M15.1 Flashcards
What is average acceleration of gravity?
9.8 meters per second
What is the equation for force?
Force x distance
What is the equation for power?
Work / time
1j = nm
1
1w = nm/s
1nm/s
Newtons 1st law?
A body at rest and a body in motion moves at a constant velocity unless acted upon by a un balanced external force
Newtons 2nd law?
Force = mass x acceleration
Newtons 3rd law?
Every action has a equal and opposite reaction
What’s the working cycle of engines?
Induction
Compression
Combustion
Exhaust
What is the cycle in a piston engine and a GTE
Piston = intermittent
GTE = continuous
What happens to pressure and volume in a GTE
Pressure stays the same
Volume increases
Why does pressure not rise in a GTE engine during combustion? And what is this called?
Because it’s not in an enclosed space
Heating at constant pressure or isobaric heating
What octane fuel does GTE use?
Low octane
The GTE is essentially what?
A heat engine that uses air as a working fluid to produce thrust
How is velocity of air increased in a GTE?
Increase pressure energy
Increase heat energy
A final conversion back to kinetic energy in form of a high velocity jet efflux
What are the functions of a a/c engine?
Generate thrust
Hydraulic power
Electrical power bleed air
What are the advantages of piston engines?
More fuel efficient
What’s the disadvantage of piston engines?
Decrease in performance
Lower altitudes
Too large for a/c
Weight to power ratio decreased
What are the 4 types of GTE
Turbojet engine
Turbofan engine
Turboprop engine
APU
What is the basic principle of jet propulsion?
Jet propulsion is the propelling force which is generated in the opposite direction to the flow of mass through the jet nozzle
A jet engine that uses propulsion is called what?
Reaction engine
What happens to un used gasses in a turbojet engine?
Used to drive the compressor and the accessories is converted into thrust
What’s the negatives of turbojet engines?
Extremely loud
Not very efficient
How do turboprop engines provide thrust?
By small acceleration of large quantities of air with a propeller
How is the propeller driven in turboprop engines?
By the compressor shaft or by free turbine and long centre drive shaft
Why does a turboprop engine have a reduction gear?
To reduce the high gas turbine engine rotation to speeds that can be managed by the propeller
What does a turbofan engine combine?
Turbojet and turboprop engine
How many spools does a turbofan engine have?
Twin or triple
What is the fan driven by?
A turbine via drive shaft
Does a turbofan engine have reduction gears?
No
How much total thrust is produced by turbofan engine?
80%
What is a bypass ratio?
Ratio of air that passes through fan duct compared to air passing through core
What is the bypass ratio on modern a/c?
4:1 or 9:1
What does the GTE power?
Either a single fan or set of counter rotating fans via a gearbox
Why are propfan engines not commonly found on a/c?
Because of mounting difficulties
What is a non modular engine?
The engine is designed in a way where it is hard to remove components from the engine
What is a modular construction on engines?
Used on modern a/c where engine is set into major modules so components are easy to remove and replace
Where are aluminium alloys mainly used on engines?
Used on gearbox housing
Fan stator castings
Other low loaded parts of fan module
Where are ceramic coatings used?
In the combustor and high pressure turbine
The coatings serve as heat and corrosion protection
Where are steel alloys used?
On the N1 drive shaft
Engine bearings
Main structural frames
Where is cobalt used?
Highly heat resistant
Found in stator of first stage of the hp turbine
Where are titanium alloys used?
Where there are high centrifugal forces
Where are nickel alloys used?
Hp compressor
Combustion section for lp/ hp turbine
