Pre-ignition identification and suppression method for hydrogen internal combustion engine under multiple working conditions

Abstract

The invention discloses a preignition recognition and suppression method for a hydrogen internal combustion engine under multiple working conditions, and belongs to the technical field of engines. Comprising the following steps that firstly, the absolute deviation of a 5% heat release rate point relative to a median is calculated, and whether preignition occurs in the combustion process or not is judged; secondly, the current working condition of the hydrogen internal combustion engine is judged; then, a corresponding method is adopted for preignition suppression; then, the preignition suppression effect is judged; then, optimal control parameters are sought through TOPSIS; and finally, the suppressed data is calculated to judge the suppression effect. According to the pre-ignition identification and inhibition method for the hydrogen internal combustion engine under the multiple working conditions, pre-ignition is identified by using statistics of the sample median and the absolute deviation of the median, and whether pre-ignition occurs under different working conditions can be judged by using the difference value between the median and the absolute deviation of the median as the pre-ignition threshold value; measures for restraining preignition under three different working conditions of low-speed medium load, low-speed high load and high-speed high load are provided, and preignition is effectively restrained.

Description

Technical Field

[0001] The present invention relates to the field of engine technology, and in particular to a method for identifying and suppressing pre-ignition of a hydrogen internal combustion engine under multiple working conditions. Background Art

[0002] For port-injected hydrogen internal combustion engines, hydrogen accounts for about 30% of the cylinder capacity, resulting in a loss of output power. In order to increase power density, the adoption of miniaturized, turbocharged and direct-injected engines is becoming more and more common. The miniaturization of engines increases the peak in-cylinder pressure during combustion, increasing the risk of low-speed pre-ignition. Current methods for identifying low-speed pre-ignition generally rely on monitoring the peak cylinder pressure and monitoring whether the pressure oscillation amplitude exceeds a preset fixed threshold. These methods can be detected online, but can only identify obvious severe knock cycles, such as strong knock and super knock. They are ineffective for mild knock and no knock cycles, and the fixed threshold lacks universal applicability under different engines or test conditions. Another method involves determining the start of combustion (SoC: Start of Combustion). There is still some controversy about the setting of the threshold, and an inappropriate judgment threshold is prone to miss and misidentify mild pre-ignition cycles. Therefore, the calculation of the SoC threshold is of certain significance for judging pre-ignition events, and when the SoC threshold is used for judgment, the occurrence of pre-ignition events can be judged in advance compared to the method of using cylinder pressure online diagnosis. In addition, there has never been a control strategy that uses multiple hydrogen injection methods to suppress pre-ignition in hydrogen internal combustion engines. Therefore, accurately identifying the pre-ignition cycle of hydrogen internal combustion engines under multiple operating conditions and proposing a suppression method can further improve the performance of hydrogen internal combustion engines. Summary of the invention

[0003] The purpose of the present invention is to provide a method for identifying and suppressing pre-ignition under multiple operating conditions of a hydrogen internal combustion engine, adopt an outlier combustion theory to identify the pre-ignition phenomenon of a hydrogen internal combustion engine in advance, and perform corresponding strategic control according to different operating conditions and pre-ignition degrees of the hydrogen internal combustion engine.

[0004] To achieve the above object, the present invention provides a method for identifying and suppressing pre-ignition of a hydrogen internal combustion engine under multiple operating conditions, comprising the following steps:

[0005] Step 1, calculate the absolute deviation MAD of the 5% heat release rate point MFB05 relative to the median to determine whether pre-ignition occurs in the combustion process. If pre-ignition occurs, execute step 2; otherwise, determine that pre-ignition does not occur;

[0006] Step 2, determining the current operating condition of the hydrogen internal combustion engine under the pre-ignition condition, the operating conditions of the hydrogen internal combustion engine are specifically: low speed and medium load, low speed and high load, and high speed and high load;

[0007] Step 3, using different methods to suppress pre-ignition of the hydrogen internal combustion engine according to the current operating conditions of the hydrogen internal combustion engine in step 2;

[0008] Step 4, judging the effect of inhibiting pre-ignition by comparing the cyclic variation of the indicated mean effective pressure IMEP of the hydrogen internal combustion engine before and after inhibition, the amplitude strength of the in-cylinder pressure of the pre-ignition cycle, and the maximum pressure amplitude;

[0009] Step 5: Find the optimal control parameters through TOPSIS;

[0010] Step 6: Determine whether the optimal control parameters obtained in step 5 satisfy MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, the pre-ignition suppression is completed, otherwise the pre-ignition suppression is performed again.

