A test method and test system for an engine with spark ignition and compression ignition

Abstract

The present invention provides a test method for an ignition compression ignition engine, which relates to the field of vehicles. The test method includes: controlling the engine speed and load to change according to a preset rule so that the engine switches between an ignition state and an ignition compression ignition state; obtaining cylinder pressure data of each cylinder of the engine by a pressure sensor, and obtaining concentration data of hydrocarbons in the exhaust gas discharged by the engine by a capture device; determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons. The present invention also provides a test system for an ignition compression ignition engine. Such a test method and test system can improve the accuracy of the reliability test of the engine.

Description

Technical Field

[0001] The present invention relates to the field of automobiles, and particularly to a test method for a spark compression ignition engine. Background Art

[0002] A spark compression ignition engine is an engine that can operate in a combustion mode of spark compression ignition. Exemplarily, the combustion mode of spark compression ignition includes: first, a part of the fuel in the cylinder is ignited by a spark plug, and a fire kernel is formed by the ignited fuel to heat the unignited fuel, and finally, the unignited fuel in the cylinder is compressed and ignited as a whole by a piston. Before the engine is put into formal mass production, it is necessary to conduct reliability tests on the engine. The related test methods are difficult to detect combustion instability or misfire of the spark compression ignition engine, and the detection accuracy is not high. Summary of the Invention

[0003] The present invention actually provides a test method and a test system for a spark compression ignition engine, which are used to solve the problem of how to improve the accuracy of the reliability test of the spark compression ignition engine.

[0004] An embodiment of the present invention provides a test method for a spark compression ignition engine. The test method includes: controlling the speed and load of the engine to change according to a preset rule, so that the engine switches between a spark ignition state and a spark compression ignition state; obtaining the cylinder pressure data of each cylinder of the engine by a pressure sensor, and obtaining the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons.

[0005] Further, the controlling the speed and load of the engine to change according to a preset rule includes: keeping the speed of the engine at a first preset speed, and increasing the load of the engine to a first preset load.

[0006] Further, the first load is the maximum load of the engine, and the increasing the load of the engine to a first preset load includes: within a first preset time period, increasing the load of the engine from zero load to the maximum load.

[0007] Further, after the increasing the load of the engine to a first preset load, the controlling the speed and load of the engine to change according to a preset rule further includes: keeping the speed of the engine at a first preset speed, and keeping the load at the first load; keeping the speed of the engine at a first preset speed, and reducing the load from the first load to zero load within a second preset time period.

[0008] Further, the rotation speed and load of the engine are controlled to change according to a preset law: the rotation speed of the engine is increased from zero to a second rotation speed, and at the same time, the load of the engine is increased from zero to a third load.

[0009] Further, after the rotation speed of the engine is increased from zero to a second rotation speed and at the same time the load of the engine is increased from zero to a third load, the control of the rotation speed and load of the engine to change according to a preset law further includes: maintaining the load of the engine at the third load and increasing the rotation speed of the engine from the second rotation speed to a third rotation speed within a third preset time period; maintaining the rotation speed of the engine at the third rotation speed and increasing the load of the engine from the third load to a fourth load; increasing the rotation speed of the engine from the third rotation speed to a fourth rotation speed within a fourth preset time period; maintaining the rotation speed of the engine at the fourth rotation speed and increasing the load of the engine from the fourth load to a fifth load.

[0010] Further, after maintaining the rotation speed of the engine at the fourth rotation speed and increasing the load of the engine from the fourth load to a fifth load, the control of the rotation speed and load of the engine to change according to a preset law further includes: maintaining the rotation speed of the engine at the fourth rotation speed and decreasing the load of the engine from the fifth load to the third load; making the load of the engine at the third load and decreasing the rotation speed of the engine from the fourth rotation speed to the second rotation speed.

[0011] Further, the fourth preset time period is greater than the third preset time period.

