Anti-knock ignition method and system for hydrogen internal combustion engine

Abstract

The invention provides an anti-knock ignition method and system for a hydrogen internal combustion engine. The method comprises the steps that the knock index of the hydrogen internal combustion engine is calculated in real time; judging the magnitude of the knock index and the threshold value; if the knock index is larger than the threshold value, the ignition advance angle of the hydrogen internal combustion engine is adjusted, and the suppression sensitivity of the ignition advance angle to knock is obtained according to the adjusted ignition advance angle; the nitrogen injection amount is increased and corrected until the knock index is smaller than the threshold value, the upper limit of the nitrogen injection amount is set, and the cycle change rate of the hydrogen internal combustion engine is limited; a hydrogen injection pulse width and an excess air coefficient target of a hydrogen internal combustion engine are compensated based on an ECU, and a boost or throttle valve is adjusted. According to the method, the nitrogen injection amount is increased till the knock index is smaller than the threshold value, so that time-sharing cooperative control over nitrogen and hydrogen is achieved, abnormal combustion such as knock and preignition can be effectively restrained, and the heat efficiency of the engine can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen internal combustion engine control, and in particular to a hydrogen internal combustion engine anti-knock ignition method and system. BACKGROUND

[0002] Automobile industry researchers and engineers are urgently seeking low-carbon or carbon-free automobile power solutions. Hydrogen, as a clean zero-carbon energy source with abundant resources, has the characteristics of low mass heat value, rapid combustion propagation and good anti-knock performance, and is therefore considered one of the most promising zero-carbon emission energy sources for vehicle power systems in the 21st century. Hydrogen internal combustion engines have relatively low requirements for hydrogen fuel purity and are compatible with traditional internal combustion engine structures, retaining the main structures and systems of traditional internal combustion engines and having no difference in working principle from traditional fuel engines. They can rely on the existing mature internal combustion engine industry system and, through corresponding adaptive research and design of hydrogen supply and injection systems, special cold-type spark plugs, turbochargers, and lubrication and crankshaft ventilation, achieve mass production and large-scale application at low cost. Compared with hydrogen fuel cells, which are more technically challenging, hydrogen internal combustion engines have a huge industrial advantage. However, due to the physicochemical properties of hydrogen, such as low ignition energy, high combustion speed, and wide combustion limit, it is easy to produce knock in internal combustion engines, which seriously affects the stability, efficiency, and durability of the engine. Therefore, how to control the knock of hydrogen internal combustion engines is a major difficulty.

[0003] To control the knock of hydrogen internal combustion engines, the existing patent CN116857099A designs a straight gas passage hydrogen internal combustion engine structure to solve the problem of insufficient in-cylinder mixing in direct injection internal combustion engines, which leads to knock; the existing patent CN117231357A selects different operating modes and injection strategies under different operating conditions to ensure stable operation at small loads, high efficiency at medium loads, and no knock at large loads; and the existing patent CN115839273A controls the excess air ratio to suppress knock. It can be seen that the above-mentioned patents mainly suppress knock through structure optimization, injection strategy optimization, and excess air ratio adjustment.

[0004] In summary, in the prior art, hydrogen and nitrogen cannot be used to control abnormal combustion such as knock and pre-ignition through time-sharing cooperation, so as to improve the thermal efficiency of the engine. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a hydrogen internal combustion engine anti-knock ignition method and system to solve the above-mentioned problems in the prior art.

[0006] In a first aspect, the present application provides a hydrogen internal combustion engine anti-knock ignition method, which comprises: calculating the knock index of the hydrogen internal combustion engine in real time; judging the size of the knock index and the threshold value; if the knock index is greater than the threshold value, causing the hydrogen internal combustion engine to adjust the ignition advance angle, and obtaining the sensitivity of the knock suppression to the ignition advance angle according to the adjusted ignition advance angle; increasing the nitrogen injection amount, and correcting the nitrogen injection amount until the knock index is less than the threshold value, and setting the upper limit of the nitrogen injection amount and limiting the cycle variation rate of the hydrogen internal combustion engine; compensating the hydrogen injection pulse width and the excess air coefficient target of the hydrogen internal combustion engine based on the ECU, and adjusting the supercharging or the throttle.

