1. Inlets and Nozzles: Design Considerations EGR 4347 Analysis and Design of Propulsion Systems

2. Subsonic Inlets: Major Design Variables/Choices Inlet total pressure ratio and drag at cruise Engine location on wing or fuselage Aircraft attitude envelope Inlet total pressure ratio and distortion envelope Engine out windmilling airflow and drag Integration of diffuser and fan flow path contour Integration of external nacelle contour with thrust reverser or accessories Flow field interaction with nacelle, pylon or wing Noise suppression requirements

3. Inlet Considerations n Proximity to Ground - FOD n Proximity to nose gear - FOD n Proximity to Gun and Missile Bays - Smoke n Boundary layer buildup / diverter / stealth n Hide compressor face - stealth n Engine running during combat turn - access n Vortex ingestion - strake wakes

4. Subsonic Inlets

6. Subsonic Inlets: Total Pressure Ratio

7. Subsonic Inlets: Typical Airflow Requirements

8. Subsonic Inlets: Total Pressure Distortion

9. Subsonic Inlets: Drag

10. Subsonic Inlets: Diffusers

11. Subsonic Inlets: Boundary Layer Control

12. Inlet Integration Keep ducts as short as possible – reduces volume, reduces viscous losses – limits on turning flow without separation Keep offset ducts long enough to prevent separation Use the wing and fuselage to shield the inlet, reduce distortion Watch proximity to ground

13. Nozzle Design Considerations Accelerate the flow to high velocity with minimum total pressure loss Match exit and atmospheric pressures as closely as desired Permit afterburner operation without affecting main engine operation – requires variable-area nozzle Allow for cooling of walls if necessary Mix core and bypass streams of turbofan if necessary Allow for thrust reversing if desired Suppress jet noise and infrared radiation (IR) if desired Thrust vector control if desired

14. Nozzle Geometry

15. Gross Thrust Coefficient Exhaust velocity vector angularity Friction in the boundary layers Loss of massflow – leakage in nozzle Flow nonuniformities

16. Nozzle Integration Smooth boat tails (e.g., F-18) Minimize interference between... –Nozzle and control surfaces –Nozzle and nozzle Pay attention to rotation geometry Evaluate trades – 2-D or round (axi) nozzles? – integrated into trailing edge? – shielded above? below? from the side? – thrust vectoring? reversing?