Turbulence studies of high pressure dynamic nitrogen arcs

Experimental studies were conducted to determine the spatial and temporal distributions of average temperature and the fluctuations of a dynamic nitrogen arc column in a single-flow-nozzle arrangement. The arc was operated at a stagnation pressure of 14 bars absolute. The test section contained a converging-diverging (shock-free) nozzle with a throat diameter of 10 mm and an electrode spacing of 10 mm. Provisions were incorporated for measurements of static pressures along the nozzle wall and observation of plasma radiation through viewing windows located 3 mm and 20 mm downstream of the throat. The data indicated that under comparable current levels, lower centerline arc temperature and higher fluctuations occur 20 mm downstream from the throat as compared to results obtained near the throat (about 30% and 3%, respectively). The results also showed that turbulence starts at the outer edge and progresses inward to the center of the arc column. A one-dimensional arc model has been applied, and the computed timewise distributions of centerline arc temperature and arc diameter showed reasonably good agreement with experimental results.<>