2007-12-06 06:16:24 · 6 answers · asked by cheenarca 3 in Science & Mathematics ➔ Engineering
A propeller moves some physical object like a boat or an airplane.
A fan moves the air.
?
2007-12-06 06:41:37 · answer #1 · answered by J C 5 · 0⤊ 0⤋
The application makes a difference as well. A hovercraft, for example. Any hovercraft that uses the main thrust engine to also provide lift will use a fan, and not a propeller. The difference being the ability to maintain a static pressure. A prop has only two blades, and the cushion air will escape, whereas a fan uses many blades, and keeps the cushion air pressure up. A fan also takes up much less space, compared to a prop, to get the same thrust. A lot of fans used to power hovercraft will have 12 blades, sometimes 13 in an attemp to cancel some of the blade noise. Also, fan shrouds can be used to increase the velocity of the air by reducing the outlet opening.
2007-12-06 19:23:01 · answer #2 · answered by Anonymous · 0⤊ 0⤋
I think I understand what you're asking -
The goal of a fan is to accelerate the largest possible air mass. But a propeller's job is to generate thrust, slightly different goal. The difference becomes clear when you examine each. Fans generally have a constant cross-section or thickness, usually made out of a single layer of sheet material. But propellers have an airfoil shaped cross-section, like an airplane wing. This airfoil shape not only moves a large airmass backward, but also creates a vacuum in front of the propeller. In all, about half the thrust generated by a propeller is from pushing air behind it, and the other half from the partial vacuum created in front of it - so it's half-push, half-suck.
Flat-bladed fans do have some suction, just not as much as if it were an airfoil shape.
2007-12-06 15:35:18 · answer #3 · answered by Gary H 6 · 0⤊ 0⤋
A fan's purpose is to move air. A propeller's purpose is to move (propel) an object through air.
For a jumbo jet, for example, the blades (Fans) inside the engine feed air into the turbine for ignition. The primary method of propulsion is the turbine.
A propellor airplane directly uses the contact with air to cause acceleration.
2007-12-06 15:08:26 · answer #4 · answered by stingjam 6 · 0⤊ 0⤋
A fan is stationary, and increases the velocity of the air through it.
A propeller (and it's attached vehicle) is in motion, and the air or water is relatively stationary.
2007-12-06 14:57:22 · answer #5 · answered by David F 7 · 0⤊ 0⤋
The only basic difference is their purpose.
The principle upon which they both work is exactly the same.
2007-12-06 16:35:40 · answer #6 · answered by dmb06851 7 · 0⤊ 0⤋