15.1 Fundamentals Flashcards
What is the acceleration due to gravity on average on earth
9.81 m/s squared
What is force measured in
Newtons
What is the formula for weight
Mass X acceleration due to gravity
Units: Newtons
What is the formula for force
Mass X acceleration
Units: Newtons
What is work done
Work = Force X distance
Units: NM
What is power
Power = Work/Time
Units: W or watts
1 watt = 1NM/s
What’s the definition of potential energy
Potential energy is the energy a body has by virtue of its position
What two sub categories can mechanical energy be divided in to
- Potential Energy (PE)
- Kinetic Energy (KE)
What is the definition on Kinetic Energy
Kinetic Energy is the energy a body has by the virtue of its motion
What is Newton’s first law
The law of inertia
A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an unbalanced external force
What is Newton’s second law
Newton’s second law of motion
FORCE = MASS X ACCELERATION
The acceleration produced in a mass by a force acting on it is directly proportional to the force and inversely proportional to the mass
What is Newton’s third law
Every action has an equal and opposite reaction.
(This is the turbojet. The action is the exhaust gas rapidly leaves the engine. Reaction is the thrust force propelling the aircraft forward.)
What 3 steps must take place according to the Brayton cycle
- The pressure energy is increased
- Addition of heat energy
- Final conversion back into Kinetic energy in the form of a high velocity jet efflux
What does a gas turbine engine use as a working fluid to provide thrust
Air
What 3 things must be done in order to increase the velocity of the air to produce thrust
- Pressure is increased
- Addition of Heat Energy
- Final conversion back to Kinetic energy in the form of a high velocity jet efflux
What is Heating at a constant pressure or isobaric heating
As the combustion chamber is not an enclosed space the pressure of the air does not rise during combustion. Volume does increase
What are the 4 cycles of the gas turbine engine
- Induction
- Compression
- Combustion
- Exhaust
What happens continuously on a gas turbine engine that only happens intermittently on a piston engines
The working cycle i.e. Induction, compression, combustion, exhaust
On a piston engine only one piston (stroke) is producing power
In addition to thrust what 3 other things does an engine produce
Hydraulic power, Electric Power and bleed air for the pneumatic system
What are the two different types of aircraft engine
- Piston engine
- Gas turbine engine
What is the main advantage of piston engines
Good fuel efficiency
What are the two main disadvantages of piston engines
High weight to power ratio
Performance loss in high altitudes
What are the 4 types of gas turbine engines
- Turbojet
- Turbofan
- Turboprop
- APU
What is the most fuel efficient type of engine
Piston engine
An engine which uses jet propulsion is called what
A reaction engine
What must be done to air to accelerate it
The pressure must be increased
When did making gas turbine engines take a while to put into practice after the technology was around
They were only possible to produce when sufficient heat resistant materials were produced for continuous combustion
What is required to reduce the high gas turbine engine rotation to speeds that can be managed by the propeller
A reduction gear
What engine combines the advantages of the turbojet and turboprop engine
The turbofan
How many spools do turbofan engines usually have
2 or 3
What are the advantage of open rotor engines and propfans
Use up to 20% less fuel than turbofans and can have a bypass ratio of 90:1
What are open rota or propfan engines not commonly used on commercial aircraft even though they have more advantages than turbofan engines
They are very difficult to mount which makes them uncommon on modern jet aircraft
What are the two different types of engine design known as
- Modular
- Non modular
What was the biggest advantage and disadvantage of non modular engines
Advantage - saved weight, worked well
Disadvantage - design was complicated and parts were hard to access. Parts were usually designed for that engine specifically
Non modular engine construction is usually only found on what type of engines
Older engines and APU
What must the modules of a modular engine be before they are fitted together
They must be fully assembled and balanced
What is the purpose of ceramic coatings
They serve as heat and corrosion protection
Where are steel alloys used in engines
N1 drive shaft, the engine bearings and main structural frames
Where are ceramic coatings used on engines
The combustor and high pressure turbine
Where is aluminium alloy normally used on the engine
Gearbox housings, fan stator casings and other low loaded parts
Why are cobalt alloys normally used
They are highly heat resistant
Where are cobalt based alloys used
Stator of the first stage of the high pressure turbine
Why are titanium based alloys used
They are very strong and and half as heavy as steel
What is the main disadvantage and advantage of titanium alloys
They can withstand high centrifugal force but are very expensive
Where are titanium alloys normally used on the engine
The fan, the low pressure compressor, and the front stages of the high pressure compressor
What is the advantage of Nikel based alloys
They can withstand high centrifugal loads and high temperatures
Where are nikel based alloys used
High pressure compressor, the combustion section, the high and low pressure turbines
