15.1 Fundamentals Flashcards
What is the purpose of the compressor?
To increase static pressure.
What is dynamic pressure also known as?
Velocity.
What is the purpose of the combustion chamber?
To increase energy.
How does the combustion chamber increase energy?
By adding fuel.
What happens to the air after the combustion chamber?
It is directed to the turbines and absorbs more energy which turns the shaft to turn the compressor continuously.
What type of duct is at the rear of the engine?
Convergent.
How is potential energy defined?
Energy at rest or stored energy.
What is the equation for potential energy?
PE= m x g x h
How is kinetic energy defined ?
Energy in motion.
What is the equation for kinetic energy?
KE= 1/2 x m x v^2
What is Newton’s first law?
Law of inertia.
What is Newtons 2nd law?
F=m x a
What is newtons 3rd law?
Every action has an equal and opposite reaction.
How does the Brayton cycle provide thrust?
By using air as a working fluid.
Describe the volume and pressure of the Brayton cycle?
Variable volume, constant pressure.
How is the air accelerated through the engine in the Brayton cycle?
Increasing pressure.
Adding heat energy.
Final conversion back to KE as high velocity jet efflux.
What are the 4 stages of the Brayton cycle?
Intake, compression, combustion, exhaust.
What happens at the inlet duct?
Pressure increases.
What happens to pressure at the compressor?
It further increases.
What happens to pressure at the combustion chamber?
Remains constant, volume increases.
What happens to pressure at the turbine?
It decreases.
What stages does isobaric heating occur?
2 to 3
Where does isobaric heating take place ?
In the combustion chamber
What is the hottest point in the engine?
The rear of the combustion chamber/ 1st stage of the nozzle guide vane.
At what stages does isentropic compression occur?
1 to 2.
At what stages does isentropic expansion occur?
3 to 5.
What do the stationary vanes/ stators do?
They straighten and guide air onto the rotor blades.
What happens in stage 4 to 5?
Remaining energy, on its discharge to the atmosphere, provides a propulsive jet in the nozzle.
What is the process from 0 to 5 called?
Isobaric heat release.
Where is the point with the highest static pressure?
The start of the combustion chamber.
What is the equation and unit for Force?
F= m x a.
Newtons.
What is the equation and unit for Weight?
W= m x a.
Newtons.
What is the equation and unit for Work done?
W= F x d
Joules.
What is the equation and unit for power?
P= W/t
Watt.
What is the role of the turbine?
To supply power to turn the compressor.
How is motion defined?
The continuous change of position of place.
How is acceleration defined?
The rate of change of velocity.
What is equation and unit for acceleration?
A= change in V/ t
m/s^2.
How is speed defined?
How far an object will travel in a specific time.
How is velocity defined?
The rate of change of motion in a particular direction.
Vector quantity.
What was the first type of engine?
Piston type.
What was the pro and con of the piston type engine and where was it used?
+ fuel efficient.
- performance decreases at high altitudes.
Only used on small aircraft.
What are the 3 things an aircraft engine supplies.
Hydraulic power.
Electric power.
Bleed air.
What are the 4 types of gas turbine engines in aircraft?
Turobojet, turbonfan, turboprop, turboshaft.
What are the advantages of the turbojet engine?
+ relatively simple design
+ capable of very high speeds
+ takes up little space
What are the disadvantages of the turbojet engine?
- high fuel consumption
- loud
- poor performance at slow speeds
- limited in range and endurance
Why is a convergent duct used?
To increase thrust.
In a turbofan engine, what do the front fan set do?
They produce 80% of thrust from energy.
What is a spool?
A turbine driving a compressor through a shaft.
What does a twin spool engine consist of?
A high pressure turbine driving a high pressure compressor.
A low pressure turbine driving a low pressure compressor and fan.
Describe a 3 spool engine?
A high pressure turbine driving a high pressure compressor.
An intermediate turbine driving an intermediate compressor.
A low pressure turbine driving a fan.
What are the advantages of a turbofan engine?
Fuel efficient.
Quieter than turbojet.
Streamlined.
What are the disadvantages of a turbofan engine?
Heavier than turbojet.
Large frontal area.
Inefficient at very high altitudes.
Describe the function of a turboprop engine?
To produce shaft horsepower to drive a propellor.
What are the advantage of a turboprop engine?
Very fuel efficient.
What are the disadvantages of a turboprop engine?
Limited forward airspeed.
Gearing systems are heavy and can break down.
What is the purpose of a turboshaft engine?
To produce shaft horsepower to drive machinery instead of thrust.
What does a turboprop engine incorporate?
A compressor, combustion and turbine within a gas generator.
How does a turboprop engine differ from a turbojet?
Additional turbines.
Power shaft.
A reduction gearbox.
All to drive the propeller.
What are the advantages of a turboshaft engine?
Higher power to weight ration than piston engine.
Smaller than piston engine.
What are the disadvantages of a turboshaft engine?
Loud.
Complex gear system connected to shaft can break down.
What are the disadvantages of a turboshaft engine?
Loud.
Complex gear system connected to shaft can break down.
Where is a turboshaft engine used?
APU and helicopters.
What is the cold section of an engine?
From the inlet to the compressors/ diffusers.
What is the hot section of an engine?
From the combustion chamber to the exhaust.
What materials are engines made from?
Aluminium, ceramic, composite, cobalt, nickel, CRES, titanium.