[0011] Preferably, the calculation expression of the absolute deviation MAD of the 5% heat release rate point MFB05 relative to the median in step 1 is as follows:

[0012]

[0013] In the formula, x i Represents a single data value, Represents the median.

[0014] Preferably, the process of determining whether pre-ignition occurs in the combustion process in step 1 is as follows:

[0015] S11. Adopt the outlier detection theory in statistical analysis, use the statistics of sample median and median absolute deviation to identify pre-ignition, and use the difference between median and median absolute deviation as the pre-ignition threshold verification deviation. The calculation expression of verification deviation is as follows:

[0016]

[0017] In the formula, x i Represents a single data value, represents the median;

[0018] S12. Determine whether MFB05 satisfies MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, then no pre-ignition occurs; if MFB05 <MAD-3.5*|σ MAD |, then pre-ignition occurs.

[0019] Preferably, in step 3, when the current operating condition of the hydrogen internal combustion engine is at low speed and medium load, and MAD-4.5*|σ MAD | <MFB05<MAD-3.5*|σ MAD |, then the abnormal combustion at this time is a mild pre-ignition, and the occurrence of pre-ignition can be suppressed by delaying the ignition angle.

[0020] Preferably, in step 3, when the current operating condition of the hydrogen internal combustion engine is at low speed and medium load, and MFB05 <MAD-4.5*|σ MAD |, then the abnormal combustion at this time is an obvious pre-ignition. This situation occurs because multiple slight pre-ignitions will aggravate the formation of hot spots in the cylinder, thereby causing obvious pre-ignition. At this time, if the pre-ignition is suppressed only by delaying the ignition angle, the effective thermal efficiency of the hydrogen internal combustion engine will be reduced. Therefore, the excess air coefficient should be increased at the same time. Such operation can reduce the occurrence of pre-ignition to a greater extent and improve the effective thermal efficiency.

[0021] Preferably, in step 3, when the current operating condition of the hydrogen internal combustion engine is at low speed and high load, lean combustion is adopted, and the excess air coefficient is controlled at about 2, and secondary injection is adopted at the same time, and abnormal combustion of the hydrogen internal combustion engine is suppressed by adjusting the timing and amount of secondary injection.

[0022] Preferably, in step 3, when the current operating condition of the hydrogen internal combustion engine is at high speed and high load, the variable valve timing VVT phase is adjusted to increase the air mass flow to suppress pre-ignition; inappropriate injection start time and intake valve closing IVC will cause obvious pre-ignition, so it is necessary to adjust the VVT ​​phase. On the one hand, this allows maximizing the intake inertia from the late valve closing to increase the air mass flow; on the other hand, this is also crucial to prevent interference between IVC and SOI.

[0023] Preferably, the cyclic variation CoV of the indicated mean effective pressure IMEP in step 4 is IMEP , the cylinder pressure amplitude intensity ΔP of the pre-ignition cycle PI The calculation formula of the maximum pressure amplitude MAPO is as follows:

[0024]

[0025] Among them, σ IMEP is the standard deviation of IMEP, is the average IMEP;

[0026]

[0027] Among them, IMEP i It represents the IMEP of the i-th cycle, N represents the number of cycles, and the value is less than 3% during stable combustion;

[0028]

[0029] In the formula, Indicates the average maximum cylinder pressure, N PI Indicates the number of pre-ignition times, ΔP PI Indicates the amplitude strength of the cylinder pressure during the pre-ignition cycle, P PiIndicates the maximum in-cylinder pressure of the pre-ignition cycle;

[0030]

[0031] Among them, N 1 represents the calculated number of cycles, represents the filter pressure in the cylinder, θ i It represents the crank angle when knock occurs, w is the duration of knock combustion, the evaluation of knock intensity mainly depends on the change of cylinder change, and the evaluation indicators of knock mainly include the maximum pressure amplitude.

