Effects of incident angle of sealing ring clearance on internal flow and cavitation of centrifugal pump

High-energy fluid at the outlet of the impeller might get access to the impeller inlet via the sealing ring clearance of the centrifugal pump with shrouded impeller. In this case, the great velocity and energy differences between the fluid at the inlet and outlet of the impeller might trigger unsteady flows during the collision with large energy loss produced. As a result, the flow status of the impeller inlet can be exacerbated; causing that the centrifugal pump is susceptible to cavitation. A centrifugal pump with a low specific speed was studied in this paper. To begin with, five incident angles, that is the original angle (90°), 75°, 60°, 45°, and 30° were formed between the incident section of the sealing ring clearance and the inlet circumference of the impeller through changing the front cover of the impeller and the outer contour of the centrifugal pump. Then, the accuracy of the calculation results of the prototype pump (90°) was verified experimentally with analyses on the entropy generation, velocity streamline, backflow at the inlet section, internal entropy generation distribution of the centrifugal pump, and distribution of cavitation in specific conditions at the incidence of clearance of the centrifugal pump with different incident angles of sealing ring clearance. As can be seen from the results, changing the incident angle of the sealing ring clearance exerts a certain influence on the external characteristics of the centrifugal pump. To be specific, the sealing ring clearance with a small incident angle can lower the flow loss in the front cavity flow area and the impeller flow area of the centrifugal pump as well as can restrain the backflow prewhirl at the inlet section of the centrifugal pump and the cavitation inside the centrifugal pump.