A variable environment fuel atomization quality testing system and method

Abstract

This invention discloses a variable environment fuel atomization quality testing system and method. The system includes a high-pressure common rail injection system, a cryogenic refrigeration system, an electronic control system, an image data acquisition system, and an environmental test chamber. The cryogenic refrigeration system reduces the temperature of the fuel inside the injector through convective heat transfer. The environmental test chamber simulates the ambient air pressure, temperature, and humidity based on actual in-cylinder environmental parameters during engine operation. The image data acquisition system acquires and processes images of the cryogenic fuel spray in the variable environment. By measuring the cyclic injection volume during fuel injection, the Sauter mean diameter is calculated using different empirical formulas, and the fuel atomization characteristics are comprehensively analyzed. This invention provides a reliable experimental means for studying fuel atomization in low-temperature environments during engine cold starts, deeply analyzing the impact of complex environments on engine cold starts, and thus seeking to improve engine cold start performance.

Description

Technical Field

[0001] This invention relates to the field of engine environmental adaptability technology, specifically to a variable environment fuel atomization quality testing system and method. Background Technology

[0002] Engines are widely used in automobiles, construction machinery, agricultural machinery, ships, drones, and military equipment due to their high thermal efficiency, simple structure, and reliable operation. Northern my country experiences hot and rainy summers, cold and dry winters, and distinct seasons, placing increasingly stringent demands on engines in the machinery industry. Environmental factors affect engine power and fuel economy, and can impact engine mileage and lifespan during cold starts. Especially in the northwestern high-altitude and cold regions, engine cold starts are difficult, with poor fuel atomization and incomplete combustion being significant contributing factors. Improving fuel spray combustion can appropriately increase the success rate of engine cold starts.

[0003] During cold starts of engines in low-temperature or high-altitude environments, the lower intake air temperature and density, heat transfer losses due to low-temperature walls, and significant blow-by losses caused by the larger clearances between the piston, piston rings, and cylinder liners in the cold state result in a significantly lower in-cylinder thermal state at top dead center compared to normal operating conditions. This poor in-cylinder thermal state inhibits fuel atomization and evaporation, prolonging the combustible mixture preparation time and potentially leading to misfires and cold start failures. Furthermore, the limited space within the combustion chamber restricts fuel atomization, and the additional turbulence caused by the interaction between the fuel spray and the combustion chamber walls directly impacts fuel atomization. In conclusion, fuel atomization directly affects engine starting and efficiency; therefore, measuring and evaluating fuel atomization quality is crucial.

[0004] Fuel atomization characteristics refer to the atomization and spatial distribution of fuel after it is injected into the combustion chamber, mainly including the spray cone angle, spray penetration distance, and spray particle size. The injected fuel initially exists in the form of a liquid column, which then begins to break into small droplets. The more droplets the liquid column breaks into and the smaller the droplet diameter, the better the atomization effect, which is conducive to the formation of a combustible mixture.

[0005] Fuel viscosity and atomization vary under changes in ambient temperature, pressure, and humidity, and intake air temperature and oxygen content also change accordingly. To test the fuel atomization characteristics of an engine in a variable environment and measure the quality of low-temperature fuel atomization, an environmental test chamber and a low-temperature fuel preparation device were developed. This study investigates the fuel atomization at low temperatures during engine cold starts, providing a comprehensive analysis of the impact of complex environments on engine cold starts, thereby improving engine cold start performance. Summary of the Invention

[0006] This invention aims to study the low-temperature fuel injection atomization characteristics during cold start, and provides a variable environment fuel atomization quality testing system and method. This system can reduce the fuel temperature to -60℃; adjust the air pressure and temperature and humidity in the environmental test chamber to simulate the in-cylinder thermal state at the top dead center of compression in a high-altitude cold environment, and explore the low-temperature fuel atomization characteristics during cold start.

[0007] The technical solution adopted in this invention is:

[0008] A variable environment fuel atomization quality testing system, comprising a high-pressure common rail injection system, an electronic control system, a cryogenic refrigeration system, an image data acquisition system, and an environmental test chamber;

[0009] The high-pressure common rail injection system includes a fuel tank 1, a high-pressure fuel pump 2, a common rail pipe 3 and an injector 4 connected in sequence. Fuel flows through the high-pressure fuel pump 2 to be pressurized and enters the common rail pipe 3 and supplies fuel to the injector 4.

