Engine control method for optimizing combustion

Abstract

The invention provides an engine control method for optimizing combustion. The engine control method comprises the following steps that during operation of an engine, the knocking intensity of the engine is monitored; one or more countermeasures are applied to the engine such that the operating state of the engine tends to knock and the knock intensity lies in a first interval. The engine control method for optimizing combustion has the advantages of being simple, reliable, convenient to apply, good in safety performance and the like.

Description

Technical Field

[0001] The present application relates to the field of engine control. More specifically, the present application relates to an engine control method for optimizing combustion, which is intended to provide an improved knock protection function and improve engine operating efficiency. Background Art

[0002] Heavy-duty gas engines usually work in high-load areas and are operated in an ignition mode. Engines using such fuels may experience knock during operation, which can have adverse effects on the engine. Current gas engines are usually controlled using some basic combustion parameters and correction values, and the engine is continuously monitored for knock and misfire. Such basic combustion parameters and correction values ​​are usually calibrated before the engine leaves the factory and pre-stored in the engine's control unit.

[0003] Typical spark-ignition heavy-duty gas engines may use natural gas, etc. The characteristics of such fuels are that products produced in different regions have differences in composition. In addition, the engines may be operated in different operating conditions or environments, and there are differences between the individual characteristics of a single engine. Therefore, the performance of the pre-stored parameters and correction values ​​under some operating conditions or usage scenarios may have room for improvement. Summary of the invention

[0004] One aspect of the present application is to provide an engine control method for optimizing combustion, which is intended to reduce the possibility of engine knock and improve the operating efficiency of the engine.

[0005] The purpose of this application is achieved through the following technical solutions: An engine control method for optimizing combustion comprises the following steps: During engine operation, monitoring the engine knock intensity; One or more countermeasures are applied to the engine so that the operating state of the engine tends to cause knock to occur and the knock intensity is in a first interval. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present application will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments. Those skilled in the art will appreciate that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be used as a limitation on the scope of the present application. In addition, unless otherwise specified, the drawings are intended only to conceptually represent the composition or structure of the described objects and may contain exaggerated displays. The drawings are not necessarily drawn to scale.

[0007] Figure 1 is a flow chart of an embodiment of an engine control method for optimizing combustion of the present application.

[0008] Figure 2 It is an embodiment of the engine universal characteristic diagram. DETAILED DESCRIPTION

[0009] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings. It will be appreciated by those skilled in the art that these descriptions are only illustrative and exemplary and should not be construed as limiting the scope of protection of the present application.

[0010] First, it should be noted that the top, bottom, upward, downward, and other directional terms mentioned in this article are defined relative to the directions in the various drawings. These directions are relative concepts and will therefore vary depending on the position and state they are in. Therefore, these or other directional terms should not be understood as restrictive.

[0011] In addition, it should be pointed out that for any single technical feature described or implied in the embodiments of this document or any single technical feature shown or implied in the accompanying drawings, these technical features (or their equivalents) can be further combined to obtain other embodiments not directly mentioned in this document.

[0012] It should be noted that in different drawings, the same reference numerals denote the same or substantially the same components.

[0013] Figure 1 It is a flow chart of an embodiment of the engine control method for optimizing combustion of the present application. According to one embodiment of the present application, the engine can be a spark-ignition engine. That is, the fuel is ignited by a component such as a spark plug and then burns. In one embodiment, the engine can use non-standardized fuels, including but not limited to natural gas, liquefied petroleum gas, methanol, hydrogen, etc. The characteristic of such non-standardized fuels is that the composition of the fuels mined or synthesized in different regions may be different, and this difference in composition causes the engine to exhibit different characteristics during operation. In one embodiment, the engine can be a gas engine or a commercial vehicle engine using natural gas.

[0014] More specifically, the present application provides an engine control method for actively optimizing combustion parameters based on knock monitoring. In the technical solution of the present application, the combustion parameters will be adjusted so that the engine tends to have slight knock. By maintaining the engine in a state of slight knock, better engine performance can be obtained. In the technical solution of the present application, the knock intensity of the engine will be continuously monitored, and the combustion parameters will be selectively adjusted according to the control method described in detail below.

