The role of preferential vaporization in bi-component n-dodecane/iso-octane non-premixed spray cool flames

Experimental studies are performed on the bi-component n-dodecane/iso-octane non-premixed spray cool flames in counterflow configuration to investigate the role of preferential vaporization. In spray phase experiments, a twin-fluid atomizer is employed in an atmospheric counterflow burner to produce polydisperse fuel spray to stabilize the spray flames. To investigate the preferential vaporization effects in spray cool flames, gas phase experiments are designed and performed at the same flow conditions. By measuring the extinction limits for three test fuels, it is found that for both gas and spray phase experiments, the blending of iso-octane weakens the cool flame and therefore yields lower extinction limits as its blending ratio increases. It is also found that the deviation of extinction limits between two phases for the same test fuel increases with the blending ratio due to the preferential vaporization effects. The more volatile fuel component iso-octane would vaporize first from the bi-component droplets, weaken the spray cool flame and extend the induction time of low temperature oxidation of n-dodecane, thus yielding lower extinction limits. These results will contribute to the development of advanced low-temperature combustion engines and spray combustion models with multicomponent liquid fuels in the future.