Method and apparatus for knock regulation of an internal combustion engine operated on hydrogen

Abstract

The invention relates to a method and a device for knock regulation of an internal combustion engine operated with hydrogen, wherein, for the knock regulation, the tendency of the internal combustion engine to knock is reduced by influencing the ignition angle and by influencing the lambda value.

Description

Technical Field

[0001] This invention relates to a method and apparatus for adjusting knock in an internal combustion engine that operates on hydrogen. Background Technology

[0002] Knock regulation is known in some internal combustion engines that operate on gaseous fuels, such as CNG or LPG. Typically, knock regulation in these engines is achieved simply by affecting the ignition timing. Summary of the Invention

[0003] In contrast, the method and apparatus according to the invention have the following advantages: improved knock regulation is achieved for internal combustion engines operating on hydrogen. By using knock regulation through the influence of the ignition angle and the λ value, additional degrees of freedom are achieved for the control of the internal combustion engine, enabling improved control and mastery of the engine. This ensures improved operation of the internal combustion engine, achieving both energy savings and exceptionally clean exhaust gases.

[0004] The preferred implementation provides further advantages and improvements. A particularly simpler method for knock regulation is obtained by first considering only one possible parameter or adjustment parameter for knock regulation, and only considering another possibility affecting knock tendency when that parameter exceeds a threshold. Alternatively, ignition angle and λ value can be used simultaneously for knock regulation, wherein the degree of influence of both is weighted and adapted to the respective operating points of the internal combustion engine. Particularly precise knock regulation can be achieved if "adjustment towards a lower knock tendency," "adjustment towards an increased knock tendency," and "knock-free waiting time" are individually determined for each of the two parameters, ignition angle and λ value. Here, these adjustments can be related to the operating parameters of the internal combustion engine. Another possibility is that the two possible parameters affecting knock tendency influence each other. Another simple possibility for knock regulation is that the two possibilities, ignition angle and λ value, are used independently of each other, wherein they are each bounded to their maximum values. For optimized adaptation, the various methods for knock regulation can be implemented individually for each cylinder or based on an average value for all cylinders. Attached Figure Description

[0005] Embodiments of the invention are shown in the accompanying drawings and explained in detail in the specification. The drawings show: Figure 1 This is the first method for adjusting knock. Figure 2 Another method for knock control; and Figure 3 This is another method for adjusting knock. Detailed Implementation

[0006] This invention relates to a method and apparatus for knock regulation in a hydrogen-powered internal combustion engine. Such engines are conventional Otto cycle engines fueled by hydrogen, wherein hydrogen is either blown into the engine's intake manifold or directly into the combustion chamber. Thus, an air-fuel mixture, or an air-hydrogen mixture, is formed in the combustion chamber and ignited by an electric spark from a spark plug. Alternatively, a hydrogen-powered internal combustion engine can be used, wherein the air-hydrogen mixture in the combustion chamber is ignited by injecting a small amount of diesel fuel. The combustion of the air-hydrogen mixture increases the pressure in the combustion chamber, thereby driving a piston, which transmits this motion to the crankshaft of the engine via a connecting rod. Thus, the pressure increase is converted into mechanical work. Typically, such hydrogen-powered internal combustion engines operate with a significant excess air, i.e., the amount of air supplied to the combustion chamber is significantly greater than the amount of air required for the combustion of the hydrogen. Excess air is usually represented by the so-called λ value, where a λ value of 1 represents a stoichiometric mixture (air volume corresponding to hydrogen volume), and a λ value greater than 1 represents excess air. Since a mixture of hydrogen and air can still be ignited by a spark plug even under high excess air conditions, internal combustion engines running on hydrogen typically operate with a λ value between 1 and 4 (i.e., four times the excess air).

