Performance evaluation of MHD generators: the lumped parameter model and its validation

The authors present stationary model of magnetohydrodynamic (MHD) linear and disk generators. The active region of the device has been modelled by a 3D lumped parameter network which takes into account both the electrical characteristics of ionized gas and the external load apparatus. The 3D equivalent electrical network of the generator has been realised by subdividing the plasma into many elementary volumes, each of which is modelled by composite branches placed along the axes of a suitable Cartesian or cylindrical inertial coordinate system. These branches simulate all local characteristics and physical phenomena which influence the plasma behaviour around the centre of gravity of each brick. Then, in order to complete the stationary model of the device, the equivalent electrical network of the external load apparatus is attached to the previously defined network. The proposed model has been validated comparing the results of the simulation both with experimental data coming from measurements on various test facilities and with numerical values obtained by other researchers using sophisticated analytical models. The main advantage in using this model comes both from its 3D nature, which allows an accurate simulation of the device, and from the circuit approach, which allows it to attain important information on generator behaviour with small computational resources.