Variable property analysis-is there anything to it?

Abstract

This paper discusses a few situations in combusting flows and attempts to demonstrate that including variable thermodynamic and transport properties in the analysis does more than simply improve the accuracy of predictions. The qualitative behaviour of the result itself is altered. Three examples are considered-single droplet combustion, forced convective turbulent boundary layer combustion, and free convective combustion. The flame to droplet radius ratio is very well predicted by variable property theory and the improvement is a direct consequence of the property variation. In the case of turbulent boundary layer combustion of solid/liquid fuels it is shown that the fuel exerts a significant influence on regression rate as is found in the experiments. The constant property theory, however, shows relative independence of regression rate with regard to the nature of the fuel. The prediction of regression rate is improved substantially in the case of free convective combustion.