Numerical analysis of the unsteady fluid force acting on an axially oscillating balance piston (2nd report, Comparison of dynamic characteristics of fluid forces acting on front and back shrouds)

Abstract

Dynamic response of the fluid force acting on an axially oscillating balance piston was numerically investigated. The balance piston of a rocket engine turbopump was modeled and forced to oscillate in the axial direction. The flow field around the rotor was simulated using unsteady CFD simulation changing the oscillation frequency. The dynamic characteristics of the fluid forces acting on the front and on the back shrouds were estimated and compared. From the analysis of these coefficients, it was found that the dynamic characteristics of the fluid force on the back shroud with a balance piston dominated that of the whole rotor. The dependency of damping coefficients on the frequency of the axial oscillation seemed to be related to the unsteady flow structure such as vortices caused by the oscillation of the rotor.