[0007] During the combustion of the air-hydrogen mixture in the combustion chamber of an internal combustion engine, spontaneous ignition of the air-fuel mixture (so-called pre-ignition, or knock) may occur at multiple points in the combustion chamber before the ignition timing, or multiple flame fronts may form at the ignition timing (so-called knock), resulting in unacceptable high pressure peaks in the combustion chamber. Due to these high pressure peaks and the associated potential damage to the internal combustion engine, pre-ignition and knock should be avoided. In conventional gasoline-powered internal combustion engines, knock control is implemented to prevent knocking combustion: under this control, when a knocking event occurs, the ignition angle is shifted towards a later ignition direction, i.e., towards a direction with a lower knocking tendency. In the following text, the term "knock control" should be understood as a control used to avoid these two unconventional combustion phenomena: pre-ignition and knocking.

[0008] According to the present invention, in an internal combustion engine operating with an air-hydrogen mixture, knock regulation (i.e., prevention of knock combustion) is achieved not only by influencing the ignition angle but also by influencing the λ value in the combustion chamber. Due to the wide range of λ values ​​between 1 and 4, the λ value, in addition to the ignition angle, is also provided as another parameter for influencing the knock tendency of the internal combustion engine. Here, the coordination of "how to regulate the knock tendency of the internal combustion engine through these two parameters of knock regulation (i.e., by influencing the ignition angle and by influencing the λ value)" is also addressed.

[0009] To achieve the desired λ value, both the air volume and the injected fuel quantity can be influenced. Changes in the air volume can be made relatively slowly, while changes in the injected fuel quantity can be made very quickly, even with the intake valves in the combustion chamber closed (provided the fuel is injected directly into the combustion chamber). Therefore, it is generally preferable to adjust the λ value by influencing the injection quantity.

[0010] Figure 1 This paper describes a first method for knock regulation of a hydrogen-powered internal combustion engine using a flowchart. In step 10 of the first method, it is determined whether the ignition angle or the value of λ should be used as the parameter for knock regulation first. Here, "first" means that in cases of low knock tendency (i.e., when knock events or pre-ignition events are extremely rare), the response should either be made by influencing the ignition angle or only by influencing the value of λ. If it is decided in step 10 that the ignition angle should be used first, then step 11 is performed after step 10, in which knock regulation by influencing the ignition angle is activated. Therefore, in this method, after step 11, a knock event is responded to by delaying the adjustment (adjusting in the direction of delayed ignition) of the ignition angle for the next combustion. Step 12 is performed after step 11, in which it is determined whether the ignition angle exceeds a threshold for adjusting the ignition angle. Here, "exceeds" should be understood as any unacceptable deviation from the threshold, as the ignition angle can also be negative, and mathematically, "exceeds" is actually "below". If it is determined in step 12 that the ignition angle exceeds the threshold for delay adjustment, then step 13 is performed after step 12. In step 13, in addition to adjusting the ignition angle, the influence on the λ value is also set. Therefore, in step 13, both the ignition angle and the λ value are affected to reduce the knock tendency of the internal combustion engine. To reduce the knock tendency by adjusting the ignition angle, the ignition angle is adjusted towards a later ignition angle; to reduce the knock tendency by adjusting the λ value, the λ value is adjusted towards a larger λ value. Typical influencing parameters are, for example, adjusting the crankshaft angle by 0.5 degrees towards the later ignition direction, or increasing the λ value by 0.2. Depending on the type of internal combustion engine, other values ​​for the ignition angle or λ value are also reasonable. If it is determined in step 12 that the ignition angle has not yet exceeded the threshold for delay adjustment, then step 14 is performed after step 12. In step 14, knock regulation is achieved only by adjusting the ignition angle; that is, in the event of a knock event, the ignition angle for the next combustion is adjusted towards a later ignition angle.

[0011] If in step 10 it is determined that the λ value is used first to influence the knock tendency, then step 15 is performed after step 10. In step 15, knock adjustment by influencing the λ value is activated, that is, when a knock event occurs, the λ value is adjusted towards a larger λ value to reduce the knock tendency of the internal combustion engine. Step 16 is performed after step 15, where it is checked whether the λ value exceeds a threshold due to the knock adjustment in step 15. If it is determined in step 16 that the threshold for the λ value is exceeded, then step 17 is performed after step 16. In step 17, knock adjustment by influencing the ignition angle is additionally activated, that is, the knock adjustment in step 17 is performed simultaneously by influencing both the ignition angle and the λ value. If it is determined in step 16 that the threshold for λ is not exceeded, then step 18 is performed after step 16, where it is determined that knock adjustment by influencing the ignition angle is not activated.

