Combustion Branch (AFRL/RQTC), Turbine Engine Division Wright-Patterson Air Force Base United States
During the past fiscal year, researchers with the Air Force Research Laboratorys Combustion Branch made substantial progress in numerous areas including 1 ultra-compact combustors, 2 inter-turbine burner concepts, 3 bluff-body stabilized turbulent flames, 4 well-stirred reactors for chemical kinetics, and 5 detonation-stabilized turbulent flames.Lean blowout data was collected on propane and jet fuel bluff-body stabilized flames and was combined with data taken from past literature to create a database of over 1,100 data points. The best correlation for the overall dataset included pressure, temperature, the ratio of flameholder diameter to lip velocity, oxygen level, and the hydrogen-to-carbon ratio of the fuel as factors. The R-squared value of this correlation was 0.873. The exponents on the factors indicated that high pressure and temperature lowered the equivalence ratio at lean blowout, as did high levels of oxygen. The correlation for the ignition delay dataset with pressure, temperature, and the ratio of flameholder diameter to lip velocity as factors had an R-squared value of 0.942. This relatively small, uniform dataset correlates very well. When ignition delay time replaces pressure and temperature, the data continues to correlate well, with an R-squared value of 0.918. For this limited dataset, the ignition delay time is an adequate representation of the chemical timescale.