Combustion of Carbon in an Air Stream

An investigation was made to determine the combustion rate of C operating at a surface temperature between 1000 and 3000 deg K in a stream of air. Relatively general forms of the surface reaction rate equations were used in the analysis, with the boundary layer equations simplified by letting Le = Pr = 1, so that the effect of the chemical kinetics could be elucidated. The results of the analysis can be used to make rapid engineering estimates of mass loss rate for a wide range of flight conditions. The accuracy of these estimates is limited primarily by the accuracy of the reaction rate parameters used rather than by the approximations used in the boundary layer equations, except when the combustion rate is controlled solely by diffusion and convection. Specific calculations, involving the graphical solution of two algebraic equations, were made at various stations on a blunted slender body for a flight Mach number of 15 and an altitude of 100,000 feet: The ablation rate for porous carbon approached the diffusion controlled value at the stagnation point for nose radii greater than 1 centimeter, but was found to be between the two limiting cases of reaction rate controlled and diffusionmore » controlled at a distance of 400 centimeters downstream of the stagnation point. The ablation rate for non-porous carbon, however, was reaction rate controlled for every station and geometry considered. (auth)« less