An Investigation of Alternative Aviation Fuel Spray Characteristics at Lean Blowout Conditions Using Hybrid Air-Blast Pressure-Swirl Atomizer

Many efforts on reducing pollutant emissions from the aviation gas turbines have been to mitigate the climate change and air quality. The National Jet Fuel Combustion Program (NJFCP) was initiated to develop new alternative aviation fuels, which are composed solely on hydrocarbons (non-petroleum), and to understand better the impact of chemical/physical properties of the fuels on combustion. One of the major objectives of NJFCP is to study the spray characteristics of the alternative jet fuels compared to conventional jet fuels to ensure that the performance of the alternative jet fuels is comparable to conventional jet fuels. In this study, spray measurements for alternative jet fuels with Phase Doppler Anemometry are presented. The major objective of this work is to study spray characteristics such as droplet size, drop velocity, and spray cone angle for candidate alternative jet fuels for operating conditions corresponding to lean blowout (LBO). A hybrid air-blast pressure swirl atomizer from Parker-Hannifin Corporation is used in the experiments. The spray cone angles are investigated using shadowgraph imaging with a high speed camera. Six fuels selected by the NJFCP on the basis of chemistry are A-2, C-1, C-5, C-7, C-8, C-9. The droplet sizes and velocities are measured and compared among six fuels at LBO conditions. For spray cone angles, three fuels (A-2, C-1, and C-5) were investigated at LBO conditions. The effects of the fuel injection pressure and the pressure drop across the injector swirler assembly on the spray characteristics have been studied. The droplet sizes and velocities were varied for each fuel. However, the differences were minimal among the fuels. The fuel injection pressure was observed to have minimal effect on the mean drop sizes and velocities, while the pressure drop across the swirler assembly had a significant effect on those characteristics. For spray cone angles, it was observed that the effects of the injection pressure, pressure drop, and fuel type were not significant.