Turbine engine Flashcards
Four forces of flight?
Lift, weight, thrust, and drag
What is Newtons third law?
For every action there has to be an equal and opposite and reaction
What is thrust?
The forward directed force produced by the reaction from a rearward accelerated mass of air
What is the law of conservation of energy?
Energy can neither be created nor destroyed, but it can be changed from one form into another
What is potential energy?
Is the energy possessed by an object because of its position
What is kinetic energy?
Energy due to motion
What is Bernoulli’s principle?
The total energy in a column of moving fluid remains constant throughout the column
What type of air flows through a CD duct?
Subsonic
What is a convergent duct and what happens to the air as it passes?
The duct becomes smaller in the direction of flow. The air velocity increases and the pressure decreases
What is a divergent duct and what happens to the air as it flows?
The duct becomes larger in the direction of flow. The air velocity decreases and the pressure increases
What happens with supersonic flow through a converging duct?
Density increases, velocity decreases, pressure increases
What happens to supersonic flow through a diverging duct?
Density decreases, velocity increases, and its pressure decreases
What are the three types of pressure in a turbine engine?
Absolute
Gage
Differential
How is absolute pressure measured?
From zero or a vacuum
What is gauge pressure?
From existing atmospheric pressure
What is differential pressure?
The difference between two pressures
What are the two additional important pressures in turbine engines?
Static and total pressure
What are the basic components of a GTE?
Inlet
Compressor
Diffuser
Combustors
Turbine
Accessory gear box
What are the four types of GTE?
Turbojet
Turboprop
Turbofan
Turboshaft
How do you add more power to a turboprop?
Adding more turbine states or a free turbine to turn the propeller
What does a turbofan engine use for engine cooling?
By-pass air
What are the advantages of a turbofan over a turbojet?
Higher propulsive efficiency
Lower noise level
Lower specific fuel consumption
What is the bypass ratio?
The amount of air flow from the fan bypass to the core flow
What is the engine pressure ratio?
The ratio of the turbine discharge total pressure to the compressor inlet total pressure
What is EPR for?
To measure thrust on a GTE
What are the two parameters used to measure engine thrust?
Percentage of RPM
EPR
What is N1?
Low compressor speed
What is N2
High compressor speed
What are the factors affecting thrust?
Airspeed
Air temperature
Air pressure
Altitude
Ram effect
What happens with air density and thrust as temp increases?
Air density and thrust decreases
What happens with air density and thrust as pressure increases?
air density and thrust increase
What happens to thrust as altitude increases?
Thrust decreases
Why do jets fly at high altitudes?
Less drag
Engines need less power to move forward
More fuel efficient
What are the two ways to increase thrust in a jet engine?
Water injection-increased mass airflow and low EGT
Afterburners-reheat the air after the turbine state
The two kinds of air in a turbofan engine?
Core-used for combustion process to produce thrust
By-pass air- produces thrust and used for cooling
What is a free-turbine engine?
An engine that uses a separate turbine to drive the propeller in a turboprop or fan in a turbo fan
What are the components of the cold section?
Inlet
Compressor
Diffuser
What is a station designation?
Where along the length of the engine a component is located
How does inlet anti-icing work?
Warm air is bled from the engine’s compressor and is ducted through the inlet
What must supersonic aircraft use CD inlet ducts?
To slow the air to subsonic speeds
What is a compressor?
To supply the correct amount of air for the fuel and to supply it with correct pressure and velocity
What is a secondary function of a compressor?
To supply bleed air for various purposes in the engine and aircraft
What are the types of compressors?
Centrifugal
Axial flow
Hybrid
What are the components of a centrifugal compressor?
Impeller-rotating part
Diffuser-captures the air and forms divergent ducts
Manifold-collects air and directs it toward the combustion chamber
What are the two components of a axial flow compressor?
Rotor blades-spun by axle powered by the turbine
Stator vanes-do not spin
What is the purpose of inlet guide vanes?
Changes the direction of the airflow so that it hits the first stage rotors at the optimum angle
Why are stator vanes behind rotor vanes?
To form a series of divergent ducts converting velocity to pressure
Each consecutive pair of rotor and stator blades constitutes what?
A pressure stage
What is compression ratio?
Compressor discharge pressure/compressor inlet pressure
What is a blade stall?
The blade AOA becomes excessive, blades stall and airflow separates
What design features prevent compressor stall?
Surge bleed valves
Variable stator vanes
Multiple spools
What are surge bleed valves?
Dump pressure from the last sages of the compressor to increase airflow
What are variable stator vanes?
Repositions the stator vanes to optimize rotor blade AOA
Multiple spools
Each spool operates at its optimum speed
What is a 2-spool engine?
An engine with two separate compressors each driven by its own turbine section
What is a mid-span shroud?
Provides stiffness and to prevent flutter
Where is the highest pressure located in an engine?
At the diffusor
