直线发动机低转速空燃比及燃烧特性

基于自主研发的直线发动机台架,进行直线发动机起动试验,采用速度-密度法,分析得到直线发动机在低转速时的循环进气量计算公式,并试验标定了直线发动机电控喷油器的流量特性。基于循环进气量计算公式与试验标定的直线发动机电控喷油器的流量特性,利用直线发动机起动试验测得的进气压力及缸压信号,计算得到当直线发动机起动循环喷油脉宽为5.4ms、点火时刻为上止点前1.0mm、发动机转速为575r/min时的空燃比为7.92,燃烧累积放热量为66J。研究表明,当活塞位于上止点前26mm时,循环进气量与此时进气道的瞬时进气压力线性度为0.03,线性特性最好。研究结果可为后续直线发动机空燃比计算及燃烧特性分析提供参考。

Air-fuel ratio and combustion characteristics for linear engine at low speed

Based on the linear engine prototype designed independently, the starting experiment of linear engine was carried out. The calculation formula of the cycle intake air of linear engine in low revolution was obtained by using the speed-density method and the injector flow characteristic was calibrated through experiments. With this formula and the flow characteristics of injector in linear engine, as well as intake pressure and cylinder pressure data, it was calculated that the air fuel ratio was 7.92 and the total heat release was 66 J at the engine speed of 575 r/min when the fuel injection pulse width was 5.4 ms and the ignition timing was 1.0 mm before the top dead center. The results showed that, when the piston was at 26 mm before the top dead center, the linearity between the cycle intake air quality and the intake air pressure in intake port reached the best value of 0.03. The results can provide reference materials to the analyses of air fuel ratio and combustion characteristics of linear engine.