Preferential Vaporization Impacts on Lean Blow-Out of Liquid Fueled Combustors

US Transportation Collection2019PDFManuscriptWon, Sang HeeRock, NicholasLim, Seung JaeNates, StuartCarpenter, DaltonEmerson, BenjaminLieuwen, TimEdwards, TimDryer, Frederick LUnited States. Federal Aviation Administration. Center of Excellence for Alternative Jet Fuels and EnvironmentGeorgia Institute of TechnologyUnited States. Department of Transportation. Federal Aviation Administration. Office of Environment and EnergyElsevierUnited StatesJet engine fuelsAlternate fuelsVolatilizationCetane numberCombustionj.combustflame.2019.04.00813-C-AJFE-GIT-008This manuscript is made available under the Elsevier user licensehttps://www.elsevier.com/open-access/userlicense/1.0/Journal ArticleRecent experimental works have shown that the global equivalence ratio defining lean blowout (LBO) in model gas turbine combustors correlates with the derived cetane number (DCN) of the tested fuel, which represents the chemical reactivity potential of the fuel, but additional physical and kinetic parameters of the fuel also have influence. The current work explores the significance of preferential vaporization impacts on LBO behaviors; i.e., rather than parameterizing the fuel by overall averaged fuel properties, it looks at DCN correlations based upon distillation properties prior to full vaporization. Preferential vaporization potentials of six fuels are evaluated by measuring the DCN values of five distillation cuts (each of 20% liquid distillation volume recovered). In spite of relatively large disparities in total fuel DCN values (~9.1), two petroleum-derived jet fuels are found to have nearly the same LBO equivalences, which is attributed to the relatively indiscernible difference of DCN values (~ 2) for the initial 20% distillation cut of each fuel. Trade-off impacts between fuel chemical and physical properties are demonstrated by comparing n-dodecane and Gevo-ATJ, which do not have preferential vaporization potential. LBO results suggest that fuel physical properties (particularly fuel boiling characteristics) predominantly control LBO behaviors at low air inlet temperature conditions, whereas fuel chemical properties appear to gain significance with increasing air inlet temperature. Further evidence of preferential vaporization effects on LBO is discussed with two surrogate mixtures formulated to emulate the fully pre-vaporized combustion behaviors of Jet-A, but having drastically different preferential vaporization potentials. Finally, the relationship between DCNs and LBO equivalence ratios is re-examined using the DCN values of initial 20% distillation cuts of all six fuels. The results display a significantly improved correlation, suggesting that the relevance of preferential vaporization on LBO can be significant for fuels that exhibit significant departure of the DCN for high volatile fractions (i.e., the initially vaporized constituents) in comparison to the overall fuel DCN.120