[0015] An embodiment of the engine control method for optimizing combustion of the present application may generally include the following steps: 1) monitoring the knock intensity of the engine; 2) taking one or more countermeasures for different conditions so that the knock intensity tends to be within a first interval; and 3) updating the parameters of the countermeasures. Figure 1 The details of these three steps are shown in detail. The first step can include Figure 1 The upper left corner of the middle part includes sub-steps S100 to S120. The third step may include Figure 1 The right part of the middle part includes sub-steps S300 to S320, and the second step may include Figure 1 The remaining part includes sub-steps S200 to S290.

[0016] The engine control method for optimizing combustion starts from sub-step S100. Therefore, sub-step S100 represents that the engine is running. In the first step, after the engine starts running or during the running, the knock monitoring function is activated (sub-step S110). The embodiment of the present application can use a knock sensor to sense the knock state of the engine. Figure 1 In the example, the letter Y represents a "yes" judgment path, and the letter N represents a "no" judgment path. In one embodiment, the knock sensor is a commercially available vibration sensor and can be installed at a suitable position on the engine. For a multi-cylinder engine, one or more knock sensors can be arranged near the cylinders. For example, one knock sensor can be associated with several cylinders, and another knock sensor can be associated with another several cylinders.

[0017] In one embodiment, after the engine enters the knock sensitive area, the knock intensity of the engine is continuously monitored. In other words, knock state monitoring and knock sensitive area monitoring can be performed independently or in association. In the illustrated embodiment, knock monitoring is activated between knock sensitive area monitoring. That is, at sub-step S120, monitor whether the engine is in the knock sensitive zone. In one embodiment, knock monitoring can be activated after knock sensitive area monitoring. That is, in one embodiment, knock monitoring is started only after entering the knock sensitive area. In one embodiment, knock monitoring is performed continuously after entering the knock sensitive area.

[0018] The knock sensitive area can be determined based on multiple parameters. Such parameters include, but are not limited to, engine design, engine layout (such as the structure and layout of the cylinders), the installation position of the knock sensor, the engine speed and load, etc. In one embodiment, the knock sensitive area is embodied as certain areas on the engine universal characteristic diagram. In one embodiment, when the engine is running in the knock sensitive area, the combustion efficiency of the engine has not reached the optimal state, and the engine is sensitive to changes in combustion parameters when running in this area, and knock is prone to occur. At the boundary of the knock sensitive area, changes in combustion parameters are likely to cause significant changes in the knock state. In addition, the sensing resolution or signal quality of the knock sensor should be configured to be good enough to distinguish between knocks of different intensities. For example, the precision signal quality of the knock sensor can at least determine whether the intensity of the knock is relatively large or relatively small.

[0019] In one embodiment, the knock intensity can be calculated according to the following steps: First, the sensing result of the knock sensor is recorded within a predetermined time, wherein the sensing result can be a series of electrical signals in time sequence, and the electrical signal represents the vibration amplitude of the engine cylinder. Then, the sensing result is filtered to filter the background signal and the interference signal, and the filtering result is obtained. Finally, the filtering result is integrated, for example, the filtering result is used to integrate the time to obtain the integration result. The integration result can be used to represent the knock intensity. The filtering operation can eliminate noise or occasional knock vibration interference, so that the signal is smooth and avoids unexpected operation.

[0020] Therefore, for a specific engine, the knock intensity when no knock occurs or there is no knock may be a predetermined value. Different intervals and thresholds will be defined below based on the knock intensity when no knock occurs.

[0021] The concepts of no knock, micro-knock, weak knock and strong knock are defined herein. In one embodiment, micro-knock represents that the knock intensity of the engine is between the first interval, for example, between certain multiples of the knock intensity when no knock occurs. In one embodiment, the lower limit of the first interval may be between 1.35 and 1.65 times, for example, 1.5 times, of the integral result when no knock occurs, and the upper limit of the first interval may be between 2.5 and 3.5 times, for example, 3 times, of the integral result when no knock occurs. Weak knock represents that the knock intensity of the engine is greater than the upper limit of the first interval and is less than or equal to the first threshold value. In one embodiment, the first threshold value may be set between 5 and 7 times, for example, 6 times, of the integral result when no knock occurs. Strong knock represents that the knock intensity of the engine is greater than the first threshold value. In this article, the upper limit of the knock intensity of strong knock is not limited. No knock represents that the knock intensity of the engine is less than the lower limit of the first interval. It should be noted that the various multiples and interval ranges disclosed herein are specific reference values. According to specific engineering practices, those skilled in the art may set other multiples or intervals of numerical values ​​for different projects or different engines.