[0010] The cryogenic refrigeration system includes a first circulation pump 6, a sleeve 7, a thermocouple 21, and a temperature measuring instrument 8. Coolant circulates in the cavity of the sleeve 7. The oil supply section of the injector 4 is fitted inside the sleeve 7. The temperature measuring instrument 8 detects the temperature at the nozzle through the thermocouple 21 connected to it and located at the nozzle of the injector 4.

[0011] The electronic control system includes an ECU controller 5 and a synchronous trigger 22 connected thereto. The ECU controller 5 regulates the fuel pressure, and the fuel injector 4 transmits a synchronous signal to the synchronous trigger 22 while injecting fuel.

[0012] The image acquisition system includes a high-speed camera 13, a computer 9, and a light source 12. The high-speed camera 13 and the light source 12 are arranged on the same optical axis. The synchronous trigger 22 is connected to the high-speed camera 13 and triggers the high-speed camera 13. The high-speed camera 13 acquires fuel spray image information by backlighting and transmits the acquired image to the computer 9 connected to it.

[0013] The environmental test chamber includes a spray chamber 11, an air pump 15, a humidifier 14, a second circulation pump 16, a heating tube 17, an optical platform 10, and a pressure sensor 18, a temperature sensor 19, and a humidity sensor 20. The spray chamber 11 is cuboid in shape and is arranged on the optical platform 10. The air pump 15 and the humidifier 14 are connected to the observation windows on its left and right sides. The bottom of the spray chamber 11 is provided with a heating tube 17 connected to the second circulation pump 16. The pressure sensor 18, temperature sensor 19, and humidity sensor 20 are arranged inside the spray chamber 11.

[0014] Furthermore, the spray chamber 11 is made of double-layered quartz glass on all sides and top, and observation windows are provided on all sides and top, with the observation window portion being made of single-layered quartz glass.

[0015] Furthermore, the spray chamber 11 is heated by the heating pipe 17, the air density is reduced by the air pump 15 to decrease the oxygen content of the air, and the air humidity is controlled by the humidifier 14 to change the oxygen content.

[0016] Furthermore, the high-speed camera 13 is located on the front side panel of the spray chamber 11, and the humidifier 14 and the air pump 15 are respectively arranged on the left and right side panels of the spray chamber 14.

[0017] Furthermore, while the ECU controller 5 sends an injection electromagnetic signal to the injector 4, it also transmits another electrical signal to the high-speed camera 13 through the synchronous trigger 22, so as to realize the synchronous operation of fuel injection and high-speed camera 13.

[0018] Furthermore, the high-speed camera 13 and the light source 12 are respectively arranged on the front and rear plates of the spray chamber 11, so that the high-speed camera 13, the light source 12, and the nozzle tip of the fuel injector 4 are coaxial and located on the same horizontal line. Adjusting the intensity of the light source and parameters such as the camera's shooting speed and resolution allows for the acquisition of spray images with clear outlines. The computer 9 acquires image information based on the entire fuel spray process, processes the images to obtain quantified values ​​of the macroscopic characteristic parameters of the fuel spray, namely the spray cone angle and the spray penetration distance.

[0019] A testing method utilizing a variable environment fuel atomization quality testing system includes:

[0020] S1 determines the optical diagnostic method for image acquisition, adjusts the position and height of the camera so that the camera can capture the complete spray field, thereby recording the complete oil jet morphology;

[0021] S2 sets spray parameters such as injection pulse width, injection quantity, pressure, and injection frequency based on a preset scheme, enabling the ECU controller to control fuel injection based on the input values.

[0022] S3 starts the first circulation pump to lower the fuel temperature and inject low-temperature fuel;

[0023] S4 lowers the fuel temperature while regulating the temperature, air pressure, and humidity levels inside the spray chamber.

[0024] The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronization trigger to activate the high-speed camera, enabling the high-speed camera to capture image information of the entire fuel spray process.

