Carbon Ablative Shock-Layer Radiation with High Surface Temperatures

摘要

Despite the prominence of carbon-based materials for use in thermal protection systems, much uncertainty remains in predicting thermochemical ablation rates at high surface temperatures. To address this issue, experiments using preheated graphite models with surface temperatures up to 3300K were conducted in the X2 expansion tunnel at the University of Queensland. Calibrated shock-layer emission measurements in the wavelength region from 353 to 391nm were taken to observe the effect of surface temperature on radiation from the CN violet Delta v=0 and Delta v=+1 bands. Numerical simulations were conducted using US3D with modified Park as well as Zhluktov and Abe surface thermochemistry models. Lines of sight extracted from the flowfield data were simulated in NEQAIR to reproduce the experimental radiance profiles. It was found that the experimental CN radiance showed no significant dependence on surface temperature, whereas the numerical simulations predicted a monotonic increase with temperature for all surface models. Several potential mechanisms for these discrepancies have been identified and discussed.