[0022] In the second step, first determine whether the knock intensity leaves the first interval at sub-step S200. Specifically, sub-step 200 determines whether the knock intensity is above the first interval or below the first interval. In this article, the "yes" or Y path of sub-step 200 represents that the knock intensity is above the first interval, that is, the knock intensity is greater than the upper limit of the first interval. The "yes" or Y path of sub-step 200 represents the state of the engine having an unexpected knock, for example, a weak knock or a strong knock. The "no" or N path of sub-step 200 represents that the knock intensity is below the first interval, that is, the knock intensity is less than the lower limit of the first interval. The "no" or N path of sub-step 200 represents the knock-free state of the engine. It should be noted that the lower limit of the first interval is set to a certain multiple of the integral result when no knock occurs, in order to prevent the false signal caused by the disturbance during the operation of the engine from unexpectedly activating the engine control method of the present application.

[0023] If the knock intensity does not leave the first interval, it means that the engine is in a desired operating state. At this time, it is desired that the engine remains in this state, and the engine control method of the present application will stay at sub-step 200.

[0024] In the case where it is sensed that the knock intensity of the engine has left the first interval, the engine control method for optimizing combustion of the present application will take one or more countermeasures so that the knock intensity of the engine tends to return to the first interval. In one embodiment, the countermeasures include: increasing the target exhaust gas recirculation (EGR) rate and reducing the ignition angle. In one embodiment, the countermeasures include increasing the ignition angle and reducing the target exhaust gas recirculation rate. Different countermeasures may be taken depending on different knock states.

[0025] In one embodiment of the present application, countermeasures can be selected according to different situations. For example, in sub-step S210, the knock intensity is judged based on whether the data from the knock sensor is greater than a first threshold. The first threshold can be a fixed value calibrated during factory inspection, and can be calibrated based on the reading of the knock sensor. The first threshold can be used to determine whether the intensity of the knock is relatively large or relatively small. For strong knocks with relatively large relative intensity, it is desired to eliminate the knock as soon as possible, and countermeasures such as reducing the ignition angle can be taken. For weak knocks with relatively small intensity, the urgency of eliminating the knock as soon as possible is not very prominent, so measures such as increasing the target exhaust gas recirculation rate can be taken. Therefore, when the knock intensity is greater than the first threshold, countermeasures such as reducing the ignition angle can be directly taken (sub-step S260).

[0026] For the countermeasure of increasing the target exhaust gas recirculation rate, it can be achieved by reducing the throttle setting pressure ratio (sub-step S240). It should be noted that reducing the throttle setting pressure ratio is an auxiliary measure. The purpose of reducing the throttle setting pressure ratio is to reduce the pressure downstream of the EGR valve, which plays an auxiliary role. Therefore, before taking the countermeasure of increasing the target exhaust gas recirculation rate, it can be first determined whether the exhaust gas recirculation margin supports the adjustment operation (sub-step S220) and whether the throttle needs to be adjusted (sub-step S230). Specifically, before determining whether the throttle needs to be adjusted, it can be determined in sub-step S220 whether the exhaust gas recirculation margin is greater than the second threshold. It is easy to understand that the adjustment range of the target exhaust gas recirculation rate is limited, and in the case of insufficient exhaust gas recirculation margin, it will be difficult to achieve the purpose of eliminating knock by adjusting the target exhaust gas recirculation rate. Therefore, in the case where the exhaust gas recirculation margin is less than or equal to the second threshold, the countermeasure of reducing the ignition angle can be taken (sub-step S260). When the knock intensity is less than or equal to the first threshold and the exhaust gas recirculation margin is greater than the second threshold, a countermeasure of increasing the target exhaust gas recirculation rate may be taken (sub-step S250).