[0032] Preferably, the method for seeking the optimal control parameters by TOPSIS in step 5 is as follows:

[0033] S51. Construct a weighted normalized matrix Z according to the weights of different pre-ignition parameters. The pre-ignition parameters include the number of pre-ignitions, the cyclic variation of IMEP, MAPO, and the amplitude intensity of the cylinder pressure of the pre-ignition cycle. The expression of the weighted normalized matrix Z is as follows:

[0034]

[0035] Z ij =e ij *ω j

[0036] i=1,2,3…,mj=1,2,3,…n

[0037] Determine the positive ideal solution of the jth index and negative ideal solution The calculation expression is as follows:

[0038]

[0039] S52, obtaining the score matrices of different solutions and ideal solutions for suppressing premature ignition corresponding to different working conditions, and calculating the similarity between each solution and the positive ideal solution and the negative ideal solution by using the Euclidean distance similarity metric. The calculation expression of the Euclidean distance is as follows:

[0040]

[0041] In the formula, represents the positive ideal solution distance, K ij It represents the weight of the i-th evaluation object on the j-th evaluation index. represents the negative ideal solution distance;

[0042] The positive ideal solution distance represents the distance between each evaluation object and the positive ideal solution, which is the most favorable value combination of all evaluation indicators. The smaller it is, the closer the solution is to the optimal one.

[0043] The negative ideal solution distance represents the distance between each evaluation object and the negative ideal solution, which is the most unfavorable value combination of all evaluation indicators. The larger the value, the further away the solution is from the worst case.

[0044] S53. Calculate the total score D for the evaluation of pre-ignition under these schemes i , the calculation expression is as follows:

[0045]

[0046] Total evaluation score: D i The higher it is, the better the effect of controlling pre-ignition is under this strategy parameter.

[0047] Therefore, the present invention adopts a method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine with the above structure; it has the following advantages:

[0048] 1. For the first time, the secondary injection strategy is used to reduce the number of pre-ignitions, improve the mixture distribution and enhance engine performance;

[0049] 2. For the pre-ignition phenomenon at high speed, the VVT ​​control strategy can enhance the peak braking power at high speed;

[0050] 3. Use the TOPSIS method to find the best control parameters under different measures to achieve the best performance of the hydrogen internal combustion engine;

[0051] 4. It can provide valuable support for the performance improvement, numerical simulation and energy management of hydrogen internal combustion engines.

[0052] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is an overall flow chart of a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine according to the present invention;

[0054] Figure 2 A corresponding relationship diagram of the 5% heat release rate point and the abnormal combustion cycle cylinder pressure of a hydrogen internal combustion engine multi-operating condition pre-ignition identification and suppression method of the present invention;

[0055] Figure 3 A diagram for identifying pre-ignition conditions using a median discrimination method of a method for identifying and suppressing pre-ignition in multiple operating conditions of a hydrogen internal combustion engine according to the present invention;

[0056] Figure 4 It is a diagram of the effective pressure indicated by each cylinder of a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine according to the present invention;

[0057] Figure 5A diagram showing measures for reducing pre-ignition at low speed and medium load in a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine according to the present invention;

[0058] Figure 6 It is a TOPSIS score diagram of each control strategy of low speed and medium load of a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine of the present invention;

[0059] Figure 7 A diagram showing measures for reducing pre-ignition at low speed and high load in a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine according to the present invention;

[0060] Figure 8 It is a TOPSIS score diagram of each control strategy of low speed and high load of a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine of the present invention;