[0012] Further, determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of the hydrocarbon includes: calculating a weighted sum of the reciprocals of the cylinder pressure data and the concentration data to obtain a stability coefficient; determining that the engine is in a combustion instability state when the stability coefficient is less than a first stability threshold, and determining that the engine is in a misfire state when the stability coefficient is less than a second stability threshold, where the second stability threshold is less than the first stability threshold.

[0013] An embodiment of the present invention further provides a test system for an ignition-compression ignition engine. The test system is used to execute the test method provided in the above embodiment. The test system includes: a control module for controlling the engine speed and load to change according to a preset rule so that the engine switches between the ignition state and the ignition-compression ignition state; an acquisition module for acquiring the cylinder pressure data of each cylinder of the engine by a pressure sensor and acquiring the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; and a processing module for determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons.

[0014] The present invention provides a test method for an ignition-compression ignition engine. The test method includes: controlling the engine speed and load to change according to a preset rule so that the engine switches between the ignition state and the ignition-compression ignition state; acquiring the cylinder pressure data of each cylinder of the engine by a pressure sensor and acquiring the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; and determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons. By changing the engine speed and load according to a preset rule and acquiring the cylinder pressure data of the engine and the concentration of hydrocarbons in the capture device, the combustion instability state or misfire state of the engine is detected when the combustion mode of the engine switches between the ignition state and the ignition-compression ignition state, thereby improving the accuracy of the reliability test of the ignition-compression ignition engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic flowchart of a test method for an ignition-compression ignition engine provided by an embodiment of the present invention;

[0016] Figure 2 It is a schematic flowchart of another test method for an ignition-compression ignition engine provided by an embodiment of the present invention;

[0017] Figure 3 It is a schematic flowchart of another test method for an ignition-compression ignition engine provided by an embodiment of the present invention;

[0018] Figure 4 It is a schematic flowchart of another test method for an ignition-compression ignition engine provided by an embodiment of the present invention;

[0019] Figure 5 It is a schematic flowchart of another test method for an ignition-compression ignition engine provided by an embodiment of the present invention;

[0020] Figure 6 It is a schematic structural diagram of another test system for an ignition-compression ignition engine provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] In the various specific technical features described in the specific embodiments, without conflict, they can be combined in any suitable manner. For example, different embodiments and technical solutions can be formed by combining different specific technical features. To avoid unnecessary repetition, various possible combination methods of the various specific technical features in the present invention will not be described separately.

[0023] In the following description, the terms "first / second / ..." involved are only used to distinguish different objects and do not indicate that there are any same or related relationships between the objects. It should be understood that the orientation descriptions "above", "below", "outside", and "inside" involved are all the orientations in the normal use state, and the "left" and "right" directions represent the left and right directions shown in the specific corresponding schematic diagram, which can be the left and right directions in the normal use state or not.

[0024] It should be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of additional identical elements in the process, method, article or device including the element. The term "connection" includes both direct connection and indirect connection without special explanation.

[0025] In the following specific real-time modes, the ignition compression ignition engine to which the test method and test system are applied can be an engine of any vehicle type. Exemplarily, the engine can be applied to a sedan, and exemplarily, the engine can also be applicable to a truck.

[0026] As Figure 1 shown, Figure 1 A flowchart of a test method for an ignition compression ignition engine is provided. The test method includes:

[0027] Step S101, controlling the engine speed and load to change according to a preset law so that the engine switches between the ignition state and the ignition compression ignition state.