[0012] Therefore, by means of Figure 1 The method achieves the following knock adjustment: Under this knock adjustment, when the knock tendency is low, only one of two possible parameters is initially used for knock events, namely, a later (delayed) ignition angle or an increased λ value. If the knock tendency then increases, causing the above measures to be insufficient or exceeding the threshold, then another measure is added.

[0013] Figure 2Another method for knock control is illustrated graphically. In the first step 20, a knock event is identified (i.e., knocking occurs during ongoing combustion). After step 20, steps 21 and 24 are performed simultaneously. In step 21, knock control is performed by decreasing the ignition angle for the next combustion. In step 24, knock control is performed by increasing the λ value for the next combustion. Simultaneously, in step 25, weighting coefficients are calculated, using the engine's operating parameters or ambient conditions as input parameters for this calculation. Such operating parameters or ambient conditions are, for example, engine speed, engine load, ambient temperature, engine temperature, intake air temperature, or exhaust air temperature. The calculation of the weighting coefficients in step 25 can be configured, for example, as a mathematical relationship between the input parameters and the output weighting coefficients. Alternatively, a characteristic graph (i.e., a multi-dimensional table assigning corresponding output parameters to the input parameters) can be simply used. Here, the weighting coefficients are, for example, values ​​between 0 and 1. Depending on the weighting calculation method, other values, such as those greater than 1, can also be used. The weighting coefficients are assigned to multiplication units 22 and 26, which multiply the results of steps 21 and 24, respectively. Then, through the multiplications performed at multiplication units 22 and 26, the output parameters for the actual output of the next combustion are calculated. In step 22, the ignition angle calculated in step 21 is converted to the actual output ignition angle 23 by multiplying it with the weighting coefficients. In step 26, the λ value calculated in step 24 is converted to the actual output λ value 27 by multiplying it with the weighting coefficients.

[0014] By using weighting, knock regulation can be specifically adapted to the operating conditions of an internal combustion engine. For example, it can be set such that a very strong influence on the ignition angle is allowed in the low-load operating region of the internal combustion engine, while the influence of the ignition angle is small under high load conditions. Correspondingly, the λ value has a small influence on knock regulation under low load conditions, while it has a relatively strong influence under high load conditions. However, depending on the type of internal combustion engine, different weighting coefficients can also be assigned to other operating regions. The determination of each weight must be individualized for each type of internal combustion engine.

[0015] Figure 3 Another method for adjusting knock is described, which affects both the ignition angle and the λ value. Figure 3 The diagram shows a timeline with various time points t1, t2, ... up to t12. The ignition angle ZW for knock adjustment is shown below, and the λ value for knock adjustment is shown above. Here, only the summation resulting from knock adjustment is discussed. A base ignition angle and a base value for λ are set for each operating point of the internal combustion engine. Figure 3The diagram shows the summation obtained due to knock adjustment. When knock occurs, a positive λ value is added to the base value used for λ to reduce the knock tendency. Furthermore, when knock occurs, an ignition angle for knock adjustment is added to the base ignition angle, such as... Figure 3 The negative value shown indicates that the base ignition angle is shifted towards the direction of ignition.

[0016] To discuss knock control, we first need to examine the process of ignition angle change, i.e. Figure 3 The changes in the lower part will be explained: At time t1, a knock occurs, and the ignition angle for knock adjustment is adjusted towards a larger negative ignition angle at time t1. At time t2, another knock occurs, and the ignition angle for knock adjustment is further adjusted towards a negative value. No further knock events occur after time t2, and after a relatively long waiting period, the ignition angle is adjusted towards an earlier ignition direction at time t5. Here, the adjustment value towards an earlier ignition direction at time t5 is significantly smaller than the ignition angle adjustments at time t1 and t2 when knocks occurred. Since no further knock events occur after time t5, after a waiting period corresponding to the time interval between t2 and t5, the ignition angle is adjusted towards an earlier ignition angle.

