内燃机分支管道三维不稳定流场的数值模拟

Numerical simulation of three-dimensional unsteady flow in diesel manifold pipe

为了提高换气系统流动性能,采用数值计算方法,对内燃机换气系统直分支管道和弯曲分支管道分别进行了稳定流动和不稳定流动的数值模拟计算.模拟计算采用三维、可压、粘性、湍流模型.通过研究发现,分支管道内速度、压力分布比较均匀,在支管入口处有一回流区,最大速度、最大压力以及压力梯度出现在支管、总管接口处总管一侧;在相关尺寸大致相同的情况下,直分支管道与弯曲分支管道流场分布随时间的变化无太大差别;由于分支管分流的作用,两种类型分支管道中各参数随时间变化程度基本相同.计算结果可作为换气系统管道简化计算和接口边界简化处理的理论依据.

In order to improving the flow in diesel pipes,steady and unsteady flows in the manifold pipes of a in gas-exchange system were calculated with three-dimensional compressible viscous turbulent numerical model. Several laws were established through calculations. It is poiuted our that the differences of flow distribution and unsteady variation between straight manifold pipes and bent ones are not obvious. There is a biggish circumfluence near the junction of the main pipe and the branch. In the unsteady process, as a result of the influence of the branch, the variety of all parameters in two manifolds against time is basically the same.