车用四气门汽油机工作过程三维动态模拟

Dynamic Simulation on the Working Process of Four-valve Gasoline Engines for Vehicles

针对2.4L车用汽油机的工作过程,采用RNGk-ε湍流模型、Weller湍流燃烧模型和PISO算法并结合动网格技术,进行了缸内流场及燃烧过程三维动态模拟。计算过程中,将流场三维动态模拟的结果作为初场应用于燃烧三维动态模拟中,克服了凭经验给定初场时造成的误差,使燃烧模拟更接近于实际工作状态。研究发现,大角度蓬顶形燃烧室中形成的滚流在压缩过程后期并未破碎成紊流;通过合理设计气道及燃烧室结构,在保持滚流的状态下也可获得较高的湍流强度,组织较为完善的燃烧过程。试验结果表明气道和燃烧室结构调整后计算所得压力曲线与实测示功图有良好的一致性。

Aiming at the working process research of independently designed 2.4L gasoline engine, RNG κ- ε model, Weller combustion model, PISO arithmetic and moving meshes techniques were employed to carry out three-dimensional dynamic simulations of the flow-field and combustion process in the cylinder. The results of three-dimensional dynamic flow-field simulations were applied into three-dimensional dynamic combustion simulations as the initial conditions. Thus, original field error supposed by experience can be avoided, and combustion simulations can approximate to the actual working conditions more. It was discovered that tumbles formed in large-angle pent-roof combustion chambers do not break into turbulence during compression. By optimization design of ports and combustion chamber structures, high turbulence intensity can still be obtained, and the combustion process can be perfected even when tumbles are maintained. Compared with experimental result of layout Ⅱ , cylinder pressure of simulated result is almost identical with the experimental data.