[0017] At time point t1, the λ value is adjusted towards a larger λ value, as this reduces the knock tendency of the internal combustion engine. For the knock event at time point t2, the λ value is also adjusted. After a waiting period, the λ value is decreased again at time point t3, adjusting it towards a potential increase in knock tendency. Here, the waiting time between time points t2 and t3 is chosen to be significantly shorter than the waiting time between time points t2 and t5, meaning that the attempt to push the λ value back towards the baseline value is significantly faster. Since no further knocking occurs, the λ value is also decreased at time points t6, t7, t8, and t9, so that at time point t9, no further adjustment of the λ value is set for knock regulation. Figure 3 For example, the waiting time for a non-knock engine, used to adjust towards a greater knock tendency, is significantly shorter than the non-knock waiting time for the ignition angle from t2 to t5. Different waiting times and adjustments can also be selected for other types of internal combustion engines or operating points.

[0018] Therefore, by selecting the corresponding adjustment parameters for each knock adjustment, such as "adjustment value towards a smaller knock tendency," "waiting time until knock-free adjustment towards a larger knock tendency," and "adjustment value towards a larger knock tendency," the individualized characteristics of knock adjustment can be achieved using either the ignition angle or the λ value. Thus, knock adjustment can be individually adapted to each internal combustion engine using either the ignition angle or the λ value. Furthermore, the corresponding adjustment parameters can also be related to the operating conditions of the internal combustion engine. For example, at low speeds, a different "waiting time until knock-free adjustment towards a larger knock tendency" can be selected compared to at high speeds. Additionally, appropriate adjustment parameters can be individually selected for knock adjustment using the ignition angle and knock adjustment using the λ value.

[0019] Figure 3 The paper also describes another possibility for the parameters that affect the corresponding knock adjustment, which is that these parameters influence each other. Figure 3 As shown, at time point t9, the knock adjustment based on the λ value reverts to the base value used for λ. Based on this λ value, the knock adjustment is then affected by the ignition angle as follows: the waiting time for readjusting the ignition angle in an earlier direction is shortened. Although the waiting time since the last adjustment is significantly shorter than the waiting time from t2 to t5, the ignition angle is still adjusted towards the direction with a greater knock tendency at time point t10. Correspondingly, the ignition angle is also readjusted towards the direction with a greater knock tendency at time points t11 and t12, where the waiting time is also significantly shorter than the waiting time from t2 to t5. Therefore, here, the knock adjustment based on the λ value affects the knock adjustment based on the ignition angle.

[0020] Furthermore, other possible influences can be set. For example, in the case of detonation combustion, the adjustment value for the direction of less detonation tendency can be related to the values ​​of other parameters used for different detonation control. For example, if there is already a large intervention in detonation control based on the λ value, a smaller adjustment value for the ignition angle can be set. Correspondingly, the adjustment value for the direction of greater detonation tendency can also be related to another corresponding value.

[0021] Another method for knock control involves setting knock control using the ignition angle and knock control using the λ value independently. However, here, the corresponding adjustment range is limited. For example, the ignition angle is not adjusted by the same magnitude as when knock control can be achieved using only the ignition angle. Accordingly, the adjustment range using the λ value is limited, that is, the maximum adjustment amount of the λ value is limited to a lower value than when knock control can be achieved using only the λ value.

