The ambient temperature during the test was selected at four points, ie, 5°C, 0°C, -5°C, and -10°C, and the test was performed in accordance with standard [3]. In order to ensure the reliability of the test data, this test uses the TEAC tape recorder to record the speed signal of the starting process, the pressure signal of each cylinder, the starting current and voltage signal, and the exhaust temperature signal. Then use the AVL646 digital analyzer to process and analyze each signal. The entire process of starting the tester was monitored with an SC16 light oscilloscope. In order to make the test results more in line with the actual situation, the accessories of the vehicle diesel engine are not removed. In the test, the diesel engine used Lanzhou refinery to produce QF-CD, SAE10W/30 lubricants, antifreeze was ethylene glycol and ten water; specific gravity was 1.073g/cm3, and the freezing point was -42°C. The analysis of the cold start process is the change of the starter speed of the tester with time at different ambient temperatures, which is an index of cold start performance. The results show that the tester can start smoothly at +5°C and 0°C, but the start time and the stable operation time at +5°C are smaller than those at 0°C, which proves that the tester is at ambient temperature greater than 0 degrees. At °C, starting performance is good without any measures. Schematic diagram of the test setup +5°C diesel engine starting process 0°C diesel engine starting process -5°C diesel engine starting process -10°C diesel engine starting process When the ambient temperature is reduced to -5°C, the start can be successful. However, the stable operation time was significantly increased (164s). The results showed that if the testing machine does not take auxiliary measures at this time, the cold start performance deteriorates. When the ambient temperature is further reduced to -10°C, the start-up process fails, as shown. This indicates that the starter boundary temperature of the tester is -5°C. Dynamic Analysis of Cylinder Pressure during Cold Start From the cold start test, it was found that when the vehicle diesel engine is started in the boundary state, it is an extremely unstable process. Therefore, the pressure changes of each cylinder of the diesel engine must be dynamically analyzed and the diesel cold start process must be thoroughly discussed. In order to highlight the instability of the combustion of each cylinder during the low temperature starting of the diesel engine, the start-up process test at room temperature (24°C) was first performed, which is the peak pressure of the first cylinder cycle. As a result, it was found that the peak pressure of the second, third, and fourth cylinders during the entire start-up process was almost the same as that of the first cylinder, and each work cycle had a pressure increase phenomenon, and each work cycle was ignited. No fire has ever occurred. Moreover, the peaks of the combustion pressure in each cycle are almost equal. About 66bar. This shows that after careful adjustment of the 4D105 diesel engine cylinder compression conditions, fuel conditions are basically the same. 24 °C each cylinder per working cycle pressure peak -5 °C 1st cylinder cycle pressure peak -5 °C 2nd cylinder cycle pressure peak 0-5 °C 3rd cylinder cycle pressure peak ~ 1 is boundary state temperature -5 o'clock, each The change of the peak pressure of each cycle of the cylinder during the start-up process showed that it was obviously different from the normal temperature state, and the difference between the ignition conditions of each cylinder was relatively large. The first cylinder fired at the 38th working cycle and then there was a fire phenomenon after a period of time. After the intermittent fire cycle, continuous ignition occurred after 69 cycles. Although the second and third cylinders had a fire, there was no continuous fire phenomenon during the starting time, and the pressure peak size was also different. The first cylinder never had a fire during the start-up time. This shows that: At -5 °C, the speed change of the tester during the start-up time is relatively large. The fundamental reason is that each cylinder intermittently fires at the peak temperature of each cycle of the 1-5 °C fourth cylinder. After a steady operating time of 164 seconds, the final tester started successfully. From the analysis of the pressure peaks of each cylinder, the reason for the successful start of the tester was that the fourth cylinder had a continuous ignition phenomenon within the start, thus driving the other three cylinders to move through the fuel, Due to the effect of heat accumulation, each cylinder fires in succession until it reaches stable operation. Although the working conditions of the four cylinders of the 4D105 diesel engine are the same, the first cylinder continuously fires in the low temperature condition and the first cylinder does not catch any fire. The reason is that after the diesel engine antifreeze is cooled by the diesel engine cooling system, it first enters the first cylinder so that the temperature of the first cylinder antifreeze is low and the temperature in the cylinder is low, so it is not easy to ignite. The fourth cylinder of antifreeze is heated by the first three cylinders and enters the fourth cylinder to flow out of the water outlet. The temperature of the antifreeze is increased, resulting in a higher temperature of the fourth cylinder, which is conducive to ignition. This phenomenon has guiding significance for optimizing diesel engine design and improving the cold start process. Conclusion The cold start process of diesel engine is very different from the normal temperature start process. During the cold start, the combustion in each cylinder is extremely unstable and there is a misfire phenomenon. To make the cold start of a multi-cylinder diesel engine successful, at least one cylinder must continuously fire during the start-up time. During the start-up time, there is a large difference in the magnitude of pressure peaks of intermittent fires, which makes the diesel engine extremely unstable and may cause cold start failure. Cap and Tubular Embroidery Machine Hat Embroidery Machine,Flat Embroidery Machine,Computer Embroidery Machine Baolun Computerized Embroidery Machinery Co., Ltd. , http://www.cnembroiderymachine.com