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Projeto e fabrico de um tĂșnel de vento de circuito aberto em escala reduzida
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Abstract(s)
No presente trabalho foi concretizado a conceção, projeto e fabrico de um tĂșnel de vento subsĂłnico de circuito aberto em escala reduzida com o objetivo de criar uma ferramenta acessĂvel para estudos didĂĄticos nos cursos do departamento de engenharia mecĂąnica do ISEP. O tĂșnel de vento foi dimensionado com base na literatura apresentada, visando garantir um escoamento estĂĄvel e uniforme. Tomou-se como base a secção de teste, tendo sido definida uma secção de entrada de 200x200 mm, comprimento de 500 mm e uma secção de saĂda de 203x203 mm. Aplicando uma razĂŁo de contração de 6:1 obteve-se uma secção de entrada da contração de 490x490 mm e um comprimento de cerca de 613 mm aplicando um fator de 1,25 vezes o diĂąmetro hidrĂĄulico da secção de entrada. Relativamente ao difusor foi selecionada uma razĂŁo de expansĂŁo de 1:2,5 e Ăąngulo de expansĂŁo de 4°, resultando numa secção de saĂda de 321x321 mm e comprimento de 844 mm. Com os meios disponĂveis, foram selecionados materiais possĂveis de operar manualmente, com exceção da etapa de corte de materiais para a contração atravĂ©s de uma mĂĄquina fresadora CNC. Utilizou-se PVC, madeira, placas de poliuretano, espuma expansiva, manta de fibra de vidro e juta para a construção da contração, tendo esta demorado cerca de um mĂȘs para ser finalizada. A estrutura do favo de abelha foi construĂda a partir de um aro com ripas de madeira e tubos de PVC com 16 mm de diĂąmetro interior e 2 mm de espessura. Selecionou-se uma razĂŁo entre đżâ e đ·â de 7,5, resultando num comprimento de 120 mm. Para a cĂąmara de estabilização, utilizou-se placas de madeira contraplacada e ripas de madeira. A seleção da rede teve em conta a razĂŁo de ĂĄrea aberta recomendada na literatura. Para construir a secção de teste selecionou-se o ABS e recorreu-se
a uma impressora 3D, tendo sido necessårio dividir a secção de teste em quatro partes devido às dimensÔes da impressora. Cada base demorou cerca de 16 horas e cada tampa cerca de 7 horas. Posteriormente foram acopladas e coladas placas de policarbonato, permitindo a visualização para o interior da secção de teste. Para o difusor utilizou-se madeira contraplacada e ripas de madeira. A seleção do ventilador MV 30 teve em consideração o caudal necessårio
para a velocidade de escoamento inicialmente estipulada de 20 m/s, no entanto devido a questĂ”es burocrĂĄticas o mesmo apenas foi entregue na Ășltima semana da submissĂŁo da dissertação. Assim sendo, foi utilizado um ventilador de um radiador de um automĂłvel, um manĂłmetro de pressĂŁo diferencial digital e um tubo de Pitot estĂĄtico para a realização de cinquenta mediçÔes da pressĂŁo dinĂąmica e da velocidade do escoamento ao longo da secção de teste, tendo-se verificado que o escoamento permanece estĂĄvel e uniforme, apresentando variaçÔes de velocidade entre 0,1 e 0,3 m/s e uma velocidade mĂ©dia de 13,6 m/s. MediçÔes realizadas entre a entrada e a saĂda da secção de teste com o ventilador MV 30 devolveram variaçÔes de velocidade idĂȘnticas e uma velocidade mĂ©dia de cerca de 18 m/s. Com os
resultados obtidos constatou-se que o tĂșnel de vento se revela adequado para fins educativos e para o teste de corpos em pequena escala, contribuindo como uma base prĂĄtica para conciliar com a teoria abordada durante as aulas, assim como para investigar e desenvolver melhorias em objetos de estudo.
