Experimental and Numerical Study of Nonequilibrium Ultraviolet NO and N Emission in Shock Layer

Abstract

The results on an investigation of nonequilibrium uv radiation in the systems of molecular bands NO and (12) in a shock layer in air are presented. The studies included the experiments on a measurement + N 2 of the nonequilibrium radiation behind a strong shock wave in an electric arc-driven shock tube within the range of shock-wave velocity change V s = 5 to 10 km/s at the initial air pressure P 1 = 0.1 torr, and numerical simulation of radiation processes behind the shock wave and in a hypersonic viscous shock layer, where the ow was simulated on the basis of Navier -Stokes equations. A numerical model of the radiation behind the strong shock wave has been used to verify a kinetic scheme of radiation processes by comparison with experimental results. Examples of emission calculations in the NO and (12) sys-+ N 2 tems for the conditions of a ight test are presented. Nomenclature B = rotational constant c = speed of light, cm /s D = energy of dissociation, K e = electron H = ight altitude, km h = Planck's constant I = radiation intensity, W /cm 3 sr mm k = rate constant of reaction m = mass, g n = concentration, cm 2 3 P = pressure, torr R = radiance, W /cm 2 sr mm T = temperature, K t = time, s or ms U = rate of electron energy exchange V = ight or shock wave velocity, km /s v = vibrational number x = distance behind shock wave, cm y = stagnation line distance, cm b, g = parameters in vibration -dissociation model l = wavelength, nm or mm u = characteristic vibrational temperature, K n = collision frequency, s 2 1 s = cross section, cm 2 t = time, lifetime, s, ns, or ms v 0 , v 0 x 0 , v 0 y 0 , v 0 z 0 = vibrational constants ai = associative ionization e = electron, electronic el = elastic f = forward m = maximum R = rotational r = reverse s = shock-wave condition v = vibrational 1 = condition ahead of a shock wavè = freestream condition Superscripts 9 = upper excited state 0 = lower excited state

Non-Boltzmann Modeling for Air Shock-Layer Radiation at Lunar-Return Conditions

“…Figure 6. It is seen that the Teulet et al 39 value, which was the largest of the rates considered, drives the N 2 + (B) state to a Boltzmann distribution, while the Gorelov et al 38 value, which was the smallest of the rates considered, decreases the flux about 10% below the present rate value. Table 3.…”

“…Gorelov et al 38 should be consulted. The present section discusses the modeling of only N 2 + , while a similar discussion is presented by Johnston 18 for N 2 .…”

State-Resolved Dissociation Rates for Extremely Nonequilibrium Atmospheric Entries

“…Advances in the qualitative and quantitative understanding of such postshock phenomena [1][2][3][4] are being driven by the definition of interplanetary missions involving the entry (or reentry) of a spacecraft in a planetary atmosphere. Maneuvers such as planetary aerobraking, aerocapture, or direct entry of a spacecraft inbound from another planet follow hyperbolic trajectories where crossing of the planetary atmosphere occurs at velocities well in excess of 10 km=s.…”

Survey of high-enthalpy shock facilities in the perspective of radiation and chemical kinetics investigations

“…Tests have been conducted for nitrogen and air [113,114] for measuring UV emission by NO, N 2 and N 2 þ . Experimental campaigns have also been conducted for Mars and Venus entry conditions [111,[115][116][117] with a special care to investigate radiation of CN and C 2 and CO systems.…”