Numerical Study Of The Two-phase Flow In The Mixer For Liquid Metal MHD Power Generation Systems

Mixer is one of the important parts of multi-phase liquid metal MHD(Magneto-Hydro-Dynamic)power generation systems.How to improve outlet speed of the liquid metal and achieve efficient transportation of the two-phase flow have great influences on power generation of the systems.Based on the research progresses of liquid metal MHD power generation systems,this paper has carried out related numerical researches to provide theoretical guidances for engineering applications of the systems.The specific research contents and main conclusions are as follows:Under the foundation of the promoting mechanism of liquid metal flow driven by bubbles which come from low boiling point working,a mixer with spherical tank as the main body was designed independently.We analysed flow processes of the bubbles and the two-phase flow in the mixer.The simulation results show that with the increase of inlet velocity of liquid gallium(Ga),the effects on flow pattern of the two-phase flow are increased at first and then decreased,which is beneficial to the vaporization process of R113.The influences of boundary conditions(inlet velocity and temperature)and physical parameters(density,viscosity,heat capacity and thermal conductivity)of the working pairs(Ga and R113)on the two-phase flow were studied as well.Their boundary conditions and physical parameters which were satisfied for efficient transport of the two-phase flow were also determined.Based on a deep understanding of the principle mentioned above,we proposed a new driving mechanism which the bubbles come from liquid metal itself,and the low boiling point working is no longer introduced in the mixer.A self-evaporation mixer consisting of a high temperature nozzle and an adiabatic circle was designed creatively based on this new driving mechanism.In addition,the four main impacting factors,namely velocity,temperature,volume fraction and flow field distributions of the two-phase flow in the mixer were analyzed,which indicate that the changes of boundary conditions have little effects on the distributions of the above factors,but only the size changes.And the adiabatic circular pipe can effectively delay the formation of annular flow.Moreover,the influences of liquid metal,nozzle section boundary conditions(inlet velocity and temperature)and gas-liquid two-phase physical parameters(density,viscosity,heat capacity and thermal conductivity)on the two-phase flow transport were obtained.Furthermore,the boundary conditions and physical parameters which were met for efficient transport of the two-phase flow were determined.