Investigation on Clocking Effect of Diffuser in a Multi-Stage Centrifugal Pump

Abstract The clocking effect is an important phenomenon in the multi-stage Rotating machinery. In order to master the rules and mechanism of diffuser clocking effect on the performance of multi-stage centrifugal pump, the orthogonal tests were applied to design the test scheme. The energy performance and outlet pressure pulsation of a multi-stage centrifugal pump with different diffuser clocking positions were synchronously measured. It was found that the diffuser clocking position had little influence on the energy performance, but had an obvious effect on the outlet pressure pulsation. When the diffuser clocking positions were 0°, 30°, 30° and 30° (CL4), the effective value of outlet pressure pulsation and its amplitude at the main frequency (Impeller Rotation Frequency) were decreased the most, approximately 27.2 % and 38.5 % ,respectively. The CFD method was used to simulate the unsteady flow in the pump with the optimal diffuser clocking position (CL4) and without diffuser clocking position (CL1) respectively to reveal the mechanism of diffuser clocking effect. The simulation results showed that the change of diffuser clocking position can improve the inlet and outlet velocity distribution and reduce the area of high turbulent kinetic energy and the number of cores in the outlet flow passage, which is beneficial to the operation stability of the pump. Compared with the CL1, the hydraulic loss in the four diffusers was reduced by 2.43 %, 12.15 %, 11.43 % and 13.19 % respectively under the optimal diffuser clocking scheme (CL4), and the total reduction of hydraulic loss is about 1.11 % of the pump head.