Variable environment fuel oil atomization quality test system and test method

Abstract

The invention discloses a variable environment fuel oil atomization quality test system and test method. The system comprises a high pressure common rail injection system, a low temperature refrigeration system, an electronic control system, an image data acquisition system and an environment test chamber. The low-temperature refrigerating system reduces the temperature of fuel oil in the oil injector through convective heat exchange; the environment test cabin simulates the environment air pressure, temperature and humidity in the cabin according to the actual environment parameters in the cylinder in the engine operation process; the image data acquisition system acquires spray image information of low-temperature fuel oil in a variable environment and performs image processing, and by actually measuring the circulating oil injection quantity during fuel oil injection, the Sott average diameter is calculated according to different empirical formulas, and the fuel oil atomization characteristics are comprehensively analyzed. The invention provides a reliable experimental means for researching the fuel oil atomization condition of the fuel oil in a low-temperature state in a low-temperature environment in the cold start process of the engine, deeply analyzing the influence of a complex environment on the cold start of the engine, and seeking to improve the cold start performance of the engine.

Description

Technical Field

[0001] The invention relates to the technical field of engine environmental adaptability, and in particular to a variable environment fuel atomization quality testing system and a testing method. Background Art

[0002] Engines are widely used in automobiles, construction machinery, agricultural machinery, ships, drones, military equipment and other fields due to their high thermal efficiency, simple structure and reliable operation. In northern my country, it is hot and rainy in summer, cold and dry in winter, with four distinct seasons. The changeable climate places increasingly stringent requirements on engines in the mechanical field. Environmental factors affect the power and economy of the engine, and will affect the engine mileage and life during the cold start process. In particular, the northwestern region is located in a plateau cold zone, and it is difficult to cold start the engine. Among them, poor fuel atomization and incomplete combustion process are important reasons. Improving fuel spray combustion can appropriately increase the probability of successful cold start of the engine.

[0003] During the cold start of the engine in a low temperature environment or a high altitude environment, the thermal state in the cylinder at the compression top dead center is much lower than the normal operating condition due to the low intake temperature and density, the heat transfer loss caused by the low temperature wall, and the large clearance between the piston, piston ring and cylinder liner in the cold state. The poor thermal state in the cylinder inhibits the atomization and evaporation process of the fuel spray, prolongs the preparation time of the combustible mixture, and may cause problems such as misfire and cold start failure. In addition, the fuel spray is limited by the limited space in the combustion chamber, and the additional turbulence caused by the interaction between the spray and the combustion chamber wall directly affects the atomization of the fuel spray. In summary, the atomization effect of the fuel directly affects the starting and efficiency of the engine, so measuring and evaluating the atomization quality of the fuel is also a crucial link.

[0004] The fuel atomization characteristics refer to the atomization and spatial distribution of the 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 first exists in the form of a liquid column, and then the liquid column begins to split into small droplets. The more droplets the liquid column splits, the smaller the droplet diameter, the better the atomization effect, which is conducive to the formation of a combustible mixture.

[0005] Under the change of ambient temperature, pressure and humidity, the fuel viscosity and atomization will show different states, and the intake temperature and oxygen content will also change. In order to test the fuel atomization characteristics of the engine in a changing environment, measure the atomization quality of low-temperature fuel, develop an environmental test chamber and a low-temperature fuel preparation device, study the fuel atomization of the low-temperature fuel in the low-temperature environment during the cold start process of the engine, and deeply analyze the impact of complex environments on the cold start of the engine, so as to improve the cold start performance of the engine. Summary of the invention

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

[0007] The technical solution adopted by the present invention is:

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

[0009] The high-pressure common rail injection system comprises a fuel tank 1, a high-pressure fuel pump 2, a common rail pipe 3 and a fuel injector 4 which are connected to each other in sequence. The fuel flows through the high-pressure fuel pump 2 to increase the pressure and enter the common rail pipe 3 and provide the fuel to the fuel injector 4.

[0010] The low temperature refrigeration system comprises a first circulation pump 6, a sleeve 7, a thermocouple 21 and a temperature measuring instrument 8. The coolant circulates in the cavity of the sleeve 7. The oil supply section of the fuel injector 4 is sleeved in the sleeve 7. The temperature measuring instrument 8 detects the temperature at the nozzle of the fuel injector 4 through the thermocouple 21 connected thereto and arranged at the nozzle of the fuel injector 4.

