Study On The Influence Mechanism Of Thermodynamic Effects On Cavitation Flow Of Turbo Pump

With the rapid development of our country's aerospace industry,the demand for engine thrust is also increasing.For liquid rocket engines,turbo pump is an important core component and it is of great significance to improve its operational safety and stability.This kind of ultra-low specific speed turbo pump has a high speed,low inlet pressure,and is prone to cavitation.Besides,it uses cryogenic fluids such as liquid oxygen,liquid hydrogen as conveying medium.The cryogenic fluids show obvious thermodynamic effects in the process of cavitation,so it will affect the cavitation flow in the turbo pump.Therefore,this paper studies the influence of thermodynamic effects in the cavitation flow in the turbo pump by numerical simulation.The main research contents and conclusions are as follows:(1)Revise the existing isothermal cavitation model,and study the cavitation flow characteristics with and without thermal effects using typical models(airfoil,venturi)as the model,and verify the thermal-effects cavitation model by comparing with the experiment effectiveness.The research shows that the results obtained by the thermal-effect cavitation model are more in line with the experimental results.The existence of the thermal effects will reduce the local temperature of the cavitation,reduce the vapor phase volume fraction of the cavitation area,and will inhibit the development of cavitation,so that the volume of cavitation will be reduced.In terms of energy loss,the existence of thermal effects reduces the energy loss in the basin,which is mainly due to the reduction of the dissipation loss caused by the velocity gradient.(2)Steady numerical simulation of the turbo pump was carried out by using isothermal and thermal-effects cavitation models respectively,so as to study the influence of thermal effects on cavitation flow in the turbo pump.The results show that in a certain range of cavitation number,the thermal effects have little influence on the external characteristics of the turbo pump;the existence of the thermal effects will not change the location of cavitation,but will reduce the volume fraction of the vapor phase in the cavitation area.The surrounding turbulence intensity will affect the thermodynamic effects.When the turbulence intensity is large,the thermal effects will delay the collapse of the cavitation,which will increase the volume of the cavitation,showing an unfavorable side.When the turbulence intensity is small,the thermal effects will be suppressed the development of cavitation,which will reduce the volume of cavitation,showing a favorable side.In terms of energy loss,the thermal effects mainly affect the energy loss caused by the velocity gradient.When the thermal effects show a favorable side,the existence of thermal effects will reduce this part of the energy loss.(3)The unsteady numerical simulation of the turbo pump with or without thermal effects is carried out at the same working point.The frequency comp osition and source of pressure fluctuation in each basin are analyzed,and the difference of pressure fluctuation with or without thermal effect is compared.The results show that the pressure pulsation in the turbo pump basin is mainly caused by dynamic a nd static interference,and the thermal effects have little influence on this kind of frequency.There are pulsating frequencies caused by cavitation in the inducer-centrifugal basin,one is the pulsating frequency caused by the periodic shedding of cavitation,the other is the pulsating frequency caused by the periodic occurrence and collapse of cavitation.The existence of thermal effect will affect the pulsating frequency caused by cavitation,which is specifically manifested in the reduction of the frequency of cavitation shedding,the frequency of the periodic occurrence and collapse of cavitation has been an increase.