Spectroscopic Studies of Vibrational Nonequilibrium in Supersonic Nozzle Flows PDF Download

Author: I. R. Hurle
Publisher:
ISBN:
Category : Aerothermodynamics
Languages : en
Pages : 0

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Book Description
Studies have been made of the extent of vibrational nonequilibrium produced in supersonic expansions of undissociated N2 from known initial equilibrium conditions attained behind reflected shock waves. The N2 was shock heated and compressed to reservoir temperatures and pressures in the ranges 2800 to 4600K, and 24 to 82 atm. It was then allowed to expand through a 15 degree axisymmetric nozzle coupled to the end of the shock tube. The extent of vibrational nonequilibrium was determined by measurements of local vibrational temperatures using the spectrum-line reversal method. The measurements showed the vibrational temperatures in the expansion flows to be much closer to equilibrium than the Landau-Teller relaxation theory predicts. Observations at two area ratios showed that the flow was not completely frozen in the vibrational sense. The probability of N2 vibrational de-excitation inferred from these measurements of vibrational relaxation made behind normal shock waves. Reasons for this apparent difference are discussed in terms of the basic environmental and kinetic differences between shock-wave and nozzle-expansion flows. The validity of the application of Landau-Teller relaxation assumptions and shock-tube measured rates to predict nonequilibrium in expansion flows is thus questioned. (Author).