Experimental study on stability of axial direction of Balance Piston mechanism

Abstract

Vibration problems often occur in development of rocket engine turbopump, and an axial vibration is one of these problems. Rocket turbopumps often use balance piston mechanism (BP) which is a self-balancing system in order to balance the large axial thrust derived from high discharged pressure. Turbopump rotor with BP is movable in axial direction and supported by fluid stiffness generated by BP. Although BP has a stable characteristic statistically, it becomes dynamically unstable in some cases because of compressibility of the fluid in BP chamber. Stability of BP has been studied in analysis approaches, but experimental approach has not been conducted yet. In this paper experimental research is conducted to confirm the occurrence of self-excited oscillation and compare the experimental results with one dimensional theoretical analysis. From the experimental results, effect of BP parameters on stability is revealed and it is concluded that there is contradictory relationship between BP static and dynamic characteristics.