Effect of Molar Mass Variation on a Flame Temperature and a Burning Rate

Abstract

Difference in the molar masses of a combustible gas and its combustion products has a strong effect on a flame temperature and a burning rate. Instead of a molar mass difference, one may consider a heat capacity difference at a constant pressure. There are two heat sources in a combustion zone. One of them is chemical, and the other one is similar to heat release (heat absorption) during a first-order phase transition, but, depending on the process, it can be partially chemical. The higher the heat capacity of the fuel in comparison with the heat capacity of the combustion products, the higher the burning rate and the flame temperature. For the physical completeness of the issue under discussion, an ideal thermodynamic cycle is considered, and it is shown that Carnot’s formula should contain a correction factor that takes into account a change in heat capacity.