Intake ramp
An intake ramp is a rectangular, plate-like device within the air intake of a jet engine, designed to generate a number of shock waves to aid the inlet compression process at supersonic speeds.[1] The ramp sits at an acute angle to deflect the intake air from the longitudinal direction.[2] At supersonic flight speeds, the deflection of the air stream creates a number of oblique shock waves at each change of gradient along at the ramp. Air crossing each shock wave suddenly slows to a lower Mach number, thus increasing pressure.
Ideally, the first oblique shock wave should intercept the air intake lip, thus avoiding air spillage and pre-entry drag on the outer boundary of the deflected streamtube. For a fixed geometry intake at zero incidence, this condition can only be achieved at one particular flight Mach number, because the angle of the shock wave (to the longitudinal direction) becomes more acute with increasing aircraft speed.
More advanced supersonic intakes feature a ramp with a number of discrete changes of gradient in order to generate multiple oblique shock waves. The first known aircraft to use this is the North American A-5 Vigilante with fully-variable wedge-type side air intakes[3] In the case of Concorde, the first (converging) intake ramp is followed by a diverging ramp. After the air passes the end of the first ramp it has become subsonic such that the diverging ramp further contributes towards the reduction in airstream velocity and consequently its increase in pressure. This intake design thus ensures excellent pressure recovery and contributes to Concorde's improved fuel efficiency whilst cruising supersonically at up to Mach 2.2 (beyond which airframe heating effects limit any further increase in speed).[4]
Variable geometry intakes, such as those on Concorde, vary the ramp angle to focus the series of oblique shock waves onto the intake lip, control of which is accomplished by complex non-linear control laws using the ramp void pressure (the pressure of the air in the gap between the two ramps) as a control input.
The intake ramp for rectangular intakes has its equivalent in the inlet cone for circular intakes. Much lighter fixed-geometry alternatives are used on modern aircraft which are designed with greater emphasis on durability and survivability (stealth). These inlets preserve the performance of variable intake ramps by controlling shock position using the downstream pressure. They include the caret compression surface, used in the Boeing F/A-18E/F Super Hornet and Lockheed Martin F-22 Raptor inlets, and the diverterless supersonic inlet used on the Lockheed Martin F-35 Lightning II and Chengdu J-20.[5][6]
Intake gallery
- The ramps in two of the Concorde intakes are visible and clearly labelled as such.
- A-5 Vigilante with inlet ramps
- F-14 with internal ramps forming upper surface of intake duct
- Vertical ramps on inboard surface of intake duct XB-70
- F-15 internal ramps form upper surface of intake duct behind the intake upper lips which are shown in different positions
See also
- Index of aviation articles
- Inlet cone
- NACA duct
- Splitter plate
References
- ^ Naval Fighters Number Sixty-Four North American A-5A, RA-5C Vigilante by Steve Ginter. ISBN 0-942612-64-7. J79-GE-8 ENGINE AIR INDUCTION SYSTEM p.21 & 22
- ^ Gunston and Gilchrist 1993, pp. 188-189.
- ^ Gunston and Gilchrist 1993, p. 188.
- ^ A Case Study By Aerospatiale And Bristol Aerospace On The Concorde, Jean Rich and Clive S. Leyman, AIAA Professional Study Series, section 6.2 Intakes
- ^ Hamstra, Jeffrey W.; McCallum, Brent N. (2010). "Tactical Aircraft Aerodynamic Integration". Encyclopedia of Aerospace Engineering. 4.1.1 Caret Inlet. doi:10.1002/9780470686652.eae490. ISBN 9780470754405.
- ^ "The intake".
External links
- A-5 Vigilante intake ramp photos
- [1]
- v
- t
- e
- Aft pressure bulkhead
- Cabane strut
- Canopy
- Crack arrestor
- Cruciform tail
- Dope
- Empennage
- Fabric covering
- Fairing
- Flying wires
- Former
- Fuselage
- Hardpoint
- Interplane strut
- Jury strut
- Leading edge
- Lift strut
- Longeron
- Nacelle
- Rib
- Spar
- Stabilizer
- Stressed skin
- Strut
- T-tail
- Tailplane
- Trailing edge
- Triple tail
- Twin tail
- V-tail
- Vertical stabilizer
- Wing root
- Wing tip
- Wingbox
- Aileron
- Airbrake
- Artificial feel
- Autopilot
- Canard
- Centre stick
- Deceleron
- Dive brake
- Dual control
- Electro-hydraulic actuator
- Elevator
- Elevon
- Flaperon
- Flight control modes
- Fly-by-wire
- Gust lock
- HOTAS
- Rudder
- Rudder pedals
- Servo tab
- Side-stick
- Spoiler
- Spoileron
- Stabilator
- Stick pusher
- Stick shaker
- Trim tab
- Wing warping
- Yaw damper
- Yoke
devices
- Active Aeroelastic Wing
- Adaptive compliant wing
- Anti-shock body
- Blown flap
- Channel wing
- Dog-tooth
- Drag-reducing aerospike
- Flap
- Gouge flap
- Gurney flap
- Krueger flap
- Leading-edge cuff
- Leading-edge droop flap
- LEX
- Slats
- Slot
- Stall strips
- Strake
- Variable-sweep wing
- Vortex generator
- Vortilon
- Wing fence
- Winglet
instrument systems
- ACAS
- Air data boom
- Air data computer
- Aircraft periscope
- Airspeed indicator
- Altimeter
- Annunciator panel
- Astrodome
- Attitude indicator
- Compass
- Course deviation indicator
- EFIS
- EICAS
- Flight management system
- Glass cockpit
- GPS
- Head-up display
- Heading indicator
- Horizontal situation indicator
- INS
- ISIS
- Multi-function display
- Pitot–static system
- Radar altimeter
- TCAS
- Transponder
- Turn and slip indicator
- Variometer
- Yaw string
devices and fuel systems