Measurement and Modeling of Carbon Monoxide Production from Graphite Ablation in a Shock Tunnel

Results of a campaign conducted in Sandia’s Hypersonic Shock Tunnel measuring carbon monoxide (CO) temperatures and concentrations are provided. Samples were exposed to f low conditions in air at freestream velocity = 2.7 km/s, presure = 180 Pa, translational rotational temperature = 170 K, and Mach number = 9.8. The total enthalpy was 3.8 MJ/kg. Prior to experiments, the samples were resistively preheated to wall temperatures ranging between approximately 1775 K and 2200 K with two different types of graphite investigated. Measurements of CO concentrations and temperatures were conducted downstream of a graphite wedge model in which a tunable diode laser absorption spectroscopy diagnostic capable of measuring nonequilibrium temperatures was employed. Experimental results of measured CO production and temperatures are given with notable differences between the different graphite materials. Results are also compared to computational fluid dynamics predictions of COtemperature and concentration as modeled using multiple air-carbon gas-surface kinetics mechanisms.