[0025] The spray image information acquired by S6 can be processed to obtain the quantified values ​​of the spray cone angle and spray penetration distance.

[0026] If the test needs to be continued, S7 resets the test parameters, determines the temperature at the nozzle, and repeats S2 to S6.

[0027] Since the fuel is cooled using external circulating coolant, the S3 process also includes the following steps:

[0028] (1) The coolant in the first circulation pump circulates through the sleeve to reduce the internal fuel temperature. The coolant circulates and cools at the same time, resulting in a better cooling effect.

[0029] (2) Cut the nozzle 3-4mm from the tip and attach thermocouples to both the inside and outside of the nozzle end face to obtain the temperature. The temperature of the low-temperature fuel is calibrated by measuring the temperature difference between the inside and outside. Temperature calibration needs to be performed at least three times, and the average temperature difference should be taken.

[0030] (3) Attach the thermocouple to the outer surface of the nozzle to determine the internal fuel temperature after cooling, and then conduct a low-temperature fuel injection test.

[0031] Because the spray droplet region has a strong scattering and extinction effect on incident light, the liquid spray area appears dark and the background appears bright white in images captured using the backlighting technique. Therefore, the camera can capture a clear gas-liquid boundary, and the liquid spray structure parameters can be obtained after processing. S6 also includes image processing in MATLAB:

[0032] (1) First, import the spray oil jet images captured by the high-speed camera into the computer;

[0033] (2) Use the MATLAB image processing toolbox to perform operations such as contrast enhancement, filtering, threshold segmentation, and edge extraction on the spray image;

[0034] (3) The spray penetration distance is obtained through the coordinate method, that is, by using relevant function codes to extract the uppermost and lowermost image coordinates A(x1,y1) and B(x2,y2) in the oil jet region respectively. The penetration distance can be represented by the difference between the ordinates of point B and point A, as shown in the following formula:

[0035] L=(|y2-y1|)×k

[0036]

[0037] L is the spray penetration distance, and k is the actual distance represented by a unit pixel;

[0038] (4) The spray cone angle β is obtained by least squares linear fitting. Least squares fits the discrete pixels of the oil jet boundary, and uses these pixels to fit a straight line. Typically, its measurement results...

[0039] The result is related to the number of fitted pixels; the more pixels there are, the better the result reflects the true contour shape of the oil jet.

[0040] Furthermore, a sponge is placed at the tip of the nozzle, and the amount of fuel actually injected each time is measured by the increase in weight of the sponge.

[0041] Furthermore, spray particle size plays a crucial role in the fuel evaporation process and mixture formation. Two different semi-empirical formulas were used to calculate the spray Sauter Mean Diameter (SMD):

[0042] SMD1 = 23.9(Pj - Pc) -0.135 (ρa) 0.121 (gb) 0.131

[0043]

[0044] SMD = (SMD1 + SMD2) ÷ 2

[0045] Where: SMD1 is the estimated particle size based on the actual low-temperature fuel injection quantity, SMD2 is the estimated particle size based on the low-temperature cold start cylinder temperature, Pj is the injection pressure, Pc is the ambient pressure, ρa is the ambient air density, gb is the cycle injection quantity, Δp is the pressure difference between the injection pressure and the ambient pressure, and Ta is the ambient temperature. The SMD of diesel fuel is generally approximately 20–40 μm.

[0046] The beneficial effects of this invention are:

[0047] As can be seen from the above technical solution, the low-temperature fuel atomization quality testing system provided by this invention can lower the fuel temperature to -60℃, simulating the injection of low-temperature fuel into a spray chamber in a specific environment. It acquires the macroscopic characteristics of the spray using high-speed photography, calculates the Sauter mean diameter using empirical formulas, analyzes the atomization characteristics of the injected fuel, and evaluates the atomization quality of low-temperature fuel during cold starts. This invention can adjust the air pressure, temperature, and humidity within the environmental test chamber to simulate the in-cylinder thermal state at top dead center of compression in high-altitude cold regions, completing the test of low-temperature fuel atomization characteristics during cold starts. It provides a reliable experimental method for studying the fuel atomization of fuel in low-temperature environments during engine cold starts, deeply analyzing the impact of complex environments on engine cold starts, and thus seeking to improve engine cold-start performance. Attached Figure Description

[0048] The invention will be further described below with reference to the accompanying drawings.

