Protection of pyrolysis gases combustion against charring materials’ surface ablation

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractCharring ablation materials are widely used for thermal protection systems in a vehicle during hypersonic reentry. The pyrolysis gases from the charring materials can react with oxygen in the boundary layer, which makes the surface ablation rate decrease. The problem of protection of combustion of pyrolysis gases in charring material against surface ablation is solved by the detached normal shock wave relations and the counterflow diffusion flame model. The central difference format for the diffusion term and the upwind scheme for the convection term are used to discretize the mathematical model of the counterflow diffusion flame. Numerical results indicate that the combustion of pyrolysis gases in the boundary layer can completely protect the material surface from recession when the velocity of pyrolysis gases injecting to the boundary layer is higher than the critical velocity. There is an allometric relationship between the critical velocity and Mach number, and the combustion heat has little influence on the temperature distribution originating from the aerodynamic heating. This study will be helpful for the design of the thermal protection system in hypersonic reentry vehicles.

Sugar‐Derived Nanocrystalline Graphite Matrix C/C Composites with Excellent Ablative Resistance at 3000 °C

“…This phenomenon occurs because the pyrolysis gases in the carbon material can react with oxygen in the boundary layer, thus slowing the ablation of the material surface. [ 37 ] After 30 s of heat flux, the top of the sample gradually heats and glows until ≈90 s, when the surface response temperature gradually exceeds 1000 °C. The sample gradually recedes under the heat flux, but the overall shape remains cylindrical.…”

Aerodynamic and thermal environment of a gap under hypersonic flight

“…In the flight of a high speed vehicle, the air around the vehicle is severely compressed, and the temperature of it increases to a sufficiently high level. In order to protect the high speed vehicle from the heat of the high temperature air, it is covered with the thermal protection system which consists of ceramic thermal insulation tiles [1][2][3][4][5][6]. Considering of the brittleness of ceramic tiles and the thermal expansion, a gap must be left between these tiles to avoid that ceramic tiles break against others.…”

Influence factors of methane-air counterflow diffusion flame

“…Counterflow diffusion flame which takes an important role in both theoretic and experimental research has received considerable attention over the past 50 years [1]. The application of counterflow diffusion flame fits the surface ablation of charring materials for reentry of vehicles [2][3][4][5][6][7][8][9]. The physical and mathematical models for counterflow diffusion flame have been studied by many researchers.…”