traditional fuel engines in working principles. Relying on the existing mature internal combustion engine industrial system, through the corresponding adaptive research and design of hydrogen supply and injection systems, special cold spark plugs, turbochargers, lubrication and crankshaft ventilation, it can achieve mass low-cost production and large-scale promotion and application. Compared with hydrogen fuel cells, which are more technically difficult, hydrogen internal combustion engines have huge industrial advantages.

[0003] Existing hydrogen internal combustion engines mainly focus on a single injection mode, intake port injection or direct injection into the cylinder. For example, patent CN200610150571.9 designs a method and device for hydrogen injection in the intake pipe of a hydrogen fuel internal combustion engine, which is used to solve the flashback problem of hydrogen injection in the intake pipe; patent CN201611161865.1 provides a cross-sectional branch injection system and a control method for a hydrogen fuel internal combustion engine, which effectively solves the problem of intake pipe blockage by setting an auxiliary hydrogen injector on the intake pipe; patent CN201810148049.X designs a direct injection gas nozzle and its engine and power system, wherein the nozzle is composed of a shell, a gas collecting chamber, a nozzle orifice and a gas channel. The gas direct injection nozzle can be used for direct injection of gases such as oxygen, hydrogen, natural gas, and argon, and can withstand high temperature, high pressure, and is not easy to flashback. It can use the injected gas for self-cooling to increase its service life.

[0004] However, the above single injection mode cannot flexibly adapt to different load and speed requirements when facing complex working conditions, and often cannot provide the best combustion effect in the entire working range. Moreover, when the traditional intake hydrogen internal combustion engine is at high speed and high load, the intake volume of the supercharger increases, and a certain back pressure is formed in the manifold, making it difficult to inject hydrogen, resulting in reduced combustion efficiency and unfavorable combustion stability. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a compound injection hydrogen internal combustion engine and an injection control method thereof, which can optimize the performance and combustion efficiency of the hydrogen internal combustion engine under a wider range of operating conditions.

[0006] The object of the present invention can be achieved by the following technical solutions: A compound injection hydrogen internal combustion engine, comprising an intake system, a low-pressure intake duct hydrogen supply system, a high-pressure cylinder direct injection hydrogen supply system, an ignition system and a control system, wherein the intake system is used to introduce external air into the ignition system;

[0007] The low-pressure intake hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system are used to inject hydrogen into the ignition system respectively;

[0008] The control system is used to correspondingly control the working states of the intake system, the low-pressure intake duct hydrogen supply system, and the high-pressure in-cylinder direct injection hydrogen supply system to dynamically adjust the ratio of low-pressure intake duct hydrogen injection and high-pressure in-cylinder direct injection hydrogen.

[0009] Furthermore, the air intake system includes an air filter, a throttle valve, and an air mass flow sensor which are connected in series in sequence, and the air filter, the throttle valve, and the air mass flow sensor are respectively connected to a control system.

[0010] Furthermore, the air intake system is also provided with a supercharging unit.

[0011] Furthermore, the low-pressure inlet hydrogen supply system includes a first hydrogen bottle, a low-pressure hydrogen pressure reducing valve, a first hydrogen mass flow sensor and an inlet hydrogen injector connected in series in sequence, and the low-pressure hydrogen pressure reducing valve and the first hydrogen mass flow sensor are respectively connected to the control system.

[0012] Furthermore, the high-pressure in-cylinder direct injection hydrogen supply system includes a second hydrogen bottle, a high-pressure hydrogen pressure reducing valve, a second hydrogen mass flow sensor and an in-cylinder direct injection hydrogen injector connected in series in sequence, and the high-pressure hydrogen pressure reducing valve and the second hydrogen mass flow sensor are respectively connected to the control system.

[0013] Furthermore, the ignition system includes a hydrogen injector and a spark plug respectively connected to the control system.

[0014] Furthermore, the control system is connected to a knock sensor, and the knock sensor is installed on the pre-combustion chamber cavity.

