Diesel engine starts stably under extreme conditions of high altitude and low ambient temperature, which is of great significance to national economic development, national defense force and user safety. However, there are few studies on cold start performance and transient emission of diesel engines with ambient temperature below 0°C and altitude above 2000m. A simulation test system for high altitude and low temperature cold start of diesel engine is established in this paper. The cold start-up of a high-pressure common rail turbocharged heavy diesel engine discharged from the fifth stage in China at altitudes of 0m, 3000m and 4000m at 10°C, 0°C, -10°C and -20°C is studied. The ignition mechanism of diesel engine at high altitude and low temperature is put forward. The combustion characteristics of diesel engine at variable altitude and ambient temperature were studied.
Conclusion: The cold start performance of diesel engine will deteriorate with the increase of altitude and the decrease of ambient temperature. When the ambient temperature is below -10°C and the altitude is above 3000m, the engine has obvious cold start difficulty or even failure, and the cold start speed increase and idle speed are obvious, and the speed fluctuation is obvious. The startup can still be successful when the altitude is above 3000m. Start failure at an altitude of 4000m and an ambient temperature of -20°C, the single peak and misfire appear one after another, and the engine speed fluctuates sharply and cannot be increased. The peak cylinder pressure and the average effective pressure of the diesel engine during the cold start-up period gradually increase with the decrease of the ambient temperature, and gradually decrease with the increase of the altitude. The maximum instantaneous heat release rate and the phase of the combustion start point gradually increase.