Research On Performances Of Magnetohydrodynamic Power Generator With Liquid Metal Self-Evaporating

Magnetohydrodynamic Generator(MHDG)system driven by liquid metal "self-evaporation" has some advantages,such as simple and compact structure without gas-liquid separation.It can not only use various heat source to generate electricity efficiently,but also combine with other power generation systems.For instance,in the deep space of the universe where solar energy is difficult to exploit,MHDG can be combined with the nuclear reactor heat source to solve the demand for high-power propulsion and power supply.This paper focuses on investigating the flow field of the MHDG power generation channel and studying the key parameters affecting the power generation performance.The "self-evaporation" driving MHDG system with liquid metal sodium as the working medium combined with the practical application of the project was designed.Relevant research contents and results are as follows:(1)The effects of key parameters,such as different load coefficients,inlet velocity,magnetic field intensity and dryness,on the flow field and electric field in MHDG power generation channel were studied through numerical simulation.The results show that the output power varies parabolically with the load factor,and is proportional to the squares of the inlet velocity and magnetic field strength but decreases linearly with the increase of void fraction.The channel power generation efficiency is virtually linear with the load coefficient but is negligibly affected by the inlet velocity,the magnetic field intensity and void fraction.(2)The load coefficient influences the turbulence intensity and the average wall friction coefficient of the flow field.The smaller the load coefficient is,the greater the current density and Lorentz force are,resulting in more inhibition effect on turbulence and average wall friction coefficient.That shows that turbulence intensity and average wall friction coefficient at smaller load coefficient are less than that of at large load coefficient furthermore the fluctuations at smaller load coefficient are also less.(3)The effect of inlet velocity and magnetic field strength on channel pressure drop error is infinitesimal,therefore this effect can be ignored whereas,the load factor and the void fraction have a great influence on the pressure drop error.The error curves of the simulated and theoretical pressure drop of different load factors and void fraction are fitted to obtain a modified formula of the theoretical pressure drop.(4)Combined with the numerical simulation results of power generation performance parameters and the actual working conditions,a MHDG system with liquid metal working fluid "self-evaporation" expansion to drive the gas-liquid two-phase flow to generate power is designed.The overall loop structure of the system was determined,and the thermal parameters of the main components in the loop were calculated.When the margin was considered,the output power of the designed power generation system was 115 kW,the generation efficiency of MHDG generation channel was 55.22%,and the enthalpy extraction rate was 1.32%.