[0015] A method for controlling injection of a composite injection hydrogen internal combustion engine comprises the following steps:

[0016] S1. Obtaining engine speed, target power and thermal efficiency data to calculate the total injection amount corresponding to the target power and the injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen;

[0017] S2. According to the total injection volume and injection ratio, combined with the real-time knock index of the engine, the working states of the intake system, the low-pressure intake duct hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system are dynamically adjusted accordingly.

[0018] Furthermore, the total injection amount corresponding to the target power in step S1 is specifically:

[0019]

[0020] Where n is the engine speed, P target is the target power of the engine, η is the thermal efficiency of the engine, and LHV is the lower heating value of hydrogen, which indicates the heat released per unit mass of fuel;

[0021] The specific injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen is:

[0022]

[0023] Among them, k is the sensitivity coefficient, n max is the maximum speed, P max is the maximum power, β1 is the load conversion experience value, β2 is the speed conversion experience value, w1 and w2 are weight coefficients.

[0024] Furthermore, the specific process of step S2 is as follows:

[0025] According to the total injection amount, the throttle of the intake system is adjusted to control the total intake amount so that the excess air coefficient meets the preset threshold range, wherein the excess air coefficient is specifically:

[0026]

[0027] Among them, m air is the air intake volume;

[0028] According to the injection ratio, the initial low-pressure intake port hydrogen injection amount and the high-pressure cylinder direct injection hydrogen amount are:

[0029] m intake =α·m

[0030] m direct =(1-α)·m

[0031] Among them, m intake is the amount of hydrogen injected into the low-pressure intake duct, m direct is the amount of high-pressure direct-injection hydrogen in the cylinder;

[0032] The real-time knock index of the engine is compared with the preset knock threshold. If the real-time knock index of the engine is less than the preset knock threshold, the current pre-combustion chamber hydrogen injection amount is maintained; otherwise, the pre-combustion chamber hydrogen injection amount is reduced until the real-time knock index of the engine is less than the preset knock threshold.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The present invention is provided with an intake system, a low-pressure intake hydrogen supply system, a high-pressure in-cylinder direct injection hydrogen supply system, an ignition system and a control system, wherein the intake system is used to introduce external air into the ignition system; the low-pressure intake hydrogen supply system and the high-pressure in-cylinder direct injection hydrogen supply system are used to respectively inject hydrogen into the ignition system; the control system controls the working states of the intake system, the low-pressure intake hydrogen supply system and the high-pressure in-cylinder direct injection hydrogen supply system accordingly, so as to dynamically adjust the ratio of low-pressure intake hydrogen injection and high-pressure in-cylinder direct injection hydrogen. Thus, a composite dual injection scheme is realized, which can provide higher flexibility and adaptability, thereby optimizing the performance and combustion efficiency of the hydrogen internal combustion engine in a wider range of working conditions.

[0035] The present invention provides a spark plug connected to a control system in the ignition system. In addition, the control system is connected to a knock sensor, which can further improve ignition stability, reduce the risk of knock, further widen the lean burn limit, and reduce the emission of nitrogen oxide gas Nox.

[0036] The present invention is based on the engine speed, target power and thermal efficiency data to calculate the total injection amount corresponding to the target power, and calculate the injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen. Then, according to the total injection amount and injection ratio, combined with the real-time knock index of the engine, the working state of the intake system, the low-pressure intake hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system is dynamically adjusted accordingly. That is, the injection ratio and injection amount are dynamically adjusted in combination with the target power and speed of the engine, so as to achieve more accurate combustion control-at low load and low speed, intake injection is preferred to improve the uniformity of the mixture, and at high load and high speed, it turns to direct injection in the cylinder to improve power output and combustion efficiency. It can flexibly select the most suitable injection ratio under different working conditions, and avoid the problem that hydrogen is difficult to inject due to the increase of the supercharger intake volume at high speed and high load of the traditional intake hydrogen internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the structure of the composite injection hydrogen internal combustion engine of the present invention;

