Abstract: To improve the performance of sewage pump impellers, this study applies a response surface model to optimizing the three main design parameters of the impellers based on the orthogonal tests of three factors and three levels. Comparison of the external characteristic curves between the optimized model and the original model reveals that relative to the latter, the former has a wider head range, a higher efficiency, and a wider high efficiency range; it is featured with smaller low-pressure zones of smoother and more even internal flows. The energy loss of the pump under different working conditions is calculated using the entropy generation theory. The results show that entropy production in the impeller of the optimized model is significantly lower, while its distribution pattern in the volute is not much different from that of the original model. At low flows, the zones with a high entropy production rate are mainly concentrated on the pressure side of the blades and near the blade outlet; as the flow increases, the energy loss gradually decreases and the high entropy production zones shift to the volute outlet and the diaphragm. The dynamic and static dryness of the volute involves the impinging and return of high-speed water jets on the volute wall, causing the major part of energy loss in the pump. It is found that the entropy generation distribution of the original model follows a pattern similar to that of the optimized model, while the high entropy generation zones and the generation rate are both significantly larger.

Key words: response surface, sewage pump, numerical calculation, external characteristic curve, entropy production analysis