[0007] Compared with the prior art, the beneficial effects of the present application are: by calculating the knock index of the engine in real time, and judging the size between the knock index and the threshold value, if the knock index is greater than the threshold value, adjusting the engine ignition advance angle, and increasing the nitrogen injection amount until the knock index is less than the threshold value, thereby realizing the time-sharing collaborative control of nitrogen and hydrogen, which can effectively suppress abnormal combustion such as knock and pre-ignition, and can effectively improve the thermal efficiency of the engine.

[0008] Further, the calculation expression of the knock index is: ; In the formula, represents the knock index, represents the final integration time, represents the initial integration time, represents the hydrogen-related frequency factor, represents the instantaneous pressure in the cylinder, represents the pressure index, represents the index, represents the hydrogen activation energy, R represents the gas constant, and T represents the instantaneous cylinder temperature, represents the correction function related to the excess air coefficient of the mixture.

[0009] Further, the calculation expression of the correction function related to the excess air coefficient of the mixture is: ; In the formula, k0, k1, k2 respectively represent three groups of empirical fitting parameters, the excess air coefficient of the mixture, respectively represent the square of the excess air coefficient.

[0010] Further, the expression of adjusting the ignition advance angle is: θ spark,new= θ spark-k·( KI - KIcritical ); wherein, θ spark,new represents the adjusted spark advance angle, θ spark represents the spark advance angle, and k represents the adjustment coefficient, represents the knock index, KIcritical represents the threshold value.

[0011] Further, the expression for correcting the nitrogen injection amount is: ; wherein, represents the increment of the nitrogen injection amount, represents the knock intensity feedback coefficient, represents the dynamic correction coefficient, represents the sensitivity correction coefficient, represents the knock index, KIcritical represents the threshold value, represents the sensitivity of the knock index to the spark advance angle, represents the differential of the nitrogen injection amount expression; The calculation expression for the sensitivity of the knock index to the spark advance angle is: ; wherein, θ spark represents the spark advance angle, represents the differential of the sensitivity calculation.

[0012] Further, after the step of judging the magnitude of the knock index and the threshold value, the method further comprises: if the knock index is less than the threshold value, maintaining the spark advance angle of the engine.

[0013] In a second aspect, the present application also provides a hydrogen internal combustion engine anti-knock ignition system, which is controlled by the hydrogen internal combustion engine anti-knock ignition method described above, and the system comprises an engine, a spark plug, a hydrogen injector, a nitrogen injector, an ECU control unit, and a cylinder pressure sensor. The engine is provided with a cylinder body and a piston, the hydrogen injector, the nitrogen injector, the cylinder pressure sensor, and the spark plug are all arranged in the cylinder body, and the ECU control unit is electrically connected with the hydrogen injector, the nitrogen injector, the cylinder pressure sensor, and the spark plug. The ECU control unit is configured to control the hydrogen injector and the nitrogen injector to inject hydrogen and nitrogen respectively into the cylinder for time-sharing and cooperative control. The cylinder pressure sensor is configured to detect the pressure value in the cylinder and transmit the pressure value to the ECU control unit. The spark plug is controlled by the ECU control unit to ignite the hydrogen in the cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Flow chart of the anti-knock ignition method for the hydrogen internal combustion engine in the first embodiment of the present application; Figure 2 Structure schematic diagram of the anti-knock ignition system for the hydrogen internal combustion engine in the second embodiment of the present application.

[0015] Main element symbol explanation: 1, engine; 11, cylinder; 12, piston; 10, spark plug; 20, hydrogen injector; 30, nitrogen injector; 40, ECU control unit; 50, cylinder pressure sensor.

[0016] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0017] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The drawings show several embodiments of the present application. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and complete.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0020] Embodiment one Please refer to Figure 1, as shown is the anti-knock ignition method of the hydrogen internal combustion engine in the first embodiment of the present application, the method comprising steps S1 to S5: S1, calculating the engine knock index in real time; It can be understood that the calculation expression of the knock index is: ; In the formula, represents the knock index, represents the final integration time, represents the initial integration time, represents the hydrogen-related frequency factor, represents the instantaneous pressure in the cylinder, represents the pressure index, represents the index, represents the hydrogen activation energy, R represents the gas constant, and T represents the instantaneous cylinder temperature, represents a correction function related to the excess air coefficient of the mixture.

[0021] It needs to be explained that the final integration time and the initial integration time are usually the key time points from the compression stroke to the combustion stage.

