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Application of Micro Combustion In Boundary Layer Control

Yahyavi Koochaksarai, Mohammad Reza | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48459 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Javadi, Khodayar; Mardani, Amir
  7. Abstract:
  8. The present study focus is on finding a new solution to control laminar separation bubble phenomenon by combustion actuators in micro scale, which is investigated in flows with low Reynolds number surface effect and free flows. The main parameters in this problem are classified in three groups of formation location of laminar separation bubble, its length, and transition from laminar to turbulent around airfoil SD8020 in attack angle of 5 and 8 degree. Following that, the new combustion actuators in micro scale method the comparison it with cold (and hot) air jet injection is introduced to control boundary layer flow with separation bubble point of view. Some mechanisms are identified in improvement and modification of methane-air premixed flame and stabilization of it in micro scale, which includes effects of added hydrogen to methane as an additive, and a central conductive wire insertion with creating steps in the case. The finite volume method is used to solve the turbulent, viscos, and unsteady flow equations. The results are compared to experimental and numerical data obtained by other researchers, which have good conformity with aerodynamic coefficient predicting.The SIMPLE-C method is used in numerical algorithm utilized to coupling pressure and velocity fields, the second order upwind method is used to discretization of momentum equation, and finally sst transient k-w four equation model is used to turbulent flow modeling. The results show that numerical solution method used to flow modeling with low Reynolds number is able to recognize reverse pressure gradient and laminar separation bubble and flow transition from laminar to turbulent are observed in boundary layer. The bubble formation location and flow transition are also inclined towards airfoil leading edge under surface effect and pressure distribution is changed in laminar separation bubble formation location. Moreover, the utilization of combustion actuators with flow separation point of view leads to a decrease in flow Reynolds number along with airfoil wall and a trend of flow to laminar flow manner. This causes a more increase in lift coefficient than hot jet air injection. But the friction effects on the surface is increased by laminar flow, that leads to an increase in friction drag coefficient of explosive jet to hot air jet and generally an increase in drag coefficient. The stall phenomenon control by combustion actuator also leads to an increase in stall angle limit to 16 degrees and lift coefficient improvement to 26% (than without jet injection) through flow separation delay
  9. Keywords:
  10. Boundary Layer ; Surface Effect ; Aerodynamic Coefficient ; Separation Bubble Control ; Flow Transition ; Combustion Jet Injection

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