发动机起动过程中活塞漏气模拟分析

采用AMESim建立了柴油机单缸机及活塞漏气模型,假设气体流动为一维非稳态可压缩的绝热流,采用方形小孔流量计算方法,分析了不同转速下的活塞漏气和缸压变化。通过分析表明,转速每降低50 r/min,循环漏气量增加0.03g,漏气量占进气量百分比提高3.74%,最大爆压降低0.112 MPa。按照柴油机起动最低缸压1.7 MPa要求,起动转速应为大于200 r/min。

Analysis and Simulation of Blow-by from Piston in Engine Starting Procedure

Single-cylinder diesel engine and blow-by model was established by using AMESim. The influence of the starting speeds on blow-by rate and cylinder pressure has been investigated by using square holes flow calculation method with the assumption that the gas is one dimensional unsteady compressible adiabatic flow. The results show that, when speed decreases 50 r/min, the cycle gas leakage increases 0.03 g, and air leakage percentage accounted for the air input increases to 3.74%,the maximum cylinder pressure reduces 0.112 MPa. According to the minimum required cylinder pressure（1.7 MPa） for diesel engine starting, the starting speed is greater than 200 r/min. The method can be used for starting motor matching and can provide a reference for improving the piston ring gap to improve the cold startup performance.