基于CFD的汽车水泵优化设计

Optimization of automobile pump based on CFD

以时均Navier-Stokes方程作为基本控制方程,对某款WP7柴油机冷却水泵的原模型进行优化设计,并采用CFX提供的标准k-ε双方程湍流模型及多相流模型进行全流场数值计算.为了提高数值计算的精度,采用结构化网格处理技术进行六面体网格划分.对比分析原模型泵及优化模型泵的压力分布、湍动能分布、气泡体积分数分布、外特性及汽蚀性能,结果表明:优化模型泵的叶轮叶片进口处的湍动能及气泡体积分数明显低于原模型泵;优化模型泵的外特性及汽蚀性能也优于原模型泵;在泵的其他几何参数保持不变情况下,叶轮叶片进口前伸并增加一定的斜度,不仅能够减少叶片进口处的冲击损失,提高泵的外特性,使计算扬程提高约3.16 m,还可以极大地改善叶片进口处液体的流动,改善泵的汽蚀性能,使临界汽蚀余量降低约1.10 m;通过对比模型泵的试验值与模拟值,发现两者之间存在一定的误差,但整体变化趋势一致.

The hydraulic design of an original model of the WP7 diesel engine cooling pump was opti- mized by solving the time-averaged Navier - Stokes equations, the standard k -ε two-equation turbu- lence model and the multiphase flow model with CFD code-CFX. A structured hexahedral mesh has been generated for improving accuracy of numerical simulation. A comparison of fluid static pressure, turbulent kinetic energy and vapor volume fraction contours, hydraulic and suction performance was made between the original pump and optimized one. It was shown that the optimized pump not only ex- hibits obviously low turbulent kinetic energy and vapor volume fraction at the impeller entrance, but al- so has a better hydraulic and suction performance compared with the original impeller. The impeller with the blade leading edge that was properly extended into the impeller eye and with a certain inclined angle with respect to the pump shaft has an improved hydraulic and suction performance due to reduced shock losses at the leading ledges and more uniformed flow pattern at the impeller entrance, causing the head was raised by around 3. 16 m and NPSHC was declined as low as about 1. 10 m. Even thought the performance predicted by CFD has a certain difference from the experimental one, the varia- tion tendency of them is consistent with each other.