[0027] In addition, in the non-knock state, the operations of increasing the ignition angle (sub-step S270) and reducing the target exhaust gas recirculation rate (sub-step S290) can be adopted. One aspect of such operations is to push the operating state of the engine toward the occurrence of micro-knock, and in the process further improve the operating efficiency and output efficiency of the engine. On the other hand, such operations also provide space for the countermeasures recorded above. For example, when the target exhaust gas recirculation rate is continuously reduced, the exhaust gas recirculation margin is continuously released. When increasing the ignition angle, space is also provided for the operation of reducing the ignition angle.

[0028] It should be noted that in the non-knock state, increasing the ignition angle and reducing the target exhaust gas recirculation rate can be performed simultaneously. For the target exhaust gas recirculation rate, it is also necessary to pay attention to whether the exhaust temperature of the engine is lower than the boundary, or in other words, whether it is lower than the third threshold. Sub-step S280 determines whether the exhaust temperature is lower than the third threshold. When the exhaust temperature is higher than the boundary, the engine control method for optimizing combustion of the present application will return (as shown in the N or no judgment path of sub-step S280) and will not further reduce the target exhaust gas recirculation rate, thereby ensuring the normal operation of the entire engine. When the exhaust temperature is lower than the boundary, the engine control method for optimizing combustion of the present application will further reduce the target exhaust gas recirculation rate (sub-step S290), thereby pushing the engine to a state where micro-knock tends to occur.

[0029] The adjustment of the above countermeasures can take different step sizes. For example, the operation of increasing the ignition angle and reducing the target exhaust gas recirculation rate can have different step sizes.

[0030] In the third step, the engine control method for optimizing combustion of the present application continuously monitors whether the knock intensity returns to the first interval (sub-step S300). The monitoring can be performed using a knock sensor. After the knock intensity returns to the first interval, the parameters of the countermeasures can be updated. For example, the parameters of the countermeasures may include: ignition angle, target exhaust gas recirculation rate correction, throttle set pressure ratio, etc. These parameters may be stored in a memory not shown and used by an engine control system or an electronic control unit (ECU).

[0031] It is easy to understand that the steps of the above control method are performed when the engine is at a specific speed and torque, and therefore correspond to an area on the engine universal characteristic diagram. In one embodiment, in addition to the corresponding area, the above control method also includes calculating the parameters of the countermeasures for other speed and load areas (sub-step S310), and updating the parameters of the countermeasures for other speed and load areas (sub-step S320). That is to say, when the parameters of the countermeasures in one of the engine speed and load areas are updated, the others in the engine speed and load areas will also be updated accordingly. In one embodiment, the update is performed synchronously and in the same direction. In one embodiment, the greater the distance of other areas from the parameter update area, the smaller the update amplitude.

[0032] Figure 2 It is an embodiment of the engine universal characteristic diagram. Figure 2 The division into engine speed and load ranges is shown schematically. Figure 2 The horizontal axis is the speed, and the vertical axis is the torque. Figure 2 The multiple nested annular dotted line areas are the fuel consumption rate curve or the equal power curve of the engine. Figure 2 The vehicle body is divided into a plurality of regions by a plurality of vertical dashed lines L1 to L6 and a plurality of horizontal dashed lines L1 ′ to L6 ′, and each region corresponds to a different rotation speed and torque.

[0033] In combination with the above description, for example, when the parameters of the countermeasures of the engine speed and load area marked as Z1 are updated, the parameters of the countermeasures of multiple areas around it can be updated at the same time. Areas Z2, Z3, Z4 and Z5 are located adjacent to area Z1, and area Z6 is located adjacent to area Z3 and relatively far away from area Z1. Therefore, the update amplitude of the parameters of the countermeasures in area Z6 can be smaller than the update amplitude of the parameters of the countermeasures in area Z3. In one embodiment, as the load or torque decreases, the update amplitude of the parameters of the countermeasures will decrease or decay.

[0034] The engine control method for optimizing combustion of the present application has the advantages of being simple and reliable, easy to apply, and having good safety. Compared with the prior art, the technical solution of the present application can keep the engine running under micro-detonation, thereby improving the operating efficiency of the entire engine.