[0038] Figure 2 It is a schematic flow chart of the injection control method of the present invention;

[0039] Figure 3 It is a schematic diagram of the application process of the embodiment;

[0040] Description of symbols in the figure: air filter 15, throttle valve 14, air mass flow sensor 13

[0041] 1. First hydrogen cylinder, 2. Second hydrogen cylinder, 3. Low-pressure hydrogen pressure reducing valve, 4. First hydrogen mass flow sensor, 5. High-pressure hydrogen pressure reducing valve, 6. Second hydrogen mass flow sensor, 7. Intake manifold hydrogen injector, 8. In-cylinder direct injection hydrogen injector, 9. Control system, 10. Knock sensor, 11. Ignition system, 111. Hydrogen injector, 112. Spark plug, 12. Boost unit. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Example

[0044] A composite injection hydrogen internal combustion engine comprises an intake system, a low-pressure intake duct hydrogen supply system, a high-pressure in-cylinder direct injection hydrogen supply system, an ignition system and a control system, wherein the intake system is used to introduce external air into the ignition system; the low-pressure intake duct hydrogen supply system and the high-pressure in-cylinder direct injection hydrogen supply system are used to respectively inject hydrogen into the ignition system; the control system is used to correspondingly control the working states of the intake system, the low-pressure intake duct hydrogen supply system and the high-pressure in-cylinder direct injection hydrogen supply system, so as to dynamically adjust the ratio of low-pressure intake duct hydrogen injection and high-pressure in-cylinder direct injection hydrogen.

[0045] like Figure 1 As shown, the air intake system is connected in series with an air filter 15, a throttle valve 14, an air mass flow sensor 13, and a supercharging unit 12;

[0046] The low-pressure inlet hydrogen supply system is connected in series with a first hydrogen bottle 1, a low-pressure hydrogen pressure reducing valve 3, a first hydrogen mass flow sensor 4, and an inlet hydrogen injector 7;

[0047] The high-pressure in-cylinder direct injection hydrogen supply system is connected in series in sequence with a second hydrogen bottle 2, a high-pressure hydrogen pressure reducing valve 5, a second hydrogen mass flow sensor 6, and an in-cylinder direct injection hydrogen injector 8;

[0048] The ignition system 11 includes a spark plug 112 and a hydrogen injector 111;

[0049] In addition, a knock sensor 10 is installed on the pre-combustion chamber cavity;

[0050] The control system 9 is respectively connected to the air filter 15, the throttle 14, the air mass flow sensor 13, the low-pressure hydrogen pressure reducing valve 3, the first hydrogen mass flow sensor 4, the high-pressure hydrogen pressure reducing valve 5, the second hydrogen mass flow sensor 6, the spark plug 112, the hydrogen injector 111, and the knock sensor 10 for communication.

[0051] For the above-mentioned compound injection hydrogen internal combustion engine, this scheme also designs a corresponding injection control method, such as Figure 2 As shown, the following steps are included:

[0052] S1. Obtaining engine speed, target power and thermal efficiency data to calculate the total injection amount corresponding to the target power and the injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen;

[0053] S2. According to the total injection volume and injection ratio, combined with the real-time knock index of the engine, the working states of the intake system, the low-pressure intake duct hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system are dynamically adjusted accordingly.

[0054] This embodiment applies the above solution, such as Figure 3 As shown, a control process of adjusting the injection ratio and injection amount based on the target power and speed is realized:

[0055] During the operation of the engine, obtain the engine speed n and target power P target And thermal efficiency η, calculate the total injection amount under target power:

[0056]

[0057] Among them, LHV is the lower heating value of hydrogen, which represents the heat released by unit mass of fuel to determine the injection amount under each operating condition.

[0058] The throttle valve is adjusted according to the amount of hydrogen injection to control the total amount of intake air, so that the excess air coefficient λ is around 2.5:

[0059]

[0060] Among them, m air The air intake volume.

