Study On The Influence Of Thermodynamic Effect On Cavitation Of Inducer

The inducer is an important component for liquid rocket engine turbopump,which could work under condition of low inlet pressure or partial cavitation and provide necessary inlet pressure for centrifugal impeller to prevent cavitating erosion.Consequently,the inducer could improve the turbopump and engine performance significantly.The inlet pressure and tank wall thickness can be decreased significantly by improving inducer anti-cavitation performance,which could increase the rocket payload effectively.The formation of bubbles during the cavitation is a vaporization process,and the heat absorbed by vaporization leads to temperature difference between vapour and liquid phases,which can have an effect on the formation and growth of bubbles,which is the thermodynamic effect of liquid.At present,the influence of mechanism of the thermodynamic effect on the cavitation characteristics is not clear,and there is no integral system to evaluate the effect of thermodynamic effects on cavitation.Unable to consider the influence of the thermodynamic effect,the cryogenic fluid inducer is still designed in the conventional method under water,which leads to the design objective of inducer cavitation performance lower than the foreign level.With the requirements of turbopump performance improving,making full use of the thermodynamic effect on cavitation is conducive to improve the turbopump and engine design level.In this thesis,based on a liquid hydrogen circulating pump,the test inducer was redesigned.The inducer cavitation performance in water and liquid nitrogen was studied by implying computational fluid dynamics and test research methods.A cavitation model considering the thermal effect has been developed on the base of the isothermal cavitation model.The influence of cryogenic fluid thermodynamic effect of inducer cavitation performance has been presented quantificationally.The accuracy of numerical simulation of inducer cavitation in real cryogenic medium has been discussed.The evaluation method of different fluid thermodynamic effect using the thermodynamic parameter has been presented.The three dimensional viscous steady cavitation flow simulation of pump and inducer has been complicated in water and liquid nitrogen using isothermal cavitation model and thermodynamic cavitation model respectively.The pump with inducer cavitation performance test and inducer visualization test has been conducted under water,in order to verify the accuracy of the numerical method to predict pump cavitation performance and inducer cavitation flow field characteristics.The pump cavitation performance test has been conducted under liquid nitrogen,in order to validate the accuracy of the thermodynamic cavitation model to predict thermodynamic effect.Comparing the pump cavitation performance between water and liquid nitrogen,the influence of cryogenic thermodynamic effect has been present quantificationally.With the idea of the same thermodynamic parameter signifying the same thermodynamic effect,simulation of pump with inducer under high temperature water has been complicated,and the feasibility of the evaluation method of different fluid thermodynamic effect using the thermodynamic parameter has been discussed.When water at room temperature,the thermodynamic effect of can be neglected,and the isothermal cavitation model can simulate the pump with inducer cavitation performance and the flow characteristics in inducer accurately.The thermodynamic cavitation model can improve the accuracy of predicting influence of the thermodynamic effect for the inducer working in cryogenic medium,with the error of NPSHr reduced from 11.6% to 5.2%.The thermodynamic effect can inhibit the cavitation process,and not change the position of cavitation inception and the development of cavitation.At the same speed of rotation,quantitative influence of thermodynamic effect on cavitation performance of liquid nitrogen is about 17.9%.According with water at room temperature,the high temperature water and liquid nitrogen,which have the same thermodynamic parameter,exhibit the similar cavitation performance,which validate the evaluation method of different fluid thermodynamic effect using the thermodynamic parameter prelimitively,and prvide reference for cryogenic alternative media test.