Experimental and Numerical Study of Carbon-Dioxide Dissociation for Mars Atmospheric Entry

• Published in: Journal of thermophysics and heat transfer 2018-04, Vol.32 (2), p.503-513
• Main Authors: Lin, X, Chen, L. Z, Li, J. P, Li, F, Yu, X. L
• Format: Article
• Language: English
• Subjects: Atmospheric entry; Carbon dioxide; Computer simulation; Density; Initial pressure; Low pressure; Mars atmosphere; Mathematical models; Semiconductor lasers; Shock waves; Spectrum analysis; Temperature; Tunable lasers
• ISSN: 0887-8722; 1533-6808
• DOI: 10.2514/1.T5152

The mechanism of CO2 dissociation during entry in the Mars atmosphere is experimentally investigated. A hydrogen–oxygen combustion-driven shock tube is used to simulate physical and chemical conditions in a CO2–N2 mixture. Two shock velocity/initial pressure conditions are studied: 7.09±0.05  km/s at 100 Pa (called the low-pressure condition) and 5.68±0.07  km/s at 300 Pa (called the high-pressure condition). The temperature behind the shock wave is obtained by analyzing the high-temporal-resolution and high-spatial-resolution experimental spectra of the CN violet (B2Σ+→X2Σ+, Δv=0) system. The CO number density is derived using a tunable diode laser absorption spectroscopy system based on CO absorption near 2.33  μm. Moreover, a numerical code is developed to reproduce the experimental results (temperatures and species densities). The kinetic code in this work is based on Park’s two-temperature model. Comparisons between experiments and calculations are presented. Such a relatively simple two-temperature model fails to accurately describe the nonequilibrium temperature and CO number density but is suitable for equilibrium temperature predictions.