ANALYSIS AND DESIGN OF AN ULTRAHIGH TEMPERATURE HYDROGEN-FUELED MHD GENERATOR

A coupled gas dynamics/radiative heat transfer analysis of partially ionized hydrogen, in local thermodynamic equilibrium, flowing through an ultrahigh temperature (10,000-20,000 K) magnetohydrodynamic (MHD) generator is performed. Gas dynamics are modeled by a set of quasi-one-dimensional. nonlinear differential equations which account for friction, convective and radiative heat transfer, and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using nongray, absorbing-emitting, two- and three-dimensional P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation and through the temperature- and density-dependent absorption coefficient. The resulting nonlinear elliptic problem is solved by iterative methods. Design of such MHD generators as onboard, open-cycle, electric power supplies for a particular advanced airbreathing propulsion concept produced an efficient and compact 128-MW, generator characterized by an extraction ratio (electric power extracted from the gas flow to total power into the ps) of 35.5%, a power density of 10,500 MW(e)/m3 and a specific (extracted) energy of 324 MJ(e)/kg of hydrogen. The maximum wall heat flux and total wall heat load were 453 MW/m2 and 62 MW, respectively.