An aerothermochemical analysis of combustion of carbon in the stagnation flow

Abstract

An aerothermochemical analysis is made of the combustion of solid carbon exposed to the stagnation flow of oxidizing gas, and the effects of the surface Damköhler number and the oxygen concentration in the oxidizing flow on the combustion rate of solid carbon are examined. A rather high surface temperature of solid carbon (higher than 1500 °K) and a very high rate of CO oxidation in gas phase are postulated; the heterogeneous reaction is taken as 2 C + CO 2→2 CO , and the homogeneous reaction as 2 CO + O 2→2 CO 2 . The analysis is reduced to a problem of solving a nonlinear second-order ordinary differential equation of energy for various combinations of the gas-phase Damköhler number and the surface Damköhler number. The surface reaction is found to have chemically the same effect as the increase of the stoichiometric ratio of gas-phase reaction and gasdynamically the increase of the fuel injection rate, so that the combustion rate of solid carbon is generally expected to be small. For the gas-phase reaction of infinitely high rate, an explicit expression for the relation between the surface Damköhler number, the oxygen concentration, and the combustion rate can be derived.