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A propeller generates lift, which results in prop-wash for thrust(same as helicopters), but when you look at the N1 fan it looks much different than propeller blades. Do turbofan blades generate lift like propeller blades to generate thrust? And why are the blades curved on a turbofan?

Turbofan curved blades

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  • $\begingroup$ It's just an aerofoil, like a wing, or a rotor blade or a propellor blade. Relative air flow speed (by rotating the fan) and angle of attack = force. It's only called "lift" when it's a wing or a rotor blade. $\endgroup$ – Simon Sep 29 '15 at 8:18
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Fan blades, propeller blades, rotor blades and wings are all aerofoils and work in much the same way. Variations in shape are just optimisations for each particular use case.

With the number of times you have asked this question (at least three here and two on http://physics.stackexchange.com ) I thought you would have grasped that by now.

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  • $\begingroup$ I am a slow learner. I process information very slowly. The shape of the blades look different than a propeller blade, thays why I asked it and also why I ask a lot of questions on one subject. $\endgroup$ – Ethan Sep 29 '15 at 4:35
  • $\begingroup$ Even with all the questions I ask and get answers too I still get confused and thats why all the questions. $\endgroup$ – Ethan Sep 29 '15 at 4:39
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Think that lift is just the result of pushing air in some direction: downwards for wings or rotors, rearwards for propellers, or in any suitable direction for compressor stages. Anything that moves air in any proportion or direction creates a force in reaction and tends to be moved in the opposite direction, and it moves unless the force is not sufficient.

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Doing that is often not so easy, because in addition of creating this force, let's name it lift, the process also creates unwanted effects, collectively named drag. Drag has numerous negative aspects: it increases fuel consumption and often reduces lift created.

Anybody can create a device which generates lift, but the role of the aerospace engineer is to increase lift while decreasing drag, and to take into account the technical feasibility, and the limits of materials.

The design will also try to minimize the fuel quantity required to produce the lift.

During this optimization the shape of the device is carefully selected and adjusted, based on result of previously performed tests, and new ones. This leads to different shapes according to conditions of lift creation: desired amount of lift, energy available for this creation, permitted volume and weight, speed of surrounding air, temperature, etc. This is a reason why a compressor blade is not shaped like a helicopter rotor blade, or B737 vertical stabilizer.

Curiosity and insistence are good drivers, but they need to be guided by some methodology, else you get exhausted soon. What you may lack is a general overview of aerodynamics. Asking isolated questions is valid, but not the most efficient way.

To understand the all aspects you need to dig into the engineer manuals or at least into good vulgarization books. There are many online for free.

By the way lift, whatever the name is used (e.g. thrust for an engine and propulsive power for a propeller), is really any force created by moving air, so when you open a door you create unwanted lift and vortex without knowing.

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  • $\begingroup$ How does opening a door generate lift? $\endgroup$ – Ethan Sep 29 '15 at 5:57
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    $\begingroup$ Back to my first sentence: Lift is just the result of pushing air. This is the way to see it in a simple way. If you want the full monty by Nasa then here we go: Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. $\endgroup$ – mins Sep 29 '15 at 6:08
  • $\begingroup$ There's mutiple types of lift. An aircraft wing doesn't push air backwards, but rather uses it to lift the weight of the aircraft upwards. $\endgroup$ – Ethan Sep 29 '15 at 6:09
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    $\begingroup$ I didn't write backwards but downwards. This creates a force upwards (more or less) which opposes gravity and maintain the plane at its altitude. Vortices around a door are created like that. See full study of door opening. $\endgroup$ – mins Sep 29 '15 at 6:31
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    $\begingroup$ @Ethan - Does your hand move air? The amount of lift is very small since your hand makes a poor airfoil, but there will be plenty of vortices because your hand makes a poor airfoil. Next time you see a campfire (or someone puts a cigarette in an ashtray) move your hand through the smoke and watch. $\endgroup$ – FreeMan Sep 29 '15 at 15:45

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