Cross-sectional current distribution in a coal-fired diagonal conducting wall magnetohydrodynamic generator with slag-coated walls

Current distribution in the cross-sectional plane of a diagonal conducting wall (DCW) magnetohydrodynamic (MHD) generator with slag-coated walls is studied. The effects of boundary layer thickness and wall temperature on the current distribution and local power density are investigated for magnetic fields of 2 and 6 tesla. The effect of sidewall boundary layer overshoot is also considered. The energy equation is solved inside the slag layer simultaneously with the electrodynamic equation for the entire cross section where real gas and slag properties are incorporated. Cold and hot wall conditions reveal quite different current distributions for all types of velocity profiles considered. For electrodes with cold walls there is substantial current flow to the sidewalls, whereas for electrodes with hot walls there is very little current flow to the sidewalls. The change in the thickness of the turbulent boundary layer has very little effect on the current distribution and local power density. The wall temperature dependence of the sidewall current flow in cases of boundary layer overshoot shows generally the same trend as that of cases without overshoot. Increasing the Hall parameter increases significantly the sidewall current. Local power density is dependent on the wall temperature since the voltage drop in the slag layer is inversely proportional to wall temperature. The temperature distribution in the slag layer depends on the current density for a specified wall temperature. There is no substantial current leakage through the slag layer between the various electrodes along the sidewall in all the cases considered. The local power density from the present investigation compared well with the experimental results and also with three-dimensional results.