Liftoff Characteristics of Ethylene and Ethane Jet Flames in Coflow

This work aimed to figure out the liftoff characteristics of ethylene and ethane, which are both promising fuels in the new energy era for flames in coflow. A free jet condition, air coflow condition, and vitiated coflow condition were chosen, and methane was chosen as the coflow fuel. Under the free jet condition and air coflow condition, the influence of coflow rate on jet flame liftoff height was studied, and under the vitiated coflow condition, the effect of equivalent ratio on liftoff height was also studied. Results indicate that increasing the coflow rate could raise the liftoff height of the two jet fuels in conventional combustion mode under all coflow conditions. A higher equivalent ratio resulted in lower initial value and faster increasing rate of liftoff height. Ethylene jet fuel showed lower liftoff height compared with ethane jet fuel under all coflow conditions. Furthermore, a conversion from conventional combustion mode to transitional combustion mode occurred under the vitiated coflow condition, and the equivalent ratio showed a more significant effect on this conversion than that by coflow rate. Additionally, the appearance of a triple-flame structure under the vitiated coflow condition was investigated. (C) 2019 American Society of Civil Engineers.