Mechanisms for non-ideal flow in low-power arc-heated supersonic nozzles

Abstract

The flow in a low-powered arc gas heater combined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quantitative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow characteristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slowmoving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Friction forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficiencies. Other factors causing the differences between ideal and real flow include: complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmental pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.

The distribution pattern of the electron density and the electron temperature in a weakly compressible argon plasma jet measured by a Langmuir triple probe

“…High-speed plasma flow has attracted an increasing amount of interest for its versatile applications in a large number of areas, such as plasma spraying in material processing [1][2][3], electric propulsion [4][5][6][7][8] and flight simulations in high-velocity rarefied wind tunnels [9][10][11]. Within the plasma flow, n e and T e are critical parameters, since most concerned issues are directly related to them, such as thermal radiation, which is highly affected by T e and has a cubic increasing relation with n e [12,13].…”

Chemical Nonequilibrium Modeling of Low-Power Nitrogen/Hydrogen Arcjet Thrusters

“…Three institutes are involved in the studies of arcjets in China. The performance and parameters measurements of the arcjet thruster have been carried out in the Institute of Mechanics at the Chinese Academy of Sciences [8][9][10][11].…”