Impacts of blade inlet angle of diffuser on the performance of a submersible pump

A diffuser acts as an energy conversion device to improve the performance of a submersible pump. The blade inlet angle of a diffuser is the most important geometric parameter that affects the performance of a submersible pump. The present paper focused on the effects of different blade inlet angles of a diffuser on the performance of a submersible pump. Firstly, the theoretical analysis of the diffuser characteristic curve was carried out; Secondly, five sets of submersible pump models with different blade inlet angles and the same impeller were built and simulated. Finally, based on the obtained results, two characteristic parameters reflecting inlet and outlet velocity distributions in the diffuser were introduced, and the quantitative relationship between internal and external characteristics of the diffuser was established. It was found that as the blade inlet angle of the diffuser increased, the optimum operating point moved in the direction of large flow rate. When the blade inlet angle of the diffuser was in the range of 27°–30°, the efficiency of the submersible pump reached more than 75%, and the maximum change in the corresponding working flow was 0.2 times of the theoretical discharge. Furthermore, the values of the maximum speed reduction ratio ([Formula: see text], that is the ratio of inlet circumferential flow velocity to minimum flow velocity on the intermediate flow surface of a diffuser.) were located near 1.6, and they were positioned ([Formula: see text], that is the relative position of the lowest flow velocity on the intermediate flow surface along the flow path of the diffuser.) near the midpoint of the flow path of the diffuser. Moreover, with the increase in the change rate of different blade inlet angles ([Formula: see text]), the high-efficiency interval breadth ([Formula: see text], that is the relative rate of change in flow rate with respect to the highest flow rate at [Formula: see text].) manifested an increasing trend. When [Formula: see text] exceeded 0.06, the value of [Formula: see text] increased significantly, and the range of applicable flow intervals expanded simultaneously. According to performance requirements, the distribution of the internal flow field was specified to further enhance the adaptability of the submersible pump to different working conditions.