[0022] Further, the calculation expression of the correction function related to the excess air coefficient of the mixture is: ; In the formula, k0, k1, and k2 respectively represent three sets of empirical fitting parameters, the excess air coefficient of the mixture, respectively represent the square of the excess air coefficient.

[0023] It is worth mentioning that the three sets of empirical fitting parameters are obtained by engine multi-condition calibration, and are used to reflect the influence of the excess air coefficient on the end gas auto-ignition reaction rate. The excess air coefficient of the mixture λ (dimensionless) is defined as the ratio of the actual air amount to the theoretically required air amount, and the square of the excess air coefficient (dimensionless) is used to describe the high-order lean combustion effect in the correction function.

[0024] S2, judging the size of the knock index and the threshold value; S3, if the knock index is greater than the threshold value, adjusting the ignition advance angle of the engine, and obtaining the sensitivity of the knock suppression to the ignition advance angle according to the adjusted ignition advance angle; It can be understood that the expression of the adjusted ignition advance angle is: θ spark,new= θ spark-k·( KI - KIcritical ); wherein, θ spark,new represents the adjusted spark advance angle, θ spark represents the spark advance angle, and k represents the adjustment coefficient, represents the knock index, KIcritical represents the threshold value, in the present embodiment, according to the experimental value, KIcritical is taken as 0.9.

[0025] S4, increase the nitrogen injection amount, and correct the nitrogen injection amount until the knock index is less than the threshold value, and set an upper limit of the nitrogen injection amount and limit the cycle variation rate of the hydrogen internal combustion engine; In the present embodiment, the expression for correcting the nitrogen injection amount is: ; wherein, represents the increment of the nitrogen injection amount, represents the knock intensity feedback coefficient, represents the dynamic correction coefficient, represents the sensitivity correction coefficient, represents the knock index, KIcritical represents the threshold value, represents the sensitivity of the knock index to the spark advance angle, represents the differential of the nitrogen injection amount expression; It is worth noting that the knock intensity feedback coefficient determines the proportional relationship between the injection correction amount and the KI overrun amplitude, the dynamic correction coefficient is used to respond to the rising rate of the knock index, and the sensitivity correction coefficient is used to prevent excessive sensitivity of the ignition angle to the knock from causing a large correction The calculation expression of the sensitivity of the knock index to the spark advance angle is: ; wherein, θ spark represents the spark advance angle, represents the differential of the sensitivity calculation.

[0026] S5, compensate for the hydrogen injection pulse width and the excess air coefficient target of the hydrogen internal combustion engine based on the ECU, and adjust the supercharger or the throttle; It is worth noting that if the knock index is less than the threshold value, the spark advance angle of the engine is maintained.

[0027] It needs to be explained that in the low load condition, only hydrogen is injected, and the nitrogen system is closed (to save nitrogen consumption); in the medium and high load condition, hydrogen is injected in the intake stroke (to form homogeneous mixture), and nitrogen is injected at the end of the compression stroke (to cover the hot spot area of the piston top and cylinder head).

[0028] Embodiment Two Please refer to Figure 2 , it is shown that the anti-knock ignition system of the hydrogen internal combustion engine in the second embodiment of the present application, which is controlled by the anti-knock ignition method of the hydrogen internal combustion engine in embodiment one, the system comprises an engine 1, a spark plug 10, a hydrogen injector 20, a nitrogen injector 30, an ECU control unit 40 and a cylinder pressure sensor 50.

[0029] The engine 1 is provided with a cylinder body 11 and a piston 12, the hydrogen injector 20, the nitrogen injector 30, the cylinder pressure sensor 50 and the spark plug 10 are arranged in the cylinder body 11, the ECU control unit 40 is electrically connected with the hydrogen injector 20, the nitrogen injector 30, the cylinder pressure sensor 50 and the spark plug 10, wherein the ECU control unit 40 is used for controlling the hydrogen injector 20 and the nitrogen injector 30 to respectively inject hydrogen and nitrogen in the cylinder body 11 for time-sharing cooperative control, the cylinder pressure sensor 50 is used for detecting the pressure value in the cylinder body 11 and transmitting the pressure value to the ECU control unit 40, and the spark plug 10 is controlled by the ECU control unit 40 for igniting the hydrogen in the cylinder body 11.

