Experimental investigation on spark ignition and flame propagation of swirling kerosene spray flames

The ignition of kerosene spray in an aero-engine combustor is complex due to the fuel injection, mixing, and combustion to occur within limited time and space scales. Fundamentals of the gas–liquid two-phase ignition with realistic flow patterns remain virtually unexplored. In our study, a well-defined simplified combustor was designed to investigate the spark ignition of swirling kerosene spray flames. Non-contact optical diagnosis on flow filed and spray atomization shows that a large central recirculation zone and two small side recirculation zones, filled with small kerosene droplets below 60 μm, are formed inside the combustor with swirling air above 300 SLM. The mixture of kerosene and air in the combustor is highly sensitive to the injection pressure and air velocity. The ignition characteristic and flame behavior in four locations were compared. Ignition place at the wall where is corresponding to the maximum width of the recirculation zone is more likely to result in full flame. High-speed CH* chemiluminescence indicates that successful ignition sparks are associated with flame kernels that move upstream towards the spray nozzle. A shrinking flame kernel in failed event extinguishes after a few milliseconds. Different propagation paths after the spark depend on the ignition location, which can be understood from the flow field and the spray atomization.