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Experimental Investigation of the Performance of a Body Integrated Diverterless Supersonic Inlet

Askari, Rasoul | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52829 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Soltani, Mohammad Reza
  7. Abstract:
  8. Supersonic inlets, as one of the most important components of fighter aircraft, are designed to provide the required airflow with an acceptable level of energy and quality and with a minimum drag. From the inlet design point of view, there exist various configurations that are based on different criterion such as supersonic flow compression region, flow dimensions, and installation position, to name a few. The flight Mach number, M∞, could further complicate the design and structure of these types of inlets. One of the requirements for minimum drag is that at supersonic speed the shock wave that forms in front of the inlet must impinge on the cowl lip, called shock on lip condition (SOL). However, in a real flight, the aircraft encounter various flight conditions (including flight Mach number, altitude, angles of attack and side slip angle) where the impingement point might be located away from the cowl lip. In such situations, variable structures are usually adapted to adjust the inlet geometry to recover the SOL condition. The variable geometry and the corresponding mechanisms are very complex and increases the aircraft empty weight significantly, which is undesirable. In addition, design, manufacturing, and maintenance costs are other disadvantages of these systems. To overcome these complexities, a new design concepts called bumped or diverterless supersonic inlets (DSIs) have attracted designers’ attention and have been substituted for the variable geometry inlets. This design is used in the new generations of the fighter aircraft. These inlets have fixed geometries, low weight, however, their behavior for different aircraft are not well known.In the present study the performance of a body integrated diverterless supersonic inlet equipped with a Y-shaped diffuser is experimentally investigated. For this purpose, extensive wind-tunnel tests were performed on a Y-shaped diverterless supersonic inlet. The experiments were conducted at a free stream Mach numbers of M∞=0.75 (subsonic Mach number), M∞=1.65 (the design Mach number for this inlet), and M∞=1.85 (higher than M∞ for supersonic design point), and for angles of attack ranging from -2 to +6 degrees. All tests were at zero degrees side slip angle. The experiments were performed at various inlet operating conditions comprising supercritical, critical, and subcritical conditions that covered almost all ranges of the engine operating for this DSI.The results showed that the newly designed DSI had acceptable performance characteristics when operating at its design condition, supersonic Mach numbers, and is able to provide the required mass flow and static pressure ratios. Furthermore, its operation in the subsonic condition, M∞ = 0.75, was satisfactory. The results for the effects of AOA showed that the present DSI had acceptable performance characteristics for all ranges of AOA tested. A symmetric supersonic flow pattern was observed at subcritical, supercritical, and critical operating conditions of the present Y-shaped DSI. However, at high subcritical operating conditions, the supersonic flow structures became suddenly asymmetric and a new flow pattern was developed. This flow pattern was highly unstable and resulted in a significant asymmetric shock wave oscillations, boundary-layer thickening, and shock-/boundary-layer interaction. To the authors’ knowledge, this novel phenomenon of asymmetric flow behavior in a perfectly symmetric Y-shaped DSI encountering symmetric flow (at zero degrees AOA and AOS) has not been noticed by the previous researchers and, if so, the results have not been published yet
  9. Keywords:
  10. Inlet ; Shock Wave ; Supersonic Intake ; Air Inlet ; Mach Number ; Diverterless Supersonic Inlet (DSI)

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