[0049] Figure 1 This is a schematic diagram of the overall structure of the testing system of the present invention;

[0050] Figure 2 This is a schematic diagram of the composition of the testing system of the present invention;

[0051] Figure 3 This is a schematic diagram of the environmental test chamber of the present invention;

[0052] Figure 4 This is a flowchart of the low-temperature fuel atomization quality testing method of the present invention.

[0053] The attached figures are labeled as follows:

[0054] 1-Fuel tank, 2-High-pressure fuel pump, 3-Common rail, 4-Injector, 5-ECU controller, 6-First circulation pump, 7-Sleeve, 8-Thermometer, 9-Computer, 10-Optical platform, 11-Spray chamber, 12-Light source, 13-High-speed camera, 14-Humidifier, 15-Evaporator, 16-Second circulation pump, 17-Heating element, 18-Pressure sensor, 19-Temperature sensor, 20-Humidity sensor, 21-Thermocouple, 22-Synchronous trigger. Detailed Implementation

[0055] The technical solution of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0056] See Figures 1-3 A variable environment fuel atomization quality testing system mainly includes a high-pressure common rail injection system, a low-temperature refrigeration system, an image data acquisition system, an electronic control system, and a spray test chamber. The system specifically includes: a fuel tank 1, a high-pressure fuel pump 2, a common rail pipe 3, an injector 4, an ECU controller 5, a first circulation pump 6, a sleeve 7, a thermometer 8, a computer 9, an optical platform 10, a spray chamber 11, a light source 12, a high-speed camera 13, a humidifier 14, an air pump 15, a second circulation pump 16, a heating element 17, a pressure sensor 18, a temperature sensor 19, a humidity sensor 20, a thermocouple 21, and a synchronous trigger 22.

[0057] The cryogenic refrigeration system includes a first circulation pump 6, a sleeve 7, a thermocouple 21, and a temperature measuring instrument 8. Coolant circulates within the sleeve 7 cavity to lower the temperature of the fuel in the injector 4. The temperature measuring instrument 8 detects the temperature at the injector 4 nozzle via the thermocouple 21. The cryogenic refrigeration system lowers the fuel temperature by circulating coolant within the sleeve 8, and the thermocouple 21 attached to the front end of the injector 4 measures the reduced temperature. The front end of the injector 4 nozzle passes through the top window of the spray chamber 11, allowing fuel to be injected into the test chamber.

[0058] The electronic control system includes an ECU controller 5 and a synchronous trigger 22. The ECU controller 5 regulates the fuel pressure in the hydraulic system's oil circuit to ensure the normal operation of the hydraulic system, and controls the movement of the needle valve in the injector to inject fuel.

[0059] The image acquisition system includes a high-speed camera 13, a computer 9, and a light source 12. The high-speed camera 13 and the light source 12 are arranged coaxially, and the fuel spray image information is acquired by backlighting and transmitted to the computer 9.

[0060] The environmental test chamber includes a spray chamber 11, an air extraction pump 15, a humidifier 14, a second circulation pump 16, a heating element 17, an optical platform 10, and pressure sensors 18, temperature sensors 19, and humidity sensors 20. The spray chamber 11 is cuboid in shape and is positioned on the optical platform 10. The air extraction pump 15 and humidifier 14 are externally connected to the observation windows on both sides. A heating element 17, connected to the second circulation pump 16, is located at the bottom of the spray chamber 11, comprehensively regulating the air pressure, temperature, and humidity of the spray chamber 11. The sensors located in the spray chamber 11 monitor the air pressure, temperature, and humidity inside the chamber to determine the environmental parameters. During the environmental regulation process inside the spray chamber 11, the air extraction pump 15, in conjunction with the humidifier 14, changes the vacuum level and humidity value inside the chamber to simulate atmospheric pressure at different altitudes, reducing the oxygen content in the air. The heating element 17 circulates and heats the gas inside the chamber. Pressure sensor 18, temperature sensor 19, and humidity sensor 20 monitor changes in the cabin environment and feed the data back to the computer in real time. The cabin environment is repeatedly adjusted based on the thermal state of the cylinder during the engine cold start process.

