COMBUSTION CHARACTERISTICS OF ISOLATED FREE-FALLING DROPLETS OF JET A BLENDED WITH ETHANOL AND BUTANOL

Recent studies on experimental gas turbines suggest that the addition of ethanol or butanol to Jet A are viable alternatives for reducing CO and NOx emissions while maintaining similar performance to that of pure Jet A. In light of this potential, experimental data regarding the burning characteristics of Jet A/ethanol and Jet A/butanol blends are required in order to better understand their combustion process. Following a previous study on Jet A/butanol droplet combustion, the scope has been extended in order to also include ethanol and a Jet A/ethanol mixture as well as to perform a more detailed characterization. In this work the combustion characteristics of Jet A, butanol, ethanol and their mixtures (20% vol. alcohol in kerosene) are presented for different test conditions. The evaluated combustion characteristics include droplet, flame and soot shell size evolutions, burning rates and image-based soot estimations. The influence of oxygen availability is also ascertained. The evolution of droplet diameter and burning rates for Jet A and its blends with both alcohols are very similar, whereas pure ethanol and butanol display more distinct behaviors. Soot indices are found to be quite different, with a clear reduction in the sooting propensity of the Jet A/alcohol mixtures when compared to neat kerosene. These results support the feasibility of kerosene-alcohol mixtures as promising alternative fuels with similar combustion characteristics, but with much lower sooting propensity than pure kerosene.