喷油策略对低压缩比柴油机不同海拔

Effects of the Fuel Injection Strategy on Low Compression Ratio Diesel Engine During Cold Start at Different Altitudes

摘要:

基于高原环境模拟试验台，以一台压缩比为14.25的增压柴油机为试验对象，进行了平原0 m、模拟海拔高度1 000,2 000,3 000,3 750,4 500 m处的起动性能试验，并研究了供油提前角和循环供油量对低压缩比增压柴油机在不同模拟海拔时的起动性能影响.结果表明,随着海拔升高，低压缩比柴油机起动过程初始期延长，升速期转速升高率降低，下冲转速增大，过渡期时间延长，起动性能恶化.且在高海拔条件下，海拔高度的上升对低压缩比柴油机起动性能的影响更加显著.在海拔高度2 000 m及以下，海拔高度每升高1 000 m，升速期及过渡期平均延长1.10 s和1.47 s；在海拔高度3 000 m及以上，海拔高度每升高1 000 m，起动过程中升速期及过渡期平均延长18.48，2.75 s.在平原时，增大供油提前角使起动性能恶化：起动阶段初始期延长，升速阶段转速升高率降低，升速期和过渡期时间延长；不同循环供油量策略对平原起动过程影响较小.当海拔为4 500 m时，适当增大供油提前角和适当减少喷油可改善低压缩比柴油机高原起动性能，循环喷油量过大会导致升速期内滞速现象的出现，起动稳定性变差，循环喷油量过小会导致初始期和升速期延长.

Abstract:

An experimental study on the fuel injection strategy for low compression ratio diesel engine at different altitudes was conducted. Tests were conducted on a midspeed heavyduty intercooledturbocharged diesel 14.25∶1 CR (compression ratio) engine whose intake and exhaust pressure was controlled by the Plateau simulation test system to stimulate the altitude conditions including 0, 1 000, 2 000, 3 000， 3 750 and 4 500 m. The results indicate that the time of cranking period is increased with the altitude, the rising ratio of speed of startup period is reduced, the time and undershoot speed of after start period is increased, and the starting performance is deteriorated. Besides, under the conditions of high altitude, the starting performance is more significantly effected by altitude, at an altitude of 2 000 m and below, the time of startup period and after start period is reduced by an average of 1.10 and 1.47 s for every increase in altitude of 1 000 m. At an altitude of 3 000 m and above, the time of startup period and after start period is reduced by an average of 18.48 s, 2.75 s for every increase in altitude of 1 000 m. On the plain, the increase of fuel advance angle, the starting performance is deteriorated, the time of cranking period is increased and the rising ratio of the speed of startup period is reduced, and the time of startup period and after start period is increased. Different total fuel mass injection strategies has little influence on the cold start process on the plain. At an altitude of 4 500 m, the appropriate increase of the fuel supply advance angle and the appropriate reduction of the total fuel mass injection could improve the starting performance. Too large an amount of total fuel mass may lead to the fluctuation in startup period, and the starting stability is deteriorated, however, too small amount of total fuel mass may prolong the time of cranking period and startup period.