15.1 Fundamentals Flashcards
Newton’s first law denotes what?
A body at rest will remain at rest and a body at motion continues to move at motion until acted upon by an external force
Equation for Newton’s second law?
Force=Mass x Acceleration
4 stages of an engine?
- Intake (Suck)
- Air compression (squeeze)
- Combustion (Bang)
- Expansion/Exhaust (Blow)
Newton’s third law denotes what?
Every action has a equal and opposite reaction
Within the compressor does the static pressure?
A- Increase
B- Decrease
C- Stay the same
A- Increase
The process of adding heat into the compressor at a constant pressure is known as what?
Isobaric Heating
What is the main function of an engine?
Provide thrust
Apart from thrust, what are three other functions of aircraft engines?
Supply hydraulic power
Supply electrical power
Supply bleed air for pneumatic systems
An engine which uses jet propulsion can also be known as what?
A reaction engine
Performance of piston engines decrease when and why?
Decrease at high altitude due to there being less airflow/dynamic pressure
To accelerate air, air pressure must what?
Increase
All gas not used to drive compressor, does what?
Used as thrust
Turboprop engines produce the majority of their thrust how?
Small acceleration of a large quantity of air with a propeller
Turboprop engines convert all gas energy to what?
Torque
Compressors are made up of what?
Rotors and stators
What is the bypass ratio?
Ratio of air that passes through the fan duct compared with what passes through the core engine
The fan produces what percent of thrust
80%
On modern aircraft the bypass ratio is what?
Between 4:1 and 9:1
Advantage of prop fan over turbo fan?
Up to 20% less fuel as they have bypass ratio of 90:1
Characteristics of non modular construction?
Saved weight
Design is complicated and hard to get to
Engine has to be removed for access
Found on old a/c
Characteristics of modular construction?
Whole engine is split into a set of separate major modules
Engine modules pre assembled and balanced
Further divided into sub modules
Advantages of modular construction for manufacturer
Rotating module parts can be pre balanced
Less spare engines are needed in stock
More flexibility when changes are made to individual parts
Main engine modules can be easily stored and transported
Advantages of modular construction for operator?
No rebalancing required
Most modules can be replaced while the engine remains of the aircraft
Less spare parts while engine is on AC
Replacements of modules are considered minor so can be done by a maintenance organisation
Characteristics of engine materials
Must be strong for individual tasks
Light and cheap
Aluminium alloy is mainly used for what?
Gearbox housing
Fan stator casings
Where are ceramic coatings used and why?
In the combust or and pressure turbine
Serve as heat and corrosion protection
Where are steel alloys used?
Used in shaft, engine bearings and main structural frames
Cobalt base alloys are highly heat resistant, where would they be found?
Found in stators and first stage of HP turbine
Characteristics of titanium?
As strong as steel but half the weight
Withstand high centrifugal loads
Expensive
Where is titanium used?
Mainly used in fan
Low pressure compressor
And front stages of high compressor
Characteristics of nickel base alloys?
Withstand high centrifugal loads at high temperatures
Where are nickel based alloys used?
Used in High pressure compressor
Combustion section and high and low pressure turbines
What are two forms of mechanical energy?
Potential energy
Kinetic energy
What is the brayton cycle
The working cycle of a gas turbine engine
How is power defined?
Work done/ time
