Experimental and CFD Simulation of a Multiphase Canned Motor Pump

Abstract

Canned motor pumps are well suited for pumping hazardous and radioactive fluids due to their compact design and low maintenance cost. However, their application on artificial lift has not been investigated yet. ESP (Electric Submersible Pump) has been used as an artificial lift method for pumping high volume flow rate in deep wells. However, due to its seal leaking and bearing abrasive problems, pump performance is deteriorated during operation. This work investigated utilizing a canned motor pump instead of ESP in downhole application. The performance of a canned motor pump under multiphase flow was studied experimentally and computationally.

A canned motor pump demonstrator manufactured by Curtiss-Wright EMD was installed in the pump test loop built at Turbomachinery Laboratory at Texas A&M University. The water baseline performance test and multiphase flow (water/air) test was performed. GVF (Gas Volume Fraction) in pump stator jacket was varied from 0% to 20%, and the pump speed varied from 2000 RPM to 3930 RPM. The pump’s performance at these flow conditions was recorded and learned.

The air inside the bearing house and rotor-stator annulus causes cooling and lubrication problems for normal pump operation. The air distribution of the secondary circulation flow inside the pump is the main concern. Thus, multiphase flow inside the pump was simulated with CFD commercial code, ANSYS Fluent. Different GVF with different water flow rate was simulated. Also, pressure at flow region outlet and bubble diameter effect were also simulated. Flow rate distribution trend predicted by CFD method is validated by experimental test results.

Impedance probe was designed and built to measure multiphase flow in a pipe. The GVF is the main calibrated parameter. The fluid’s dimensionless admittance was found to have linear correlation with GVF. The phase of CPSD from probe’s signal is a promising calibration tool for the future probe application.