| The work is supported by the Natural Science Foundation for Distinguished Young Scholars of Zhejiang Province under Grant No.LR20E090001.The anti-cavitation performance of turbopump and waterjet propulsor has obvious influence on the safety,and stability of launch process as well as the efficiency of ship propulsion.As a special designed axial-flow impeller,inducer has a very wide range of applications in aerospace,shipbuilding,chemical and energy fields.It is mainly used in the inlet of rocket turbine pump,chemical high-speed pump and the leading edge of waterjet propulsor to boost the pressure of fluid medium,so as to improve the anticavitation performance of pump and propulsor.In addition,when the pump is transporting lowtemperature fluid medium.a slight temperature change will lead to strong energy conversion.Therefore,the main work of this project is to determine the general rules of internal energy transport and energy loss characteristics in the process of inducer cavitation evolution.Because the mechanism of unsteady flow induced by cavitation is still unclear,and the phenomenon is very complex,it is of great physical and engineering significance to develop numerical simulation and research on cavitation flow of cryogenic fluid for in-depth understanding of cavitation flow mechanism of inducer.In this work,the flow characteristics,thermal effect and energy features in the cavitating flows of fluoroketone over a three-dimensional NACA 0015 hydrofoil and liquid methane cavitating flow in inducer are studied as follows:1.Based on the energy balance equation,the Schnerr-Sauer cavitation model is extended by considering the thermal effect to simulate the cavitating flow of cryogenic fluid accurately.In addition,the partial Reynolds time averaged method and viscosity correction are adopted for SST k-ω turbulence model in order to obtain more precise turbulence coherent structure.The accuracy of the modified numerical framework is verified by simulating a cavitating flow of liquid nitrogen around a three-dimensional ogive.2.The thermal effect,flow separation on surface,wall vorticity and the interactions with cavitation are analyzed in detail.The results show that the boundary vorticity dynamics theory(BVDT)can effectively depict the relationship between flow separation and re-entrant jet.The distributions of wall vorticity and its first-order moment show that shedding,collapse and reattachment of cavity enhance the effect of vorticity on wall.Besides,the distribution of enstrophy indicate that the stable attached sheet cavity can stabilize the flow field,and is conducive to suppress the energy loss.In contrast,the multi-scale detachment or the collapse of cavity leads to a rapid increase in enstrophy,which manifests as the energy loss becomes evident.3.The simulation results of cavitating flow in turbopump suggest that higher inlet pressure inhibits the size and growth of vortex core structure in impeller and inducer,and makes the flow field tend to be orderly.The analysis on enstrophy shows that the losses in the high-pressure volute,the cavities,the impeller and the inducer are the main energy dissipation sources.For the main cavitation region-inducer,the decrease of inlet pressure improves the cavitation intensity,and the vortex cores distributed in the inlet and outlet of the inducer blade grow up obviously.As a result,the energy loss become evident. |
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