During the operation of Progressive Cavity Pumps (PCPs), the problem of internal slip which defines the pump performance in terms of volumetric efficiency and lifting capacity always occurs. However, due to the complex geometrical structure and coupling interactions between the stator and the oil lifted, it is difficult to solve the internal slip analytically.

In our study, a new finite element model of PCP with fluid-solid interaction is developed to investigate the internal slip. We established the simulation models of fluid and solid respectively, solved the control equations of them in different solvers and exchanged the results through the fluid-solid interface. Partitioned solution algorithm is employed to tackle the problem of two-way fluid-solid interaction.

Two leakage mechanisms, longitudinal slippage and transversal slippage, were found from our numerical simulation results. For specified design parameters, the fluid leakage can be computed with different hydraulic pressure, thus the volumetric efficiency of PCPs can be obtained. Our computed volumetric efficiency is consistent with experimental results of laboratory test, which can verify our model and simulation method. Furthermore, we studied the influence of different material and structure parameters on internal slip of PCP. The developed model could also be used to compare the volumetric efficiency of different PCPs and optimize the design of PCPs. Our work can be of great significance for the optimization design of new specified PCPs.

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