[0061] Fig. 9 A diagram of measures for reducing pre-ignition at high speed and high load in a method for identifying and suppressing pre-ignition in multiple working conditions of a hydrogen internal combustion engine according to the present invention;

[0062] Fig.10 It is a TOPSIS score chart of various high-speed and high-load control strategies of a multi-condition pre-ignition identification and suppression method for a hydrogen internal combustion engine of the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0064] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0065] like Figure 1-10 The present invention provides a method for identifying and suppressing pre-ignition of a hydrogen internal combustion engine under multiple working conditions; the method comprises the following steps:

[0066] Step 1: Calculate the absolute deviation MAD of the 5% heat release rate point MFB05 relative to the median to determine whether pre-ignition occurs in the combustion process. The calculation expression is as follows:

[0067]

[0068] In the formula, x i Represents a single data value, Represents the median.

[0069] The process of judging whether pre-ignition occurs during the combustion process is as follows:

[0070] S11. Adopt the outlier detection theory in statistical analysis, use the statistics of sample median and median absolute deviation to identify pre-ignition, and use the difference between median and median absolute deviation as the pre-ignition threshold verification deviation. The calculation expression of verification deviation is as follows:

[0071]

[0072] In the formula, x i Represents a single data value, represents the median;

[0073] S12. Determine whether MFB05 satisfies MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, then no pre-ignition occurs; if MFB05 <MAD-3.5*|σ MAD |, then pre-ignition occurs, go to step 2.

[0074] Step 2, determining the current operating condition of the hydrogen internal combustion engine under the pre-ignition condition, the operating conditions of the hydrogen internal combustion engine are specifically: low speed and medium load, low speed and high load, and high speed and high load;

[0075] Step 3, using different methods to suppress pre-ignition of the hydrogen internal combustion engine according to the current operating conditions of the hydrogen internal combustion engine in step 2;

[0076] When the current operating condition of the hydrogen internal combustion engine is low speed and medium load, if MAD-4.5*|σ MAD | <MFB05<MAD-3.5*|σ MAD |, then the abnormal combustion at this time is a slight pre-ignition, and the occurrence of pre-ignition can be suppressed by delaying the ignition angle; if MFB05 <MAD-4.5*|σ MAD |, then the abnormal combustion at this time is an obvious pre-ignition. This situation occurs because multiple slight pre-ignitions will aggravate the formation of hot spots in the cylinder, thereby causing obvious pre-ignition. At this time, if the pre-ignition is suppressed only by delaying the ignition angle, the effective thermal efficiency of the hydrogen internal combustion engine will be reduced. Therefore, the excess air coefficient should be increased at the same time. Such operation can reduce the occurrence of pre-ignition to a greater extent and improve the effective thermal efficiency.

[0077] When the current operating condition of the hydrogen internal combustion engine is at low speed and high load, lean combustion is adopted, and the excess air coefficient is controlled at about 2. At the same time, secondary injection is adopted to suppress abnormal combustion of the hydrogen internal combustion engine by adjusting the timing and amount of secondary injection.

[0078] When the current operating condition of the hydrogen internal combustion engine is at high speed and high load, the variable valve timing VVT phase is adjusted to increase the air mass flow to suppress pre-ignition; inappropriate injection start time and intake valve closing IVC will cause obvious pre-ignition, so it is necessary to adjust the VVT ​​phase. On the one hand, this allows the intake inertia to be maximized from the late valve closing to increase the air mass flow; on the other hand, it is also crucial to prevent interference between IVC and SOI.

