Study on the effect of rotordynamic fluid force caused by floating ring seal on rotor stability of rocket turbopump

Abstract

A rocket turbopump is the high-speed and high-power turbomachinery, and one of major vibration sources of the rotor is associated with rotordynamic fluid forces generated by its shaft seals. In this study, we investigate the effect of rotordynamic fluid force of floating ring seal on the rotor dynamic stability up to the rated operating speed. A finite-element model of a liquid oxygen turbopump is used to analyze natural frequencies and damping ratios of the rotor system. Rotordynamic fluid force generated by floating ring seal is modeled using the cross-coupled stiffness. As a result, it was found that the cross-coupled stiffness of floating ring seal with 1/100 to 1/10 absolute value of the support stiffness is effective in improving rotor stability.