Internal flow and stability of balance piston for a rocket pump

In centrifugal pumps, axial thrust balancing is an important factor for stable operation. In particular, in rocket pumps, the stability of rotor assembly is very important to realize reliable high-pressure fluid delivery. Although balance piston, which is one of the self-compensating axial thrust balancing systems, was often used, there are sometimes axial vibration problems on the rotor. In this study, we examine static and dynamic characteristics of balance piston by performing experiments, computational fluid dynamics (CFD), and one-dimensional (1D) simulations, and we calculate parameters such as the static pressure in balance piston chamber and flowrate, orifice flow coefficient, phase difference from the rotor axial displacement to the static pressure fluctuation in the balance piston chamber. The results confirm that the experimental results can be predicted to some degree by performing simulations. Especially, it is found that the CFD simulation can be used to effectively predict the stability of balance piston..