PLASMADYNAMICS MODEL FOR NONEQUILIBRIUM PROCESSES IN N-2 H-2 ARCJETS/

A two-temperature chemical nonequilibrium model is developed for nitro gen/hydrogen (N-2/H-2) arcjet thrusters. All viscous flow properties a re considered assuming steady, laminar, continuum, and axisymmetric fl ow. A seven-species N-2/H-2 plasma composition of molecules, atoms, io ns, and electrons is assumed, and a finite rate chemistry model is emp loyed to model collisional processes among the species. Separate energ y equations are formulated for the electrons and heavy species. The an ode temperature distribution is included, and propellant electrical co nductivity is coupled to the plasma properties, allowing for a self-co nsistent current distribution. Tile numerical solution employs the com pressible form of the pressure-implicit with splitting of operators al gorithm to solve the continuity and momentum equations Numerical resul ts are presented for a law-power simulated hydrazine thruster The cent erline constrictor region of the arcjet flowfield is predicted to be n ear thermal equilibrium, whereas a high degree of thermal non-equilibr ium is predicted in the near-anode region of the arcjet nozzle. Strong electric fields near the anode produce elevated electron temperatures that enhance ionization levels and electrical conduction through the arcjet boundary layer. Radial diffusion of electrons from the arc core also enhances the near-anode ionization levels, Thus, the nonequilibr ium approach is required to accurately model the plasma current distri bution.