Axial thrust instability analysis and estimation theory of high speed centrifugal pump

Abstract

High-speed centrifugal pumps are widely used in the aerospace and chemical industries. However, the large axial thrust of a rotor due to high rotating speeds exacerbates the device operation instability. Herein, the axial thrust characteristics of a high-speed centrifugal pump under variable speed conditions are analyzed via numerical simulations and experiments. Results show that at high rotating speeds, although the dynamic reaction of the impeller and axial force on the inducer blade only account for a small proportion of the axial thrust, they are the main sources of axial thrust instability. Moreover, axial thrust exhibits a linear relation with the axial force acting on the front and back surfaces of the impeller, and the values of these parameters are very close. However, huge errors are afforded when these two parameters are interchanged, and many axial thrust estimation models ignore this. Therefore, considering the influence of the impeller dynamic reaction and the axial force of the inducer blade on axial thrust, this study proposes an estimation theory for predicting axial thrust. Comparison of the prediction results of the estimation theory and the numerical simulation results reveals that the maximum and minimum relative errors of these two parameters are 11.1% and 2.6%, respectively, under different rotational speeds, thereby suggesting that the prediction results of the estimation theory are sufficiently accurate. The estimation theory can greatly reduce the calculation cost, shorten the design cycle of the centrifugal pump, and provide certain reference for engineering practice.