辅助加温对柴油机变海拔起动性能的影响

Effects of Auxiliary Heating Strategy on Cold Start Performance of Diesel Engine During Cold Start at Different Altitudes

摘要:

利用高原环境模拟试验台，以一台压缩比为14.25的增压直喷柴油机为试验对象，在0、3 000、4 500 m海拔条件下进行了冷态（20 ℃）、30、40、50、60 ℃不同冷却液辅助加温起动、以及进气加热辅助起动试验，研究不同海拔条件下冷却液加温和进气加热辅助措施对柴油机起动性能的影响.结果表明：随着海拔的升高，低压缩比柴油机起动升速期出现做功能力差的子孕峰循环和做负功的失燃循环，降低了燃烧做功能力，升速期时间迅速延长，起动性能恶化.冷却液加温和进气加热可明显减少升速期子孕峰和失燃循环个数，恢复燃烧做功能力，改善起动性能.当冷却液温度达到某个温度界限后，进一步升高冷却液温度不能进一步改善子孕峰和失燃循环的出现机率，起动性能改善效果不明显.与进气加热比较，冷却液加温辅助起动措施在增加压缩终了温度的同时降低了摩擦阻力，对起动性能的改善效果优于进气加热.

Abstract:

The cold start tests of a direct inject turbocharged diesel engine with a low compression ratio of 14.25 were conducted respectively at an altitude of 0, 3 000, and 4 500 m at different coolant auxiliary heating temperatures of 20, 30, 40, 50 and 60 ℃, as well as using intake heating auxiliary, by utilizing the plateau environment simulation test bench, to study the influence of coolant heating temperature and intake heating on its start performance of the diesel engine under different altitude conditions. The results indicate that the afterburn cycle with a poor work ability and the misfire cycle with negative work appear more and more frequent at a higher altitude in the cold start of a low compression ratio diesel engine, which caused the reduction of combustion work capacity, the extension of startup time, and the deterioration of starting performance with elevation increasing. When started under conditions of heating coolant or intake air, the number of afterburn and misfire cycle was significantly reduced during startup, then the power ability were resumed and the engine starting performance were improved. However, the occurrence probability of afterburn and misfire cycle could not be further reduced when the temperature of the coolant reached a certain degree such as 40 ℃, and a further higher coolant temperature will not be effective for improving the starting performance. Compared with intake heating, coolants heating auxiliary can both increase the temperature at the end of the compression process and reduce the friction resistance during start process at the same time, then obtain more better improvement for cold starting of low compression ratio diesel engine.