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MHD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。通过循环分析，考察了性能特性对系统参数的敏感性，如系统温度、两相流段的空隙率、气液滑移比、各种工作流体组合的组件效率，表明该系统的循环效率可与传统的蒸汽轮机和燃气轮机循环相媲美。对于温度为1000℃的热源，循环效率可达50% ~ 60%以上。然而，循环效率在很大程度上取决于两相流段的气液滑移比和发电机效率。在木材-金属-氮气进行重金属两相自然循环的基础实验中，研究了MHD功率负荷对两相流段气液滑移比或空隙率的影响。从本实验中发现，两相流的空隙率主要由发生器处的压降与两相段浮力之间的力平衡决定。本研究结果对今后研究本系统在高温核电站的应用具有鼓舞作用。

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.