AEROSPACE 410

AEROSPACE PROPULSION

ENGINE INTAKE AND NOZZLE SYSTEMFOR A SUPERSONIC TRANSPORT PLANE

CONCORDE

SUBSONIC-SONIC-SUPERSONIC OPERATION

Dr. Cengiz Camci

The Rolls-Royce/Snecma Olympus engines that arefitted to Concorde are a highly developed versionof the Bristol-Siddeley Olympus that was fitted tothe Vulcan bomber, which generated 11,000Lbs ofthrust.

The Olympus engines are 2 spool engines. The inner shaftrevolves within the outer shaft. The engine consists of14 compressor stages, 7 on each shaft, driven by theirrespective turbine systems. At supersonic speeds whenthe air approaches the combustion chamber is is very hotdue to the high level of compression of 80:1.

The darker (black areas) are the areas more susceptibleto heat and are thus constructed out of the nickel-alloy.

To protect the later compression stages the last 4 stagesare constructed of a nickel-bassed alloy, the nickel alloyis usually reserved only for the turbine area.

Concorde is the only civil airliner in service with a 'military style' afterburner system installed toproduce more power at key stages of the flight.

The reheat system, as it is officially known, injects fuel into the exhaust, and provides 6,000Lb of the totalavailable thrust per engine at take off.

This hotter faster exhaust that is used on take off and is whatis mainly responsible for the additional noise that Concordemakes. The reheats are turned off shortly after take offwhen Concorde reaches the noise abatement area.

MACH 2.0 INLET FOR THE

SUPERSONIC TRANSPORT CONCORDE

spilldoors

ramps

delta vortexforming atlow speedhigh angle of attackCCW

AIR FLOW and INTAKES

To further improve engine system performance,the air flow through the engine area is changedat different speeds via a variable geometryintake control system. Altering this airflow changesthe amount of air available to theengine and the amount of air thatin itself is producing thrust viathe complex ramp and nozzleassemblies.

ramps

rampsspilldoors

The air intake ramp assemblies main job isto slow down the air being received at the engineface to subsonic speeds before it then enters the engines.

At supersonic speeds the engine would be unstable if the air being feed to it was alsoat a supersonic speed so it is slowed down before itgets there.

Subsonic Speeds (take off/subsonic cruise)

At take-off the engines need maximum airflow, therefore the ramps are fully retracted and the auxiliary inlet vane is wide open. The auxiliary inlet begins to close as the Mach number builds and it completely closed by the time the aircraft reaches Mach 0.93.

SUBSONIC CRUISE

At slow speeds all the air into the engine is primary airflowand the secondary air doors are kept closed. Keeping themclosed also prevents the engine ingesting any of itsown exhaust gas. At around Mach 0.55 the secondary exhaust buckets beginto open as a function of Mach number to be fully open whenThe aircraft is at M=1.1

SecondaryExhaustbuckets

Shortly after take off the aircraft enters the noiseAbatement procedure where the re-heats are turned offand the power is reduced.

The ramps begin move into position at Mach 1.3 which shock wave start to form on the intakes.

The secondary nozzles are opened further to allowmore air to enter, therefore quietening down the exhaust.The secondary air doors also open at this stage to allow airto by pass the engine.

SUPERSONIC SPEEDS At the supersonic cruse speed of Mach 2.0 the ramps havemoved over half their amount of available travel,slowing down the air by producing a supersonic shockwave(yellow lines) at the engine intake lip.

SUPERSONIC CRUISE

Some of the inlet fluid from the shock-boundary layerinteraction zone is removed in the ramp area

Back to low speeds

When the throttles are brought back to start the decent the spill door is opened to dump out excess airthat is no longer needed by the engine, this allows the ramp to go down to their maximum level of travel.

As the speed is lowered the spill doors are closed and theramps begin to move backso by M=1.3 are again fully retracted.

ENGINE FAILURE

Should an engine fail andneed to be shut down during supersonic cruise,

the ramps move fully down and thespill door opens to dump out excess air that is no longerrequired by the failed engine.

The procedure lessens thechances of surges on the engine.

ENGINE FAILURE

THRUST REVERSAL

After touch down the engines move to reverse power mode. The main effect of this is that the secondary nozzle buckets move to the closed position directing airflow forwards to slow the aircraft down.

SUBSONIC FLIGHT

ENGINE 4 ENGINE ROTATING STALL PROBLEM

The main issue is that at slow airspeeds the enginesuffers vibrations on the low pressure compressor bladesfrom air vortices, that are created by the wing leading edgesections, entering it from both the air intake and fully openSpill door that moving in an anti-clockwise direction, which is the opposite direction to the engine's direction of rotation.

The effect is not seen on engine No1, as the vortices travel inthe same direction as the aircraft.

The No4 engine is limited on take off to 88% N1 at speeds below 60 Knots.

If you stand underneath or behind Concorde duringtake off it can be clearly seen that the no4 spill door isnot as open as the other three.

The reheat flame on engine 4 is also not as bright or stableas the other three during the initial take off roll, until the aircraft is around 60 knts when it matches the others.

Engine rotational direction is clockwise

VORTICAL STRUCTURESOF FLOW at engine inletIS IN COUNTER CLOCKWISEDIRECTION

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