[0028] It can be understood that by controlling the change of the engine speed and load, the combustion mode of the engine is switched from the spark ignition mode to the spark compression ignition mode, or the combustion mode of the engine is switched from the spark compression ignition mode to the spark ignition mode, so that the combustion instability state or misfire state of the engine can be detected during the transient response period after the combustion mode of the engine is switched between the spark ignition mode and the spark compression ignition mode, thereby providing a detection basis for the reliability of the spark compression ignition engine. It should be noted that the above-mentioned speed and the preset law of the engine can be any law that can switch the combustion mode of the spark compression ignition engine between the spark ignition mode and the spark compression ignition mode. Hereinafter, an exemplary description of the principle of switching the engine between the spark ignition mode and the compression ignition mode will be given. In the control system of the engine, there is a correspondence table of engine speed, load and combustion mode. In this correspondence table, it is divided into a spark ignition interval and a spark compression ignition interval according to different engine speeds and loads. When the operating point corresponding to the engine speed and load is within the spark ignition area of the correspondence table, the control system of the engine controls the combustion mode of the engine to be the spark ignition mode; when the operating point corresponding to the engine speed and load is within the spark compression ignition area of the correspondence table, the control system of the engine controls the combustion mode of the engine to be the spark compression ignition mode. By changing the engine speed and load to move the operating point of the engine from the spark ignition area to the spark compression ignition area, the combustion mode of the engine can be switched from the spark ignition mode to the spark compression ignition mode. By changing the engine speed and load to move the operating point of the engine from the spark compression ignition area to the spark ignition area, the combustion mode of the engine can be switched from the spark compression ignition mode to the spark ignition mode. Among them, according to the different reliability requirements of the engine to be detected under different working conditions, the above-mentioned preset law can be different change laws that can cause the combustion mode of the engine to switch. Optionally, keep the engine speed unchanged and increase the engine load so that the combustion mode of the engine is switched from the spark ignition state to the spark compression ignition state to detect the reliability of the engine when the combustion mode is switched at a certain engine speed; Optionally, keep the engine load unchanged and increase the engine load to detect the reliability when the combustion mode is switched when the engine is shifting gears.

[0029] Among them, the engine speed and load can be controlled by control parameters such as throttle opening, valve timing, fuel injection quantity, etc. Exemplarily, in the control system of the engine, there is a correspondence table of control parameters, engine speed and load. The engine speed is controlled through the correspondence table of control parameters and engine speed, and the control parameters such as throttle opening, valve timing, fuel injection quantity, etc. of the engine are controlled through this correspondence table, so as to control the engine speed and load, and then make the engine speed and load change according to the preset law.

[0030] Step S102: Obtain the cylinder pressure data of each cylinder of the engine by a pressure sensor, and obtain the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device.

[0031] It can be understood that the cylinder pressure data of each cylinder are obtained by cylinder pressure sensors arranged in each cylinder. It should be noted that the cylinder pressure data are the cylinder pressure data in each cylinder when the engine is theoretically ignited. The cylinder pressure data can be obtained in a variety of different ways. Optionally, obtain the crankshaft angle of the engine, and when the crankshaft angle is in the ignition angle state, obtain the cylinder pressure data of the cylinder; optionally, continuously obtain the real-time cylinder pressure data in the cylinder during the four-stroke cycle of the engine, and determine the maximum value of the obtained real-time cylinder pressure data as the cylinder pressure data of the cylinder. By obtaining the concentration of hydrocarbons absorbed by the capture device in the exhaust system, it can be understood that the capture device absorbs the unburned fuel in the tail gas.

[0032] Step S103: Determine whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons.

[0033] Comprehensively judge whether the engine is in a combustion instability state or a misfire state through the cylinder pressure data and the concentration data of hydrocarbons of the engine. Specifically, the combustion instability state can be understood as a state in which due to the unstable combustion state, part of the fuel entering the cylinder is not burned, and the misfire state can be understood as a state in which all the fuel entering the cylinder is not burned. When the engine is in a combustion instability state or a misfire state, the internal energy of at least part of the fuel is not released through combustion and is not converted into kinetic energy capable of driving the piston to move. If the cylinder pressure data of the engine decreases when the engine is in a combustion instability state or a misfire state, and at the same time, the concentration of unburned hydrocarbons absorbed by the capture device increases, so the cylinder pressure data of each cylinder and the concentration of hydrocarbons absorbed by the capture device can comprehensively judge whether the engine is in a combustion instability state or a misfire state. Optionally, obtain an instability coefficient by multiplying the cylinder pressure data and the reciprocal of the concentration data of hydrocarbons. When the instability coefficient is less than a first threshold, it is determined that the engine is in a combustion instability state, and when the instability coefficient is less than a second threshold, it is determined that the engine is in a misfire state, where the second threshold is less than the first threshold.

