燃烧系统对汽油早喷压燃燃烧特性影响的模拟

Simulation Study on the Influence of Combustion System on Combustion Characteristics of Gasoline Early Injection Compression Ignition

以ZR180单缸柴油机为原型,利用三维流体动力学软件CONVERGE建立仿真模型,研究不同燃烧室形状、进气道形状和喷油器位置对汽油早喷压燃发动机工作状态和燃烧特性的影响.计算结果表明:进气流动对汽油早喷压燃工作状态有明显影响,采用切向进气道的发动机处于过渡态,动力性能降低,指示平均有效压力(IMEP)比螺旋进气道方案降低了13%;采用浅盆型燃烧室,放热率峰值和最大压力升高率峰值分别比ω型燃烧室提高了85%和120%,ω型燃烧室挤压区域的低温环境可能是导致该现象的原因之一.使用高面容比的ω型燃烧室,可提高缸内温度分层以拓展负荷,但IMEP降低;汽油早喷压燃燃烧特性对喷油器位置不敏感.

A 3-D CFD simulation model of the ZR180 single-cylinder diesel engine was established based on CONVERGE software to study the effect of different combustion chamber shapes,intake port shapes and injector positions on the engine working state and combustion characteristics when the engine run gasoline early injection compression ignition mode.The calculation results show that the intake air flow has a significant impact on the working state of gasoline early injection compression ignition engine.Compared to the helical intake port,the tangential intake port makes the engine in transition operation state,leading to a 13%reduction of the indicated mean effective pressure(IMEP).The shallow basin type combustion chamber presents 85%higher of the peak heat release rate and 120%higher of the peak pressure rise rate than theωcombustion chamber,respectively,due to the low temperature environment in the squish area of theωcombustion chamber.At the same time,theωcombustion chamber with higher surface-to-volume ratio can be used to increase the temperature stratification in the cylinder to enlarge the load,but the IMEP is reduced.It is also found that the combustion characteristics under the early gasoline injection are not sensitive to the injector position.