为研究发动机减压制动性能，在分析其工作过程的基础上，利用计算流体力学软件建立三维网格模型，采用动网格技术对发动机减压制动工作过程进行了三维瞬态数值仿真分析，并对仿真结果进行实验验证．结果表明: 发动机转速越高，制动性能越好; 减压气门开度越大，制动功率峰值越高，但减压气门最大开度受到压缩间隙和活塞运动规律的限制; 转速一定时，每个减压气门开度都对应一个最佳减压气门提前角，使得发动机的减压制动性能最佳，并且最佳气门提前角随减压气门开度的增大而减小．

In order to investigate the decompression engine brake performance,a mesh model is established withthe help of the software CFD (Computational Fluid Dynamics) according to the analysis on its working process.Then,a 3D simulation of the working process of the transient decompression engine brake is performed by means ofthe dynamic mesh technology,and the simulation results are verified by experiments.The results show that (1) thehigher the rotating speed of engine is,the better its braking performance will be; (2) the larger the decompressionvalve opening is,the higher the brake power peak will be; (3) however,the maximum decompression valve openingis limited by compression clearances and piston movement rules; and (4) at a certain rotating speed,each decom-pression valve opening corresponds to an optimal decompression valve advance angle,which causes an optimal bra-king performance.Besides,the optimal valve advance angle decreases as the decompression valve opening increases.