[0034] The present invention provides a test method for an ignition compression ignition engine. The test method includes: controlling the engine speed and load to change according to a preset rule so that the engine switches between an ignition state and an ignition compression ignition state; obtaining the cylinder pressure data of each cylinder of the engine by a pressure sensor, and obtaining the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons. By changing the engine speed and load according to a preset rule and obtaining the cylinder pressure data of the engine and the concentration of hydrocarbons in the capture device, the combustion instability state or misfire state of the engine is detected when the combustion mode of the engine switches between the ignition state and the ignition compression ignition state, thereby improving the accuracy of the reliability test of the ignition compression ignition engine.

[0035] In some embodiments, as Figure 2 shown, Figure 2 a flowchart of another test method for an ignition compression ignition engine is provided. Different from the Figure 1 flowchart shown, Figure 1 step S101 in

[0036] includes:

[0037] Step S201: Keep the engine speed at a first preset speed and increase the engine load to a first load.

[0038] By increasing the engine load while keeping the engine speed the same, simulating the condition of the engine when the load is increased at a constant speed, and detecting whether the engine is in a combustion instability state or a misfire state when the combustion mode of the engine switches from the ignition state to the ignition compression ignition state during the load increase process, thereby detecting the reliability of the engine at this speed. Optionally, keep the engine speed at the first preset speed, and within a first preset time period, increase the engine load from zero load to the maximum load, thereby simulating the process of the engine quickly increasing from the shutdown state to the maximum load, and testing the combustion stability of the engine at different loads at this speed. Optionally, after the first speed test is completed, change the first speed with a preset speed step to further improve the accuracy of the test of the combustion stability of the engine at different speeds and different load states.

[0038] In some embodiments, as Figure 3 shown, Figure 3 a flowchart of another test method for an ignition compression ignition engine is provided. Different from the Figure 2 flowchart shown, Figure 2 after step S201 in

[0039] Step S302: Keep the engine speed at the first preset speed and keep the engine load at the first load.

[0040] By running the engine at the first preset speed and the first load for a period of time, thus simulating the engine running at the first speed and the first load for a preset duration, the temperature of the engine lubricating oil, the temperature of the coolant, and the temperature of the exhaust pipe are raised to the preset temperature.

[0041] Step S303: Keep the engine speed at the first preset speed and reduce the engine load from the first load to zero load within the second preset duration.

[0042] It can be understood that by reducing the engine load from the first load to zero load within the second preset duration, thus after the engine runs at the first speed and the first load for a period of time, when the engine is in the neutral gear condition within the second preset duration, and at the same time, during the process of the engine load reducing from the first load to zero load, when the combustion mode of the engine switches from the ignition compression ignition mode to the ignition mode, the combustion stability of the engine is tested. Optionally, the engine can be made to operate in a cycle under the working conditions provided in Step S201, Step S302, and Step S303, so as to test the combustion stability of the engine under the condition that the load increases, remains constant, and decreases in a cycle at the first speed, and the combustion mode of the engine cycles between the ignition mode and the ignition compression ignition mode, further improving the accuracy of the detection.

[0043] In some embodiments, as Figure 4 shown, Figure 4 provides a schematic flow chart of another test method for an ignition compression ignition engine. Different from the test flow shown as Figure 1 shown, Figure 1 Step S101 in

[0044] Step S401: Increase the engine speed from zero speed to the second speed, and at the same time increase the engine load from zero load to the third load.

[0045] It can be understood that by increasing the engine speed and load from zero to the preset speed and load respectively, thus simulating the engine starting from the shutdown state to the high idle combustion condition during the cold start process, so as to be able to test the combustion stability of the engine during the cold start process.

[0046] Optionally, as Figure 4 shown, after Step S401, Step S101 further includes:

[0047] Step S402: Keep the engine load at the third load and increase the engine speed from the second speed to the third speed within the third preset duration.

[0048] It can be understood that after the engine completes starting and reaches the high-idle combustion condition, it simulates the condition of the engine accelerating within a low-speed range while maintaining a low gear state, so as to test the combustion stability during the acceleration process of the engine within the low-speed range of the low gear.

