Influence of Tip Clearance on Cavitation Characteristics of an Inducer of Turbopump: CFD Study

The tip clearance, a compact gap between the inducer blade tip and casing wall, is critical to both the liquid leakage and cavitation-induced forces of a turbopump. In this study, we numerically investigate the effect of tip clearance on the cavitation characteristics of an inducer. Six different tip clearances, 0.1, 0.3, 0.5, 1.0, 1.5, and 2 mm, namely Models A-F, were designed to evaluate the cavitation performance, cavity structure, blade loading, radial force, etc. Model D (1.0 mm) had the relatively highest head coefficient and smallest cavity area on each blade as compared to all other models. The pressure coefficient distribution and blade loading further confirmed that Model D can maintain a higher pressure head and better suppress the cavitation onset than the other models. The radial force signals in the time and frequency domains show that Model D has an intermediate force magnitude with slightly higher noises at the rotating frequency and its harmonic frequencies. Model D also has a relatively smaller vortex region and smaller vortex strength (lambda(2) criterion). In short, all results show that Model D is the best alternative to balance the complex interactions of the bulk flow and tip leakage flow, compromising the hydraulic head and rotating cavitation.