LPG发动机稀燃流场优化及排放特性研究

将传统燃油发动机改装为LPG稀燃发动机,并在进气道内安装涡流挡板,该挡板可作不同进气模式切换,以根据发动机负载达到分层燃烧和均质燃烧两种模式。建立LPG发动机三维数值仿真模型,分别进行稳态、暂态流场优化分析以及缸内油气分布模拟,并通过稀薄燃烧实验与仿真结果进行对比。结果表明：均质模式与分层模式下的稳态流场分析结果与实验结果相吻合,流量系数误差在6%以内；暂态流场表明,分层模式下进气气流因涡流挡板的导引,在气缸内涡流增强,因喷射角度改变,燃料能有效地集中在火花塞中心,其余则为较稀的混合气,形成油气高度分层分布状态,提高稀油极限；稀油极限提高后,可降低LPG发动机CO2、NOx排放量。

Optimization of Lean Combustion Flow Field and Emission Characteristics of LPG Engine

The traditional fuel engine is refitted as a LPG lean burn engine, and installed an eddy baffle in the intake port. The baffle can be switched by different intake modes to achieve two modes of stratified combustion and homogeneous combustion according to engine load. The three-dimensional numerical simulation model of LPG engine is established, and the steady and transient flow field optimization analysis and the simulation of oil and gas distribution in the cylinder are carried out respectively, and made a comparison between the rarefied combustion experiment and the simulation. The results show that: The steady state flow field in homogeneous mode and stratified mode is consistent with the experimental results, and the error of flow coefficient is less than 6%. The transient flow field shows that the air flow in the cylinder is enhanced by the diversion of the swirl baffle in the stratified mode. The fuel can be effectively concentrated in the spark plug center because the injection angle is changed, the rest is a thinner mixture and forming a highly stratified distribution of oil and gas, which increase the limit of dilute oil. The increase of the oil limit can reduce the emission of CO2 and NOx of LPG engine.