The effects of boundary layer phenomena on the performance of disk CCMHD generator

Two dimensional calculations were carried out to clarify the behavior of boundary layer and its effects on performance of closed cycle MHD (CCMHD) generator and to investigate the relation between enthalpy extraction ratio and adiabatic efficiency. Calculation results suggest that the large Lorentz force causes propagation and separation of boundary layer where reverse current flows, because of small electromotive force. For large load resistance boundary layer becomes very thick and the eddy current arises in broad region. The push work of working gas against Lorentz force is effectively converted into electric energy under the condition at which the Lorentz force decelerates the working gas to Mach number in the range between 1.0 and 1.5 in this case of the generator. Stagnation pressure loss increases with load resistance until enthalpy extraction ratio takes maximum value. The entropy production due to Joule heating and viscosity increases with load resistance. The difference between the load resistances for which the enthalpy extraction ratio and the adiabatic efficiency take maximum value can be explained with the entropy production of Joule heating and viscosity.<
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