Determining flammability limits by analyzing diffusive-thermal flame instability. methane–air–diluent mixture

This paper describes the method for determining flammability limits with the use of equations for diffusive-thermal stability boundaries. The key parameter responsible for the existence of flammability limits is the thermal effect produced by the combustion of gas mixtures. The thermal effect and the equation for diffusive-thermal stability boundaries are used to determine a minimum flame temperature below which combustion is impossible. Flammability limits are significantly affected by the heat capacity of components of the mixture if it is strongly dependent on temperature. For upper and lower flammability limits, a minimum flame temperature is generally different and dependent on the relative concentration and properties of the diluent. The theoretical methods for calculating flammability limits are tested according to the experimental data on the combustion of a methane–air–diluent mixture.