基于活塞运动规律的自由活塞发动机燃烧放热规律  

Heat Release Rate of FPEG Based on the Piston Motion

作　　者：许洪瑜 冯慧华[1] 宋豫[1] 左正兴[1] 

机构地区：[1]北京理工大学机械与车辆学院,北京100081

出　　处：《内燃机学报》2015年第5期413-419,共7页Transactions of Csice

基　　金：国家自然科学基金资助项目(51006010);高等学校学科创新引智计划资助项目(B12022)

摘　　要：自由活塞发动机具有异于传统发动机的活塞运动规律,为研究其对自由活塞发动机燃烧放热规律的影响,提出了等效转速变换的概念,将试验示功图反算得到的燃烧放热规律以曲轴转角为计量单位表示,分析了自由活塞发动机与传统发动机放热规律的差异,最后采用三维仿真与试验的结论进行对比.结果表明:自由活塞发动机在压缩行程比传统发动机有较高的运动速度与加速度,这使其在压缩行程有良好的雾化与油气混合效果,预混燃烧量达到80%,;膨胀行程缸内容积变化率较大,缸内压力温度下降较快,因而缓燃期和后燃期持续时间远低于传统柴油机;双韦伯函数拟合的自由活塞内燃发电动力系统(FPEG)放热规律预混合燃烧品质系数和扩散燃烧品质系数分别为3.451和10.24,与传统柴油机相比均偏大;受活塞运动规律的影响,自由活塞发动机与相同缸径的传统发动机相比最高爆发压力较小,出现最高爆发压力的时间较晚,且滞燃期较短.The piston motion of FPEG is quite different from the traditional engine.To study the influence of motion on the combustion heat release rate,this paper puts forward the concept of equivalent speed transformation.Using equivalent crank angle as the unit of measurement to express heat release rate calculated from the experimental data,analyzing the difference between FPEG and traditional engine heat release rate,and comparing experimental result and CFD result.Results show that FPEG piston velocity and acceleration are larger than that of traditional engine during compression stroke.This is favorable to evaporation and oil-gas mixture,leading to pre-mixed combustion ratio up to 80%,.The fast cylinder volume change leads to quick drop in cylinder temperature.The duration of normal combustion period and post burning period is decreased.When double-wiebe function is used to calculate combustion heat release rate,pre-mixing combustion quality coefficient is 3.451 and diffusion combustion quality coefficient is 10.24.They are all larger than those of traditional engine.Under the influence of piston motion,the combustion pressure of FPEG is smaller than traditional engine with same cylinder diameter.For FPEG,maximum combustion pressure is retarded and ignition delay time is decreased.

关 键 词：自由活塞发动机 放热律 双韦伯函数 等效转速变换 燃烧过程仿真 

分 类 号：TK401[动力工程及工程热物理—动力机械及工程]