排气道压力波动对发动机二冲程减压制动性能的影响

为分析排气管内压力波动对发动机二冲程制动功率的影响，以某重型柴油机为研究对象，利用GT-Power建立发动机二冲程制动一维模型，通过修改排气型线开展排气道压力波动对制动性能影响的研究。结果表明：第二次减压制动（the second compression release braking, 2nd CRB）相位开启时的压力波动会影响到其他气缸的排气回流，进而影响发动机的制动功率。进一步对排气管进行三维流场计算，证明了其他气缸2nd CRB相位排气门开启时的压力波传递对排气回流阶段排气回流的影响。最后通过试验设计（design of experiment, DoE），结合响应面拟合和粒子群算法对排气管几何尺寸进行优化，优化后该柴油机二冲程减压制动模式下2 100 r/min工况的最大制动功率可达到395.08 kW。

Influences of Exhaust Pressure Fluctuation on the Two-Stroke Compression Release Brake Performance of An Engine

In order to analyze the influence of exhaust pressure fluctuation on two-stroke compression release brake power， taking a heavy-duty diesel engine as the research object， GT-Power software was used to establish one-dimensional model of engine two-stroke compression release brake. Through modifying the exhaust value lift， the influence of exhaust pressure fluctuation on braking performance was studied. The results show that the pressure fluctuation during the phase of the second compression release braking （2nd CRB） would affect the exhaust gas return flow of other cylinders， which affects the braking power of the engine. The three-dimensional flow field of the exhaust pipe was further calculated， and proved the influence of the pressure wave transmission when the exhaust valve was opened in the 2nd CRB phase of other cylinders on the exhaust return in the brake gas recirculation（BGR） phase. Finally， the exhaust pipe geometry was optimized by using the design of experiment （DoE）， combined with the response surface fitting and particle swarm optimization algorithm. The optimal braking power of the diesel engine can reach 395.08 kW at 2 100 r/min under two-stroke breaking mode.