Effect of Inlet Air Heating on Start Characteristics of a Common-Rail Diesel Engine in High Altitude Environment

Cold starting test of a high pressure common rail diesel engine was conducted on an engine test bench simulating plateau environment with high altitudes and low temperature. A comprehensive study of cold starting and idling performance was investigated under plateau ambient temperature of-35°C to-10°C and altitude ranged from 2km to 4km. Results show that, without inlet air heating, during engine starting up under different altitude at-10°C, average inlet temperature and pressure can drop slightly and idling rotating speed exhibits strong fluctuation. By heating up inlet air for 60 seconds, the inlet temperature shows statistically linear growing trend in the first 8 heating seconds, during which period averaged inlet temperature rises to 12.4°C, thus obviously lifting up intake temperature, improving engine starting up performance and reducing rotating speed fluctuation. At high altitude and cold plateau conditions, by prolonging the air heating time solely has limited effects on reducing engine starting up time or improving cold starting performance, nor can rotating speed fluctuation been effectively reduced. When ambient temperature reaches-30°C, by heating up inlet air for the same specified time interval, an average of temperature rise of 2.4°C can be obtained for altitude step increase of 1 kilometer, but cold starting up performance has not been therefore significantly improved.