Frequency Domain Analysis of the Dynamic Spray Behavior of Aviation-Relevant Fuel Sprays to Characterize Alternative Jet Fuels Using X-Ray Diagnostics

Abstract The fluid dynamics of fuel sprays in a gas turbine combustor can impact the combustion characteristics and ultimately the performance and operability of jet engines. Therefore, it is important to characterize how the physical properties of alternative fuels can impact dynamic spray behavior to better understand the acceptable property ranges of “drop-in” substitutes for jet fuel and predict the performance of alternative fuels. In this work, we study the dynamic spray behavior of three synthetic fuels and a Jet-A sample at varying pressure conditions. We use a non-proprietary pressure swirl atomizer and study the downstream development of the non-reacting sprays using time-resolved high-speed x-ray imaging. Our results show that the properties of the fuel can impact the dominant modes of coherent oscillation in the system. We see that fuels with similar properties at similar flow conditions can exhibit a variation in dominant frequencies and mode shapes. Additionally, the sensitivity of the oscillation mode shape to fuel composition increases with increasing injection pressure. This work is a preliminary step towards characterizing how alternative jet fuel sprays compare to the conventional petroleum-based jet fuel. Quantitative characterization of spray behavior in the spatio-temporal domain with varying fuel properties will also help inform and validate simulation tools developed for studying fuel sprays of alternative jet fuels.