Design and detailed numerical analyses of high performance nonequilibrium disk MHD generator for large scale experimental facility are performed considering supersonic nozzle and boundary layer. The present study treats a disk generator using cesium seeded helium plasma with 100MW thermal input, of which channel section has already been conceptually designed by the authors. At first, two-dimensional time-dependent calculations are carried out for the supersonic nozzle section. Then trial and error processes determine specifications of the nozzle which can not only accelerate the working plasma to the desired condition but also realize the fully ionized seed plasma. This indicates the feasibility of design of the supersonic nozzle with excellent performance. Next, two-dimensional time-dependent calculations of the whole generator considering the supersonic nozzle and the boundary layer are carried out to modify the generator height distribution using the displacement thickness of the boundary layer. The performance characteristics of the modified generator are then examined in detail. As a result, it is confirmed that the generator has the same excellent performance as expected in the conceptual design.