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- Combustion behavior of Jet-A1 single droplets and its blends with Hydroprocessed Vegetable Oil in a drop tube furnacePublication . Pacheco, Gonçalo; Silva, A. R. R.; Costa, MárioThe aeronautical sector contributes significantly to greenhouse gases and pollutant emissions. The negative impact of these emissions in the environment has raised awareness for the introduction of alternative and greener fuels. The implementation of alternative fuels remains one of the main challenges for this sector in the near future. The aeronautical industry is characterized by the dependence on single fossil fuel and by a long service time of its assets. For these reasons, the main research drive has been around the development of “drop-in” fuels, which are alternative fuels that can be used in the already existing fleet without significant modifications. One of the proposed solutions is the blending of biofuels with jet fuel, which would allow the use of greener fuels and a reduction in greenhouse gases and emissions without significant changes in the existing companies’ fleets. In this context, the present work evaluates the ignition and the combustion of single droplets of jet-fuel, hydroprocessed vegetable oil (NExBTL), and their mixtures in a drop tube furnace. The main research focus of this study is to evaluate the influence of the mixture composition in the fuel-burning characteristics. Droplets with diameters of 155 ± 5 μm, produced by a commercial droplet generator, were injected into the top of the drop tube furnace. Three temperatures were investigated 900, 1000, and 1100 °C. The ignition and combustion of the droplets were evaluated through the images obtained with a high-speed camera (CR600x2) coupled with a high magnification lens (Navitar 6000 zoom lens) and treated with an edge detection algorithm. The images allowed for the observation of the burning phenomena, and the data reported the temporal evolution of the droplet sizes and burning rates. The pure fuels and mixtures followed the D2 law, except for the mixture with 75% jet-fuel/ 25% biofuel at 1100 °C that reveals disruptive burning phenomena contributing to the enhancement of the single droplet combustion. The disruptive burning phenomena are related to the appearance of “puffing” and micro-explosions at the end of the droplet lifetime.
- Single droplet ignition and combustion of Jet-A1, vegetable oil and their blends in a drop tube furnacePublication . Pacheco, Gonçalo; Silva, A. R. R.; Costa, MárioThe aeronautical sector needs to introduce alternative fuels in order to achieve a reduction in greenhouse gas emissions. A possible solution in the near future might be the blending of biofuels with jet fuel, which would allow the use of a greener fuel without significant changes in the existing fleets of the companies, which means the development of a “drop in” fuel. The present work aims to study the ignition and combustion characteristics of single droplets of jet-A1 (JF), hydroprocessed vegetable oil (NExBTL) and their mixtures in a drop tube furnace (DTF). The droplets were injected into the DTF using a droplet generator. Experiments were conducted in air for three DTF wall temperatures (900, 1000 and 1100 ºC). The ignition and combustion of the droplets were evaluated through the images obtained with a high-speed camera coupled with a high magnification lens. The images allowed for the observation of the burning phenomena, and data are reported for temporal evolution of droplet sizes and burning rates. The results revealed that the mixtures followed the 𝐷2 law, except the mixture with 75% JF for a DTF wall temperature of 1100 ºC. This was due to the occurrence of puffing, which enhanced the burning rates. In addition, it was observed that the mixtures with higher content of JF present brighter flames, and higher burning rates.