大出口角叶轮离心泵输送粘油性能计算

Performance computations of centrifugal pump with large blade discharge angle for handling viscous oils

采用FLUENT计算了44°大出口角叶轮离心泵输送水和粘油的水力性能,通过研究叶轮理论扬程、滑移系数、水力损失系数等重要参数,重点研究了液体粘度对泵水力性能的影响,并将计算的泵扬程和效率与试验数据进行了对比.分析了"扬程突升"现象和叶轮理论扬程曲线出现驼峰的原因.结果表明,计算的泵扬程和效率与试验值仅能部分吻合.虽然能够预测出"扬程突升"现象,但是不能象试验那样在较宽粘度范围内得到维持.小流量工况的蜗壳与叶轮的强烈作用是叶轮理论扬程出现驼峰的原因.增加叶片出口角会使各个工况下的蜗壳和小流量下叶轮水力损失加大,但大流量下叶轮水力损失下降.

Hydraulic performance of centrifugal pump with a large blade discharge angle of 44°was investigated numerically with FLUENT when both water and viscous oils were used as working fluids. Attention was paid on the effect of liquid viscosity on the pump performance through examining several critical variables, such as impeller theoretical head, slip factor, hydraulic efficiency and hydraulic loss coefficient etc. Moreover, the computed pump head and efficiency were compared with the experimental data. The causes for the ＂sudden-rising head effect＂ and the peak onset on the impeller theoretical head curve at a low flow rate were clarified. It shows that a partial agreement between CFD simulations and experiments is achieved for the pump head and efficiency. Although the ＂sudden-rising head effect＂ onset is well pre- dicted, unlike that in the experiments, it cannot persist in a wide range of liquid viscosity. The substantial interaction between volute and impeller at a low flow rate gives rise to the peak occurrence in the impeller theoretical head curves. The increased blade discharge angle results in the increasing hydraulic losses in the volute at the whole working condition and in the impeller at the low flow rate, but decreasing losses in the impeller at the high flow rate.