[0079] Step 4: Determine the effect of inhibiting pre-ignition by comparing the cyclic variation of the indicated mean effective pressure IMEP of the hydrogen internal combustion engine before and after inhibition, the amplitude intensity of the in-cylinder pressure of the pre-ignition cycle, and the maximum pressure amplitude; the cyclic variation of the indicated mean effective pressure IMEP CoV IMEP , the cylinder pressure amplitude intensity ΔP of the pre-ignition cycle PI The calculation formula of the maximum pressure amplitude MAPO is as follows:

[0080]

[0081] Among them, σ IMEP is the standard deviation of IMEP, is the average IMEP;

[0082]

[0083] Among them, IMEP i It represents the IMEP of the i-th cycle, N represents the number of cycles, and the value is less than 3% during stable combustion;

[0084]

[0085] In the formula, Indicates the average maximum cylinder pressure, N PI Indicates the number of pre-ignition times, ΔP PI Indicates the amplitude strength of the cylinder pressure during the pre-ignition cycle, P Pi Indicates the maximum in-cylinder pressure of the pre-ignition cycle;

[0086]

[0087] Among them, N 1 represents the calculated number of cycles, represents the filter pressure in the cylinder, θ i It represents the crank angle when knock occurs, w is the duration of knock combustion, the evaluation of knock intensity mainly depends on the change of cylinder change, and the evaluation indicators of knock mainly include the maximum pressure amplitude.

[0088] Step 5: Find the optimal control parameters through TOPSIS; the method is as follows:

[0089] S51. Construct a weighted normalized matrix Z according to the weights of different pre-ignition parameters. The pre-ignition parameters include the number of pre-ignitions, the cyclic variation of IMEP, MAPO, and the amplitude intensity of the cylinder pressure of the pre-ignition cycle. The expression of the weighted normalized matrix Z is as follows:

[0090]

[0091] Z ij =e ij *ω j

[0092] i=1,2,3…,mj=1,2,3,…n

[0093] Determine the positive ideal solution of the jth index and negative ideal solution The calculation expression is as follows:

[0094]

[0095] S52, obtaining the score matrices of different solutions and ideal solutions for suppressing premature ignition corresponding to different working conditions, and calculating the similarity between each solution and the positive ideal solution and the negative ideal solution by using the Euclidean distance similarity metric. The calculation expression of the Euclidean distance is as follows:

[0096]

[0097] In the formula, represents the positive ideal solution distance, K ij It represents the weight of the i-th evaluation object on the j-th evaluation index. represents the negative ideal solution distance;

[0098] S53. Calculate the total score D for the evaluation of pre-ignition under these schemes i , the calculation expression is as follows:

[0099]

[0100] Total evaluation score: D i The higher it is, the better the effect of controlling pre-ignition is under this strategy parameter.

[0101] Step 6: Determine whether the optimal control parameters obtained in step 5 satisfy MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, the pre-ignition suppression is completed, otherwise the pre-ignition suppression is performed again.

[0102] Example

[0103] like Figure 1The present invention is a specific flow chart of the present invention. The present invention was tested on a 1.5L turbocharged DI H2ICE, taking 2500rpm, 1.4MPa, i.e. low speed and high load, as an example to verify the pre-ignition identification method. Figure 2 As shown in the figure, the 5% heat release rate point has an obvious corresponding relationship with the abnormal combustion cycle cylinder pressure. By identifying and calculating the 5% heat release rate point, the median calculation method can be used to determine in advance whether pre-ignition occurs. MAD , MAD can distinguish between slight pre-ignition, obvious pre-ignition and normal combustion. By calculating and counting the σ of 220 cycles MAD , multiple premature ignition phenomena occur, such as Figure 4 The cylinders 3 and 4, which are farther from the throttle, have experienced a pre-ignition event. Accordingly, the CoV of cylinders 3 and 4 is IMEP The values ​​are 5.24% and 4.24% respectively, both exceeding the 3% threshold for stable combustion. Thus, the identification of pre-ignition can be achieved.

[0104] When the pre-ignition occurs at low speed and medium load, if MAD-4.5*|σ MAD | <MFB05<MAD-3.5*|σ MAD |, the abnormal combustion at this time is a slight pre-ignition, and the pre-ignition can be suppressed by delaying the ignition angle, such as Figure 5 As shown, the number of pre-ignition can be reduced by 70.9%. <MAD-4.5*|σ MAD |, which will cause obvious pre-ignition. By delaying the ignition angle and increasing the excess air coefficient, the number of pre-ignitions can be reduced by 88.7% and the effective thermal efficiency can be improved. Figure 6 As shown in the analysis by TOPSIS evaluation method, the total score is the highest when the excess air coefficient is increased to 1.85 and the ignition timing is delayed to 3°ATDC. This is the best control strategy for pre-ignition under this working condition.

