15.1 - Fundamentals

Question 1

What is Entropy?

Answer 1

A quantitive measure of energy unavailable to do work (energy lost in a system). It always increases.

Question 2

What are turbofan engines also known as?

Answer 2

Bypass engines

Question 3

What is Boyle’s law?

Answer 3

The volume of a given mass of gas at a constant temperature is inversely proportional to pressure.

Question 4

What is Charles’ law?

Answer 4

The volume of a given mass of gas at constant pressure increases 1/273 of its volume at 0°C for every 1°C rise in temperature.

Question 5

What is an isobaric process?

Answer 5

One of constant pressure

Question 6

What is an isothermal process?

Answer 6

One of constant temperature

Question 7

What is an isochoric process?

Answer 7

One of constant volume

Question 8

What is the equation for potential energy?

Answer 8

E = mgh

Question 9

What is the equation for kinetic energy?

Answer 9

E = 1/2 mv^2

Question 10

What is the equation of force?

Answer 10

F = ma

Question 11

What is one metric horsepower equivalent to?

Answer 11

736watts or
736J/s (joules per second)

The power required to lift 75kg, 1 metre in 1 second

Question 12

What is the equation for work done?

Answer 12

Work done = force x distance

Question 13

What is Newton’s first law of motion?

Answer 13

A body at rest stays at rest unless acted on by an external force

Question 14

What is Newton’s second law of motion?

Answer 14

The rate of change of momentum of a body over time is directly proportional to the force applied (F=ma)

Question 15

What is Newton’s third law of motion?

Answer 15

To every action there is an equal and opposite reaction.

Question 16

What is the Brayton cycle also known as?

Answer 16

The gas turbine cycle

Question 17

What is the universal gas law?

Answer 17

P1 V1 P2 V2

T1 T2

Question 18

What is the Brayton cycle?

Answer 18

The gas turbine cycle. A cycle of continuous combustion. The pressure only marginally drops during combustion. The pressure changes are caused by changes in the velocity of the air.

Question 19

What does a convergent duct do to subsonic gas?

Answer 19

Increase velocity, decrease static pressure

Question 20

What does a divergent duct do to subsonic gas?

Answer 20

Decrease velocity, increase static pressure

Question 21

What is a choked nozzle?

Answer 21

The one exception to the gas flow rules. When the gas is flowing at the speed of sound (sonic velocity) just before it enters a divergent duct; it is impossible to increase the speed any further to supersonic and the nozzle is said to be choked.

Question 22

Approximately how much nitrogen is in a parcel of air at sea level?

Answer 22

12 PSI of nitrogen

Question 23

What is the equation for thrust?

Answer 23

F = W(Vjet - Vflight)

Question 24

What is adiabatic compression?

Answer 24

Compression without the loss or gain of heat

Question 25

Where is the diffuser located?

Answer 25

It's located between the compressor section and the burner section

Question 26

What is the working fluid of a gas turbine engine?

Answer 26

Air

Question 27

What happens to air density if pressure and temperature remains constant, but humidity increases?

Answer 27

It decreases (less thrust can be produced)

Question 28

Which law relates to the kinetic, pressure and potential energy in a fluid flow?

Answer 28

Bernoulli's theorem

Question 29

What is the purpose of the diffuser in a jet engine?

Answer 29

It increases the static pressure of the air before combustion

Question 30

What is the density of gas expressed as in regards to weight and volume?

Answer 30

Density = Weight/Volume

Question 31

What is the purpose of a waisted drive shaft?

Answer 31

It provides a fuse if the driven component is overloaded

Question 32

What is 1 CHU equal to in ft. lb?

Answer 32

778 ft.lb

Question 33

If the LP shaft shears, what happens to the turbine?

Answer 33

Turbine runaway occurs

Question 34

What does Nf indicate in a free power turbine dual axial flow compressor system?

Answer 34

Free power turbine speed

Question 35

Which section provides proper mixing of the fuel and efficient burning of the gases?

Answer 35

The combustion section

Question 36

How is the turbine shaft usually joined to the compressor rotor of a centrifugal compressor?

Answer 36

By a splined coupling

Question 37

What part of a jet engine has the most POTENTIAL energy?

Answer 37

Just before the combustion chamber

Question 38

Where is the highest PRESSURE in a gas turbine?

Answer 38

Just after the last compressor stage, just before the burner

Question 39

What part of a gas turbine engine produces the most amount of DISCREET noise?

Answer 39

The turbine

Question 40

As an aircraft climbs, what factor IMPROVES with altitude?

Answer 40

The specific fuel consumption

Question 41

What, on an aircraft makes an engine's compressor stall more likely to be induced during rapid altitude changes?

Answer 41

Engine intakes mounted close to the fuselage

Question 42

Why is a modular engine more favourable?

Answer 42

It provides total interchangeability of all modules

Question 43

What happens to pressure, temperature and velocity of air in the turbine stages?

Answer 43

Temperature, velocity and pressure decrease