Numerical Study on Film Pressure in a Helical Grooved Plain Bearing of a Canned Motor Pump

A canned motor pump is a type of turbopump that features a non-leakage structure that integrates the pump and the motor. It differs from a typical turbopump in that the pumping liquid also serves as the cooling liquid for the motor and the lubricating liquid for the sliding surfaces. Grooved plain bearings are generally used in canned motor pumps to supply sufficient cooling liquid to the motor. However, there is no external lubricant supply system for canned motor pumps, which means that the design guidelines for standard grooved plain bearings cannot be applied without modification. The purpose of this study is to obtain knowledge to develop design guidelines for helical grooved plain bearings for canned motor pumps. Therefore, the film pressure, which is one of the important indices in bearing design, was analyzed by Computational Fluid Dynamics (CFD). CFD simulation was performed using the steady-state single-phase flow solver implemented in OpenFOAM for analyzing fundamental trends. First, a comparison with the theoretical solution was performed for a plain bearing without grooves to investigate the film pressure. Furthermore, analysis was conducted on a helical grooved plain bearing. This analysis clarified the trend of film pressure generated in the helical grooved plain bearing. The conclusion is that the peak values of positive and negative film pressure tend to be higher in the helical grooved plain bearing than in the plain bearing without grooves, so the effects of material strength and cavitation should be handled appropriately when the bearing is used in industry.