15.1 Fundamentals

Question 1

What is a typical way an engine works?

Answer 1

Suck, Squeeze, Bang, Blow

Question 2

What is a compressors function?

Answer 2

Compress/squeeze air

Question 3

What does a compressor do to air?

Answer 3

Increases static pressure and reduces velocity

Question 4

What is the typical definition of energy?

Answer 4

Something that gives capacity to perform work

Question 5

What unit is work and energy typically measured in?

Answer 5

Joules

Question 6

What are the two types of energy?

Answer 6

Kinetic and potential

Question 7

What is the difference between potential energy and kinetic energy?

Answer 7

Kinetic energy is defined as energy in motion where as potential energy is energy that is at rest or stored

Question 8

What is Newton’s first law?

Answer 8

Law of inertia

Question 9

What is Newton’s second law?

Answer 9

Interplay between force and motion, F = MxA

Question 10

What is Newton’s third law?

Answer 10

Law of action and reaction

Question 11

What are the four stages of the brayton cycle (Continuous combustion)?

Answer 11

Suck, Squeeze, Bang, Blow

Question 12

What is the brayton cycle?

Answer 12

Name given to thermodynamic cycle of a gas turbine engine that produce thrust

Question 13

What happens at the intake stage?

Answer 13

Air enters at ambient pressure and at constant volume, leaves the intake at elevated pressure however decreased volume

Question 14

What happens at the compress stage?

Answer 14

Air is compressed and has a greater pressure and decreased volume which is created by the mechanical action of the compressors

Question 15

What happens at the combustion stage?

Answer 15

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

Question 16

What happens at the exhaust section?

Answer 16

The converging duct converts expanding volume and decreasing pressure of gases to a high final velocity

Question 17

What are the 4 idle changes of state?

Answer 17

Isobaric, isochoric, isothermal, isentropic

Question 18

What are the two most important state changes in gas turbine engines?

Answer 18

Isobaric, isentropic

Question 19

What sort of diagram is used to graphically show changes of state?

Answer 19

A pressure volume diagram

Question 20

On a pressure volume diagram what does point zero represent?

Answer 20

Atmospheric conditions (pressure & temp)

Question 21

What does the line from point zero to two represent on a pressure volume graph?

Answer 21

The isentropic compression of air (pressure increases well volume decreases).
From outside air to end of compressor stage

Question 22

What is the process between points two and three called on a pv graph?

Answer 22

Isobaric heating
Heat added to the air in the combustion chamber by introduction and burning fuel at constant pressure, considerably increasing the volume

Question 23

What does the line from 3 to 5 represent on a pv graph?

Answer 23

Isentropic expansion process (gases expand)

Question 24

What is the force equation?

Answer 24

Force = mass x acceleration

Question 25

What is the work calculation?

Answer 25

Work = Force x Distance

Question 26

What is the power calculation?

Answer 26

Power = Force x Distance / time Power = Work / Time

Question 27

What is the calculation for acceleration?

Answer 27

Acceleration = change in velocity / time

Question 28

What is the primary and secondary functions of an engine?

Answer 28

Primary function is to provide thrust Secondary function to procedure hydraulic, pneumatic and electric power

Question 29

What are the two general types of aircraft engines on an aircraft?

Answer 29

Piston type engine and gas turbine engines

Question 30

What aren’t piston type engines used at high altitudes?

Answer 30

There performance decreases

Question 31

What are the different designs of gas turbine engine on aircraft?

Answer 31

Turbojet, turbofan, turboprop, turboshaft

Question 32

What is the benefit of a gas turbine engine?

Answer 32

Increased speed Better at higher altitudes Can provide bleed air

Question 33

What are the advantages of a turbojet engine?

Answer 33

Relatively simple design Capable of very high speeds Takes up little space

Question 34

What are the disadvantages of a turbojet engine?

Answer 34

High fuel consumption Loud Poor performance at slow speeds Limited in range and endurance

Question 35

Where is the majority of the thrust generated from in a turbofan engine?

Answer 35

Through the bypass

Question 36

What are the advantages of a turbofan engine?

Answer 36

Fuel efficient Quieter than turbojets Streamlined appearance

Question 37

What are the disadvantages of a turbofan engine?

Answer 37

Heavier Larger Inefficient at very high altitudes

Question 38

Why is a turboprop engine a good compromise?

Answer 38

Achievable aircraft speed and efficiency

Question 39

What are the advantages of a turboprop engine?

Answer 39

Very fuel efficient

Question 40

What are the disadvantages of a turboprop engine?

Answer 40

Limited forward airspeed Gearing systems are heavy and can breakdown

Question 41

When is a turboshaft engine most commonly used?

Answer 41

Helicopter

Question 42

What are the advantages of a turboshaft engine?

Answer 42

Mush higher power to weight ratio then piston engines Smaller than piston engines

Question 43

What are the disadvantages of a turboshaft engine?

Answer 43

Loud Gear systems connected to the shaft can be complex and breakdown

Question 44

What does the low pressure turbine turn in the engine?

Answer 44

Low pressure compressor and fan

Question 45

What does the high pressure turbine turn in the engine?

Answer 45

High pressure compressor

Question 46

What range is a turboprop engine most efficient in?

Answer 46

Speeds between 250-400 knots and altitudes of 18000-30000 feet

Question 47

What does a two spool engine consist of?

Answer 47

Low pressure turbine and a high pressure turbine

Question 48

What does a three spool engine consist of?

Answer 48

Low pressure turbine, intermediate pressure turbine and high pressure turbine

Question 49

What typical materials are usually found on jet engines?

Answer 49

Aluminium alloy Ceramic material Composite material Cobalt base alloy Nickel base alloy Corrosion resistant steel alloy Titanium base alloy

Question 50

What are the differences between a reciprocating engine and a gas turbine engine?

Answer 50

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

Question 51

What does a typical gas turbine engine consist of?

Answer 51

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)

Question 52

Where is the cold section on an engine?

Answer 52

the parts of the engine from the inlets up through the compressors and/or diffusers

Question 53

Where is the hot section on an engine?

Answer 53

past the compressors from the combustion chambers through to the exhaust