Computation of Segmented Arc-Heater Flows Considering Injection of Electrode Shield Gas

Abstract

The computer code ARCFLO4, used to solve segmented arc-heater flows, is improved to consider argon gas injected into the electrode chambers and air injected from the constrictor wall. The additional species continuity equation for argon gas including the diffusion term is solved with the original governing equations for total working gas. Also, a numerical wall boundary condition, wherein air is injected from small gaps between constrictor disks, is applied to predict heat flux more realistically. This code is used to simulate flows at the Panel Test Facility, the Aerodynamic Heating Facility, and the Interaction Heating Facility of the NASA Ames Research Center. The computations show that the argon ratio changes dramatically in the arc heater, and it strongly influences the distribution of the thermodynamic and transport properties of the flow. At the upstream region of the constrictor, the arc column is broad and the radiation increases. In addition, a periodic distribution of conductive heat flux on the constrictor wall occurs along the axial direction due to gas injected from gaps between the constrictor disks. The average heat flux on the disk is higher than the previous result that considered working gas with a fixed argon ratio. Finally, through comparison between computation and experiment, it is confirmed that the proposed computation effectively predicts the total heat flux on the arc heater. Nomenclature c Ar = mass fraction of argon gas c i = mass fraction of species c p;i = specific heat of species at constant pressure, J=kg K D Ar = effective diffusion coefficient of argon gas, m 2 =s D ij = multicomponent diffusion coefficient, m 2 =s D im = effective binary diffusion coefficient, m 2 =s E = voltage gradient, V=m e t = total internal enthalpy, J=kg H = total enthalpy, J=kg H a = mass-averaged enthalpy, J=kg H c = centerline enthalpy, J=kg I = current, A j = current density, A=m 2 k = Boltzmann constant, 1:380622 10 23 J=K L = length of constrictor, m M i = molecular weight of species i, kg=kg mole N s = total number of species n i = number density of species i, m 3 p = pressure, Pa q C = conductive heat flux, W=m 2 q R = radiative heat flux, W=m 2 R = universal gas constant, 8314:3 J=kg mole K T = temperature, K u = axial velocity, m=s V = voltage, V v = radial velocity, m=s x = axial coordinate, m y = radial coordinate, m = arc-heater efficiency = density, kg=m 3 ij = stress tensor, N=m 2