Basic Study on MHD Power Generation System by Using High Density Liquid-Metal Two-Phase Natural Circulation

对高密度两相自然循环与液态金属磁流体发电相结合的先进能量转换系统的基本特性进行了理论和实验研究。循环分析考察了系统温度、两相流段含气率和气液滑移率、不同工质组合的部件效率等参数对系统性能特性的敏感性，表明该系统的循环效率与传统的汽轮机循环和燃气轮机循环相当。对于1000℃的热源，循环效率有望达到50-60%以上，但发现循环效率强烈地依赖于两相流段的气液滑移率和发电机效率。在以木材-金属和氮气为工质的重金属两相自然循环的基础实验中，研究了磁流体功率负荷对两相流段气液滑移率或含气率的影响。实验发现，两相流中的含气率主要由发生器压降和两相段浮力之间的力平衡决定，这一研究结果对今后高温核电站应用本系统的研究具有一定的参考价值。

Fundamental characteristics of an advanced energy conversion system using high density two-phase natural circulation combined with liquid-metal MHD power generation were investigated theoretically and experimentally.The cycle analysis performed to examine the sensitivities of the performance characteristics to the system parameters such as system temperatures, void fraction and gas-liquid slip ratio at the two-phase flow section, efficiencies of the components for the various combinations of the working fluids, shows that the cycle efficiency of the present system is competitive with those of the conventional steam-turbine and gas-turbine cycles. More than 50 - 60 % of cycle efficiency may be expected for the heat source with 1000 C.It is, however, found that the cycle efficiency depends strongly on the gas-liquid slip ratio at the two-phase flow section and also on generator efficiency.In the basic experiments on the heavy metal two-phase natural circulation performed by woods-metal and nitrogen gas, the effect of the MHD power load on the gas-liquid slip ratio or the void fraction at the two-phase flow section were investigated. It is found from the present experiment that the void fraction at the two-phase flow is mainly determined by the force balance between the pressure drop at the generator and the buoyancy of the two-phase section.The results of the present study are encouraging for future studies in the application of the present system to high temperature nuclear power plants.