Investigation on the Axial Vibration of Balance Piston Mechanism Considering Coupling of Impeller Elastic Deformation and Acoustic Vibration

Abstract

Balance Piston（BP）Mechanism is used in rocket engine tubopumps in order to balance large axial thrust generated from high discharged pressure of the pump. BP mechanism is a self-thrust balancing system and quasi-statically stable, but might become unstable due to compressibility of the operation fluid in BP. Recently open impeller, which has no front should, is often selected for rocket turbopump because it can be manufactured easily compared to closed impeller. It is concerned about coupling of impeller deformation and acoustic vibration in BP chamber fluid because an open impeller with large diameter has low stiffness. However, coupling of structure（impeller）and acoustic（BP chamber fluid）vibration has not been investigated. In this paper the relationship between static and dynamic characteristics are investigated with simplified model by numerical simulation, and it is concluded that low stiffness of structure and resonance of structure and acoustic frequency causes coupled vibration.