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

Abstract

The application provides a hydrogen internal combustion engine anti-knock ignition method and system, which comprises the following steps: 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, adjusting the ignition advance angle of the hydrogen internal combustion engine, obtaining the sensitivity of the ignition advance angle to the knock suppression 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, 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 supercharger or the throttle. The application realizes the time-sharing collaborative control of nitrogen and hydrogen by increasing the nitrogen injection amount until the knock index is less than the threshold value, so as to effectively suppress abnormal combustion such as knock and pre-ignition, and effectively improve the thermal efficiency of the engine.

Description

Technical Field

[0001] This invention relates to the field of hydrogen internal combustion engine control technology, and in particular to an anti-knock ignition method and system for hydrogen internal combustion engines. Background Technology

[0002] Automotive researchers and engineers are urgently seeking low-carbon or carbon-free automotive powertrain solutions. Hydrogen, as an abundant, clean, and zero-carbon energy source, is considered one of the most promising zero-carbon emission energy sources for 21st-century automotive powertrains due to its low ignition energy, high calorific value, rapid combustion propagation, and good anti-knock properties. Hydrogen internal combustion engines have relatively low requirements for hydrogen fuel purity and are structurally similar to traditional internal combustion engines, offering strong compatibility. They retain the main structure and systems of traditional internal combustion engines and operate on the same principle as traditional fuel engines. Leveraging the existing mature internal combustion engine industrial system, mass production at low cost and large-scale application can be achieved through adaptive research and design of hydrogen supply and injection systems, specialized cold spark plugs, turbochargers, lubrication, and crankshaft ventilation. Compared to the more technically challenging hydrogen fuel cells, hydrogen internal combustion engines have significant industrial advantages. However, due to the low ignition energy, high combustion speed, and wide combustion limits of hydrogen, it is highly prone to knocking in internal combustion engines, severely affecting engine stability, efficiency, and durability. Therefore, controlling knocking in hydrogen internal combustion engines is a major challenge.

[0003] To control knocking in hydrogen internal combustion engines, existing patent CN116857099A designs a direct-injection hydrogen internal combustion engine structure to address knocking caused by insufficient in-cylinder mixing in direct-injection engines. Existing patent CN117231357A selects different operating modes and injection strategies under different working conditions to ensure stable operation under low loads, high-efficiency operation under medium loads, and knock-free operation under high loads. Existing patent CN115839273A suppresses knocking by controlling the excess air coefficient. It can be seen that the above patents mainly suppress knocking through structural optimization, injection strategy optimization, and excess air coefficient adjustment.

[0004] In summary, current technologies cannot suppress abnormal combustion conditions such as engine knocking and pre-ignition through time-sharing coordinated control of nitrogen and hydrogen, thus failing to improve engine thermal efficiency. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide an anti-knock ignition method and system for hydrogen internal combustion engines to overcome the shortcomings of the prior art.

[0006] In a first aspect, the present invention provides an anti-knock ignition method for a hydrogen internal combustion engine, the method comprising:

[0007] Real-time calculation of knock index in hydrogen internal combustion engines;

[0008] Determine the magnitude of the knock index relative to the threshold;

[0009] 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.

[0010] 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;

[0011] 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.

[0012] Compared with the prior art, the beneficial effects of the present invention are: by calculating the knock index of the engine in real time and judging the magnitude between the knock index and the threshold, if the knock index is greater than the threshold, the engine ignition advance angle is adjusted and the nitrogen injection quantity is increased until the knock index is less than the threshold, thereby realizing the time-sharing coordinated 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.

[0013] Furthermore, the formula for calculating the knock index is:

[0014] ;

[0015] 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.

[0016] Furthermore, the calculation expression for the correction function related to the excess air coefficient of the mixture is as follows:

[0017] ;

[0018] 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.

[0019] Furthermore, the expression for adjusting the ignition advance angle is:

[0020] i spark,new= i spark-k·( KI - KIcritical );

[0021] In the formula, i spark,new indicates the adjusted ignition advance angle. i "spark" represents the ignition advance angle, and "k" represents the adjustment factor. This indicates the knock index. KIcritical This refers to the threshold value.

[0022] Furthermore, the expression for the modified nitrogen injection quantity is as follows:

[0023] ;

[0024] In the formula, This indicates the increment in nitrogen injection volume. This represents 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;

[0025] The expression for calculating the sensitivity of the knock index to the ignition advance angle is as follows:

[0026] ;

[0027] In the formula, i "Spark" indicates the ignition advance angle. The differential symbol represents the sensitivity calculation.

