Electronic edition ISSN 1574-0579

Numerical study on heat and mass transfer characteristics of premixed seed injection process in shock tunnel magnetohydrodynamic power generation

Xiaoqiang Chen¹ - Baolin Liu¹ - Qi Xia¹ - Feng Wang¹ - Jian Li¹ - 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
Shock tunnel magnetohydrodynamic (MHD) power generation technology provides a pure and controllable experimental platform for MHD energy conversion under extreme conditions, whereas the alkali-metal seed fraction and its spatial uniformity directly affect plasma conductivity, ionization stability, and generator output. This study focuses on the upstream premixed seed-injection process before the working gas enters the MHD generation stage. Aiming at the complex process of injecting premixed argon-cesium mixed gas into the low-pressure section of the shock tunnel, this paper establishes a three-dimensional full-scale numerical calculation model considering cesium phase change and wall deposition effect. The condensation coefficient of the Lee phase change model is calibrated against a theoretical mass-transfer benchmark derived from the two-film theory. The evolution patterns of cesium gas-liquid phase change, spatial distribution and wall deposition during the injection process are revealed through numerical simulation, and the influences of the gas injection position and injection pipe diameter on cesium distribution uniformity are analyzed. The results show that the initial stage of the injection process is supersonic flow with a maximum Mach number of 6.8. At 300 s, the mass of cesium deposited on the wall of the low-pressure section accounts about 30 percent of the total cesium mass, and considering the wall deposition effect reduces the average cesium mass fraction in the low-pressure section by 33.67 percent. Reducing the gas injection time and optimizing the injection port position can significantly improve the distribution uniformity and the effective mass fraction of cesium. Comparative system-level experiments show that the optimized gas injection structure increases the peak power by about 25 percent and produces a more stable waveform, consistent with the predicted optimization trend. The research results provide a theoretical basis for the design and optimization of the seed injection system of shock tunnel MHD power generation systems. Tables 3, Figs 17, Refs 16.