Theoretical investigation of operation modes of MHD generators for energy-bypass engines

A MHD generator with different arrangements of electromagnetic fields will lead the generator working in three modes. A quasi-one-dimensional approximation is used for the model of the MHD generator to analyze the inner mechanism of operation modes. For the MHD generator with a uniform constant magnetic field, a specific critical electric field E_cr is required to decelerate a supersonic entrance flow into a subsonic exit flow. Otherwise, the generator works in a steady mode with a larger electric field than E_cr in which a steady supersonic flow is provided at the exit, or the generator works in a choked mode with a smaller electric field than E_cr in which the supersonic entrance flow is choked in the channel. The detailed flow field characteristics in different operation modes are discussed, demonstrating the relationship of operation modes with electromagnetic fields.