[0061] Fuel injection is performed when the low-temperature fuel and low-temperature, low-pressure environment meet the test settings. The high-pressure low-temperature fuel injection process includes: fuel entering the high-pressure fuel pump 2 and being pressurized before being transmitted to the common rail 3; the ECU controller 5 precisely controls the fuel pressure in the common rail 3, so that the fuel flows into the injector 4 at a certain pressure. Simultaneously, excess fuel in the gap between the needle valve and the injector is depressurized through the return line and sent back to the fuel tank 1.

[0062] The spray image acquisition process includes: simultaneously, the ECU controller 5 sends a fuel injection electrical signal, and another electrical signal is transmitted to the synchronous trigger 22. The synchronous trigger 22 is connected to the high-speed camera 13, and fuel injection and spray image acquisition by the high-speed camera 13 are performed synchronously. The high-speed camera 13, the light source 12, and the front end of the injector 4 are arranged coaxially. The high-speed camera 13 captures spray images through the observation window on the front side panel of the test chamber 11, and the light source 12 is directly arranged on the inner wall of the rear panel of the spray chamber. The spray image information is acquired using a backlight optical diagnostic method. The acquired spray images are transmitted to the computer 9, and the spray cone angle and spray penetration distance can be obtained through MATLAB image processing.

[0063] See Figures 1-4 A method for testing fuel atomization quality in variable environments, comprising:

[0064] S1 determines the optical diagnostic method for image acquisition, adjusts the position and height of the camera so that the camera can capture the complete spray field, thereby recording the complete oil jet morphology;

[0065] S2 sets spray parameters such as injection pulse width, injection quantity, pressure, and injection frequency based on a preset scheme, enabling the ECU controller to control fuel injection based on the input values.

[0066] S3 starts the first circulation pump to lower the fuel temperature and inject low-temperature fuel;

[0067] S4 lowers the fuel temperature while regulating the temperature, air pressure, and humidity levels inside the spray chamber.

[0068] The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronization trigger to activate the high-speed camera, enabling the high-speed camera to capture image information of the entire fuel spray process.

[0069] The spray image information acquired by S6 can be processed to obtain the quantified values ​​of the spray cone angle and spray penetration distance.

[0070] If the test needs to be continued, S7 resets the test parameters, determines the temperature at the nozzle, and repeats S2 to S6.

[0071] Since the fuel is cooled using external circulating coolant, the S3 process also includes the following steps:

[0072] The coolant in the S31 first circulation pump circulates through the sleeve to reduce the internal fuel temperature. The coolant circulates and cools simultaneously, resulting in better cooling effect.

[0073] The S32 nozzle is cut off 3-4mm from the nozzle tip. Thermocouples are attached to both the inner and outer ends of the nozzle to obtain the temperature. The temperature of the low-temperature fuel is calibrated by measuring the temperature difference between the inner and outer ends. Temperature calibration must be performed at least three times, and the average temperature difference is taken.

[0074] S33 attaches a thermocouple to the outer surface of the nozzle to determine the internal fuel temperature after cooling, and then conducts a low-temperature fuel injection test.

[0075] Because the spray droplet region has a strong scattering and extinction effect on incident light, the liquid spray area appears dark and the background appears bright white in images captured using the backlighting technique. Therefore, the camera can capture a clear gas-liquid boundary, and the liquid spray structure parameters can be obtained after processing. S6 also includes image processing in MATLAB:

[0076] S61 first imports the images of the spray oil jets captured by the high-speed camera into the computer;

[0077] S62 uses the MATLAB Image Processing Toolbox to perform operations such as contrast enhancement, filtering, thresholding, and edge extraction on spray images;

[0078] The S63 spray penetration distance is obtained using a coordinate method. Specifically, the uppermost and lowermost image coordinates A(x1, y1) and B(x2, y2) in the oil jet region are extracted using relevant function codes. The penetration distance can be represented by the difference between the ordinates of points B and A, as shown in the following formula:

[0079] L=(|y2-y1|)×k

[0080]

[0081] L is the spray penetration distance, and k is the actual distance represented by a unit pixel;

[0082] The S64 spray cone angle β is obtained through least squares linear fitting. Least squares fits discrete pixels of the oil jet boundary, using these pixels to fit a straight line. The measurement result is usually related to the number of fitted pixels; the more pixels, the better it reflects the true contour shape of the oil jet.

