15.7 EXHAUST👌🏼 Flashcards
In general, the exhaust system does what?
- guides exhaust gases from rear of turbine into atmosphere
On a jet engine, what is the exhaust system for
- to accelerate airflow coming from turbine
What is the main task of the exhaust system in the turboprop engine
Safely guide exhaust gases overboard
What is the exhaust system of the APU for
Guides exhaust gases overboard because all the gas energy will be absorbed by the turbine
How is the APU noise of the exhaust system reduced
- through mufflers in the exhaust duct
List the 3 components of the exhaust section
- exhaust cone
- tailpipe
- exhaust nozzle
Explain the exhaust cone
- collects exhaust gases from turbine section
- velocity of gases is decreased slightly, pressure increases
What is the function of the radial hollow struts in the exhaust cone assembly
- support inner cone
- straightens swirling exhaust gases that would leave turbine at 45* angle
What is the function of the small hole located at the exit tip of the cone
- cooling air circulated from the aft end of cone
The tail-pipe is usually constructed so that it is semi-flexible (T OR F)
T
What are the 2 suitable methods of protecting fuselage structure
- insulation blankets (most common)
- Shrouds
What does the insulation blanket consist of
- several layers of aluminium foil separated by a layer of fibreglass
What is the primary reason of the insulation blanket
Reduce heat loss from exhaust system
What are the 2 types of exhaust nozzles
- Converging (subsonic)
- Converging-diverging (supersonic)
Why is there a converging nozzle before exhaust gases are discharged
- so velocity can be increased
- producing 15%-20% extra thrust
Turboprop exhaust nozzle produce how much thrust
10%-15%
The turboprop nozzle is mainly used for what
Discharge exhaust gases from aircraft
On turboprop, the exhaust nozzle is also referred as ?
Tailpipe
When would a variable area exhaust nozzle be used
- when augmenter or afterburner is used
-due to increased mass flow when afterburner is activated
Convergent duct increases gas velocity, therefore providing more thrust (T or F)
T
Why would you use a convergent-divergent duct
- when EPR is high (>MACH 1)
- more thrust can be gained
In a C-D nozzle, what is the convergent section for
Designed to handle gases while they remain subsonic
In a C-D nozzle, what is the divergent section for
- further increases velocity
- becomes supersonic
What is the common type of noise suppressor used
- integral, airborne part of aircraft engine installation
- engine exhaust nozzle
How is the noise produced by the engine exhaust
- caused by high degree of turbulence of high velocity jet stream
Large engines operating at partial thrust are less noisy than smaller engines operating at full thrust
True
What are the 2 types of noise suppressors
- corrugated perimeter type
- multi- tube type
In the engine nacelle, the area between engine and the cowl has what
- ## acoustic linings (converts energy into heat)
Explain the construction of the acoustic linings
- consist of porous skin supported by honeycomb backing
Explain thrust reverser
- braking force by deflecting exhaust gas stream in opposite direction
On modern turbofan engines which airflow is reversed
- fan airflow reversed as this creates most of the engines thrust
What are the 2 types of thrust reverser
- Clamshell
- bucket
Explain clamshell type thrust reverser
- older jets with low bypass ratio
- usually pneumatically operated by bleed air
Explain bucket type thrust reverser
- older jets with low bypass ratio
- usually hydraulically operated
On turbofan engines what air is deflected to give reverse thrust
Fan air
Fan reversers are most commonly what type of thrust reverser
Cascade type
In a turbo fan what are the blocker doors function
- ensure all fan air is discharged through cascade vanes
How are the pivoting door reversers operated
Hydraulically
Why should you not use thrust reversers at low speeds
- Engine will ingest its own reversed airflow
- Cause compressor stall and high EGT
At what speeds should thrust reversers be activated
- high speeds
To minimise disadvantages caused by reverser operation, the reversed airflow is matched to engine position .(T or F)
True
Explain thrust vectoring
- for manoeuvring in flight to change direction