[0011] The electronic control system includes an ECU controller 5 and a synchronization trigger 22 connected thereto. The ECU controller 5 adjusts the pressure of the fuel, and the injector 4 transmits a synchronization signal to the synchronization trigger 22 while injecting the 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 synchronization trigger 22 is connected to the high-speed camera 13 and triggers the high-speed camera 13. The high-speed camera 13 collects fuel spray image information by backlight method and transmits the collected image to the computer 9 connected thereto.

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

[0014] Furthermore, the spray chamber 11 is made of double-layer quartz glass on the sides and top, and observation windows are arranged on the sides and top, and the observation window part is made of single-layer quartz glass.

[0015] Furthermore, 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.

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

[0017] Furthermore, while the ECU controller 5 sends an injection electromagnetic signal to the injector 4 , it transmits another electrical signal to the high-speed camera 13 through the synchronization trigger 22 , so that the fuel injection and the shooting of the high-speed camera 13 are synchronized.

[0018] Furthermore, the high-speed camera 13 and the light source 12 are arranged on the front and rear plates of the spray chamber 11, respectively, so that the high-speed camera 13, the light source 12 and the front end of the nozzle of the injector 4 are coaxial and located on the same horizontal line. The intensity of the light source and the camera shooting speed, resolution and other parameters are adjusted to collect a spray image with a clear outline. The computer 9 collects image information based on the entire process of fuel spray, processes the image to obtain the quantitative values ​​of the macroscopic characteristic parameters of the fuel spray, the spray cone angle and the spray penetration distance.

[0019] A test method using a variable environment fuel atomization quality test system, comprising:

[0020] S1: Determine the optical diagnostic method for image acquisition, adjust the position and height of the camera so that the camera can capture the complete spray field and record the complete oil beam morphology;

[0021] S2 sets the spray parameters such as injection pulse width, injection amount, pressure and injection frequency based on the preset scheme, so that the ECU controller can control the fuel injection based on the input value;

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

[0023] S4 lowers the fuel temperature while adjusting the temperature, air pressure and humidity in the spray cabin;

[0024] The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronous trigger to start the high-speed camera, so that the high-speed camera can collect image information of the entire process of fuel spray;

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

[0026] If the test needs to be continued in S7, the temperature at the nozzle is determined by resetting the test parameters and repeating S2 to S6.

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

[0028] (1) The coolant in the first circulation pump circulates through the sleeve to reduce the internal fuel temperature. The coolant refrigerates while circulating, and the refrigeration effect is better;

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

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

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

[0032] (1) First, the spray oil beam image taken by the high-speed camera is imported into the computer;

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

[0034] (3) The spray penetration distance is obtained by the coordinate method, that is, the upper and lower image coordinates A (x1, y1) and B (x2, y2) in the oil beam area are extracted respectively using the relevant function code. The penetration distance can be expressed 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, k is the actual distance represented by the unit pixel;

[0038] (4) The spray cone angle β is obtained by the least squares method of straight line fitting. The least squares method is to fit the discrete pixel points of the oil beam boundary and use these pixel points to fit the straight line.

[0039] The result is related to the number of fitting pixels. The larger the number, the better it can reflect the true contour shape of the oil beam.

[0040] Furthermore, a sponge is placed at the front end of the nozzle, and the actual amount of fuel sprayed during each injection is measured by the weight gain of the sponge.

[0041] Furthermore, the spray particle size plays an important role in the evaporation process of the fuel and the formation of the mixture. Two different semi-empirical formulas are used to calculate the spray mean diameter SMD:

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

[0043]

[0044] SMD=(SMD1+SMD2)÷2

[0045] Among them: SMD1 is the particle size estimated based on the actual low-temperature fuel injection amount, SMD2 is the particle size estimated based on the low-temperature environment 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 amount, Δp is the pressure difference between the injection pressure and the ambient pressure, and Ta is the ambient temperature. The SMD of general diesel is about 20 to 40μm.

[0046] Beneficial effects of the present invention:

[0047] It can be seen from the above technical scheme that the low-temperature fuel atomization quality test system provided by the present invention can reduce the fuel temperature to -60°C, simulate the injection of low-temperature fuel into a spray chamber in a specific environment, collect the macroscopic characteristics of the spray by high-speed photography, calculate the Sauter mean diameter using an empirical formula, analyze the atomization characteristics of the injected fuel, and evaluate the atomization quality of the low-temperature fuel during the cold start process. The present invention can adjust the air pressure, temperature and humidity in the environmental test chamber, simulate the thermal state of the cylinder at the compression top dead point in a high-altitude cold zone environment, complete the test of the atomization characteristics of the low-temperature fuel during the cold start process, and provide a reliable experimental means for studying the fuel atomization of the fuel in the low-temperature state during the cold start process of the engine in a low-temperature environment, and deeply analyzing the influence of the complex environment on the cold start of the engine, thereby seeking to improve the cold start performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention is further described below in conjunction with the accompanying drawings

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

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

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

[0052] Figure 4 The figure is a flow chart of the low-temperature fuel atomization quality testing method of the present invention.

