Theoretical and experimental study of the gas- phase ignition of an evaporating fuel in a stagnant hot oxidizing gas
The gas-phase ignition theory of a condensed phase fuel suddenly exposed to a stationary hot oxidizing gas is presented for the nonconvective case of the heat feedback ignition model. Use is made of the heat balance condition as well as the Clausius-Clapeyron equation relating the fuel concentration to its temperature at the fuel surface. Analytical approximate solutions are derived for the gas temperature, the fuel concentration and the oxidizer concentration in the gas phase, and for the temperature and fuel concentration at the fuel surface. Ignition data are calculated for an organic condensed phase fuel in the oxygen atmosphere as an example. These results show qualitatively the same basic characteristics as those presented in a recent numerical analysis by Hermance et al. In the temperature range investigated, T = 1250-2500 °K, the predicted ignition delays agree fairly well with the corresponding experimental data obtained in a shock tube. Thus, the gas-phase ignition behavior of condensed phase fuels can be described properly by the analytical solutions achieved in the present paper. Because of their less restrictive nature, these analytical solutions could be applied to metal vapor ignition problems in rocketry.