[0028] Furthermore, after the step of determining the magnitude of the knock index and the threshold, the method further includes:

[0029] If the knock index is less than the threshold, the ignition advance angle of the engine is maintained.

[0030] Secondly, the present invention also provides a hydrogen internal combustion engine anti-knock ignition system, which is controlled by the above-mentioned hydrogen internal combustion engine anti-knock ignition method. The system includes an engine, spark plugs, hydrogen injectors, nitrogen injectors, an ECU control unit, and a cylinder pressure sensor.

[0031] 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.

[0032] 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. Attached Figure Description

[0033] Figure 1 This is a flowchart of the anti-knock ignition method for a hydrogen internal combustion engine in the first embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the anti-knock ignition system for a hydrogen internal combustion engine in the second embodiment of the present invention.

[0035] Explanation of key component symbols:

[0036] 1. Engine; 11. Cylinder block; 12. Piston;

[0037] 10. Spark plug; 20. Hydrogen injector; 30. Nitrogen injector; 40. ECU control unit; 50. Cylinder pressure sensor.

[0038] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0040] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0041] 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 invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] Example 1

[0043] Please see Figure 1 The figure shows an anti-knock ignition method for a hydrogen internal combustion engine according to the first embodiment of the present invention, the method comprising steps S1 to S5:

[0044] S1, calculates the engine knock index in real time;

[0045] It is understood that the formula for calculating the knock index is:

[0046] ;

[0047] 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.

[0048] It should be explained that the final integral time and the initial integral time are usually the key time points from the compression stroke to the combustion stage.

[0049] Furthermore, the calculation expression for the correction function related to the excess air coefficient of the mixture is as follows:

[0050] ;

[0051] 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.

[0052] It is worth noting that the three sets of empirical fitting parameters were obtained through 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 λ (dimensionless) of the mixture is defined as the ratio of the actual air volume to the theoretically required air volume. The square of the excess air coefficient (dimensionless) is used to describe the higher-order lean combustion effect in the correction function.

[0053] S2, determine the magnitude of the knock index relative to the threshold;

[0054] S3, if the knock index is greater than the threshold, the engine is made to adjust the ignition advance angle, and the knock suppression sensitivity of the ignition advance angle is obtained according to the adjusted ignition advance angle.

[0055] It is understood that the expression for adjusting the ignition advance angle is:

[0056] i spark,new= i spark-k·( KI - KIcritical );

[0057] In the formula, i spark,new indicates the adjusted ignition advance angle. i "spark" represents the ignition advance angle, and "k" represents the adjustment factor. This indicates the knock index. KIcritical The threshold value, in this embodiment, is based on experimental experience. KIcritical Take 0.9.

[0058] S4, increase the nitrogen injection quantity and correct 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;

[0059] In this embodiment, the expression for correcting the nitrogen injection quantity is:

[0060] ;

[0061] In the formula, This indicates the increment in nitrogen injection volume. This represents 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;

[0062] It is worth noting that the knock intensity feedback coefficient determines the ratio between the injection correction and the KI over-limit, the dynamic correction coefficient is used to respond to the rate of increase of the knock index, and the sensitivity correction coefficient is used to prevent large corrections when the ignition angle is overly sensitive to knock.

[0063] The expression for calculating the sensitivity of the knock index to the ignition advance angle is as follows:

[0064] ;

[0065] In the formula, i "Spark" indicates the ignition advance angle. The differential symbol represents the sensitivity calculation.

[0066] S5, based on the ECU, compensate for the hydrogen injection pulse width and excess air coefficient target of the hydrogen internal combustion engine, and adjust the boost or throttle.

[0067] It is worth noting that if the knock index is less than the threshold, the ignition advance angle of the engine is maintained.

[0068] It should be explained that under low load conditions, only hydrogen is injected and the nitrogen system is shut off (to save nitrogen consumption); under medium to high load conditions, hydrogen is injected during the intake stroke (to form a homogeneous mixture), and nitrogen is injected at the end of the compression stroke (to cover the piston top and cylinder head hot spots).

[0069] Example 2

[0070] Please see Figure 2 The figure shows the anti-knock ignition system for a hydrogen internal combustion engine in the second embodiment of the present invention, which is controlled by the anti-knock ignition method for a hydrogen internal combustion engine in the first embodiment. The system includes 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.