[0049] Step S403: Keep the engine speed at the third speed and increase the engine load from the third load to the fourth load.

[0050] Specifically, by keeping the engine speed unchanged and increasing the engine load from the third load to the fourth load, it simulates the upshift process of the engine at medium and low speeds, and then tests the combustion stability of the engine under the condition of shifting from a low gear to a high gear at medium and low speeds.

[0051] It should be noted that when the engine is in the condition provided by steps S401 to S403, the engine is at medium and low speeds and the load is in the medium and low load range, and the combustion mode of the engine is the spark ignition mode.

[0052] Step S404: Increase the engine speed from the third speed to the fourth speed within the fourth preset duration.

[0053] It can be understood that while keeping the engine gear in the medium gear state, the engine speed is increased from medium and low speed to high speed. At the same time, during the process of increasing the speed from the third speed to the fourth speed, the combustion mode of the engine switches from the spark ignition state to the spark ignition and compression ignition state, that is, under the condition that the engine accelerates from medium and low speed to high speed in the medium gear and the combustion mode switches from spark ignition to spark ignition and compression ignition, the combustion stability of the engine is tested.

[0054] Step S405: Keep the engine speed at the fourth speed and increase the engine load from the fourth load to the fifth load.

[0055] It can be understood that under the condition of the engine switching from the medium gear to the high gear at high speed, the combustion stability of the engine is tested. Among them, in the high-speed and high-gear state, the combustion mode of the engine is the spark ignition and compression ignition mode. Optionally, after the engine speed is increased to the fifth load, the engine speed is maintained at the fourth speed and the engine load is maintained at the fifth load within the preset duration, so as to test the combustion stability of the engine under the condition of running at high speed and high gear for a period of time.

[0056] It should be noted that the working conditions provided in steps S401 to S404 simulate the process of the engine gradually accelerating, shifting gears, and reaching a high speed and high gear from cold start, and test the combustion stability of the engine at each stage during the acceleration process and during the process of increasing to a high speed when the combustion mode switches from the ignition state to the ignition-compression ignition state. Optionally, the fourth preset duration in step S404 is greater than the third preset duration in step S402. It can be understood that the duration for the engine to switch from the middle gear to the high gear is greater than the duration for the engine to switch from the low gear to the middle gear. While reducing the risk of the engine stalling or being damaged due to too rapid load increase, it can also make the load increase process of the engine closer to the actual operating state of the engine during gear shifting, thereby further improving the accuracy of the detection of the engine's reliability.

[0057] Optionally, as Figure 4 shown, after step S405, step S101 further includes:

[0058] Step S406, maintain the engine speed at the fourth speed and reduce the engine load from the fifth load to the third load.

[0059] It can be understood that the combustion stability of the engine is tested when the engine switches from a high-speed state to a low-gear state.

[0060] Step S407, keep the engine load at the third load and reduce the engine speed from the fourth speed to the second speed.

[0061] It can be understood that after the engine gear is reduced to the low gear, the engine speed is reduced, thereby detecting the combustion stability of the engine under deceleration conditions. Optionally, by reducing the engine speed from the fourth speed to the second speed within a preset duration, the combustion stability of the engine under rapid deceleration conditions can be detected. At the same time, during the process of the engine downshifting or decelerating, the combustion mode of the engine switches from the ignition-compression ignition mode to the ignition mode. Steps S406 and S407 can also detect the combustion stability of the engine when the combustion mode switches from the ignition-compression ignition mode to the ignition mode.

[0062] In some embodiments, as Figure 5 shown, Figure 5 provides a flow chart of another test method for an ignition-compression ignition engine. Different from the flow shown in Figure 1 , the step S103 in Figure 1 includes:

[0063] Step S501, calculate the weighted sum of the reciprocals of the cylinder pressure data and the concentration data to obtain a stability coefficient.

