Effects of exothermicity on unsteady diffusion flames

The effects of exothermicity on unsteady diffusion flames are analysed for one-dimensional geometries and homogeneous isobaric flow. The diffusive burning is described in terms of the mixture fraction by a non-linear integro-differential equation, depending on two parameters: the initial FO ratio and an exothermicity factor, which is function of the heat of reaction and the initial fuel concentration. The rates of fuel consumption with variable density increase significantly when compared to the fuel consumption rates with constant density for cylindrical and spherical flames. Their burning times are also significantly reduced, as a consequence of the stretching in flame area and smaller concentration gradients. Analytical expressions are obtained for flame position, flame sheet velocity, induced flow field, composition, temperatures, and consumption rates.