[0061] The injection ratio α is calculated according to the following formula:

[0062]

[0063] α ranges from [0-1], where k is the sensitivity coefficient and n max is the maximum speed, P max is the maximum power, β1 is the load conversion experience value, β2 is the speed conversion experience value, w1 and w2 are weight coefficients.

[0064] The final intake port hydrogen injection amount and direct injection amount are:

[0065] m intake =α·m

[0066] m direct =(1-α)·m

[0067] This makes α closer to 1 at low load and low speed, with intake port injection being the main method. Conversely, at high speed and high load, α is closer to 0, with direct injection into the cylinder being the main method. This enables flexible selection of the most suitable injection ratio under different operating conditions and avoids the problem of difficulty in injecting hydrogen at high speed and high load in traditional intake port hydrogen internal combustion engines due to the increase in supercharger intake volume.

[0068] In addition, for the control of the hydrogen injection amount in the pre-combustion chamber, the engine knock index KI is calculated in real time and compared with the threshold KI critical Compare, if KI<KI critical , maintain the current pre-combustion chamber hydrogen injection amount; if KI ≥ KI critical , reduce the amount of hydrogen injected into the pre-combustion chamber until KI < KI critical .

[0069] The KI calculation formula is:

[0070]

[0071] Where A is the frequency factor related to hydrogen, P is the instantaneous pressure in the cylinder read by the knock sensor, s is the pressure index, and E a is the activation energy of hydrogen, R is the gas constant, T is the instantaneous temperature in the cylinder, f(φ) is the correction function related to the excess air coefficient of the mixture, t o and t end It is the integration time interval, usually the key time point from the compression stroke to the combustion stage.

[0072] In summary, this solution provides a composite injection hydrogen internal combustion engine, including a composite injection hydrogen internal combustion engine structure, combined with a pre-combustion chamber spark plug to widen the lean combustion boundary; on the other hand, it also provides a control method for adjusting the injection ratio and injection amount based on the target power and speed, which can dynamically adjust the ratio of intake port injection and direct injection in the cylinder according to the working conditions of the engine (including speed and target power), thereby optimizing the performance of the hydrogen internal combustion engine, improving combustion efficiency, and reducing harmful emissions. By accurately calculating the injection amount and reasonably allocating the ratio of the two injection modes, this solution effectively improves the combustion stability and fuel economy of the engine, especially under different loads and speeds, it can automatically adjust the injection strategy to adapt to various working conditions.

[0073] Compared with the existing technology, this solution can flexibly select the most suitable injection mode under different working conditions by dynamically adjusting the ratio of intake port injection and direct injection. Intake port injection is used under low load and low speed conditions to improve the uniformity of the mixture and reduce incomplete combustion; direct injection is used under high load and high speed conditions to improve combustion efficiency and power output. This can optimize the hydrogen combustion process in the entire working range and significantly improve the overall performance of the engine.

[0074] This solution can effectively solve the problem of difficulty in injecting hydrogen at high speed and high load in traditional intake hydrogen internal combustion engines due to the increase in the intake volume of the supercharger. This solution uses the spark plug in the pre-combustion chamber and adjusts the amount of hydrogen injected in the pre-combustion chamber in real time to further reduce the risk of knock.

Claims

1. A compound injection hydrogen internal combustion engine, characterized in that: It comprises an intake system, a low-pressure intake duct hydrogen supply system, a high-pressure cylinder direct injection hydrogen supply system, an ignition system (11) and a control system (9), wherein the intake system is used to introduce external air into the ignition system (11); The low-pressure intake hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system are used to inject hydrogen into the ignition system (11) respectively; The control system (9) is used to correspondingly control the working states of the intake system, the low-pressure intake duct hydrogen supply system, and the high-pressure in-cylinder direct injection hydrogen supply system, so as to dynamically adjust the ratio of low-pressure intake duct hydrogen injection and high-pressure in-cylinder direct injection hydrogen.