[0035] This specification discloses the present application with reference to the accompanying drawings, and also enables those skilled in the art to implement the present application, including making and using any device or system, selecting suitable materials, and using any combined method. The scope of the present application is defined by the technical solution for protection, and includes other examples that occur to those skilled in the art. As long as such other examples include structural elements that are not different from the literal language of the technical solution for protection, or such other examples include equivalent structural elements that are not substantially different from the literal language of the technical solution for protection, such other examples should be deemed to be within the scope of protection determined by the technical solution for protection of the present application.

Claims

1. An engine control method for optimizing combustion, characterized in that: The following steps are involved: During engine operation, monitoring the engine knock intensity; One or more countermeasures are applied to the engine so that the operating state of the engine tends to cause knock to occur and the knock intensity is in a first interval.

2. The engine control method according to claim 1, characterized in that: The knock intensity is calculated based on the following steps: recording a sensing result signal of a knock sensor within a predetermined time, filtering the sensing result to obtain a filtering result, and integrating the filtering result to obtain an integration result; The lower limit of the first interval is set between 1.35 times and 1.65 times the integration result when no engine knock occurs, and the upper limit of the first interval is set between 2.5 times and 3.5 times the integration result when no engine knock occurs.

3. The engine control method according to claim 2, characterized in that: The following steps are also included: When it is detected that the knock intensity leaves the first range, one or more countermeasures are taken to make the knock intensity tend to return to the first range; and After monitoring that the knock intensity returns to the first interval, updating the parameters of the countermeasure; Among them, the countermeasures include one or more of the following: reducing the ignition angle, increasing the target exhaust gas recirculation rate;.

4. The engine control method according to claim 3, characterized in that: When the knock intensity is greater than a first threshold or the exhaust gas recirculation margin is less than or equal to a second threshold, the countermeasure includes reducing the ignition angle, wherein the first threshold is set to be between 5 and 7 times the integration result when no knock occurs in the engine; and When the knock intensity is greater than the upper limit of the first interval and less than or equal to the first threshold and the exhaust gas recirculation margin is greater than the second threshold, the countermeasure includes increasing the target exhaust gas recirculation rate, wherein the implementation method of increasing the target exhaust gas recirculation rate includes reducing the throttle setting pressure ratio.

5. The engine control method according to claim 3, characterized in that: Updating the parameters of the countermeasures includes storing the ignition angle, the target exhaust gas recirculation rate correction, and the throttle set pressure ratio in the electronic control unit of the engine for a single engine speed and load range.

6. The engine control method according to claim 3, characterized in that: For different engine speed and load regions on the universal characteristic diagram, the following corresponding parameters are stored respectively: ignition angle, target exhaust gas recirculation rate correction, and throttle valve set pressure ratio.

7. The engine control method according to claim 6, characterized in that: When parameters in one of the engine speed and load regions are updated, parameters in other engine speed and load regions are updated synchronously and in the same direction; wherein, as the distance from one of the engine speed and load regions increases, the update amplitude of the parameters in other engine speed and load regions decreases.

8. The engine control method according to claim 2, characterized in that: When the knock intensity is less than the lower limit of the first interval, the ignition angle of the engine is continuously increased and the target exhaust gas recirculation rate is reduced, so that the knock intensity tends to increase and move toward the first interval, thereby obtaining higher operating efficiency.

9. The engine control method according to claim 8, characterized in that: During operation, the exhaust temperature of the engine is monitored; when the exhaust temperature of the engine is monitored to reach a third threshold, the target exhaust gas recirculation rate is maintained unchanged.

10. The engine control method according to any one of claims 1 to 9, characterized in that: After detecting that the engine has entered a knock-sensitive region, the knock intensity of the engine is continuously monitored.

11. The engine control method according to claim 10, characterized in that: The knock sensitive area is determined based on one or more of the following parameters: engine type, engine design and layout, and installation location of the knock sensor.

12. The engine control method according to claim 10, characterized in that: The knock sensitive region has one or more of the following characteristics: the knock boundary is sensitive to changes in combustion parameters; the knock sensor is selected so that the signal quality of the knock sensor is sufficient to distinguish knocks of different intensities.

13. The engine control method according to any one of claims 1 to 12, characterized in that: The engine is a spark ignition engine and is operated using one of the following fuels: natural gas, liquefied petroleum gas, methanol, hydrogen.

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