[0083] S65 spray particle size plays a crucial role in the fuel evaporation process and mixture formation. The spray Sauter Mean Diameter (SMD) is calculated using two different semi-empirical formulas:

[0084] SMD1 = 23.9(Pj - Pc) -0.135 (ρa) 0.121 (gb) 0.131

[0085]

[0086] SMD = (SMD1 + SMD2) ÷ 2

[0087] in:

[0088] SMD1 estimates particle size based on actual low-temperature fuel injection volume;

[0089] SMD2 estimates particle size based on the cylinder temperature during cold starts in a low-temperature environment.

[0090] Pj is the injection pressure (given by ECU controller 5);

[0091] Pc represents the ambient pressure (measured by pressure sensor 18);

[0092] ρa represents the ambient air density, which is mainly affected by air temperature and altitude. At lower temperatures, humidity has little effect on air density and can be ignored. The gas constant is typically 8.314 J / (mol·K);

[0093] gb represents the cyclic fuel injection quantity (obtained through actual measurement);

[0094] Δp is the pressure difference between the injection pressure and the ambient pressure;

[0095] Ta is the ambient temperature (measured by temperature sensor 19).

[0096] The surface depth (SMD) of diesel fuel is generally around 20–40 μm. However, the low ambient temperature and air density inhibit the atomization and evaporation processes of the fuel spray.

[0097] The cyclic fuel injection quantity gb obtained by actual measurement can be obtained by placing a sponge at the front end of the nozzle, and measuring the actual amount of fuel injected each time by increasing the weight of the sponge.

Claims

1. A variable environment fuel atomization quality testing system, characterized in that, The testing system includes a high-pressure common rail injection system, an electronic control system, a cryogenic refrigeration system, an image data acquisition system, and an environmental test chamber; The high-pressure common rail injection system includes a fuel tank (1), a high-pressure fuel pump (2), a common rail (3) and an injector (4) connected in sequence. The fuel flows through the high-pressure fuel pump (2) to be pressurized and enters the common rail (3) and supplies the fuel to the injector (4). The cryogenic refrigeration system includes a first circulating pump (6), a sleeve (7), a thermocouple (21), and a thermometer (8). Coolant circulates in the cavity of the sleeve (7). The oil supply section of the injector (4) is fitted inside the sleeve (7). The thermometer (8) detects the temperature at the nozzle through the thermocouple (21) connected to it and located at the nozzle of the injector (4). The electronic control system includes an ECU controller (5) and a synchronous trigger (22) connected thereto. The ECU controller (5) adjusts the fuel pressure, and the fuel injector (4) transmits a synchronous signal to the synchronous trigger (22) while injecting fuel. The image data acquisition system includes a high-speed camera (13), a computer (9) and a light source (12). The high-speed camera (13) and the light source (12) are arranged on the same optical axis. The synchronous trigger (22) is connected to the high-speed camera (13) and triggers the high-speed camera (13). The high-speed camera (13) acquires fuel spray image information by backlighting and transmits the acquired image to the computer (9) connected to it. The environmental test chamber includes a spray chamber (11), an air pump (15), a humidifier (14), a second circulation pump (16), a heating tube (17), an optical platform (10), and a pressure sensor (18), a temperature sensor (19), and a humidity sensor (20). The spray chamber (11) is cuboid in shape and is arranged on the optical platform (10). The air pump (15) and the humidifier (14) are connected to the observation windows on the left and right sides of the spray chamber (11). The bottom of the spray chamber (11) is provided with a heating tube (17) connected to the second circulation pump (16). The pressure sensor (18), temperature sensor (19), and humidity sensor (20) are arranged inside the spray chamber (11). The spray chamber (11) is heated by the heating tube (17), the air density is reduced by the air pump (15) to reduce the oxygen content of the air, and the air humidity is controlled by the humidifier (14) to change the oxygen content.