[0053] The reference numerals in the figure are:

[0054] 1- fuel tank, 2- high pressure oil pump, 3- common rail pipe, 4- injector, 5- ECU controller, 6- first circulation pump, 7- sleeve, 8- temperature meter, 9- computer, 10- optical platform, 11- spray cabin, 12- light source, 13- high speed camera, 14- humidifier, 15- vacuum pump, 16- second circulation pump, 17- heating pipe, 18- pressure sensor, 19- temperature sensor, 20- humidity sensor, 21- thermocouple, 22- synchronization trigger. DETAILED DESCRIPTION

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

[0056] See also Figure 1-Figure 3 A variable environment fuel atomization quality test 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 temperature meter 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 tube 17, a pressure sensor 18, a temperature sensor 19, a humidity sensor 20, a thermocouple 21 and a synchronous trigger 22.

[0057] The low temperature refrigeration system includes a first circulation pump 6, a sleeve 7, a thermocouple 21 and a thermometer 8. The coolant circulates in the sleeve 7 cavity to reduce the temperature of the fuel in the injector 4, and the thermometer 8 detects the temperature at the nozzle of the injector 4 through the thermocouple 21. The low temperature refrigeration system reduces the temperature of the fuel by circulating the coolant in the sleeve 8, and measures the reduced temperature through the thermocouple 21 attached to the front end of the injector nozzle 4. The front end of the injector nozzle 4 passes through the top window of the spray chamber 11, so that the fuel is sprayed into the test chamber.

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

[0059] The image acquisition system includes a high-speed camera 13, a computer 9 and a light source 12. The high-speed camera 13 is coaxially arranged with the light source 12, and acquires fuel spray image information by a backlight method and transmits it to the computer 9.

[0060] The environmental test chamber includes a spray chamber 11, an air pump 15, a humidifier 14, a second circulating pump 16, a heating pipe 17, an optical platform 10, a pressure sensor 18, a temperature sensor 19, and a humidity sensor 20. The spray chamber 11 is in a cubic shape and is arranged on the optical platform 10. The air pump 15 and the humidifier 14 are externally connected to the observation windows on the left and right sides. A heating pipe 17 connected to the second circulating pump 16 is provided at the bottom of the spray chamber 11 to comprehensively adjust the air pressure, temperature and humidity of the spray chamber 11. The sensors arranged in the spray chamber 11 are responsible for monitoring the air pressure, temperature and humidity of the air in the chamber and determining the environmental parameters in the chamber. In the internal environment adjustment process of the spray chamber 11, the air pump 15 cooperates with the humidifier 14 to change the vacuum and humidity values ​​in the chamber, simulate the atmospheric pressure at different altitudes, reduce the oxygen content in the air, and the heating pipe 17 circulates and heats the gas temperature in the chamber. The pressure sensor 18, the temperature sensor 19, and the humidity sensor 20 respectively monitor changes in the cabin environment and feed back the data to the computer in real time, repeatedly adjusting the cabin environment according to the thermal state in the cylinder during the engine cold start process.

[0061] When the low-temperature fuel and the low-temperature and low-pressure environment meet the test setting requirements, fuel injection is performed. The high-pressure and low-temperature fuel injection process includes: the fuel enters the high-pressure fuel pump 2 and is then transferred to the common rail pipe 3 after being pressurized, and the ECU controller 5 accurately controls the fuel pressure in the common rail pipe 3 so that the fuel flows into the injector 4 at a certain pressure. When the fuel is injected, the excess fuel in the gap between the needle valve and the injector is depressurized from the return oil pipeline and then transferred back to the fuel tank 1.

[0062] The spray image acquisition process includes: while the ECU controller 5 sends out an electrical signal for fuel injection, another electrical signal is transmitted to the synchronization trigger 22, the synchronization trigger 22 is connected to the high-speed camera 13, and the fuel injection and the collection of the spray image 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 shoots the spray image through the observation window of the front side plate of the test chamber 11, the light source 12 is directly arranged on the inner wall surface of the rear plate of the spray chamber, and the backlight optical diagnosis method is used to collect the spray image information. The collected spray image is transmitted to the computer 9, and the quantitative values ​​of the spray cone angle and the spray penetration distance can be obtained through MATLAB image processing.