[0064] Exemplarily, the stability coefficient C is calculated by the following formula:

[0065]

[0066] In the formula, C is the stability coefficient, k1 is the first weight coefficient corresponding to the cylinder pressure, A is the cylinder pressure data, k2 is the second weight coefficient corresponding to the concentration data, and B is the concentration data. Among them, the specific values of the first weight coefficient k1 and the second weight coefficient k2 are specifically determined according to the influence degree of combustion instability on the cylinder pressure and the concentration of hydrocarbon mixture. Exemplarily, in the ignition combustion mode, the excess air coefficient of the engine is small, and the influence of combustion instability on the concentration of hydrocarbon compounds is greater. Therefore, the second weight coefficient k2 is set to a larger value. For example, the first weight coefficient k1 is 0.4 and the second weight coefficient k2 is 0.6; in the ignition-compression ignition combustion mode, the excess air coefficient of the engine is large, the engine is in a lean combustion state, and the influence of combustion instability on the cylinder pressure data is greater. Therefore, the first weight coefficient k1 is set to a larger value. For example, the first weight coefficient k1 is 0.6 and the second weight coefficient k2 is 0.4.

[0067] It should be noted that when combustion instability or misfire occurs in the engine, the cylinder pressure in the engine will decrease, and the concentration of hydrocarbon compounds absorbed by the air replenishing device will increase. Moreover, the lower the cylinder pressure or the higher the concentration of hydrocarbon compounds, the more serious the combustion instability phenomenon of the engine. When the severity of the combustion instability of the engine exceeds a certain degree, all the fuel entering the cylinder cannot be ignited, and at this time, the engine is in a misfire state. Taking the weighted sum of the reciprocals of the cylinder pressure data and the concentration data as the stability coefficient can comprehensively judge the combustion stability of the engine.

[0068] Step S502: When the stability coefficient is less than the first stability threshold, it is determined that the engine is in a combustion instability state; when the stability coefficient is less than the second stability threshold, it is determined that the engine is in a misfire state.

[0069] Among them, the second stability threshold is less than the first stability threshold. It can be understood that when the degree of combustion instability of the engine exceeds a certain level and the fuel entering the engine cannot burn completely, it is determined that the engine is in a misfire state. That is, the misfire state is a severe combustion instability state. When the stability coefficient reflecting combustion stability is less than the first threshold, it can be considered that the difference between the cylinder pressure data and the concentration data of hydrocarbon compounds of the engine and the normal state has reached a level that cannot be considered as caused by detection error. At this time, it is determined that the engine is in a combustion instability state; when the stability coefficient is less than the second threshold, the severity of the combustion instability of the engine has reached a very serious level, and it can be considered that the fuel entering the cylinder has basically not burned. At this time, it is determined that the engine is in a misfire state.

[0070] An embodiment of the present invention further provides a test system for an engine. This test system is applied to execute the test method for the spark compression ignition engine provided in the above embodiment, and this test system can be a control system of a test bench.

[0071] In some embodiments, as Figure 6 shown, the test system includes: a control module 100, an acquisition module 200, and a processing module 300. The control module 100 is used to control the engine speed and load to change according to a preset rule, so that the engine can switch between the spark ignition state and the spark compression ignition state. The acquisition module 200 is used to acquire the cylinder pressure data of each cylinder of the engine by a pressure sensor arranged in the cylinder, and acquire the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a trapping device arranged in the exhaust pipe. The processing module 300 is used to determine whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of hydrocarbons.

[0072] In some embodiments, as Figure 6 shown, the control module 100 is further used to keep the engine speed at a first preset speed and increase the engine load to a first load. The control module 100 is further used to keep the engine speed at the first preset speed and keep the engine load at the first load. The control module 100 is further used to keep the engine speed at the first preset speed and reduce the engine load from the first load to zero load within a second preset time period.

