SUMMARYThe purpose of this study is to examine the influence of the shape of the cross-section of a scramjet engine-driven experimental diagonal conducting wall (DCW)-MHD generator on generator performance by three-dimensional numerical analyses. We have designed MHD generators with symmetric square and circular cross-sections, based on an experimental MHD generator with an asymmetric square cross-section. Under the optimum load conditions, the electric power output reaches 26.6 kW for the asymmetric square cross-section, 24.6 kW for the symmetric square cross-section, and 22.4 kW for the circular cross-section. The highest output is obtained for the experimental generator with the asymmetric square cross-section. The difference in the electric power output is induced by the difference of flow velocity and boundary layer thickness. For the generator with the asymmetric square cross-section, the average flow velocity is highest and the boundary layer is thinnest. The compression wave is generated with dependence on the channel shape. The difference in the flow velocity and boundary layer thickness is induced by the superposition of the compression wave. C⃝ 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(2): 9-16, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com).