Analytical Model for the Flow in Progressing Cavity Pump with the Metallic Stator and Rotor in Clearance Fit

As the metallic stator progressing cavity pump (PCP) operates with the stator and rotor in clearance fit, the slippage between cavities has a significant influence on the pump performance. In this paper, an analytical model is developed for the flow in the metallic stator PCP. Based on the analyses of the meshing movement and the clearance geometry inside the pump, the slippage through the transversal and longitudinal sealing regions is calculated considering different slippage mechanisms. Then the flow rate is obtained by subtracting the total slippage from the theoretical volumetric rate. This model is validated against results obtained from the performance experiments of commercial metallic stator PCP products from Shihong Petroleum Equipment Company. The model results show that the metallic stator PCP with smaller clearance or more stages is more capable of achieving good performance at high differential pressure. It is suitable for pumping the fluid with certain viscosity, and the influence of the slippage can be compensated by adopting appropriate high rotational speed. Furthermore, the model can be used to predict the pump performance and provide guidance for the pump design and performance optimization in field applications.