Impact of Inducer Tip Clearance on Cryopump Performance

To investigate the influence of different tip clearances on the hydraulic performance and cavitation characteristics of a cryogenic inducer, this study builds upon previous research by employing the SST k-ω turbulence model and modifying the empirical coefficients for evaporation and condensation in the Zwart cavitation model. Numerical simulations of the full flow field within an LNG cryogenic inducer were conducted. The results yielded cavitation performance curves, pressure distributions at incipient cavitation, vapor volume fraction contours, and leakage flow streamlines for various tip clearances. The impact of tip clearance on the overall hydraulic performance and cavitation behavior of the LNG inducer was systematically examined, with particular attention given to the microscopic evolution of the Tip Leakage Vortex (TLV) during the initial stages of cavitation. Experimental findings indicate that as the tip clearance increases, the tip leakage flow intensifies, leading to greater energy losses within the inducer and a consequent slight reduction in pump head and efficiency. A critical clearance value, δ, exists within the range of 0.4 mm to 0.6 mm, which governs the development pattern of the TLV. When the clearance is smaller than δ, the TLV forms more rapidly, and cavitation development is significantly more sensitive to increases in tip clearance. Conversely, when the clearance exceeds δ, the formation of the TLV is delayed, and cavitation progression becomes less responsive to further increases in tip clearance.