Chapter 1.1: Thermodynamic of engine Flashcards
which FAR part is on engine regulation?
FAR part 33
Which Newton law is thrust and engine based on?
thrust: 2nd law (F = ma)
whole engine: 3rd law (equal & opposite reaction)
what are the 5 stages of the engine?
inlet > compressor > combustion > turbine> exhaust
which part of the engine is responsible for producing thrust?
exhaust nozzle
what is the convergent-divergent duct based on?
mass flow rate = ρAV
ṁ and ρ is constant so only A & V can change
where can Bernoulli’s Theorem be applicable within the engine?
inlet, diffuser, exhaust
other parts have mechanical interference
which part of the engine has the highest pressure?
compressor outlet or combustor inlet/outlet
what should be constant in the combustion chamber?
pressure
which part of the engine has the highest temperature and stress?
turbine inlet temperature (TIT) or combustion outlet
what is an air-breathing engine?
engine that uses atm air as engine working fluid
how does turbojet and turboprop engines produce thrust?
turbojet: big acceleration, small mass of air
turboprop: small acceleration, big mass of air
what does the turbine do?
extract energy from hot gas to turn compressor
what will be the same for a set of turbine and compressor?
rpm on same spool
where does the remaining energy from turbine go?
exit exhaust as thrust
what is the use of the compressor?
add energy to gas (compressor work on gas)
what is the combustor job?
burn fuel air mixture to create large amount of energy to gas
thrust producing and torque producing engines
thrust: turbojet & turbofan
torque: turboshaft & turboprop
at which condition does turboprop engine gives maximum thrust?
low speed
what does the turboprop compressor turbine drive?
centrifugal compressor, accessory gearbox
what is a free turbine and what is it for?
not mechanically connected with compressor
drive propeller output shaft
what will be different between propeller shaft and compressor?
rpm
on which types on engine would free turbines appear on?
turboshaft/prop
what is the reduction gearbox responsible for?
converting high rpm to low rpm
why does turboprop propeller need to have low rpm?
high radius and low rpm to prevent mach 1 ( v = rω)
how does turboshaft engine work?
delivers power through shaft to main gear box that drives rotor blades
at what condition does turboshaft engine deliver maximum shaft output?
low speed and altitudes
application of turboshaft?
APU and helicopters
which part of turbofan produces the most of the thrust?
80% of thrust by fan blades
turbofan features
improved fuel consump. , propulsive efficiency, reduced noise level
by increasing mass flow, decrease exhaust velocity
turbojet characteristics
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
turboprop characteristics
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)
turbofan characteristics
1) propulsive efficiency increases as airspeed up till mach 1
2) weight and TSFC between jet and prop
3) lesser noise than turbojet
advantages of gas turbine engines
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
disadvantages of gas turbine engines
1) higher cost
2) complex machining
3) less fuel efficient than piston engines