[0022] Another method for knock regulation involves, in an internal combustion engine with multiple cylinders, setting up individual knock regulation for each cylinder and knock regulation based on the average value of these cylinders. The methods described above are described individually for each cylinder. This means that when knock occurs in one cylinder, the ignition angle and λ value for the next combustion are adjusted accordingly for that cylinder. However, alternatively, an average value for multiple cylinders can be calculated, i.e., an average value for the adjustments of the ignition angle and λ value for each cylinder can be calculated. This has the advantage that adjustments towards a smaller knock tendency do not necessarily occur when knock events occur individually in each cylinder. Many parameters affecting knock tendency, such as fuel quality, engine temperature, or ambient temperature, act simultaneously on all cylinders, making it advantageous that when knock occurs in one individual cylinder, certain adjustments towards a smaller knock tendency are also made in other cylinders. Here, the choice can be made between different methods for knock regulation: whether to perform individualized knock regulation for each cylinder or to calculate an average value for knock regulation. For example, knock adjustment using ignition angle can be individualized for each cylinder, while knock adjustment using λ value can calculate the average value for all cylinders. Furthermore, it is possible to adapt to operating parameters, such as using knock adjustment with averaging when the internal combustion engine is under high load, and performing individualized knock adjustment for each cylinder when the internal combustion engine is under low load.

[0023] The adjustment methods described above can be combined arbitrarily. In particular, specific methods for knock adjustment can be set for each operating region, and these methods are then not applied to other operating regions.

Claims

1. A method for adjusting knock in an internal combustion engine running on hydrogen, characterized in that, To achieve the aforementioned knock control, the knock tendency of the internal combustion engine is reduced by influencing the ignition angle and the λ value.

2. The method according to claim 1, characterized in that, First, the knock adjustment is performed solely based on the ignition angle until the ignition angle for the knock adjustment reaches a predetermined threshold, and then the knock adjustment is additionally performed based on the λ value; or, first, the knock adjustment is performed solely based on the λ value until the λ value for the knock adjustment reaches a predetermined threshold, and then the knock adjustment is additionally performed based on the ignition angle.

3. The method according to claim 1, characterized in that, For the purpose of the knock adjustment, values ​​for the ignition angle and for the λ value are set respectively, wherein the values ​​for the ignition angle and for the λ value are weighted according to the corresponding operating points of the internal combustion engine.

4. The method according to claim 1, characterized in that, For the purpose of knock adjustment, when a knock event occurs, the ignition angle and the λ value are adjusted towards the direction of knock-free operation with a first adjustment value. After a waiting period without knock events, the ignition angle and the λ value are adjusted towards the direction of higher knock tendency. The adjustment of the ignition angle and the λ value towards the direction of higher knock tendency is performed with a second adjustment value. The first adjustment value, the waiting time, and the second adjustment value for the ignition angle are related to the λ value, and the first adjustment value, the waiting time, and the second adjustment value for the λ value are related to the ignition angle.

5. The method according to claim 1, characterized in that, For the purpose of knock adjustment, when a knock event occurs, the ignition angle and the λ value are adjusted towards a knock-free operating direction by a first adjustment value. After a knock-free waiting period, the ignition angle and the λ value are adjusted towards a direction with a higher knock tendency. The adjustment of the ignition angle and the λ value towards a direction with a higher knock tendency is performed by a second adjustment value. The first adjustment value, waiting time, and second adjustment value for the ignition angle, as well as the first adjustment value, waiting time, and second adjustment value for the λ value, are related to the corresponding operating points of the internal combustion engine.

6. The method according to claim 1, characterized in that, A first adjustment circuit is provided for knock adjustment using the ignition angle, and a second adjustment circuit is provided for knock adjustment using the λ value, wherein the influence of the ignition angle and the influence of the λ value are respectively limited to their maximum values.

7. The method according to any one of the preceding claims, characterized in that, The internal combustion engine has a plurality of cylinders, and for each cylinder, one of the methods according to the preceding claims is used individually for knock regulation, and for all cylinders, one of the methods according to the preceding claims is used based on an average value for all cylinders.

8. A device for adjusting knock in an internal combustion engine running on hydrogen, characterized in that, The device is provided for the knock adjustment, which reduces the knock tendency of the internal combustion engine by influencing the ignition angle and the λ value.

Images