1990 Volume 110 Issue 12 Pages 1027-1034
A magnetic-field driven arc damaging inter-anode insulators in MHD generators is theoretically studied. Firstly a circular arc confined within an insulator is analyzed under the condition of no magnetic field. Next we propose a new model which describes the behaviors of magnetic-field driven arcs damaging insulator. The model is based on the following assumptions: (1) extra Joule's heat in the arc column due to applying the magnetic field causes the progress of the insulator damage, (2) Lorentz's force on the arc column balances with the aerodynamic drag due to the gas flow of the vaporized insulator, and (3) whole Joule's heat in the column is removed by the convection of the gas. The calculated results from this model are compared with the experimental results reported previously. There is good agreement between the calculated and experimental values in the relationships of both arc field and damaging rate vs. magnetic field, and damage width vs. arc current.