Ignition characteristics of a two-component condensed fuel in a stagnation-point flow

Two-component condensed fuel ignition behavior is observed in a hot stagnation-point air flow. Fuels utilized in this study are mixtures composed of hexane and solid paraffin with high and low volatilities. At time zero, the mixed fuel is exposed to a hot air stream directed downward onto the fuel surface at room temperature. When the external air flow velocity increases at a fixed flow temperature (1083 K), the ignition time reaches a minimum point, and then it increases again until it goes to infinity for a certain critical flow velocity. This ignitable limit is based on a critical Damkohler number for ignition. The variation of the ignitable limit with fuel composition under fixed air flow conditions, displays a characteristic curve. As the hexane percentage increases, the critical velocity reaches a maximum around 40 wt% and a minimum around 50 wt%. A supporting ignition time tendency is also obtained. Finally, a qualitative discussion of this type of ignition behavior for binary fuel mixtures is given. The phenomenon described here is readily apparent when the difference of the volatilities of the component fuels is quite large.