[0063] See also Figure 1-Figure 4 , a variable environment fuel atomization quality test method, comprising:

[0064] S1: Determine the optical diagnostic method for image acquisition, adjust the position and height of the camera so that the camera can capture the complete spray field and record the complete oil beam morphology;

[0065] S2 sets the spray parameters such as injection pulse width, injection amount, pressure and injection frequency based on the preset scheme, so that the ECU controller can control the fuel injection based on the input value;

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

[0067] S4 lowers the fuel temperature while adjusting the temperature, air pressure and humidity in the spray cabin;

[0068] The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronous trigger to start the high-speed camera, so that the high-speed camera can collect image information of the entire process of fuel spray;

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

[0070] If the test needs to be continued in S7, the temperature at the nozzle is determined by resetting the test parameters and repeating S2 to S6.

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

[0072] The coolant in the first circulation pump of S31 circulates through the sleeve to reduce the internal fuel temperature. The coolant refrigerates while circulating, and the refrigeration effect is better;

[0073] S32 is cut off at 3-4mm from the front end of the nozzle, and thermocouples are attached inside and outside the end face to obtain the temperature. The temperature of the low-temperature fuel is calibrated by the temperature difference between the inside and outside. The temperature calibration needs to be performed at least three times, and the average temperature difference is taken;

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

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

[0076] S61 first imports the spray oil beam image taken by the high-speed camera into the computer;

[0077] S62 uses MATLAB image processing toolbox to perform contrast enhancement, filtering, threshold segmentation, edge extraction and other operations on the spray image;

[0078] The S63 spray penetration distance is obtained by the coordinate method, that is, the upper and lower image coordinates A(x1, y1) and B(x2, y2) in the oil beam area are extracted respectively by using the relevant function code. The penetration distance can be expressed by the difference between the ordinates of point B and point A, as shown in the following formula:

[0079] L=(|y2-y1|)×k

[0080]

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

[0082] The S64 spray cone angle β is obtained by least squares linear fitting. The least squares method is to fit the discrete pixel points of the oil beam boundary and fit the straight line with these pixel points. Usually, the measurement result is related to the number of fitting pixel points. The more the number, the more it can reflect the true contour shape of the oil beam.

[0083] The S65 spray particle size plays an important role in the evaporation process of the fuel and the formation of the mixture. Two different semi-empirical formulas are used to calculate the spray mean diameter SMD:

[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 the particle size based on the actual low-temperature fuel injection amount;

[0089] SMD2 estimates the particle size based on the in-cylinder temperature during cold start in low temperature environment;

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

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

[0092] ρa is the ambient air density, where ρa is mainly affected by temperature and altitude. When the temperature is low, humidity has little effect on air density and can be ignored. The value of the gas constant is usually 8.314 J / (mol·K);

[0093] gb is the cycle injection amount (actually measured);

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

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

[0096] The SMD of general diesel is about 20 to 40 μm, but the ambient temperature and air density are low, which inhibits the atomization and evaporation process of the fuel spray.

[0097] The cyclic fuel injection amount 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 sprayed during each injection as the cyclic fuel injection amount through the weight increase of the sponge.

Claims

1. A variable environment fuel atomization quality testing system, characterized in that: The test 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 comprises a fuel tank (1), a high-pressure oil pump (2), a common rail pipe (3) and a fuel injector (4) which are connected to each other in sequence, and the fuel flows through the high-pressure oil pump (2) to increase the pressure and enter the common rail pipe (3) and supply the fuel to the fuel injector (4); The low-temperature refrigeration system comprises a first circulation pump (6), a sleeve (7), a thermocouple (21) and a temperature measuring instrument (8); a coolant circulates in the cavity of the sleeve (7); the oil supply section of the fuel injector (4) is sleeved in the sleeve (7); and the temperature measuring instrument (8) detects the temperature at the nozzle of the fuel injector (4) through a thermocouple (21) connected thereto and arranged at the nozzle of the fuel injector (4); The electronic control system comprises an ECU controller (5) and a synchronization trigger (22) connected thereto, wherein the ECU controller (5) adjusts the pressure of the fuel, and the fuel injector (4) transmits a synchronization signal to the synchronization trigger (22) while injecting the fuel; The image acquisition system comprises 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; a synchronization 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 a backlight method and transmits the acquired image to the computer (9) connected thereto; The environmental test chamber comprises a spray chamber (11), an air extraction pump (15), a humidifier (14), a second circulation pump (16), a heating pipe (17), an optical platform (10), a pressure sensor (18), a temperature sensor (19), and a humidity sensor (20); the spray chamber (11) is in a square shape and is arranged on the optical platform (10), and is externally connected to the air extraction pump (15) and the humidifier (14) at the observation windows arranged on the left and right sides of the spray chamber (11); a heating pipe (17) connected to the second circulation pump (16) is arranged at the bottom of the spray chamber (11); and the pressure sensor (18), the temperature sensor (19), and the humidity sensor (20) are arranged in the spray chamber (11).

