Investigation of Axial Thrust in Centrifugal Impeller Focused on Internal Flow in Balance Holes

Abstract

Due to the high discharge pressure of rocket turbo pumps, even a slight disturbance in the pressure balance will generate excessive axial thrust. Balance holes (BH), which are holes drilled in the main plate of the impeller, are used as one of the means to reduce axial thrust, but it is necessary to evaluate the axial thrust when the diameter, number, and position of the balance holes are changed. In this study, we examined the flow field behind the impeller, BH flow rate, and axial thrust under multiple BH conditions through tests and CFD analysis and considered the relationship between BH conditions and axial thrust. It was found that the larger the BH diameter, the larger the number, and the closer the position is to the inner diameter, the more the axial thrust is reduced. In addition, it was found that the axial Reynolds number and the axial thrust in the BH, which have been made dimensionless and organized, can be expressed by a simple relationship.