turbines 6

exhaust purpose

straighten the flow of hot gases

accelerate the flow of hot gases for thrust

components of exhaust

• exhaust cone assembly

• duct

• nozzle

where does the exhaust section start and end

start from turbine exit to where exhaust gases leave the engine

cone assembly

consists of outer duct, exhaust cone and turbine support struts

collects turbine discharge gases and delivers to exhaust duct

straightens out exhaust gases by forming a divergent duct between exhaust cone and outer duct`

exhaust duct

directs gases to exhaust nozzle

exhaust nozzle

provides exhaust gases with a final boost in velocity to produce maximum thrust

types of exhaust nozzle

convergent

convergent-divergent

divergent

convergent exhaust nozzle

increase gas velocity = increase thrust

used for subsonic`

convergent-divergent nozzle

gas enters convergent section at subsonic speed and leaves at the speed of sound > duct area increases in divergent section > airflow accelerates to supersonic speed

used for supersonic

divergent exhaust nozzle

used for helicopters to enhance hover

exhaust section also houses

1. Thrust reverser assembly 

2. Afterburners

3. Thrust vectoring system

4. Noise suppression system

thrust reversers

Used to slow aircraft down on landing and rejected takeoff (RTO) (along with brakes and spoilers) for rapid deceleration

types of TR

• Bucket door

• Clamshell door

• Cascade or deflector door

bucket door TR

2 buckets normally stowed when engine is in forward thrust

2 buckets move aft on rails for reverse thrust to redirect hot and cold gas streams forward

hydraulic or pneumatic

turbojet and low bypass engines

clamshell door TR

same as bucket

installed forward of exhaust nozzle inside duct

clamshell doors and translating cowl move together

• clamshell doors close to deflect air forward

• translating cowl slides aft to expose cascade vanes to allow air to exit

blocker door TR (cold stream reverser)

4 integral bypass-duct blocker doors open when activated

deflects fan air (cold bypass air)

hydraulic

cascade TR (cold stream reverser)

translating cowl assembly moves aft

blocker doors deflect fan air out through cascade vanes

hydraulic or pneumatic

vectored thrust

used on STOVL

military aircraft

fan and exhaust nozzles redirect gases

TR operation

TR is selected on throttle quadrant by raising reverse thrust levers vertical position

only deploys when aircraft is on the ground during idle

what stops TR if we’re not at idle

mechanical interlocks

afterburners (thrust augmentation)

fuel is added to exhaust and re-ignites due to high exhaust gas temp

used on military

afterburner components

• Afterburner duct

• Fuel manifold (with nozzles)

• Flame holder

• 2 position or variable C-D exhaust nozzle (divergent with afterburners on)

water injection

Used to boost thrust during takeoff and climb by using water and methanol

sprayed into compressor inlet/diffuser to reduce air temp and increase density and thrust

methanol helps with combustion and prevents water from freezing

used on old transport category

used on military

noise suppression through

• Use acoustic (sound absorbing) materials

• Exhaust mixer/collector designs

• Install hush kits

jet taking off dB

140

pain threshold dB

130

sources of engine noise

inlet duct, fan blades, internal compressor, exhaust

common places to put noise suppression

nose cowl (intake), core panels and cowlings

exhaust nozzle noise suppression

reduces velocity

breaks up exhaust gases into smaller, higher frequency streams

types of exhaust nozzle noise suppression

• corrugated perimeter, lobe, suppressor exhaust nozzles 

hush kits

Uses noise reducing exhaust nozzle and soundproofing nacelles

used on older engines

exhaust cone assembly

turbofan engines duct and nozzle assemblies

core and bypass

• Can mix core and bypass air externally using separate ducts and nozzles

• Can mix core and bypass air internally by sharing common exhaust nozzle

convergent exhaust nozzle

convergent divergent exhaust nozzle

divergent exhaust nozzle

thrust vectoring system

thrust reverser assembly

thrust vectoring system

noise suppression system

clamshell door TR

bucket door TR

cascade or deflector door TR

vectored thrust

lobe type nozzle

corrugated nozzle