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Experimental Investigation of Cold-flow Characteristics in Near-Wake of V-gutter Flameholders

Ataei Dadavi, Iman | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43754 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mazaheri, Karim; Morad, Mohammad Reza
  7. Abstract:
  8. Bluff bodies are commonly used to stabilize flames in many high-speed flow applications. V-gutters are one of the most common bluff bodies that are mainly used in ramjet combustors and turbojet or turbofan afterburners for flameholding. Aerodynamic characteristics of flow behind V-gutter has crucial effect on mechanism of flame stabilization, therefore more experimental investigations still seem to be necessary in this area. Particle Image Velocimetry technique which has high temporal and spatial resolution has been used in this research in order to better investigate the structure and dynamics of this unsteady and complex flow filed. Experiments were done on a reference V-gutter in different Reynolds number and then on different V-gutters with different span angles, different blockage ratios and a slitted V-gutter and influences of these geometrical variations on flow parameters have been investigated and discussed. Instantaneous velocity field and dynamics of flow structure, Strouhal number, mean velocity field, length and geometry of recirculation zone, pressure coefficient, turbulent kinetic energy and vorticity field are obtained and then compared and analyzed for different V-gutters. Formation, growth and shedding of vortices periodically from either side of V-gutters have been seen in all cases. In mean velocity field, a symmetric recirculation zone has been seen immediately behind the V-gutter, which is characterized by reverse flow, low pressure, shear layers with concentrated vorticity in its both sides and maximum turbulent kinetic energy at its end. By increasing Reynolds number, length of recirculation zone increases at first and then decreases; and turbulent kinetic energy increases. By increasing span angle of V-gutter, Strouhal number and pressure coefficient decrease and length of recirculation zone and magnitude of vorticiy in shear layer increase. By increasing blockage ratio, Strouhal number increases and non-dimensional length of recirculation zone and pressure coefficient decrease. For the slitted V-gutter, the back pressure is lower and the reverse velocity and turbulent kinetic energy have more uniform distribution in entire recirculation zone
  9. Keywords:
  10. Flame Stabilization ; Particle Image Velocimetery (PIV) ; V-Gutter ; Recirculation Zone

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