[0071] The engine 1 is equipped with a cylinder block 11 and a piston 12. The hydrogen injector 20, the nitrogen injector 30, the cylinder pressure sensor 50, and the spark plug 10 are all disposed within the cylinder block 11. The ECU control unit 40 is electrically connected to the hydrogen injector 20, the nitrogen injector 30, the cylinder pressure sensor 50, and the spark plug 10. The ECU control unit 40 is used to control the hydrogen injector 20 and the nitrogen injector 30 to inject hydrogen and nitrogen respectively into the cylinder block 11 for time-sharing coordinated control. The cylinder pressure sensor 50 is used to detect the pressure value within the cylinder block 11 and transmit the pressure value to the ECU control unit 40. The spark plug 10 is controlled by the ECU control unit 40 to ignite the hydrogen in the cylinder block 11.

[0072] In summary, the anti-knock ignition method and system for hydrogen internal combustion engines in the above embodiments of the present invention calculate the engine's knock index in real time and determine the relationship between the knock index and a threshold. If the knock index is greater than the threshold, the engine's ignition advance angle is adjusted and the nitrogen injection quantity is increased until the knock index is less than the threshold. This achieves time-sharing coordinated control of nitrogen and hydrogen, effectively suppressing abnormal combustion such as knock and pre-ignition, and effectively improving the engine's thermal efficiency and lifespan. It also avoids the use of an external EGR, simplifying system complexity.

[0073] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method of anti-knock ignition for a hydrogen internal combustion engine, characterized by, The method comprises: calculating a knock index of a hydrogen internal combustion engine in real time; judging the magnitude of the knock index and a threshold value; if the knock index is greater than the threshold value, adjusting the ignition advance angle of the hydrogen internal combustion engine, and obtaining the sensitivity of the ignition advance angle to knock suppression according to the adjusted ignition advance angle, wherein the calculation expression of the knock index is: ； wherein, represents the knock index, represents the final integration time, represents the initial integration time, represents the hydrogen-related frequency factor, represents the in-cylinder instantaneous pressure, represents the pressure index, represents the index, represents the hydrogen activation energy, R represents the gas constant, and T represents the in-cylinder instantaneous temperature, represents a correction function related to the excess air coefficient of the mixture, wherein the final integration time and the initial integration time are critical time points from the compression stroke to the combustion stage; increasing the nitrogen injection amount and correcting the nitrogen injection amount until the knock index is less than the threshold value, setting an upper limit of the nitrogen injection amount, and limiting the cycle variation rate of the hydrogen internal combustion engine, wherein the correction expression of the nitrogen injection amount is: ； wherein represents an increment of the amount of nitrogen injection, represents a knock intensity feedback coefficient, represents a dynamic correction coefficient, represents a sensitivity correction coefficient, represents the knock index, KIcritical represents the threshold value, represents the sensitivity of the knock index to the ignition advance angle, represents a differential of the nitrogen injection amount expression, wherein the dynamic correction coefficient is used in response to a rise rate of the knock index; The calculation expression of the sensitivity of the knock index to the ignition advance angle is: ； In the formula, θ spark represents the spark advance angle, the differential sign indicates the sensitivity calculation; 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 supercharger or the throttle.

2. The hydrogen internal combustion engine anti-knock ignition method according to claim 1, characterized by, The calculation expression of the correction function related to the excess air coefficient of the mixture is: ； wherein k0, k1, k2 represent three sets of empirical fitting parameters, respectively, the excess air ratio of the mixture gas, respectively represent the square of the excess air ratio.

3. The hydrogen internal combustion engine anti-knock ignition method according to claim 1, characterized by, The expression of adjusting the ignition advance angle is: θ spark, new = spark - k * (1 - exp(- (t - t0) / tau)) θ spark - k * (1 - exp(- (t - t0) / tau)) KI - KIcritical ); In the formula, θ spark, new indicates the adjusted spark advance angle, θ spark indicates the spark advance angle, and k indicates an adjustment coefficient, represents the knock index, KIcritical represents the threshold value.

4. The hydrogen internal combustion engine anti-knock ignition method according to claim 1, characterized by, 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, keeping the ignition advance angle of the engine.

5. 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 4, characterized by 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 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 used to control the hydrogen injector and the nitrogen injector to inject hydrogen and nitrogen in the cylinder body respectively for time-sharing cooperative control, the cylinder pressure sensor is used to detect the pressure value in the cylinder body and transmit the pressure value to the ECU control unit, and the spark plug is controlled by the ECU control unit to ignite the hydrogen in the cylinder body.

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