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For safety purposes, reliable reignition of aircraft engines in the event offlame blow-out is a critical requirement. Typically, an external ignitionsource in the form of a spark is used to achieve a stable flame in thecombustor. However, such forced turbulent ignition may not always successfullyrelight the combustor, mainly because the state of the combustor cannot beprecisely determined. Uncertainty in the turbulent flow inside the combustor,inflow conditions, and spark discharge characteristics can lead to variabilityin sparking outcomes even for nominally identical operating conditions. Priorstudies have shown that of all the uncertain parameters, turbulence is oftendominant and can drastically alter ignition behavior. For instance, even whendifferent fuels have similar ignition delay times, their ignition behavior inpractical systems can be completely different. In practical operatingconditions, it is challenging to understand why ignition fails and how muchvariation in outcomes can be expected. The focus of this work is to understandrelight variability induced by turbulence for two different aircraft fuels,namely Jet-A and a variant named C1. A detailed, previously developedsimulation approach is used to generate a large number of successful and failedignition events. Using this data, the cause of misfire is evaluated based on adiscriminant analysis that delineates the difference between turbulent initialconditions that lead to ignition or failure. It was determined that the causeof ignition failure is different for the two fuels. While it was found thatJet-A is influenced by fuel entrainment, C1 was found to be more sensitive tosmall scale turbulence features. A larger variability is found in the ignitionmodes of C1, which can be subject to extreme events induced by kernelbreakdown.

Data-driven Analysis of Relight variability of Jet Fuels induced by Turbulence