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32

That's called a 'fuselage boundary layer diverter channel', or splitter plate. The air near the fuselage or wings is slowed down (thereby losing energy). Those plates ensure the jet engines get free stream air, which improves the engine performance. This free stream air will be undisturbed, allowing a more uniform intake of air. You can also find it on the ...


32

Inertial separators are augmented by gravity when located under the engine. It is easier to discharge ingested ice and debris downward, rather than some other direction, so that is where they go if possible. Inertia keeps solid matter low at the indicated point while air makes the turn into the engine. C130 Nacelle


27

It's for keeping the boundary layer flow from entering the intake, it's called a splitter plate. I think it's done to prevent turbulence inside the turbine (prevent compressor stall) and to make sure the intake doesn't ingest slow air, to maximize efficiency.


24

This explanation is for a subsonic aircraft, a similar process occurs at higher speeds. Causes A bird, an object or ice can disturb the flow of air entering the engine. Another source of compressor stall is an excessive engine angle relative to the air flow, when a large pitch or crab is forced, or when entering the wake of a preceding aircraft. Immediate ...


24

Both are ways to create compression shocks in order to compress and decelerate supersonic air. Spike intakes The central spike is characterized by: undisturbed flow, light weight and compactness, and easy adjustability to speed and mass flow at high flight speeds by translating the spike. Its disadvantages are: large loss of efficiency with angle of ...


22

(wikimedia.org) British Aerospace Jetstream You're right, it's the wing placement. For low-wing aircraft you find inlets above the prop, and sometimes circular inlets around the prop. The same engine shown above has different inlets depending on the plane, where you'd find an under-prop inlet in high-wing aircraft. (norebbo.com) But having the inlet above ...


20

The inlet angle is a compromise between cruise, when the aircraft has a low angle of attack, and the take-off and climb phase, when the engine runs at maximum thrust, and the angle of attack is several degrees higher than during cruise. Especially right after rotation, when the aircraft is heavy and slow, the angle of attack might reach into the lower two-...


17

Notice the path of condensation leading up from below this engine into it: That image was taken from this video, and it clearly demonstrates that there exists a path of air which flows from ground level up into the engine. Any debris on the ground is liable to be sucked up in that vortex. The nozzle is designed to break up the flowing air on that specific, ...


16

I wouldn't call the Su-27 small, but that is another issue. The main difference is the wing planform. The Su-27 wing is optimised to work over all angles of attack up to 120° with very little pitch moment change. This requires the addition of strakes which create vortex lift at higher angles of attack. With this planform the straight side intakes would be ...


15

That's the EPR inlet pressure sensor (there's another one located aft of the engine in the exhaust). EPR = Engine Pressure Ratio, one way to measure thrust. (source) See also: What is the difference between EPR and rotor speed as thrust setting parameter? How does the EPR reading behave in reverse, and in reheat modes?


12

The main purpose of having a square inlet is to have an oblique shock at the entrance so as to decelerate the air to subsonic speed before reaching the compressor. Also, the square inlet ramps are adjustable to produce optimum shock systems over a wide speed ranges. However, they are quite complicated. The turbofans used in civil airliners operate at ...


12

Vortex Dissipators Prevent vortices forming at the engine intakes which could cause gravel to be ingested by engine. These consist of a small forward projecting tube which blows pressure regulated (55psi) engine bleed air down and aft from 3 nozzles at the tip to break up the vortices. Source So basically it works by blowing air out of the tube to ...


12

EDIT: I'd just finished writing out my own answer when I stumbled across this answer to a different question, which nevertheless explains the function of the small intake in greater detail. I've included my answer below anyway. A couple of people have mentioned the splitter plate, but failed to address the smaller intake set between it and the fuselage. It'...


12

This doesn't fully answer the question, but the B727-100 also had an oval engine intake. AIRLINERS magazine Sept/Oct 99 edition: "The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center ...


9

Yes, it moves forward as the speed increases. Its purpose is "to slow the flow of air from supersonic flight speed to a subsonic speed before it enters the engine." From Wikipedia: The air flow to the engine is regulated by an inlet cone in the air intake. On early model MiG-21s, the cone has three positions. For speeds up to Mach 1.5 the cone is fully ...


