Abstract
For the purpose of balancing axial thrust, balance piston mechanism is often used in rocket engine turbopumps. Balance
piston is a self-thrust balancing system and quasi-statically stable, but might become unstable due to a compressibility of
liquid hydrogen, one of the major propellants for rockets. In past rocket engine firing tests, the self-induced axial vibration
caused by balance piston instability occurred in a liquid hydrogen turbopump. So it is needed to establish the evaluation
technique to understand the dynamic characteristics of balance piston mechanism. In this report, axial eigenvalues of balance
piston mechanism are studied analytically by one-dimensional model in various ways, and the difference of results due
to the difference of analysis methods is discussed.
