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Experimental Investigation of the Effect of the Bleed Slant Angle on the Performance and Stability of a Supersonic Air Intake

Abedi, Mahdi | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46531 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Soltani, Mohammad Reza
  7. Abstract:
  8. In the study of supersonic air intakes, two important issues including performance and stability are considered. In these types of intakes, when inlet mass flow rate is reduced to a specified amount, a self-sustained instability called Buzz phenomenon occurs. During this phenomenon, shocks and expansion waves oscillate ahead of the intake that will degrade the performance considerably due to the periodic pressure fluctuations inside the intake. In the current study, a supersonic axisymmetric air intake with mixed compression which has designed for a free stream Mach number of 2.0 has been tested were conducted for free stream Mach numbers of 1.8, 2.0, and 2.2, and the results were analyzed for both stability and performance characteristics. Furthermore, boundary layer suction method (bleed) over the compression ramp (cone) was used as a control strategy in order to increase the intake stability. To improve the stability and performance of the intake, four different tip cone geometries, one of them without bleed slot and others with bleed slot, with slant angle of 90˚, 60˚ and 45˚ were fabricated and tested, while keeping other effective parameters on the bleed design constant. Results showed that flow suction over the compression ramp surface has significant effect on both stability and performance characteristics of the intake. Moreover, the results indicate that changing the bleed slant angle has negligible effect on the performance while it has significant effect on the intake stability. Maximum flow leakage by the bleed for all test conditions was about 1% of the total inlet mass flow rate. The effect of changing the bleed slant angle on the steady condition on performance is limited to 10%, but it has increased the stability margin about 20%. Changing the bleed slant angle has directly affected the mass flow rate amount passing through the bleed, while, it has affected indirectly the stability and performance parameters. Lastly, it was found that bleed with slant angle of 45˚ has maximum positive effect on the performance parameters, while the maximum positive effect on the stability parameter is achieved with the bleed with angle of 90˚. Thus, it could be concluded that the optimum bleed slant angle should be selected according to the free stream velocity and the intake operating condition. In addition, the study has shown that presence of bleed and changing its slant angle does not have significant effect on the intake efficiency in the critical condition limits and on the critical point, which is a very desirable
  9. Keywords:
  10. Experimental Test ; Buzz Phenomenon ; Supersonic Intake ; Performance ; Stability ; Bleed Slot Slant Angle

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