[0073] In some embodiments, as Figure 6 shown, the control module 100 is further used to increase the engine speed from zero speed to a second speed, and at the same time increase the engine load from zero load to a third load. The control module 100 is further used to keep the engine load at the third load and increase the engine speed from the second speed to a third speed within a third preset time period. The control module 100 is further used to keep the engine speed at the third speed and increase the engine load from the third load to a fourth load. The control module 100 is further used to increase the engine speed from the third speed to a fourth speed within a fourth preset time period. The control module 100 is further used to keep the engine speed at the fourth speed and increase the engine load from the fourth load to a fifth load. The control module 100 is further used to keep the engine speed at the fourth speed and reduce the engine load from the fifth load to the third load. The control module 100 is further used to keep the engine load at the third load and reduce the engine speed from the fourth speed to the second speed.

[0074] In some embodiments, as Figure 6As shown, the processing module 300 is further configured to calculate the weighted sum of the reciprocals of the cylinder pressure data and the concentration data to obtain a stability coefficient. The processing module 300 is further configured to determine that the engine is in a combustion instability state when the stability coefficient is less than the first stability threshold, and determine that the engine is in a misfire state when the stability coefficient is less than the second stability threshold.

[0075] The above are only the preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

Claims

1. A test method for an engine with spark ignition and compression ignition, characterized in that, The described test method includes: Controlling the engine speed and load to change according to a preset rule so that the engine switches between an ignition state and an ignition compression state; Obtaining the cylinder pressure data of each cylinder of the engine by a pressure sensor, and obtaining the concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; Determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of the hydrocarbons; Wherein, controlling the engine speed and load to change according to a preset rule includes: Increasing the engine speed from zero speed to a second speed, and at the same time increasing the engine load from zero load to a third load; Maintaining the engine load at the third load, and increasing the engine speed from the second speed to a third speed within a third preset time period; Maintaining the engine speed at the third speed, and increasing the engine load from the third load to a fourth load; Increasing the engine speed from the third speed to a fourth speed within a fourth preset time period; Maintaining the engine speed at the fourth speed, and increasing the engine load from the fourth load to a fifth load.

2. The test method according to claim 1, wherein Controlling the engine speed and load to change according to a preset rule includes: Maintaining the engine speed at a first preset speed, and increasing the engine load to a first preset load.

3. The test method according to claim 2, characterized in that, The first preset load is the maximum load of the engine, and increasing the engine load to the first preset load includes: Within a first preset time period, increasing the engine load from zero load to the maximum load.

4. The test method according to claim 2, wherein After increasing the engine load to the first preset load, controlling the engine speed and load to change according to a preset rule further includes: Maintaining the engine speed at the first preset speed, and maintaining the load at the first preset load; Maintaining the engine speed at the first preset speed, and reducing the load from the first preset load to zero load within a second preset time period.

5. The test method according to claim 1, characterized in that, After maintaining the engine speed at the fourth speed and increasing the engine load from the fourth load to the fifth load, controlling the engine speed and load to change according to a preset rule further includes: Maintaining the engine speed at the fourth speed, and reducing the engine load from the fifth load to the third load; Making the engine load be the third load, and reducing the engine speed from the fourth speed to the second speed.

6. The test method according to claim 1, wherein The fourth preset time period is greater than the third preset time period.

7. The test method according to claim 1, wherein Determining whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of the hydrocarbons includes: Calculating the weighted sum of the reciprocals of the cylinder pressure data and the concentration data to obtain a stability coefficient; In a state where the stability coefficient is less than a first stability threshold, determining that the engine is in a combustion instability state, and in a state where the stability coefficient is less than a second stability threshold, determining that the engine is in a misfire state, wherein the second stability threshold is less than the first stability threshold.

8. A test system for an engine with spark ignition and compression ignition, characterized in that, The test system is used to execute the test method according to any one of claims 1 to 7, and the test system includes: a control module, configured to control the rotational speed and load of the engine to change according to a preset rule, so as to switch the engine between an ignition state and an ignition compression ignition state; an acquisition module, configured to acquire cylinder pressure data of each cylinder of the engine by a pressure sensor, and acquire concentration data of hydrocarbons in the exhaust gas discharged from the engine by a capture device; a processing module, configured to determine whether the engine is in a combustion instability state or a misfire state based on the cylinder pressure data and the concentration data of the hydrocarbons.

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