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Salari, Sina | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41841 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farhanieh, Bijan
  7. Abstract:
  8. Centrifugal Fans are widely used in industrial and commercial applications, from shop ventilation to material handling to boiler applications. They consume extremely high amount of energy each year. Because of this high consumption, even a small efficiency improvement could led to high amount of energy saving. Many projects have been done with this goal up to now, and present work is one of them, with aim to optimize a industrial centrifugal BI fan performance, with wheel diameter about 400 mm. The research has been done based on 3D numerical methods, done by commercial code Fluent 6.3, in steady state. MRF and k-E models have been used to simulate flow around blades, and turbulence respectively.
    Numerical results have been validated by experimental tests, based on AMCA standard, done by Nikotra Company. By comparison to experimental results, errors in pressure generation and power consumption, predictions are about almost 10 and 3 percent, respectively. Considered fan has parabolic shape shroud. A new shroud with conical shape is evaluated in this work by simulating fan with this new shroud shape. Cone shape shroud makes blade's effective area, larger than parabolic shape. Consequently pressure generation and power consumption are higher in this design. On the other hand, using cone shape shroud makes lost due to interaction between outflow from blades and recirculation flow to inlet clearance, higher in compare with parabolic shape, especially in high pressure generations. Combination of two mentioned aspects are come to one conclusion, that is better performance is obtained using cone shape in high flow rates and low rotational speeds. Besides shroud shape, inlet clearance has effect on recirculation flow too. By decreasing inlet clearance, recirculation flow rate is decreased too, so fan power consumption. Then decreasing inlet clearance, increases fan efficiency. Numerical results show, that by decreasing inlet clearance about 2.1 percent from 2.9 to 0.8 percent of fan wheel, fan efficiency increases 1.5 percent. Cut of f angle is examined in this work too. This angle is one of parameters to determine outlet area, and volume around blades to generate pressure. Decreasing outlet area could lead to high velocity and high loss. On the other hand increasing outlet area, could lead to decreasing volume around blade and decreasing pressure generation. So there is an optimum cut off angle. Numerical results show, that by choosing cut off angle about 5 instead of 13 (base fan), fan efficiency increases about 4.5 percent in best efficiency point. The best cut off angle should be design by more data and using some optimization methods.
  9. Keywords:
  10. Shrouds ; Numerical Solution ; Optimization ; Cutoff Wall ; Centrifugal Fan ; Inlet Clearance Shroud

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