变海拔条件下柴油机缸盖热状态变化规律研究

针对实际高原场景下,部分柴油机出现了缸盖局部烧蚀的问题,对不同海拔条件下柴油机缸内传热过程及其对发动机缸盖热状态的影响进行了研究,通过仿真手段计算得到了不同海拔条件下缸盖火力面的温度场分布情况。结合高原实机试验的具体数据,在确定缸盖热侧的边界条件时考虑了两种情况,分别是仅考虑对流换热以及同时考虑了对流和辐射换热的情况。通过对比两种边界条件下的仿真结果,分析研究了缸盖温度场随海拔高度的变化规律及其成因。研究结果表明,缸内对流传热量随海拔的上升逐渐下降,4 500 m海拔缸盖最高温度点温度较平原下降6.2%;缸内辐射和对流的传热总量随海拔高度的上升而上升,4 500 m海拔缸盖最高温度点温度较平原上升15.6%,说明了缸内辐射对换热产生的影响。

Changing regularity of diesel cylinder head's thermal state under variable altitude condition

Aiming at some diesel engine cylinder head partial ablation in plateau, the heat transfer process in cylinder of diesel engine and cylinder head thermal state under variable altitude condition was investigated, and temperature fields of the cylinder head under different altitudes were gotten by simulation. Boundary conditions of the bottom side of cylinder head were gotten by numerical calculation in condition of only considered the effect of convection and considered the effect of both convection and radiation according to real machine experiment. The regularity of cylinder head temperature field changing with altitude under two kinds of boundary conditions was compared. The results indicate that the convective heat transfer would reduce when altitude increases. If only considers the effect of convection, the highest temperature in cylinder head at an altitude of 4 500 meters would fall by 6. 2% when comparing with the plain. The amount of heat transfer would go up when altitude increases and the highest temperature in cylinder head at an altitude of 4 500 meters would rise by 15. 6% when comparing with the plain. And it also show the effects of radiation on the heat generates in the cylinder. [ABSTRACT FROM AUTHOR]