Radiation Modeling of a Hydrogen Fueled Scramjet

Abstract

With the difficulty and cost of full-scale flight experiments, the design of scramjet engines relies heavily on computational simulations. Radiation may play an important role in wall heating and flow cooling of scramjets. However, very few studies have focused on such. The present analysis is based on three-dimensional turbulent reacting flow simulations of the HyShot II hydrogen fueled scramjet engine running at flight conditions of Mach 7.4. A one-dimensional Discrete Ordinates Method analysis with a narrow band averaged spectral model is employed to determine wall heating and flow cooling from thermal radiation. The one-dimensional Discrete Ordinates Method is verified against a three-dimensional ray tracing method. The radiative species considered are H2O and OH. The radiative heat flux is on the order of 10 kW/m 2 , which is 0.1-0.2% of the total convective wall heat flux. Flow cooling due to radiation is found to be on the order of 2 K. Sensitivity analysis shows that radiation is highly dependent on chamber size, temperature, pressure and radiative species mole fraction. Variations in these factors can explain the differences between previous analyses in the literature that studied hypothetical engines and the current work that models an existing scramjet.

Thermal Radiative Simulations and Measurements of a Scramjet Test Rig

“…The computational results for the simulation of a Mach 6.5 flight of the HIFiRE 2 scramjet with an equivalence ratio of 1.0 for a 0.36-0.64 methane-ethylene fuel are given in the paper by Crow et al [25]. However, only the exit plane quantities are of interest in the current work and are given in Fig.…”

“…(6), where a is the quadrature weight, l is the quadrature index, and k is the spectral band index. The extreme simplification of this approach is to take a quadrature point at the statistical average of the absorption band and set the quadrature weight equal to 1 for the single point in the band [1]:…”

“…The role of thermal radiation in the energy balance inside a combustor has been little studied and is poorly understood. Previous work studied the hydrogen-fueled HyShot II combustion chamber and found the thermal radiation to be insignificant [1]. The current work considers combustion chambers similar to the Hypersonic International Flight Research Experiment 2 (HIFiRE 2) supersonic combustor [2][3][4].…”

“…= area, m 2 a = spectral quadrature weight B ν = blackbody intensity, W∕m 2 · Hz · sr c 1 = tuning parameter E = estimated error F = spectrally integrated heat flux, W∕m 2 F ν = spectrally specific heat flux, W∕m 2 · Hz f ν = scattering redistribution function I ν = radiative intensity, W∕m 2 · Hz · sr i = location index j = ordinate index k = frequency index l = spectral quadrature index N = maximum index number n = species index S ν = spectral line strength, 1∕m s = trace location, m T = temperature, K U = spectral uncertainty w = standoff position, m X = mole fraction x = streamwise position, m y = vertical position, m z = spanwise position, m θ = azimuthal angle, rad θ 0 = secondary azimuthal angle, rad κ = extinction coefficient, 1∕m μ = ordinate angle factor relative to path, cosϕ μ 0 = secondary ordinate angle factor relative to path, cosϕ 0 ν = frequency, Hz ξ n = normalized number density σ = standard deviation of extinction coefficient, 1∕m ϕ = vertical angle, rad ϕ 0 = secondary vertical angle, rad Ω = optical scattering angle, rad Subscripts band = number of frequency bands filt = quantity at filter LBL = line-by-line variable max = domain upper limit min = domain lower limit quad = correlated-k quadrature scheme sens = quantity at sensor spec = number of species ν = frequency-specific value 0 = nominal state…”

Thermal Radiative Analysis of the HIFiRE-2 Scramjet Engine

“…Previous work studied the hydrogen-fueled HyShot II combustion chamber and found the thermal radiation to be insignificant. 1 The current work considers combustion chambers similar to the HIFiRE-2 supersonic combustor. 2,3 It is anticipated that the radiative component of wall heat flux may be higher in the HIFiRE-2 combustor due to two effects: (1) its use of hydrocarbon fuel that generates significant quantities of radiating species such as carbon dioxide that are absent from HyShot II; and (2) the HIFiRE-2 combustor is significantly larger in volume than that for HyShot II.…”