Numerical Investigation of Gas-Liquid Metal Two-Phase Flow in a Multiple-Entrance Magnetohydrodynamic Generator

To achieve high efficiency for a magnetohydrodynamic (MHD) generator, this study proposed a multiple-entrance channel and numerically investigated its dynamic spatial-temporal characteristics, evolution processes, and transport mechanisms for gas-liquid metal two-phase flow with and without an external magnetic field using the volume of fluid (VOF) model for interface tracking. When considering gravity, slug flow, annular flow, columnar flow, bubblelike flow, and stratified flow were observed in sequence with different inlet gas volume fractions, inlet gas velocity ratios, and magnetic field intensities. In the absence of a magnetic field, the flow instability was enhanced with an increase in the inlet gas volume fraction. When the volume fraction ratio of gas to liquid metal was 7:3 and the inlet gas velocity ratios was 0.46, the efficient gas carrying of liquid metal was beneficial for obtaining a more stable output power. The liquid metal velocity was uniform in the generator channel with an average velocity of 0.651 m.s(-1), and the volume-average volume fraction of liquid metal in the generator channel reached 0.3641 within one period. When the generator channel was subjected to a magnetic field, the capacity of gas to carry the liquid metal was reduced, and the liquid metal velocity decreased, but the deformation of the phase interface was smooth owing to the MHD suppression effect. As the magnetic field intensity increased, the length of the stratified flow region and the volume fraction of liquid metal in the generator channel increased, however, a decrease of the liquid metal velocity also occurred. When the magnetic field intensity was 1 T, the average liquid metal velocity decreased by 13.8%, and the volume-average volume fraction of liquid metal increased by 9.59% in the generator channel compared with that without MHD effect. In addition, the 3D spatial-temporal evolution period of the flow pattern was shortened with an increase of the magnetic field intensity, and the result was obtained by estimating the power spectral densities (PSDs) of the periodic signals of the flow velocity and the liquid metal volume fraction.