Publicação
Experimental Study of a Single Droplet Impinging upon Liquid Films: Jet Fuel and Biofuel Mixtures
| Resumo: | The present work is focused on a single droplet impinging upon a liquid film of the same fluid. This particular study is a matter of interest for several research areas and has a wide variety of applications such as fuel injection in internal combustion engines and processes involving spray paints, coatings and systems cooling. The human being started searching for new alternatives to reduce pollution, and since transports contribute with a significant portion, it is extremely necessary to bet on alternatives to fossil fuels. The introduction of biofuels in the aviation sector could be an example. The huge challenge is to modify and optimize piston engines to operate efficiently with alternative fuels. In order to achieve that, in these experiments, Jet Fuel and Biofuel mixtures were used. The main goal of this dissertation is to visualize the dynamic behavior of single droplets impinging upon liquid films with different relative thicknesses, several outcomes are possible. To accomplish that, four fluids were used: water (as reference), 100% Jet A-1, 75%/25% and 50%/50% mixtures of Jet A-1 and NEXBTL, respectively, since civil aviation only accept mixtures with at least 50% Jet Fuel in volume. To assure the accuracy of the calculations, the fluids physical properties were measured. An experimental facility was designed and built, and the setup includes a high-speed digital camera that was manually triggered with a specific exposure time. The impact site was illuminated by a led lamp through a diffusion glass to provide uniform back lighting. A syringe pump connected to the needle released the droplets with a specific pumping rate. The liquid film is held by a perspex container. Five needles were used with different inner diameters to yield five distinct droplet sizes for each fluid. Additionally, three impact heights were established to provide three impact velocities and Weber numbers for each needle. The liquid films depths considered were 10%, 50% and 100% of the droplet diameter. The existence of splash was reported as well as its characteristics. Some conclusions about the influence of the impact conditions and the fluids physical properties were indicated. Using the obtained data comparisons were made with some splashing thresholds available in the literature. |
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| Autores principais: | Ribeiro, Daniela Filipa Santo |
| Assunto: | Biocombustível Estudo Experimental Filme de Líquido e Splash Impacto de Gotas Jet Fuel |
| Ano: | 2018 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade da Beira Interior |
| Idioma: | inglês |
| Origem: | uBibliorum |
| Resumo: | The present work is focused on a single droplet impinging upon a liquid film of the same fluid. This particular study is a matter of interest for several research areas and has a wide variety of applications such as fuel injection in internal combustion engines and processes involving spray paints, coatings and systems cooling. The human being started searching for new alternatives to reduce pollution, and since transports contribute with a significant portion, it is extremely necessary to bet on alternatives to fossil fuels. The introduction of biofuels in the aviation sector could be an example. The huge challenge is to modify and optimize piston engines to operate efficiently with alternative fuels. In order to achieve that, in these experiments, Jet Fuel and Biofuel mixtures were used. The main goal of this dissertation is to visualize the dynamic behavior of single droplets impinging upon liquid films with different relative thicknesses, several outcomes are possible. To accomplish that, four fluids were used: water (as reference), 100% Jet A-1, 75%/25% and 50%/50% mixtures of Jet A-1 and NEXBTL, respectively, since civil aviation only accept mixtures with at least 50% Jet Fuel in volume. To assure the accuracy of the calculations, the fluids physical properties were measured. An experimental facility was designed and built, and the setup includes a high-speed digital camera that was manually triggered with a specific exposure time. The impact site was illuminated by a led lamp through a diffusion glass to provide uniform back lighting. A syringe pump connected to the needle released the droplets with a specific pumping rate. The liquid film is held by a perspex container. Five needles were used with different inner diameters to yield five distinct droplet sizes for each fluid. Additionally, three impact heights were established to provide three impact velocities and Weber numbers for each needle. The liquid films depths considered were 10%, 50% and 100% of the droplet diameter. The existence of splash was reported as well as its characteristics. Some conclusions about the influence of the impact conditions and the fluids physical properties were indicated. Using the obtained data comparisons were made with some splashing thresholds available in the literature. |
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