Matching design of the minimum intake preheating power for diesel engine under cold start conditions

In order to improve the starting ability of diesel engine at low temperature and high altitude, considering the heat dissipation along the intake pipe downstream of the flame glow plug, a design method of matching the minimum intake preheating power of diesel engine with environmental adaptability was proposed. Firstly, based on the critical ignition conditions of diesel spray, the minimum intake air temperature requirements at different engine speeds in different environments were obtained; Secondly, the theoretical heat dissipation model of the inlet pipe downstream of the flame glow plug is established to obtain the minimum preheating temperature of the flame glow plug in different environments; Finally, the minimum intake preheating power of diesel engine in different environments is calculated. Based on the above methods, the minimum intake preheating power demand of a V-type 6-cylinder diesel engine was calculated and verified by experiments, and the map of Intake Preheating power of the diesel engine with the change of atmospheric temperature and altitude was obtained. The calculation results show that the diesel engine can start successfully without intake air preheating at 0 ℃ and 300 R/min. At the same ambient temperature, the intake preheating power decreases with the increase of altitude; At the same altitude, the preheating power of intake air generally decreases with the increase of ambient temperature, but the preheating power of intake air at -20 ℃ is higher than -30 ℃ due to the use of heater assisted starting and the reduction of heat loss along the intake port when the ambient temperature is lower than -20 ℃. The test results show that the intake preheating can greatly improve the thermal state in the cylinder and reduce the misfire rate in the cylinder. At the same time, the sensitivity of the in cylinder injection strategy to the in cylinder ignition process is reduced after the intake air preheating. Under the conditions of plain -43 ℃ and 5000m altitude of 20 ℃, the diesel engine can start successfully by using the minimum intake preheating power matching design method proposed in this paper.