Title :
Emission spectroscopic measurement of ammonia or mixture of nitrogen and hydrogen plasma in a direct-current arc jet generator with an expansion nozzle
Author :
Tahara, Hirokazu ; Yonezawa, Takashi ; Andoh, Yasutaka ; Yoshikawa, Takao
Author_Institution :
Dept. of Mech. Eng., Osaka Univ., Japan
fDate :
8/1/1998 12:00:00 AM
Abstract :
Spectroscopic measurement was carried out to understand the plasma features in a 10-kW-class water-cooled direct-current arcjet generator with a supersonic expansion nozzle. Ammonia or a mixture of nitrogen and hydrogen was used as the working gas. In the mixture of N2+nH 2, the H2 mole fraction n was varied from 0.5-3.0, in which a H2 mole fraction of 3.0 corresponded to that of simulated ammonia. The discharge voltage and the vacuum tank pressure for N2+3H2 were higher than those for NH3 at a constant discharge current and a constant input power, respectively. These characteristics agreed with those of H-atom electronic excitation temperatures in the constrictor of the nozzle throat. The NH3 and N2+3H2 plasmas in the constrictor were expected to be nearly in a temperature-equilibrium condition. On the other hand, the plasmas in the expansion nozzle were in thermodynamical nonequilibrium state because the electron number densities rapidly decreased downstream. As a result, the H-atom excitation temperature and the N2 rotational excitation temperature decreased from 7000-11000 K in the constrictor to about 4000 K and to 1000-1500 K, respectively, on the nozzle exit with mass flow rates of 0.1-0.2 g/s at input powers of 7-12 kW, although the NH rotational excitation temperature did not show a significant axial decrease
Keywords :
ammonia; arcs (electric); hydrogen neutral molecules; nitrogen; plasma diagnostics; plasma jets; plasma temperature; 1000 to 1500 K; 4000 K; 7 to 12 kW; 7000 to 11000 K; H-atom electronic excitation temperatures; N2 rotational excitation temperature; N2-H2; N2-H2 mixture; NH rotational excitation temperature; NH3; direct-current arc jet generator; discharge voltage; electron number densities; emission spectroscopic measurement; nozzle throat; plasma; supersonic expansion nozzle; temperature-equilibrium condition; thermodynamical nonequilibrium state; vacuum tank pressure; Hydrogen; Nitrogen; Plasma density; Plasma materials processing; Plasma measurements; Plasma properties; Plasma temperature; Propulsion; Spectroscopy; Thermal spraying;
Journal_Title :
Plasma Science, IEEE Transactions on