[0030] In summary, the anti-knock ignition method and system of the hydrogen internal combustion engine in the above embodiments of the present application, by calculating the knock index of the engine in real time, and judging the size between the knock index and the threshold value, if the knock index is greater than the threshold value, the engine ignition advance angle is adjusted, and the nitrogen injection amount is increased, until the knock index is less than the threshold value, so as to realize the time-sharing cooperative control of nitrogen and hydrogen, which can effectively suppress abnormal combustion such as knock and pre-ignition, and can effectively improve the thermal efficiency of the engine and the service life of the engine, and can also avoid using external EGR, and simplify the system complexity.

[0031] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0032] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for anti-knock ignition of a hydrogen internal combustion engine, characterized in that, The method includes: Real-time calculation of knock index in hydrogen internal combustion engines; Determine the magnitude of the knock index relative to the threshold; If the knock index is greater than the threshold, the ignition advance angle of the hydrogen internal combustion engine is adjusted, and the knock suppression sensitivity of the ignition advance angle is obtained based on the adjusted ignition advance angle. Increase the nitrogen injection quantity and adjust the nitrogen injection quantity until the knock index is less than the threshold, and set an upper limit for the nitrogen injection quantity and limit the cycle change rate of the hydrogen internal combustion engine; The ECU compensates for the hydrogen injection pulse width and excess air coefficient target of the hydrogen internal combustion engine, and adjusts the boost or throttle.

2. The anti-knock ignition method for a hydrogen internal combustion engine according to claim 1, characterized in that, The formula for calculating the knock index is: ； In the formula, This indicates the knock index. Indicates the final integration time. Indicates the initial integration time. The frequency factor representing hydrogen. Indicates the instantaneous pressure inside the cylinder. Indicates the stress index. Indicates an index. R represents the activation energy of hydrogen, R represents the gas constant, and T represents the instantaneous temperature inside the cylinder. This represents a correction function related to the excess air coefficient of the air-fuel mixture.

3. The anti-knock ignition method for a hydrogen internal combustion engine according to claim 2, characterized in that, The calculation expression for the correction function related to the excess air coefficient of the mixture is as follows: ； In the formula, k0, k1, and k2 represent three sets of empirical fitting parameters, The excess air coefficient of the air-fuel mixture. These represent the squares of the excess air coefficient.

4. The anti-knock ignition method for a hydrogen internal combustion engine according to claim 1, characterized in that, The expression for adjusting the ignition advance angle is: θ spark,new= θ spark-k·( KI - KIcritical ); In the formula, θ spark,new indicates the adjusted ignition advance angle. θ "spark" represents the ignition advance angle, and "k" represents the adjustment factor. This indicates the knock index. KIcritical This refers to the threshold value.

5. The anti-knock ignition method for a hydrogen internal combustion engine according to claim 1, characterized in that, The expression for correcting the nitrogen injection quantity is: ； In the formula, This indicates the increment in nitrogen injection volume. Indicates the knock intensity feedback coefficient. Indicates the dynamic correction factor. This represents the sensitivity correction factor. This indicates the knock index. KIcritical Indicates the threshold, This indicates the sensitivity of the knock index to the ignition advance angle. The differential symbol representing the expression for nitrogen injection quantity; The expression for calculating the sensitivity of the knock index to the ignition advance angle is as follows: ； In the formula, θ "Spark" indicates the ignition advance angle. The differential symbol represents the sensitivity calculation.

6. The anti-knock ignition method for a hydrogen internal combustion engine according to claim 1, characterized in that, After the step of determining the magnitude of the knock index and the threshold, the method further includes: If the knock index is less than the threshold, the ignition advance angle of the engine is maintained.

7. A hydrogen internal combustion engine anti-knock ignition system, controlled by the hydrogen internal combustion engine anti-knock ignition method according to any one of claims 1 to 6, characterized in that, The system includes an engine, spark plugs, hydrogen injectors, nitrogen injectors, an ECU control unit, and a cylinder pressure sensor. The engine is equipped with a cylinder block and a piston. The hydrogen injector, the nitrogen injector, the cylinder pressure sensor, and the spark plug are all located in the cylinder block. The ECU control unit is electrically connected to the hydrogen injector, the nitrogen injector, the cylinder pressure sensor, and the spark plug. The ECU control unit is used to control the hydrogen injector and the nitrogen injector to inject hydrogen and nitrogen into the cylinder respectively for time-sharing coordinated control. The cylinder pressure sensor is used to detect the pressure value in the cylinder and transmit the pressure value to the ECU control unit. The spark plug is controlled by the ECU control unit to ignite the hydrogen in the cylinder.

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