15.1 Flashcards
(27 cards)
What is energy
Gives a capacity to perform work
What are the two forms of energy and there equation
Potential: PE=mgh
Kinetic: 1/2mv^2. SI units =joules
What is Newton’s first law
Inertia.
What is newtons 2nd law
F=MA
Newton’s second law relates to a Gas Turbine Engine (GTE) in that the thrust is proportional to the mass of the airflow through the engine multiplied by the acceleration of the air through the engine.
What is newtons 3rd law
Every action has an equal and opposite reaction
What is the Brayton cycle
Constant pressure cycle
What happens in the combustion chamber
Constant combustion cycle
What pressure does the compressor produce
Static pressure
What are the 4 ideal changes of state
Isobaric
Isochloric
Isothermal
Isentropic
What type of change of state occurs in 0-2, 2-3, 3-5 and 0-5
0-2 isentropic (compressor)
2-3 isobaric (combustion)
3-5 isentropic Expansion
0-5 (hole engine) isobaric heat release into the atmosphere
Force
F=MA
Pounds and newtons
1lbs = 4.448N
Work
Work = force x distance
2 factors
Force
Movement through distance
Joules
1J=1NM
Power
P= (F x d)
T
Watts
1W = 1NM/s
Motion
Constant speed
Acceleration Delta V over T. Rate of change of velocity
Why are gas turbine engines preferred over piston engines at high altitudes
Piston engine has less power the Higher it goes however this not happen with gas turbines
What can help piston engines cope with high altitudes
A turbo
What are the advantages and disadvantages of a turbojet engine
Advantages
Simple design
Capable of high speeds
Disadvantages
High fuel consumption
Loud
Poor performance at low speeds
Limited range and endurance
Not good for speeds below 0.8 Mach
What are turboprop engines designed to do and how does it do this
Produce shaft houres power to drive a propeller
Extra turbines to absorb all energy to turn a propeller. This will provide extra energy as the extra turbines will absorb most of the energy and prevent losses out of the exhaust
What speeds an altitudes are turboprops designed to do
And some advantages and disadvantages
250 - 400 knots
18000 to 30000ft
Very fuel efficient how ever has a complete gear box system
What percentage of thrust comes from the fan in a turbofan engine
80% of all thrust comes from the fan
20% from the convergent duct out the exhaust
What is a twin and triple spool engine
Twin spool - 2 turbines turning 2 compressors
Triple spool- 3 turbines turning 3 compressors
What would you find in a triple spool engine
LP turbine drives fan
IP turbine
HP turbine
Shafts run inside each other on own bearing
How are the turbines named an engine
N1 LP
N2 IP
N3 HP
Twine spool has no ip
N1 LP
N2 HP
Shafts run inside each other on own bearing
What are the advantages and disadvantages of a turbofan engine
Advantages
Fuel efficiency
Quieter then turbojets
Streamlines
Disadvantages
Heavier
Large frontal area
Inefficient at very high altitudes
Where are turboshaft engine used and what are they
Used as APU or energy other generation as well as helicopters
Power to a shaft as extra turbines
Drives anything but a propeller
Much higher power to weight ration and smaller then piston engines
Loud and complex gearbox
