| Nuclear fusion is an important potential method to solve the energy problem in the future.In the nuclear fusion process,the blanket is the critical part of the fusion reactor to realize the fusion energy.The liquid metal blanket has attracted widespread attention for its superior heat conduction,heat load and tritium transport ability.Magnetohydrodynamic(MHD)effects,heat transfer characteristics and tritium transport are the problems that cannot be ignored in liquid metal blanket.Therefore,it is necessary to further explore the gas and liquid metal two-phase fluid in the liquid metal blanket.In this research work,firstly,the rise motion of bubbles in liquid metal under a uniform magnetic field was studied.The results showed that in the absence of the magnetic field,the bubble aspect ratio E_Rwas 0.182.The magnetic field inhibites the bubble deformation,the bubble aspect radio E_R increased to0.56 under horizontal magnetic field.When the conductive liquid metal around the bubble is affected by the horizontal magnetic field,there will be a Lorentz force along the vertical direction in the flow field,which makes the bubble compressed in the horizontal direction,and the bubble will become flat,the projection of the bubble in the horizontal direction will increase,and the resistance will increase.The vertical magnetic field made E_R increase to 0.6.The effect of the vertical magnetic field on the rising motion of the bubble is mainly reflected in two aspects.One is to stretch the bubble vertically,weaken the rising resistance of the bubble,so as to increase the rising speed of the bubble.When the magnetic field intensity is 0.5T,1T and 1.5T,the aspect ratio E_Rof the bubble at the same time is 0.52,0.64 and1.5;The other one is to weaken the bottom jet,thereby reducing the rising speed of the bubble.Secondly,we studied MHD pressure drop of two-phase fluid in DCLL(Dual Coolant Lead Lithium)blanket with different gas volume fractions.The results showed that the inlet velocity increased by 5times and the pressure drop increased by 5.2 times.The magnetic field intensity increased by 1.5 times,and the channel pressure drop increased by 2.1 times.The FCI can reduce the pressure drop of the main channel by two orders of magnitude.The wall conductivity increased by 100 times and the channel pressure drop increased by 42 times.The increase of the gas volume fraction will reduce the conductivity of the mixed fluid.Although the average velocity of the fluid increased slightly,the conductivity had a dominant influence on the MHD pressure drop.Therefore,when the gas volume fraction increased from0 to 0.2,the MHD pressure drop in the channel decreased by 1008Pa.In addition,on the basis of numerical simulation,we obtained the pressure drop correction coefficient k_g of gas volume fraction when the gas volume fraction was less than 0.2.Thus,the correction formula for the pressure drop of the two-phase flow is obtained,which can provide a reference for the structure optimization and pressure drop calculation of the DCLL blanket.Furthermore,we studied the tritium transport under different magnetic field strengths,inlet velocities,and the neutron heat source strengths with the consideration of buoyancy.The results showed that the existence of neutron heat source caused the circulation flow in the channel and leads to the asymmetry of"M"type velocity distribution on the central section.The increase of inlet velocity and magnetic field intensity can increase the maximum jet velocity.The jet flow is conducive to the transport of tritium and the reduction of the maximum concentration of tritium in the channel.With the strength of neutron heat source increasing,the temperature difference in the channel increases,and the inhibition of floating lift on the transport of tritium perpendicular to the flow direction increases,resulting in the accumulation of tritium. |
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