The influence of blade trailing edge modification on the pressure pulsation inside a two-stage centrifugal pump

Abstract

Adjusting the clearance between the rotor and the stator in the centrifugal pump is an effective measure to reduce the pressure pulsation. In this paper, we investigated the influence of blade trailing edge modification on the internal unsteady flow and the performance of a two-stage centrifugal pump with the V-type trailing edge (VTE) and elliptic trailing edge (ETE). The pressure pulsation on the spherical casing and the performance were analyzed based on the experimental results for the pump with the modified blade trailing edges of the cutting depths 1 mm, 2 mm and 2.5 mm. Also the unsteady flow in the pump was numerically simulated, and the velocity and the axial vorticity intensity were analyzed to evaluate the influence of the flow on the pressure pulsation and the performance of the pump. The results show that cutting the blade trailing edge will reduce the head and efficiency of the two-stage pump, and different outlet shapes under the same cutting depth have little effect on the performance. The modified impeller makes the high velocity areas at the blade outlet away from the spherical casing wall and reduces the pressure pulsation amplitude at the main frequency. At the design flow rate, the heads decrease by 7.3%, 9.8% and 11.3%, the efficiencies decrease by 2.8%, 3.5% and 4.0%, and the pressure pulsation amplitudes at the main frequency are reduced by 29%, 10.1% and 28.7% for the ETE1, ETE2, ETE2.5 blade compared with that of original impeller. Also, the heads decrease by 6.3%, 8.0% and 9.1%, the efficiencies decrease by 3.5%, 3.9% and 4.1%, and the pressure pulsation amplitudes at the main frequency are reduced by 3.2%, 11.7% and 38.1% for VTE1, VTE2, VTE2.5 blade. When the cutting depth is large, the trailing edge of the blade has a large vortex intensity. This may cause the energy loss and lead to the decrease of the efficiency and head. Considering the performance and unsteady pressure pulsation of the two-stage pump, the impeller with VTE1 blade has certain reference significance for engineering application.