Electronic edition ISSN 1574-0579

Numerical study on cesium evaporation and diffusion characteristics in a premixed seed-injection gasifier for magnetohydrodynamic power generation

Xiaoqiang Chen¹ - Baolin Liu¹ - Feng Wang¹ - Qi Xia¹ - Lingzhi Zhao^1,2 - Aiwu Peng^1,2

¹ Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
² University of Chinese Academy of Sciences, Beijing 100049, China

Abstract
The output performance of plasma magnetohydrodynamic (MHD) power generation is highly dependent on the mixing uniformity of alkali metal seeds and working fluid gases. The premixed alkali metal seed injection system can solve the problems of quantitative seed injection and uniform mixing, but the evaporation and diffusion characteristics of liquid cesium inside it have not been clarified yet. Based on the actual configuration of the premixed seed-injection gasifier, this study adopts a two-dimensional axisymmetric numerical model, couples the VOF two-phase flow model, species transport model and Lee phase change model on the ANSYS Fluent platform and carries out simulation analysis of the liquid cesium evaporation and diffusion process under argon atmosphere. The heat and mass transfer laws of the entire process of liquid cesium evaporation-diffusion under typical working conditions are systematically explored, and the influence laws of liquid cesium release position and gasifier insulation structure on the mixing uniformity of cesium vapor are comparatively analyzed. The results show that 6 g of cesium can be completely evaporated in about 100 s under typical working conditions, the cesium vapor in the main zone of the gasifier is basically uniformly diffused at 370 s, and a uniform distribution throughout the device is achieved at 4000 s. Releasing liquid cesium in the casing zone will cause long-term accumulation of the cesium vapor in the non-main zone, significantly prolonging the uniform mixing time. The structure without insulation cover can enhance the gas convection in the furnace and shorten the uniform diffusion time of the whole device to 1500 s, but it will bring additional heat loss. Figs 20, Refs 15.