[0105] When the pre-ignition occurs under low speed and high load conditions, the abnormal combustion at this time is usually obvious pre-ignition. The lean combustion plus secondary injection control strategy can be adopted to suppress the pre-ignition event by setting the second end of injection (SEOI) and the second injection mass proportion (SIMP). Figure 7 As shown in the figure, when the excess air coefficient is 2, different secondary injection time and secondary injection quality have different effects on the suppression of pre-ignition. When SEOI = -20 ° CA, SIMP = 35%, secondary injection significantly reduces the number of pre-ignition. In addition, the TOPSIS method is used to find the best control parameters, such as Figure 8As shown, when SEOI = -40°CA and SIMP = 35%, the total score of the TOPSIS method is the highest, and the best pre-ignition control is achieved at this time.

[0106] When the pre-ignition occurs at high speed and high load, abnormal combustion is usually obvious pre-ignition, and it is easy to cause knock. At this time, the pre-ignition can be suppressed by adjusting the variable valve timing VVT. Fig. 9 As shown in the figure, the number of pre-ignitions changes significantly after adjusting the intake valve opening angle and exhaust valve closing angle. Compared with IVO = -10°CA, EVC = -25°CA, the number of pre-ignitions decreases by 86.8% when IVO = 20°CA, EVC = -25°CA. The best valve timing is found by TOPSIS method, as shown in the figure. Fig.10 As shown in the figure, when IVO = 20°CA and EVC = -20°CA, the total score of the TOPSIS method is the highest, and the pre-ignition phenomenon is best controlled.

[0107] Therefore, a method for identifying and suppressing pre-ignition under multiple operating conditions of a hydrogen internal combustion engine is proposed. By using the statistics of the sample median and the median absolute deviation to identify pre-ignition, and using a simple lower confidence limit (the difference between the median and the median absolute deviation) as the pre-ignition threshold, it is possible to determine whether pre-ignition occurs under different operating conditions, and provide measures to suppress pre-ignition under three different operating conditions: low speed and medium load, low speed and high load, and high speed and high load, thereby effectively suppressing pre-ignition.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine, characterized in that: The steps include: Step 1, calculate the absolute deviation MAD of the 5% heat release rate point MFB05 relative to the median to determine whether pre-ignition occurs in the combustion process. If pre-ignition occurs, execute step 2; otherwise, determine that pre-ignition does not occur; Step 2, determining the current operating condition of the hydrogen internal combustion engine under the pre-ignition condition, the operating conditions of the hydrogen internal combustion engine are specifically: low speed and medium load, low speed and high load, and high speed and high load; Step 3, using different methods to suppress pre-ignition of the hydrogen internal combustion engine according to the current operating conditions of the hydrogen internal combustion engine in step 2; Step 4, judging the effect of inhibiting pre-ignition by comparing the cyclic variation of the indicated mean effective pressure IMEP of the hydrogen internal combustion engine before and after inhibition, the amplitude intensity of the in-cylinder pressure of the pre-ignition cycle, and the maximum pressure amplitude; Step 5: Find the optimal control parameters through TOPSIS; Step 6: Determine whether the optimal control parameters obtained in step 5 satisfy MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, the pre-ignition suppression is completed, otherwise the pre-ignition suppression is performed again.

2. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 1, characterized in that: The calculation expression of the absolute deviation MAD of the 5% heat release rate point MFB05 relative to the median in step 1 is as follows: In the formula, x i Represents a single data value, Represents the median.

3. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 2, characterized in that: The process of determining whether pre-ignition occurs in the combustion process in step 1 is as follows: S11. Adopt the outlier detection theory in statistical analysis, use the statistics of sample median and median absolute deviation to identify pre-ignition, and use the difference between median and median absolute deviation as the pre-ignition threshold verification deviation. The calculation expression of verification deviation is as follows: In the formula, x i Represents a single data value, represents the median; S12. Determine whether MFB05 satisfies MAD-3.5*|σ MAD | <MFB05<MAD+3.5*|σ MAD |, if satisfied, then no pre-ignition occurs; if MFB05 <MAD-3.5*|σ MAD |, then pre-ignition occurs.

4. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 3, characterized in that: In step 3, when the current operating condition of the hydrogen internal combustion engine is low speed and medium load, and MAD-4.5*|σ MAD | <MFB05<MAD-3.5*|σ MAD| , then the abnormal combustion at this time is a mild pre-ignition, and the occurrence of pre-ignition can be suppressed by delaying the ignition angle.

5. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 4, characterized in that: In step 3, when the current operating condition of the hydrogen internal combustion engine is low speed and medium load, and MFB05 <MAD-4.5*|σ MAD |, then the abnormal combustion at this time is an obvious pre-ignition, and it is necessary to delay the ignition angle and increase the excess air coefficient to suppress the occurrence of pre-ignition.

6. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 5, characterized in that: In step 3, when the current operating condition of the hydrogen internal combustion engine is at low speed and high load, lean combustion is adopted, and the excess air coefficient is controlled at 2. At the same time, secondary injection is adopted to suppress abnormal combustion of the hydrogen internal combustion engine by adjusting the timing and amount of secondary injection.

7. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 6, characterized in that: In step 3, when the current operating condition of the hydrogen internal combustion engine is at high speed and high load, the variable valve timing (VVT) phase is adjusted to optimize the ventilation process, reduce the high-temperature residual exhaust gas in the cylinder, and increase the air mass flow to suppress pre-ignition.

8. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 7, characterized in that: Cyclic variation CoV of indicated mean effective pressure IMEP in step 4 IMEP , the cylinder pressure amplitude intensity ΔP of the pre-ignition cycle PI The calculation formula of the maximum pressure amplitude MAPO is as follows: Among them, σ IMEP is the standard deviation of IMEP, is the average IMEP; Among them, IMEP i It represents the IMEP of the i-th cycle, N represents the number of cycles, and the value is less than 3% during stable combustion; In the formula, Indicates the average maximum cylinder pressure, N PI Indicates the number of pre-ignition times, ΔP PI Indicates the amplitude strength of the cylinder pressure during the pre-ignition cycle, P Pi Indicates the maximum in-cylinder pressure of the pre-ignition cycle; Where N1 represents the calculated number of cycles, represents the filter pressure in the cylinder, θ i represents the crank angle when detonation occurs, and w is the duration of detonation combustion.

9. A method for identifying and suppressing multi-operating-condition pre-ignition of a hydrogen internal combustion engine according to claim 8, characterized in that: The method for finding the optimal control parameters through TOPSIS in step 5 is as follows: S51. Construct a weighted normalized matrix Z according to the weights of different pre-ignition parameters. The pre-ignition parameters include the number of pre-ignitions, the cyclic variation of IMEP, MAPO, and the amplitude intensity of the cylinder pressure of the pre-ignition cycle. The expression of the weighted normalized matrix Z is as follows: z ij =e ij *ω j i=1,2,3…,mj=1,2,3,…n Determine the positive ideal solution of the jth index and negative ideal solution The calculation expression is as follows: S52, obtaining the score matrices of different solutions and ideal solutions for suppressing premature ignition corresponding to different working conditions, and calculating the similarity between each solution and the positive ideal solution and the negative ideal solution by using the Euclidean distance similarity metric. The calculation expression of the Euclidean distance is as follows: In the formula, represents the positive ideal solution distance, K ij It represents the weight of the i-th evaluation object on the j-th evaluation index. represents the negative ideal solution distance; S53. Calculate the total score D for the evaluation of pre-ignition under these schemes i , the calculation expression is as follows:

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