2. A variable environment fuel atomization quality testing system according to claim 1, characterized in that: The spray chamber (11) is made of double-layer quartz glass on the periphery and the top, and observation windows are arranged on the periphery and the top, and the observation window portion is made of single-layer quartz glass.

3. The variable environment fuel atomization quality testing system according to claim 1, characterized in that: The spray chamber (11) is heated by a heating pipe (17), the air density is reduced by an air pump (15) to reduce the oxygen content of the air, and the air humidity is controlled by a humidifier (14) to change the oxygen content.

4. 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 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).

5. The variable environment fuel atomization quality testing system according to claim 1, characterized in that: The ECU controller (5) sends a fuel injection electromagnetic signal to the fuel injector (4) and transmits another electrical signal to the high-speed camera (13) through a synchronization trigger (22), thereby achieving synchronization of fuel injection and shooting by the high-speed camera (13).

6. A variable environment fuel atomization quality testing system according to any one of claims 1 to 5, 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 high-speed camera (13), the light source (12) and the front end of the nozzle of the injector (4) are coaxial and located on the same horizontal line.

7. A method for testing a variable environment fuel atomization quality testing system according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Determine the optical diagnostic method for image acquisition, adjust the position and height of the camera so that the camera can capture the complete spray field and record the complete oil beam morphology; S2 sets the spray parameters such as injection pulse width, injection amount, pressure and injection frequency based on the preset scheme, so that the ECU controller can control the fuel injection based on the input value; S3 starts the first circulation pump to lower the fuel temperature and inject low-temperature fuel; S4 lowers the fuel temperature while adjusting the temperature, air pressure and humidity in the spray cabin; The S5 ECU sends a fuel injection signal, and another signal is transmitted to the synchronous trigger to start the high-speed camera, so that the high-speed camera can collect image information of the entire process of fuel spray; The spray image information collected by S6 can be processed to obtain the quantitative values ​​of the spray cone angle and spray penetration distance; If the test needs to be continued in S7, the temperature at the nozzle is determined by resetting the test parameters and repeating S2 to S6.

8. A variable environment fuel atomization quality testing method according to claim 7, characterized in that: The S3 further includes: (1) Cut off the nozzle 3-4 mm from the front end, attach thermocouples inside and outside the end face to obtain the temperature, and calibrate the temperature of the low-temperature fuel by the temperature difference between the inside and outside. The temperature calibration needs to be performed at least three times, and the average temperature difference is taken; (2) A thermocouple is attached to the outer surface of the nozzle to determine the internal fuel temperature after cooling, and then a low-temperature fuel injection test is performed.

9. A variable environment fuel atomization quality testing method according to claim 7, characterized in that: The S6 also includes: (1) First, the spray oil beam image taken by the high-speed camera is imported into the computer; (2) Use MATLAB image processing toolbox to perform contrast enhancement, filtering, threshold segmentation and edge extraction on the spray image; (3) The spray penetration distance is obtained by the coordinate method, that is, the upper and lower image coordinates A (x1, y1) and B (x2, y2) in the oil beam area are extracted respectively using the relevant function code. The penetration distance is expressed by the difference between the ordinates of point B and point A, as shown in the following formula: L=(|y2-y1|)×k Where: L is the spray penetration distance, k is the actual distance represented by the unit pixel; (4) The spray cone angle β is obtained by the least squares method of straight line fitting. The least squares method fits the discrete pixel points of the oil beam boundary and then fits the straight line based on these pixel points.

10. A variable environment fuel atomization quality testing method according to any one of claims 7 to 9, characterized in that: It also includes the calculation of the spray Sauter mean diameter (SMD) using two different semi-empirical formulas: SMD=(SMD1+SMD2)÷2 in: SMD1 estimates the particle size based on the actual low-temperature fuel injection amount; SMD2 estimates the particle size based on the in-cylinder temperature during cold start in low temperature environment; Pj is the injection pressure; Pc is the ambient pressure; ρa is the ambient air density, gb is the cycle injection amount; Δp is the pressure difference between the injection pressure and the ambient pressure; Ta is the ambient temperature.

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