STUDY ON UNSTEADY EVOLUTION CHARACTERISTICS OF TIP LEAKAGE VORTEX CAVITATION IN CRYOGENIC INDUCER

As the core component of the liquid rocket engine turbopump, the cryogenic inducer is prone to gap cavitation during high-speed operation, which affects the safe and reliable operation of turbopump. To reveal the unsteady evolution characteristics of tip leakage vortex (TLV) cavitation flow in cryogenic inducer, this study predicted the unsteady evolution of liquid nitrogen TLV cavitation inside the inducer by using large eddy simulation turbulence model and Singhal cavitation model. The reliability of numerical simulation was verified by the experimental results conducted by Ito et al. The numerical results show that the error of the head coefficient is 2.64% under the design condition, and the maximum prediction error is 4.31% under the small flow condition, with the evolution process of the cavity accurately captured. Two typical evolution modes of TLV cavitation in cryogenic inducer are observed, namely leakage vortex (P-TLV) and the secondary leakage vortex (S-TLV) cavitation. These two modes exhibit distinct separated evolution characteristics: the former is characterized by the shedding and collapse of large-scale cavities, while the latter continues to develop downstream along the blade surface showing the characteristics of small-scale cavity shedding. The strong shear between the tip leakage flow and the mainstream dominates the evolution process of TLV, and its development will reduce the mainstream velocity and change the distribution of high vorticity region, which promotes the coexistence of multi-vortex structures such as P-TLV and S-TLV. Based on the potential rothalpy theory, the influence of TLV cavitation and thermal effect is analyzed. It is found that the cavitation region presents the characteristics of low potential rothalpy and Coriolis force, while the S-TLV cavity presents a high potential rothalpy gradient (PRG), which is more likely to induce secondary flow along the radial direction and aggravate the flow loss. This study has design reference value for improving the flow quality in cryogenic inducer and improving the cavitation performance.