PLASMA JET GENERATORS WITH DIVERGENT NOZZLES FOR AERODYNAMIC APPLICATIONS

Studies of plasma jet injection into quiescent nitrogen and air as well freestream crossflows have been performed regarding enhancing combustion and ignition by plasma jets. A computer simulation of nitrogen plasma jet with divergent conical nozzle in a motionless nitrogen and nitrogen incident flow has been carried out. This model involves a realistic equation of state, plasma radiation associated with plasma formation inside the plasma jet as well as coupling between the internal nozzle and external flow fields. Our model uses an implicit free-Lagrange method for the computations, which have been performed for jet injection angles and conditions close to known experiments. These show the complex and non-homogeneous structure of the flow. Equilibrium densities of atoms and ions in plasma were computed. The atom concentrations are shown to be of the same order of magnitude as the neutral molecule density. Initial experiments with plasma jets have started. Two embodiments of stationary plasma generator with vortex flow stabilization and a diverging plasma nozzle have been constructed. The first plasma generator is a large device for application to complex chemically aggressive media. The second plasma generator is a compact apparatus. It can be applied for creation of a quasi-plane jet in a real scramjet using a row of such plasma generators. Analysis of radiation spectra of the first generator plasma jet shows that for the range of power (input in the plasma relaxation region just downstream of the nozzle exit) the gas temperature lies in the range Tg = (3500 - 6600°) K. This is sufficient for ignition of hydrocarbon fuels