Operational characteristics of MHD turbine with air core, superconducting rotor

The authors proposed previously the MHD rotary machine carrying out energy conversion by utilizing the induction between the magnetic field of a rotating DC magnet and MHD fluid. The most basic mode of action of MHD rotary machines is MHD turbine. In order to attain high output density in the energy conversion equipments using MHD fluid, it is required to generate high magnetic field in the fluid channel, but in case of the DC rotors of MHD turbines described above, superconducting magnets can be applied, therefore high rotary magnetic field can be generated easily. In this study, the operational characteristics of the MHD turbine with the rotor of air core construction were elucidated, especially the effectiveness of applying the superconducting rotor to the region of Rm>1 was examined. First, the effect of the permeability of rotor materials on the turbine characteristics was studied with the basic infinitely long channel model, then the difference in the operational characteristics between the rotors of air core and iron core was clarified in case of the axial flow type which is desirable as the realizable type. In case of the air core construction, the reduction of output density in the operation of high magnetic Reynolds number was not observed, and it was found that the output power proportional to magnetic Reynolds number was able to be obtained, differing from the case of the iron core construction. (Kako, I.)