Performance improvements of linear MHD generators and suppression of the magnetoaerothermal instability by the SFC-type magnetic field distribution

Abstract

This paper shows by the three-dimensional analyses on commercial- and laboratory-scale open cycle MHD generators that the shaped B-field configuration (SFC-type) suppresses the local Hall current distribution, which drives the secondary flow in the cross section, the magnetoaerothermal instability (MATI), and the boundary layer separation. Parabolized three-dimensional steady-state Navier-Stokes equations are used for the analyses with the k-ε turbulence model. The generalized Ohm law and the Maxwell equations are solved using the usual infinite segmentation assumption. A carbon combustion gas is considered as well as kerosine combustion plasma, since the electrical conductivity of the carbon plasma is a factor of 5-10 higher than that of the hydrocarbon combustion plasma. When the appropriate SFC-type magnetic field distribution is realized throughout the channel, particularly in the channel entrance region, the secondary flow field has different structures than those of the conventional uniform B-field configuration (UFC-type), such as the number and magnitude of vortices, which have important effects on the power output, boundary layer separation and the MATI.

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