Rotordynamic analysis of a high thrust liquid rocket engine fuel (Kerosene) turbopump

A rotordynamic analysis is performed for a high thrust class liquid rocket engine turbopump considering the dynamic force characteristics of ball bearings and pump impeller seals. Complex eigenvalue problems are solved to predict the rotating natural frequencies and damping ratios as a function of rotor speed. Synchronous rotor mass unbalance response and time transient response analyses are also performed to predict the rotor critical speed and the onset speed of instability. From the numerical analysis, it is found that the rear bearing stiffness is the most important parameter for the critical speed and instability because the first vibration mode is turbine side shaft bending mode. The pump seal effect on the critical speed increases as the rear bearing stiffness decreases and the front bearing stiffness increases.