CFD modeling and simulations of MHD power generation during re-entry

The flow subject to MHD power generation during re-entry is simulated by CFD in this paper. Thermal ionization with potassium seed is used to enhance the conductivity. The ionization of potassium is simulated by both finite-rate chemistry and assuming Saha equilibrium. In the Saha equilibrium approach, the ionization of potassium is computed separately from the conservation equations. The results can be seen as "chemically frozen" for potassium. The results show that the strength of the shock is over predicted. This leads to a lower flow velocity, and hence lower electric field because the electric field and electromotive force (emf) are functions of the flow velocity. The second approach is to incorporate the ioniza-tion/recombination reaction in the conservation equation set. With this model, the convection and diffusion of K and K⁺, the ionization/recombination reaction rates, and the heat of formation of potassium ions are taken into account. Results show that the thickness of the shock is less than that predicted by the Saha equilibrium. The computed velocity, emf and electric field are higher, and therefore the total extracted power is greater than what was predicted by the Saha equilibrium model.