15.1 Fundamentals Flashcards
What is a typical way an engine works?
Suck, Squeeze, Bang, Blow
What is a compressors function?
Compress/squeeze air
What does a compressor do to air?
Increases static pressure and reduces velocity
What is the typical definition of energy?
Something that gives capacity to perform work
What unit is work and energy typically measured in?
Joules
What are the two types of energy?
Kinetic and potential
What is the difference between potential energy and kinetic energy?
Kinetic energy is defined as energy in motion where as potential energy is energy that is at rest or stored
What is Newton’s first law?
Law of inertia
What is Newton’s second law?
Interplay between force and motion, F = MxA
What is Newton’s third law?
Law of action and reaction
What are the four stages of the brayton cycle (Continuous combustion)?
Suck, Squeeze, Bang, Blow
What is the brayton cycle?
Name given to thermodynamic cycle of a gas turbine engine that produce thrust
What happens at the intake stage?
Air enters at ambient pressure and at constant volume, leaves the intake at elevated pressure however decreased volume
What happens at the compress stage?
Air is compressed and has a greater pressure and decreased volume which is created by the mechanical action of the compressors
What happens at the combustion stage?
Fuel is added to the air and is ignited in the combustion chamber pressure remains constant but volume increases due to heating. Static pressure is converted into velocity and mechanical energy at the turbine
What happens at the exhaust section?
The converging duct converts expanding volume and decreasing pressure of gases to a high final velocity
What are the 4 idle changes of state?
Isobaric, isochoric, isothermal, isentropic
What are the two most important state changes in gas turbine engines?
Isobaric, isentropic
What sort of diagram is used to graphically show changes of state?
A pressure volume diagram
On a pressure volume diagram what does point zero represent?
Atmospheric conditions (pressure & temp)
What does the line from point zero to two represent on a pressure volume graph?
The isentropic compression of air (pressure increases well volume decreases).
From outside air to end of compressor stage
What is the process between points two and three called on a pv graph?
Isobaric heating
Heat added to the air in the combustion chamber by introduction and burning fuel at constant pressure, considerably increasing the volume
What does the line from 3 to 5 represent on a pv graph?
Isentropic expansion process (gases expand)
What is the force equation?
Force = mass x acceleration
What is the work calculation?
Work = Force x Distance
What is the power calculation?
Power = Force x Distance / time
Power = Work / Time
What is the calculation for acceleration?
Acceleration = change in velocity / time
What is the primary and secondary functions of an engine?
Primary function is to provide thrust
Secondary function to procedure hydraulic, pneumatic and electric power
What are the two general types of aircraft engines on an aircraft?
Piston type engine and gas turbine engines
What aren’t piston type engines used at high altitudes?
There performance decreases
What are the different designs of gas turbine engine on aircraft?
Turbojet, turbofan, turboprop, turboshaft
What is the benefit of a gas turbine engine?
Increased speed
Better at higher altitudes
Can provide bleed air
What are the advantages of a turbojet engine?
Relatively simple design
Capable of very high speeds
Takes up little space
What are the disadvantages of a turbojet engine?
High fuel consumption
Loud
Poor performance at slow speeds
Limited in range and endurance
Where is the majority of the thrust generated from in a turbofan engine?
Through the bypass
What are the advantages of a turbofan engine?
Fuel efficient
Quieter than turbojets
Streamlined appearance
What are the disadvantages of a turbofan engine?
Heavier
Larger
Inefficient at very high altitudes
Why is a turboprop engine a good compromise?
Achievable aircraft speed and efficiency
What are the advantages of a turboprop engine?
Very fuel efficient
What are the disadvantages of a turboprop engine?
Limited forward airspeed
Gearing systems are heavy and can breakdown
When is a turboshaft engine most commonly used?
Helicopter
What are the advantages of a turboshaft engine?
Mush higher power to weight ratio then piston engines
Smaller than piston engines
What are the disadvantages of a turboshaft engine?
Loud
Gear systems connected to the shaft can be complex and breakdown
What does the low pressure turbine turn in the engine?
Low pressure compressor and fan
What does the high pressure turbine turn in the engine?
High pressure compressor
What range is a turboprop engine most efficient in?
Speeds between 250-400 knots and altitudes of 18000-30000 feet
What does a two spool engine consist of?
Low pressure turbine and a high pressure turbine
What does a three spool engine consist of?
Low pressure turbine, intermediate pressure turbine and high pressure turbine
What typical materials are usually found on jet engines?
Aluminium alloy
Ceramic material
Composite material
Cobalt base alloy
Nickel base alloy
Corrosion resistant steel alloy
Titanium base alloy
What are the differences between a reciprocating engine and a gas turbine engine?
On a reciprocating engine the functions of intake, compression, combustion, and exhaust all take place in the same combustion chamber ,where as a gas turbine engine has separate sections that are dedicated to performing each function simultaneously without interruption
What does a typical gas turbine engine consist of?
An air inlet (fan blades)
Compressor section (Low-pressure Compressor (LPC) and High-pressure Compressor (HPC))
Combustion section (diffuser and combustor)
Turbine section (Low-pressure Turbine (LPT) and High-pressure Turbine (HPT))
Exhaust section (Turbine Exhaust Case (TEC))
Accessory section (main gearbox)
Where is the cold section on an engine?
the parts of the engine from the inlets up through the compressors and/or diffusers
Where is the hot section on an engine?
past the compressors from the combustion chambers through to the exhaust
