Prediction of flammability limit of an unconfined premixed gas in the absence of gravity

The existence of flammability limits in an unconfined gas mixture is investigated in the absence of gravity forces. Results of numerical calculations are presented for lean methaneair mixtures. For an adiabatic system, no flammability limit is found. However, when the heat loss due to radiative band emission from carbon dioxide and water in the burned gas region is included, a lean flammability limit is predicted. The predicted burning velocity does not approach zero at this limit, but has a finite minimum value. Comparison of the calculated flammability limit and minimum burning velocity with experiments at zero gravity shows reasonable agreement.