9

Let's assume the A320 is powered by V2500 engines, one of the options for it. This engine has an air mass flow of 355 kg/s. At sea level, air density is 1.225kg per cubic m. Hence, 355 kg/s = 355/1.225 = 290 cubic m/s. Now, let's assume the aircraft is still at sea level, but now at Mach 0.8 (unrealistic, but we'll correct that next). The fan diameter is 1....


8

Do the holes in splitter plates reduce the boundary layer? Yes. Suction is applied to remove the slow-moving layer of air close to the surface, so the air entering the intake has as uniform a speed distribution over the intake cross section as possible. That this air is used for cooling before being dumped overboard is sensible, but if cooling were the ...


8

Long, winding intake ducts can increase the drag on the airflow moving through them, reducing the amount of air which the engine can ingest as opposed to a traditional diffuser design on a nacelle. Aircraft like the Harrier as well as the F-22, F-35 and F-117 have solved this problem with the use of large, suck in doors along the length of the intake duct ...


8

The jet uses a fixed, rhombohedral shaped jet intake combined with a serpentine intake duct. It allows for speeds just north of Mach 2 without the need for a variable geometry inlet to prevent shockwave ingestion.


7

A pitot intake will decelerate supersonic flow in one single, straight shock, while a ramp or cone intake will do this in several oblique shocks. It takes its name from the pitot tube, which in turn is named after the French physicist Henri Pitot who invented it to measure flow speed. The objective of an air intake is to supply the engine with a uniform ...


6

It is a pitot intake, and the round shape makes the intake tube lighter. It is a pressure vessel, after all, because the intake converts flow speed into pressure and slows the flow of air to the engines down to approximately half of the speed of sound. Placing the intake squarely at the side would make them less efficient (a classic example for this would ...


6

The semi-ventral pitot air intakes is a compromise between Ventral and Side Mounting where the intakes and their ducts are placed on the lower corner of the fuselage. In order to prevent interaction in case of single engine failure Rafale uses two semi-circular air intakes on the windward side, separated by the body. Intakes are separated from the fuselage ...


6

The compressor would stall. This will cause a sudden rise in turbine temperature, which could damage the turbine(s). In the end, with no air intake, the flame will die out and the engine would stop.


6

I believe the main reason is simply mechanical practicalities. The bulk of the engine core is mounted overlapping the structural members of the wing, either below or above the wing spars. The propellor is driven through a speed-reduction gearbox, which usually also offsets the propellor shaft from the turbine centreline. That offset is used to place the ...


6

The intake is for the primary heat exchanger. secondary is on the other side, Same location. The ambient air flows across a large rectangular heat exchanger. Basically a air to air radiator for the Bleed air system used for most functions on the F/A-18. Air conditioning, Wave guide pressurization, cabin pressure, avionics cooling, Gun,Etc. It cuts the air ...


5

Thermodynamics is your friend here. Compression in a ram intake is ideally isentropic (meaning entropy stays constant, so the whole process is reversible). In reality, some viscous losses cannot be avoided but are in the low percentage range in a well designed intake. The temperature $T$ in isentropic compression from a state 1 to a state 2 can be ...


5

Normally, such shutters are close to the intake and covered by simple spring-operated doors which open when the pressure in the intake duct drops below ambient pressure at low speed. AV-8B air intake (picture source). The upper two doors are open while the lower three are closed. The ideal area of a jet intake varies with flight speed. At low speed, it ...


5

Subsonic speed makes the inlet self-regulating. Add blunt edges, and the inlet works for a wide variety of engine and flight speeds, as it should. An inlet is always a compromise. Therefore, it is quite a bit larger than what is needed in cruise in order to keep losses at low speed low. At low flight speed and full throttle the engine needs much more air ...


5

Are the design drivers solely based on supersonic pressure loss improvement? Yes. And sometimes a few more considerations need to be taken into account. We have covered the reason for intake shapes well on this site, but the details must be collected from several answers. In a nutshell: Higher flight Mach numbers need more elaborate and heavier intakes in ...


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