利用内燃机高海拔（低气压）模拟试验系统，研究了大气压力和冷却液温度对柴油机性能与燃烧特性的影响规律。试验结果表明：随着进气压力降低，柴油机最高燃烧压力下降，缸内平均温度大幅升高，燃烧始点推迟且持续期延长，后燃严重，燃烧过程未能及时释放热量，动力性能和燃料经济性下降明显；随着冷却液温度的升高，最高燃烧压力增大，燃烧始点提前且持续期略有延长，燃烧重心略微前移，燃烧放热率减小，且大气压力越低冷却液温度对柴油机燃烧过程的影响越明显。在高海拔（低气压）条件下，提高柴油机冷却液工作温度，可以明显减少冷却液散热量，提高柴油机的热功转换效率，显著改善柴油机的高原动力性和经济性，同时柴油机热负荷升高幅度并不大。

The effects of ambient pressure and coolant temperature on the performance and combustion characteristics of diesel engine were studied on the engine test bed of simulating high altitude (low pressure). The results indicate that the maximum combustion pressure decreases, the incylinder temperature increases greatly, the ignition timing delays and the combustion duration extends accompanied with severe post combustion, and the power and economy performance declines obviously because the combustion heat cannot release in time. With the increase of coolant temperature, the maximum combustion pressure increases, the ignition timing advances, the combustion duration extends slightly, the combustion center shifts forward and the heat release rate decreases. Moreover, the influence of coolant temperature on combustion is more obvious especially at low air pressure. Under the high altitude (low pressure) condition, increasing coolant temperature can reduce the heat release of coolant and increase the heatwork conversion efficiency, and the plateau power and economy performance of diesel engine improve greatly meanwhile without a high thermal load.