MHD effects caused by insulator coating imperfections

The imperfections of insulator coating in the MHD duct inner wall may be caused by microcrack or flaking. In this paper, the results of MHD pressure drop measurements in the presence of insulator coating flaking are presented. Those results are directly measured from transmitter and from outer wall voltage distribution and calculated from an analytical model. The results of microcrack effect on MHD pressure drop from the analytical model prediction are also included in this paper. The results showed that a very small microcrack in insulator coating caused additional MHD pressure drops, higher than those produced by the same length duct with perfect insulator coating.