Supersonic nozzle profiling for a DC low-temperature plasma generator with an expanding duct of the output electrode
In the present paper we present the results on the iterative supersonic nozzle profiling method for a DC plasma torch possessing an output electrode expanding channel with a power of up to 50 kW, taking into account the nonmonotonic dependence of the adiabatic exponent on temperature on the basis of the gas flow rate in the critical section and the gas parameters in the prechamber. The methodology was verified both using CFD commercial packages and laboratory experiments. The latter showed the efficiency of a profiled nozzle over a wide range of currents and gas flow rates, for example, at an arc current of 200 A and a gas flow rate of 1.5 g/s, the shear rate is 1500 m/s and the temperature is 5÷6 kK. When analyzing current-voltage characteristics of the plasma torch equipped with a supersonic nozzle it was found that the supersonic nozzle arc burning voltage is lower than for an open divergent duct that is associated with an increase in the gas conductivity at high pressure.