点燃式CNG发动机燃烧过程研究

利用混合气形成和燃烧三维模型建立了针对CA6SE1—21N增压点燃式CNG发动机的数值模拟研究平台,并对模型进行了试验验证,同时研究了该发动机混合气形成和燃烧的缸内微观变化历程。验证结果表明,CNG发动机混合气形成及燃烧过程的数值模拟结果和试验结果吻合较好,所选模型适合对CNG发动机进行模拟分析。模拟结果表明,缸内混合气形成可分为大幅度掺混和弱流动混合两个阶段;采用螺旋进气道与平缸盖时,在压缩后期逐渐形成强涡流、低滚流的刚性涡;点火时刻缸内混合气呈上稀下浓的分布,不利于提高点火稳定性和火焰传播速度。

Investigation on Combustion Process from Spark Ignition CNG Engine

Mixture formation and combustion process from CA6SE1-21N spark ignition CNG engine was studied by mixture formation and combustion three dimensional models. Microcosmic transformation course of mixture formation and combustion process were investigated. Validated results show that very good agreement between experiment and simulation results were observed, which indicated that numerical model and computational approach are appropriate. Simulation results show that mixture formation process was divided into intensive mixing phase and weak mixing phase. Violent swirl and weak tumbling flow were formed during the compression cycle when using helical intake passage and flat-faced cylinder head. At the ignition timing, mixture concentration distribution pattern was that the top of combustion chamber was dense and the bottom was thin, which would effect ignition stability and flame propagation velocity.