Influence of Rotating Speeds and Thermodynamic Effects on LOX Turbopump Performance

Abstract

As a key factor of a reusable turbopump, axial thrust directly determines the reliability of the bears and seals, especially considering the influence of rotational speeds and thermodynamic effects. In this study, numerical simulations and experimental tests were conducted to explore the impact of rotational speeds and the divergences of the turbopump performance with/without the thermodynamic effects. The experimental data obtained at 15000 r/min are in good agreement with the numerical results, illustrating the validity of the numerical model. The results show that the head deviations based on the affinity laws are relatively smaller, only 0.1% difference at normal condition, yet the efficiency increases from 72.5% to 73.8%, which need to be modified through the formula correction. Notably, the axial thrusts acting on impeller are significantly affected by the rotational speeds, and the values at rated flowrate decrease 17.6% after increasing the operating condition to rated speed. The affinity laws are not applicable for obtaining the turbopump axial thrusts under different speeds. Furthermore, due to the changes of the local physical properties, the values of head coefficient and efficiency decrease 2.8% and 1.3% at rated flowrate, respectively, when the thermodynamic effects of liquid oxygen are considered. Meanwhile, the relative variations of axial thrust are between 1.46% and 3.74% within the whole flow range. Finally, an in-depth analysis of the internal flow was conducted through the velocity field and vorticity method. In conclusion, both the rotational speeds and thermodynamic effects significantly affect the performance of a cryogenic turbopump, especially the axial thrust, and the unsteady results of the rotor-stator cavity leakage flow need to be analyzed in the future.