Browsing by Author "Carrolo, Gabriel Alexandre da Costa"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Aerodynamic Breakup of a Single Droplet due to a CrossflowPublication . Carrolo, Gabriel Alexandre da Costa; Silva, André Resende Rodrigues daThe present experimental work focuses on the aerodynamic breakup study of unconventional fuels. This process refers to the secondary atomization of a drop due to a cross-flow, where different velocities cause several regimes and structures appear amidst drop deformation of Jet Fuel mixtures with HVO (hydroprocessed vegetable oil) and water. The excessive use of fossil fuels has led humans to find viable and environmentally beneficial alternatives for use in various types of engines and combustion processes. With this, the use of biofuels has been one of the most sought after alternatives, and its employment in the aeronautical and aerospace sector is an example of the beneficial use of these fuels. This dissertation’s objective is to visualize and study the dynamic behaviour of a drop at the transition points between regimes, for different crossflow velocities. The drops are composed of: Jet Fuel 100%, Jet Fuel 75% - 25% HVO, Jet Fuel 50% - 50% HVO, and H2O (used as reference fluid). Considering that present legislation in the aeronautical sector allows a minimum concentration of 50% Jet Fuel in volume makes the choice of mixtures used in this study have a more restricted criterion, and therefore other mixtures are not considered. For this, an experimental facility is designed and built. Consisting of a high-speed camera, allowing the ability to visualize all the mechanisms inherent to the secondary atomization of a drop, with a specific trigger activation and desired frame rate; an infusion pump, which allows control of the insertion rate of drops into the working section. Through flat-head needles with two different internal diameters, drops of the same size are produced for all fluids; backlighting through led strips behind a diffuser glass help standardize the light captured by the camera; a properly calibrated wind-tunnel to is necessary to reach the desired speeds for regime transitions. Using the existing literature, a comparison of the phenomena and secondary atomization regimes for this new group of mixtures is made. After the dynamic study of these mechanisms, the conclusions are drawn regarding the maximum deformation rate of a drop, taking into account the dimensionless characterization of time and the dimensionless groups of relevance for this study. Drop trajectory is also presented for each regime and fluid, and a new correlation is proposed for maximum cross stream diameter evolution due to time.
- Aerodynamic Breakup of a Single Droplet due to a Crossflowed AirstreamPublication . Carrolo, Gabriel Alexandre da Costa; Ribeiro, Daniela; Barata, Jorge M M; Silva, A. R. R.The main breakup regimes are visualized and studied with the help of a high-speed camera and a continuous jet of air, provided by a wind tunnel, is used to transition the droplet into the various stages of secondary atomization. The use of Jet Fuel and Biofuel mixtures is the focal point of this study. All the known regimes are encountered and each transitional We is calculated. The variation of We due to Oh is described, in addition to the comparison between We number thresholds and correlations existent in the literature for each regime transition. The influence of these numbers on the dimensionless characterization of time and later the maximum cross stream diameter is shown. Finally, a correlation for the temporal evolution of the drops’ cross stream diameter for all regimes, assuming its deformation is not a linear function of time, is proposed.