TurboProp Vs FanJet
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TurboProp Vs FanJet
As I understand it, a turboprop is basically a jet engine with a prop stuck onto the front of it.
Turbo props tend to be fitted to the expensive end of the light aircraft market (eg. TBM700) & small commuter airlines, while the fanjets tend to be fitted to larger aircraft.
I am just wondering what's the advantages to each? If they are both basically the same sort of engine, one with a prop, and the other without, then why would one be more suited on one end of the jet market, and one to the other? Why wouldn't you fit a fanjet to a TBM700?
Just thought of this today, and it's bugging me!
Turbo props tend to be fitted to the expensive end of the light aircraft market (eg. TBM700) & small commuter airlines, while the fanjets tend to be fitted to larger aircraft.
I am just wondering what's the advantages to each? If they are both basically the same sort of engine, one with a prop, and the other without, then why would one be more suited on one end of the jet market, and one to the other? Why wouldn't you fit a fanjet to a TBM700?
Just thought of this today, and it's bugging me!
I suppose you could say that a turboprop gets most of its thrust from the prop, with only a small amount from jet efflux, whilst a tubofan gets its thrust from pure jet efflux and bypass flow.
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You need an outlet at the back for the thrust/hot air etc etc to appear with fanjet,hence if you put one on a TBM700 you would end up with a bloody large pipe running through the cabin!
The main reason for not using props on larger a/c is down to the fact that above 400 kts or so the tips of blades will be almost going supersonic and cause drag that will in turn limit max speed.(I think). Fanjets don't have this problem.
(this is rough science by the way,if any nerds want to post a more in depth explanation feel free
)
P.s I love TBM700's if I won the lottery I would buy one tommorow.
The main reason for not using props on larger a/c is down to the fact that above 400 kts or so the tips of blades will be almost going supersonic and cause drag that will in turn limit max speed.(I think). Fanjets don't have this problem.
(this is rough science by the way,if any nerds want to post a more in depth explanation feel free
)P.s I love TBM700's if I won the lottery I would buy one tommorow.
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Also the type of aircraft you have as result of a prop-jet engine or a jet engine is v. different in capability.
A jet engined aircraft will commonly be fast, low wing and need to be kept on a big airport.
Prop-jet aircraft have unreal short field capability because of 'beta' (reverse) the Cessna caravan is a good example of this.
Either of the two far exceed a piston....there is no equivalent yo will never look back after having a turbo-prop aircraft.
A jet engined aircraft will commonly be fast, low wing and need to be kept on a big airport.
Prop-jet aircraft have unreal short field capability because of 'beta' (reverse) the Cessna caravan is a good example of this.
Either of the two far exceed a piston....there is no equivalent yo will never look back after having a turbo-prop aircraft.
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I think it's a speed and height thing - horses for courses.
Turbofan engines are essentially gas turbine-driven ducted fans, with almost all of the thrust being produced by the fan, comparatively little by the residual thrust from the gas turbine. They are more efficient at the sort of speeds and heights jet transports fly at - higher and faster than prop aircraft.
Turboprop engines are a gas turbine-driven propellor, with almost all of the thrust being produced by the prop, very little by the residual thrust from the gas turbine. They are more efficient at the sort of speeds and heights fast light aircraft or small commuter airlines fly at - lower and slower than fan aircraft.
SSD
Turbofan engines are essentially gas turbine-driven ducted fans, with almost all of the thrust being produced by the fan, comparatively little by the residual thrust from the gas turbine. They are more efficient at the sort of speeds and heights jet transports fly at - higher and faster than prop aircraft.
Turboprop engines are a gas turbine-driven propellor, with almost all of the thrust being produced by the prop, very little by the residual thrust from the gas turbine. They are more efficient at the sort of speeds and heights fast light aircraft or small commuter airlines fly at - lower and slower than fan aircraft.
SSD
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On a similar note to that supersonic bit--
I was once told that the incredibly loud (almost deafening) cracking noise you get, say when a Beaver is taking off, was because the tips of the propellor blades were exceeding the speed of sound, is that true? Or is it just the exhaust sound of an old radial?
I was once told that the incredibly loud (almost deafening) cracking noise you get, say when a Beaver is taking off, was because the tips of the propellor blades were exceeding the speed of sound, is that true? Or is it just the exhaust sound of an old radial?
A turbofan might look like an enclosed turboprop, but the way they create thrust is different.
Turboprops use the props to create "pull" force (like wings create a lift force). The pull force is there from speed 0 to max speed by altering the pitch angle. This "pull" force is primarily created because the prop rotates, not because the aircraft moves forward. Therefore very efficient at low speeds, but limited because of propeller tip speeds when the aircraft does start to increase its speed.
Turbofans create thrust by displacing a huge amount of air. Therefore less efficient at low speeds since the engine has to suck the air into itself, but more efficient at high speeds where the forward speed of the aircraft already pushes huge amounts of air into the engine (and where the inlet already creates a compression).
Another evolution in between is the geared turbofan, which uses pitch control to control the amount of air displaced by the fan. Today this is done by controlling engine RPM (fan is fixed pitch). For higher thrust you need to accelerate the engine as well, which makes it "sluggish", slow in reaction time. A turboprop is already at high RPM, therefore thrust control through pitch control is very quick in reaction times at all regimes. The geared turbofan displaces huge amounts of air to create thrust, and thrust control is done through pitch control (quick reaction).
Turbojets create thrust by taking a lower amount of air compared to the turbofan, but accelerating it more (hence less propulsive efficiency).
Turboprops use the props to create "pull" force (like wings create a lift force). The pull force is there from speed 0 to max speed by altering the pitch angle. This "pull" force is primarily created because the prop rotates, not because the aircraft moves forward. Therefore very efficient at low speeds, but limited because of propeller tip speeds when the aircraft does start to increase its speed.
Turbofans create thrust by displacing a huge amount of air. Therefore less efficient at low speeds since the engine has to suck the air into itself, but more efficient at high speeds where the forward speed of the aircraft already pushes huge amounts of air into the engine (and where the inlet already creates a compression).
Another evolution in between is the geared turbofan, which uses pitch control to control the amount of air displaced by the fan. Today this is done by controlling engine RPM (fan is fixed pitch). For higher thrust you need to accelerate the engine as well, which makes it "sluggish", slow in reaction time. A turboprop is already at high RPM, therefore thrust control through pitch control is very quick in reaction times at all regimes. The geared turbofan displaces huge amounts of air to create thrust, and thrust control is done through pitch control (quick reaction).
Turbojets create thrust by taking a lower amount of air compared to the turbofan, but accelerating it more (hence less propulsive efficiency).
Why do it if it's not fun?
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Hey DP, how's it going?
I asked a similar question two years ago - not quite the same question, but related. See here for the thread.
FFF
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I asked a similar question two years ago - not quite the same question, but related. See here for the thread.
FFF
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