This work involves the conception, design, and manufacture of an open-circuit subsonic wind tunnel on a reduced scale, with the goal of creating an accessible tool for didactic studies in ISEPâs mechanical engineering department. The wind tunnel was dimensioned based on the presented literature, aiming to ensure stable and uniform flow. The test section was taken as a basis, with an inlet section of 200x200 mm, a length of 500 mm and an outlet section of 203x203 mm. Applying a contraction ratio of 6:1 resulted in a contraction inlet section of 490x490 mm and a length of around 613 mm, applying a factor of 1,25 times the hydraulic diameter of the inlet section. For the diffuser, an expansion ratio of 1:2,5 and an expansion angle of 4° were selected, resulting in an outlet section of 321x321 mm and a length of 844 mm. With the resources available, materials were selected that could be operated manually, except for the stage of cutting materials for contraction using a CNC milling machine. PVC, wood, polyurethane panels, expanding foam, fiberglass blanket and jute were used to build the contraction, which took about a month to complete. The honeycomb structure was built from a frame with wooden slats and PVC pipes with an internal diameter of 16 mm and a thickness of 2 mm. A ratio between đżâ and đ·â of 7,5 was selected, resulting in a length of 120 mm. Plywood boards and wooden slats were used for the settling chamber. The selection of the screen considered the open area ratio recommended in the literature. To build the test section ABS was selected and a 3D printer was used, requiring the test section to be divided into four parts due to the printerâs dimensions. Each base took around 16 hours and each top around 7 hours. Polycarbonate plates were then attached and glued on, allowing the test section to be visualized from the outside. Plywood and wooden slats were used for the diffuser. The selection of the MV 30 fan was based on the flow rate required for the initially stipulated flow speed of 20 m/s, however due to bureaucratic issues it was only delivered in the last week before the dissertation had to be submitted. A fan from a car radiator, a digital differential pressure gauge and a static Pitot tube were therefore used to take fifty measurements of the dynamic pressure and flow velocity along the test section, and it was noted that the flow remained stable and uniform, with speed variations between 0,1 and 0,3 m/s and an average speed of 13,6 m/s. Measurements taken between the inlet and outlet of the test section with the MV 30 fan returned identical speed variations and an average speed of around 18 m/s. The results obtained showed that the wind tunnel is suitable for educational purposes and for testing smallscale bodies, providing a practical basis for reconciling the theory covered in class, as well as for researching and developing improvements to objects of study.
This work involves the conception, design, and manufacture of an open-circuit subsonic wind tunnel on a reduced scale, with the goal of creating an accessible tool for didactic studies in ISEPâs mechanical engineering department. The wind tunnel was dimensioned based on the presented literature, aiming to ensure stable and uniform flow. The test section was taken as a basis, with an inlet section of 200x200 mm, a length of 500 mm and an outlet section of 203x203 mm. Applying a contraction ratio of 6:1 resulted in a contraction inlet section of 490x490 mm and a length of around 613 mm, applying a factor of 1,25 times the hydraulic diameter of the inlet section. For the diffuser, an expansion ratio of 1:2,5 and an expansion angle of 4° were selected, resulting in an outlet section of 321x321 mm and a length of 844 mm. With the resources available, materials were selected that could be operated manually, except for the stage of cutting materials for contraction using a CNC milling machine. PVC, wood, polyurethane panels, expanding foam, fiberglass blanket and jute were used to build the contraction, which took about a month to complete. The honeycomb structure was built from a frame with wooden slats and PVC pipes with an internal diameter of 16 mm and a thickness of 2 mm. A ratio between đżâ and đ·â of 7,5 was selected, resulting in a length of 120 mm. Plywood boards and wooden slats were used for the settling chamber. The selection of the screen considered the open area ratio recommended in the literature. To build the test section ABS was selected and a 3D printer was used, requiring the test section to be divided into four parts due to the printerâs dimensions. Each base took around 16 hours and each top around 7 hours. Polycarbonate plates were then attached and glued on, allowing the test section to be visualized from the outside. Plywood and wooden slats were used for the diffuser. The selection of the MV 30 fan was based on the flow rate required for the initially stipulated flow speed of 20 m/s, however due to bureaucratic issues it was only delivered in the last week before the dissertation had to be submitted. A fan from a car radiator, a digital differential pressure gauge and a static Pitot tube were therefore used to take fifty measurements of the dynamic pressure and flow velocity along the test section, and it was noted that the flow remained stable and uniform, with speed variations between 0,1 and 0,3 m/s and an average speed of 13,6 m/s. Measurements taken between the inlet and outlet of the test section with the MV 30 fan returned identical speed variations and an average speed of around 18 m/s. The results obtained showed that the wind tunnel is suitable for educational purposes and for testing smallscale bodies, providing a practical basis for reconciling the theory covered in class, as well as for researching and developing improvements to objects of study.
Description
Keywords
Aerodynamics Low-speed wind tunnel Dimensioning Material selection Construction/manufacturing Pressure and speed measurement AerodinĂąmica TĂșnel de vento subsĂłnico Dimensionamento Seleção de materiais Medição de pressĂŁo e velocidade Construção/Fabrico