基于CFD的汽车水泵优化设计

针对某增压直喷发动机冷却系统中水泵效率过低的问题,应用一维及三维CFD方法进行优化分析.首先根据发动机最大热负荷下冷却系统带走的热量,确定水泵的流量需求;其次采用一维CFD软件Flowmaster对该发动机冷却系统进行分析,确定水泵的扬程需求;然后根据流量及扬程需求,对水泵进行详细设计,其中叶轮设计方式为闭式离心叶轮,且叶片前缘向压力面倾斜,蜗壳设计方式为梯形截面的扩张通道;最后采用三维CFD软件Fluent对设计的叶轮及蜗壳进行计算,对设计方案进行优化.计算结果表明,CFD计算值与试验值吻合,误差小于5%;优化后水泵在设计工况下满足设计需求,总效率较原水泵提高了26%;抗气蚀性能增强,必须汽蚀余量NPSHR降低0.4m.流场分析表明,新水泵较原水泵压力分布更均匀;新水泵消除了原蜗壳内的低速旋涡,使能量损失减少,能量转换效率大幅提高.

Optimum design of automobile water pump based on CFD

Aiming at solving the problem that the water pump has low efficiency in the cooling system of a turbochargered PFI（port fuel injection） gasoline engine,a combined 1D and 3D CFD optimization simulation work was conducted.Firstly,according to maximum thermal load taken away by the engine cooling system,the total flow rate requirement of the water pump was determined.In addition,the required total head of the water pump was calculated numerically by a 1D CFD software Flowmaster.Based on the requirement of flow rate and head,the detailed geometry design of the pump was conducted.The centrifugal shrouded impeller was designed with the leading edge of the blade inclining to pressure side.The volute was designed by applying an trapezoidal cross section with expansion channel method.Finally,the impeller and volute were analyzed by a 3D CFD software,and redesign and optimization can be done.The computed results show that the calculated and experimental values are in excellent agreement,and the difference is less than 5%.The new designed water pump satisfies the requirement.In addition,the total efficiency of the new pump is increased by 26%while the NPSHR（net positive suction head） is decreased by 0.4 m.The pressure contour results demonstrate that the pressure distribution in the new pump is more uniform.Due to the elimination of low velocity vortex in original volute,the energy loss is decreased and the energy transfer efficiency is increased in this new pump.