Author Topic: Most Efficient Number of Prop Blades? (Read 826 times)

talliven · « **Reply #15 on:** June 20, 2004, 12:22:06 AM »

first comparing windmills blades to aircraft props is pointless. they work on different principles for the most part. with a windmill newton's law is prime force (for every action equal oposite action) ie. as wind hit blade it is deflected to left thust causing blade to rotate right. Whereas an Airplane prop uses bernouli's principle as prime thrust production. each blade of the propeller is in actuallity a small wing producing "lift" in the forward direction. the air being "deflected" by the prop only makes up a small percentage of the thrust.

GScholz · « **Reply #16 on:** June 20, 2004, 12:36:36 AM »

Actually Hades55 the tip of the Tu-95's prop blades break the sound barrier. It's the noisiest plane in existence, even NATO fighter pilots have complained about the noise when intercepting them.

Yes NUKE it's pretty amazing that a big lump of metal like the Bear can cruise at 575 mph. Well ... four 15,000 hp engines driving 8 four blade propellers 18 feet across would do that.

XtrmeJ · « **Reply #17 on:** June 20, 2004, 12:41:12 AM »

The more the merrier.

Hades55 · « **Reply #18 on:** June 20, 2004, 01:03:43 AM »

Heh, gscholz i mean the plane speed not the tips

hitech · « **Reply #19 on:** June 20, 2004, 10:42:51 AM »

talliven: There is no difference between windmills and planes in the use of airfoils as propelers, both work the same.

Halo: In windmills it becomes a cost effective solution, 3 blades, vs taller & stronger tower and blades.

AKIron · « **Reply #20 on:** June 20, 2004, 11:43:16 AM »

Quote

Originally posted by GScholz
Actually Hades55 the tip of the Tu-95's prop blades break the sound barrier. It's the noisiest plane in existence, even NATO fighter pilots have complained about the noise when intercepting them.

Yes NUKE it's pretty amazing that a big lump of metal like the Bear can cruise at 575 mph. Well ... four 15,000 hp engines driving 8 four blade propellers 18 feet across would do that.

Cruise speed for the Bear was only 441mph (383 knots) according to this: http://www.bearcraft-online.com/museum/museum.htm?mid=78

hogenbor · « **Reply #21 on:** June 20, 2004, 11:48:50 AM »

I once heard (not from a guy in pub) that British Tornado interceptors could not keep up with the Tu-95 without afterburners.

Of course there are many variables if you take this as a true story but it is certainly an intruiging story.

Anyone has more info on this? I love the 'Bear', born as a compromise but decidedly brilliant as an aircraft.

Grimm · « **Reply #22 on:** June 20, 2004, 12:24:49 PM »

I almost made the mistake of claiming Rare Bear as the fastest prop, but its the fastest Piston A/C.

When double checking I noted that fastest isnt the TU-95 but the TU-114 which appears to be a civilian version of the Bear. Is that correct?

On props, Common Sense would tell you...
If you have an existing A/C and then you add a more powerful engine, to make use of that power, you would have to either make bigger blades, wider blades, changed pitch, or Add another blade. So I would think as things evolved you saw the addition of more blades on a prop to make use of the more powerful engines produced.

bozon · « **Reply #23 on:** June 20, 2004, 04:42:12 PM »

The first important factor in props from what I know is the filling factor. I mean, how much of the prop disc's area is covered with blades. No matter if this is a few broad blades or many narrow blades.

you can't put too much plade area in the disc because you need the air to flow through it! at some point it will act more as a wall against the airflow instead of giving thrust.

More cover will give lower efficiency but more thrust possible at slow speeds. for high speeds you'll want to lower it.

the number of blades is as far as I know second in importance, that's why you see so many variations. But I'm no aeroengineer.

Bozon

J318 · « **Reply #24 on:** June 20, 2004, 06:09:21 PM »

It all depends on what your after. So lets assume we have the same engine, ariframe etc.. yeah.... you with me? good.
Less and short blades will not go as quick but it is easier on the engine therefore increasing fuel efficentcy but you may spent so long getting there you burn up more fuel.
More and longer props have the opposite effect. Then we go into propellor pitch but I'm not gonna go down that road I'm too tired

GScholz · « **Reply #25 on:** June 20, 2004, 07:48:31 PM »

Quote

Originally posted by AKIron
Cruise speed for the Bear was only 441mph (383 knots) according to this: http://www.bearcraft-online.com/museum/museum.htm?mid=78

That's economical cruise yes. Maximum continous level speed is 575 mph for the fastest Bear variant (Foxtrot I think).

GScholz · « **Reply #26 on:** June 20, 2004, 08:18:28 PM »

Quote

Originally posted by Grimm
When double checking I noted that fastest isnt the TU-95 but the TU-114 which appears to be a civilian version of the Bear. Is that correct?

No the Tu-95 is the fastest turboprop. The civilian Tu-114 is the fastest turboprop airliner at 545 mph.

This is a great site: http://lsss.homestead.com/trivia.html

Halo · « **Reply #27 on:** June 21, 2004, 05:58:05 PM »

Thanks for that site link, Gunther. Fascinating. Listened to a lot of favorite aircraft sounds. Many were not what I expected, and many sound different than they do on Aces High.