The Operating Region of MHD Generators

The concept of an overall operating region for segmented Faraday magnetohydrodynamic (MHD) generators is established. The resulting diagram indicating optimal operating conditions relates generator mass flow rate to inlet stagnation pressure. It provides information on the generator inlet Mach number, the electrical load factor, the total electrical power output, and the percentage enthalpy extraction (PEE) for any possible operating condition of a specifilc generator. The diagram is a useful tool in specifying the behavior of the generator under changing operational conditions and for anticipating the formation of shock fronts inside the generator channel, an occurrence which is very undesirable from an electrical engineering point of view. Conclusions drawn indicate that the optimal operating range for maximum electrical power output lies on the boundary between the transonic and supersonic flow regimes at relatively low inlet stagnation pressures. The maximum PEE occurs at a somewhat lower power with the electrical loading factor K ≃ 0.5.