Single-Droplet Combustion of Jet A-1, Hydroprocessed Vegetable Oil, and Their Blends in a Drop-Tube Furnace

The environmental impact and the dependence upon fossil fuels in the aeronautical sector have promoted the demand for alternative and greener fuels. The implementation of alternative fuels is one of the main challenges for this sector in the near future. A possible short-term solution might be the blending of biofuels with jet fuel, which would allow for the use of greener fuels and a reduction in the greenhouse gases and pollutant emissions without significant changes in the existing fleets of the companies, with the purpose to develop a drop-in fuel. In this context, this work examines the combustion characteristics of single droplets of Jet A-1 (JF), hydroprocessed vegetable oil (NExBTL), and their mixtures in a drop-tube furnace (DTF). The objective of this work is to evaluate the influence of the mixture composition on the fuel characteristics. Droplets with diameters of 155 +/- 5 mu m, produced by a commercial droplet generator, were injected into the DTF, whose wall temperature and oxygen concentration were controlled. Experiments were conducted for three temperatures (900, 1000, and 1100 degrees C). The combustion of droplets was evaluated through the images obtained with a high-speed camera coupled with a high magnification lens and an edge detection algorithm. From the images allowed for the analysis of droplet combustion, data are reported for the temporal evolution of droplet sizes and burning rates. The results revealed that the mixtures followed the D-2 law, except the mixture with 75% JF for a DTF wall temperature of 1100 degrees C. The 75% JF mixture did not follow the D-2 law as a result of the occurrence of puffing and microexplosions, which enhanced the burning rates. Additionally, it was observed that the mixtures with a higher content of JF present brighter flames and higher burning rates.

Automated summary

The study examined the combustion characteristics of different fuel mixtures in a drop-tube furnace, revealing that the composition of the mixtures influences the fuel characteristics. The 75% JF mixture at higher temperatures exhibited increased burning rates, likely due to puffing and microexplosions.