Chapter 1.1: Thermodynamic of engine

Question 1

which FAR part is on engine regulation?

Answer 1

FAR part 33

Question 2

Which Newton law is thrust and engine based on?

Answer 2

thrust: 2nd law (F = ma)

whole engine: 3rd law (equal & opposite reaction)

Question 3

what are the 5 stages of the engine?

Answer 3

inlet > compressor > combustion > turbine> exhaust

Question 4

which part of the engine is responsible for producing thrust?

Answer 4

exhaust nozzle

Question 5

what is the convergent-divergent duct based on?

Answer 5

mass flow rate = ρAV

ṁ and ρ is constant so only A & V can change

Question 6

where can Bernoulli’s Theorem be applicable within the engine?

Answer 6

inlet, diffuser, exhaust

other parts have mechanical interference

Question 7

which part of the engine has the highest pressure?

Answer 7

compressor outlet or combustor inlet/outlet

Question 8

what should be constant in the combustion chamber?

Answer 8

pressure

Question 9

which part of the engine has the highest temperature and stress?

Answer 9

turbine inlet temperature (TIT) or combustion outlet

Question 10

what is an air-breathing engine?

Answer 10

engine that uses atm air as engine working fluid

Question 11

how does turbojet and turboprop engines produce thrust?

Answer 11

turbojet: big acceleration, small mass of air

turboprop: small acceleration, big mass of air

Question 12

what does the turbine do?

Answer 12

extract energy from hot gas to turn compressor

Question 13

what will be the same for a set of turbine and compressor?

Answer 13

rpm on same spool

Question 14

where does the remaining energy from turbine go?

Answer 14

exit exhaust as thrust

Question 15

what is the use of the compressor?

Answer 15

add energy to gas (compressor work on gas)

Question 16

what is the combustor job?

Answer 16

burn fuel air mixture to create large amount of energy to gas

Question 17

thrust producing and torque producing engines

Answer 17

thrust: turbojet & turbofan

torque: turboshaft & turboprop

Question 18

at which condition does turboprop engine gives maximum thrust?

Answer 18

low speed

Question 19

what does the turboprop compressor turbine drive?

Answer 19

centrifugal compressor, accessory gearbox

Question 20

what is a free turbine and what is it for?

Answer 20

not mechanically connected with compressor

drive propeller output shaft

Question 21

what will be different between propeller shaft and compressor?

Answer 21

rpm

Question 22

on which types on engine would free turbines appear on?

Answer 22

turboshaft/prop

Question 23

what is the reduction gearbox responsible for?

Answer 23

converting high rpm to low rpm

Question 24

why does turboprop propeller need to have low rpm?

Answer 24

high radius and low rpm to prevent mach 1 ( v = rω)

Question 25

how does turboshaft engine work?

Answer 25

delivers power through shaft to main gear box that drives rotor blades

Question 26

at what condition does turboshaft engine deliver maximum shaft output?

Answer 26

low speed and altitudes

Question 27

application of turboshaft?

Answer 27

APU and helicopters

Question 28

which part of turbofan produces the most of the thrust?

Answer 28

80% of thrust by fan blades

Question 29

turbofan features

Answer 29

improved fuel consump. , propulsive efficiency, reduced noise level

by increasing mass flow, decrease exhaust velocity

Question 30

turbojet characteristics

Answer 30

1) low propulsive efficiency at low velocity
2) longer takeoff run
3) high TSFC at low altitude and speed
4) small frontal area
5) low weight

Question 31

turboprop characteristics

Answer 31

1) high propulsive efficiency at low airspeed
2) shorter takeoff run
3) low TSFC at low altitude and speed
4) large frontal area
5) efficient reverse thrust (adjusting pitch angle)

Question 32

turbofan characteristics

Answer 32

1) propulsive efficiency increases as airspeed up till mach 1
2) weight and TSFC between jet and prop
3) lesser noise than turbojet

Question 33

advantages of gas turbine engines

Answer 33

1) high power to weight ratio
2) smaller size and lesser vibration than piston engine
3) fewer moving parts
4) high operation speeds
5) can generate higher thrust

Question 34

disadvantages of gas turbine engines

Answer 34

1) higher cost
2) complex machining
3) less fuel efficient than piston engines