2. A compound injection hydrogen internal combustion engine according to claim 1, characterized in that: The air intake system comprises an air filter, a throttle valve and an air mass flow sensor which are connected in series in sequence. The air filter, the throttle valve and the air mass flow sensor are respectively connected to a control system (9).

3. A compound injection hydrogen internal combustion engine according to claim 2, characterized in that: The air intake system is also provided with a supercharging unit (12).

4. A compound injection hydrogen internal combustion engine according to claim 1, characterized in that The low-pressure inlet hydrogen supply system comprises a first hydrogen bottle (1), a low-pressure hydrogen pressure reducing valve (3), a first hydrogen mass flow sensor (4) and an inlet hydrogen injector (7) which are connected in series in sequence, and the low-pressure hydrogen pressure reducing valve (3) and the first hydrogen mass flow sensor (4) are respectively connected to a control system (9).

5. A compound injection hydrogen internal combustion engine according to claim 1, characterized in that: The high-pressure in-cylinder direct injection hydrogen supply system comprises a second hydrogen bottle (2), a high-pressure hydrogen pressure reducing valve (5), a second hydrogen mass flow sensor (6) and an in-cylinder direct injection hydrogen injector (8) which are sequentially connected in series, and the high-pressure hydrogen pressure reducing valve (5) and the second hydrogen mass flow sensor (6) are respectively connected to a control system (9).

6. A compound injection hydrogen internal combustion engine according to claim 1, characterized in that: The ignition system (11) comprises a hydrogen injector (111) and a spark plug (112) which are respectively connected to the control system (9).

7. A compound injection hydrogen internal combustion engine according to claim 1, characterized in that: The control system (9) is connected to a knock sensor (10), and the knock sensor (10) is mounted on the pre-combustion chamber cavity.

8. An injection control method for a compound injection hydrogen internal combustion engine, applied to a compound injection hydrogen internal combustion engine as claimed in claim 1, characterized in that: The following steps are involved: S1. Obtaining engine speed, target power and thermal efficiency data to calculate the total injection amount corresponding to the target power and the injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen; S2. According to the total injection volume and injection ratio, combined with the real-time knock index of the engine, the working states of the intake system, the low-pressure intake duct hydrogen supply system and the high-pressure cylinder direct injection hydrogen supply system are dynamically adjusted accordingly.

9. The injection control method of a compound injection hydrogen internal combustion engine according to claim 8, characterized in that: The total injection amount corresponding to the target power in step S1 is specifically: Where n is the engine speed, P target is the target power of the engine, η is the thermal efficiency of the engine, and LHV is the lower heating value of hydrogen, which indicates the heat released per unit mass of fuel; The specific injection ratio of low-pressure intake hydrogen and high-pressure cylinder direct injection hydrogen is: Among them, k is the sensitivity coefficient, n max is the maximum speed, P max is the maximum power, β1 is the load conversion experience value, β2 is the speed conversion experience value, w1 and w2 are weight coefficients.

10. The injection control method of a compound injection hydrogen internal combustion engine according to claim 9, characterized in that: The specific process of step S2 is: According to the total injection amount, the throttle of the intake system is adjusted to control the total intake amount so that the excess air coefficient meets the preset threshold range, wherein the excess air coefficient is specifically: Among them, m air is the air intake volume; According to the injection ratio, the initial low-pressure intake port hydrogen injection amount and the high-pressure cylinder direct injection hydrogen amount are: m intake =α·m m direct =(1-a)·m Among them, m intake is the amount of hydrogen injected into the low-pressure intake duct, m direct is the amount of high-pressure direct-injection hydrogen in the cylinder; The real-time knock index of the engine is compared with the preset knock threshold. If the real-time knock index of the engine is less than the preset knock threshold, the current pre-combustion chamber hydrogen injection amount is maintained; otherwise, the pre-combustion chamber hydrogen injection amount is reduced until the real-time knock index of the engine is less than the preset knock threshold.

Images