2. The variable environment fuel atomization quality testing system according to claim 1, characterized in that: The spray chamber (11) is made of double-layered quartz glass on all sides and top, and observation windows are provided on all sides and top, with the observation window part being a single-layered quartz glass.

3. The variable environment fuel atomization quality testing system according to claim 1, characterized in that: The high-speed camera (13) is located on the front panel of the spray chamber (11), and the humidifier (14) and the air pump (15) are respectively arranged on the left and right side panels of the spray chamber (11).

4. The variable environment fuel atomization quality testing system according to claim 1, characterized in that: While the ECU controller (5) sends an injection electromagnetic signal to the injector (4), it also transmits another electrical signal to the high-speed camera (13) through the synchronous trigger (22), so as to realize the synchronous operation of fuel injection and high-speed camera (13) shooting.

5. A variable environment fuel atomization quality testing system according to any one of claims 1-4, characterized in that: The high-speed camera (13) and the light source (12) are respectively arranged on the front and rear plates of the spray chamber (11), so that the front ends of the nozzles of the high-speed camera (13), the light source (12) and the fuel injector (4) are coaxial and on the same horizontal line.

6. A test method for a variable environment fuel atomization quality testing system according to any one of claims 1-5, characterized in that, Includes the following steps: S1 determines the optical diagnostic method for image acquisition, adjusts the position and height of the camera so that the camera can capture the complete spray field, thereby recording the complete oil jet morphology; S2 sets spray parameters such as injection pulse width, injection quantity, pressure, and injection frequency based on a preset scheme, enabling the ECU controller to control fuel injection based on the input values. S3 starts the first circulation pump to lower the fuel temperature and inject low-temperature fuel; S4 lowers the fuel temperature while regulating the temperature, air pressure, and humidity levels inside the spray chamber. The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronization trigger to activate the high-speed camera, enabling the high-speed camera to capture image information of the entire fuel spray process. The spray image information acquired by S6 can be processed to obtain the quantized values ​​of the spray cone angle and spray penetration distance; If the test needs to be continued, S7 resets the test parameters, determines the temperature at the nozzle, and repeats S2 to S6.

7. The test method according to claim 6, characterized in that, S3 further includes: (1) Cut off the nozzle 3-4mm from the tip. Attach thermocouples to the inside and outside of the nozzle to obtain the temperature. Use the temperature difference between the inside and outside to calibrate the temperature of the low-temperature fuel. Temperature calibration needs to be performed at least three times and the average temperature difference should be taken. (2) Attach the thermocouple to the outer surface of the nozzle to determine the internal fuel temperature after cooling, and then conduct a low-temperature fuel injection test.

8. The test method according to claim 6, characterized in that, S6 also includes: (1) First, import the spray oil jet images captured by the high-speed camera into the computer; (2) Use the MATLAB image processing toolbox to perform contrast enhancement, filtering, thresholding and edge extraction on the spray image; (3) The spray penetration distance is obtained by the coordinate method, that is, by using the relevant function code to extract the uppermost and lowermost image coordinates A(x1,y1) and B(x2,y2) in the oil jet region respectively. The penetration distance is represented by the difference between the ordinates of point B and point A, as shown in the following formula: ; ； Where: L is the spray penetration distance, and k is the actual distance represented by a unit pixel; (4) Spray cone angle It is obtained by least squares linear fitting, which fits the discrete pixels of the oil jet boundary and uses these pixels to fit the straight line.

9. The test method according to any one of claims 6-8, characterized in that: This also includes calculating the spray Sauter Mean Diameter (SMD) using two different semi-empirical formulas: ； ； ； in: SMD1 estimates particle size based on actual low-temperature fuel injection volume; SMD2 estimates particle size based on the cylinder temperature during cold starts in a low-temperature environment. Pj is the injection pressure; Pc is the ambient pressure. For ambient air density, ; This refers to the amount of fuel injected during the cycle. The pressure difference between the injection pressure and the ambient pressure; The ambient temperature.

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