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MT-Propeller 11 blade propeller delivers 15% increase in static thrust

mt-propeller.com

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Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#61

Post by rbanffy »

justsomehnguy wrote: post #59
buildbot wrote: post #30

Earlier quoted context omitted.

I am not sure this is really correct - turbojets (as in fighter jets) sound more like what you describe, turbofans if I remember correctly, get most of the thrust (>70%?) from bypass air around the combustion, and very little from actual combustion thrust. It just also feeds it's own combustion chamber air to keep the fan part going. Perhaps it is a fan if enclosed? Vs. a prop if not?

>Perhaps it is a fan if enclosed? Vs. a prop if not? Stipa Caproni

Dear Lord! Half of the lift is due to the repulsion Earth feels from it.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#62

Post by rbanffy »

bitwize wrote: post #25
tus666 wrote: post #17

At what point does a prop become a fan? A 777 engine has 22 fan blades, twice this thing.

Back in the 80s there were experiments run with propfans -- propellers with many stubby blades that offered near jet-like performance while consuming half the fuel. They never got anywhere because propfan engines were large and noisy and the dropping price of oil made the fuel economy concerns less urgent.

A think a lot of the noise was because the blades were counter-rotating. The size limitation was to be compatible with tail-mounted engines like the ones used in DC-9's and 727's.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#65

Post by rbanffy »

vasco wrote: post #52
WalterBright wrote: post #49

The Wright Bros achieved 90% efficiency with their propellers. Adding 15% to that gives 103.5% efficiency, which I'm not buying.

You don't add them up like this. I can make a car use 50% less fuel an infinite amount of times, not just twice.

> I can make a car use 50% less fuel an infinite amount of times,

At some point it'll be running on nuclear fission, as you won't be able to feed it a single whole atom. ;-)

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#66

Post by matthew-wegner »

jcims wrote: post #20

Props with high blade count substantially reduce noise for drones as well https://youtu.be/1nk74KEIc2c?t=138s

Huh! Thanks for posting this. I haven't seen 5" builds with props like this before.

The opposite is definitely true for toothpick or smaller builds. Bi-blade is much quieter for something like a ~60g, 3" quad.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#67

Post by diskzero »

As a former aircraft owner, I immediately began to calculate the costs of doing on overhaul on those props. My three bladed props would need an overhaul at least every 2000 hours. There is also a time minimum as well if you don't reach the hours before the time interval. It seemed like the engines and the props would hit overhaul hours around the same time, usually hitting me with a bill well over $10,000.

I wonder what the cost will be on dual, 11-blade adjustable pitch props? It makes my eyes water and feel thankful I am not the owner/operator of such an aircraft.

Perhaps it all makes sense given the fuel consumption and speed improvements?

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#68

Post by bell-cot »

WalterBright wrote: post #49

The Wright Bros achieved 90% efficiency with their propellers. Adding 15% to that gives 103.5% efficiency, which I'm not buying.

> ...results in static thrust, 15% increase over the standard certified 5-bladed...

No mention of whether that higher static thrust is at some reference RPM, or when it's receiving some fixed X horsepower from the prop. shaft, or what.

From a quick search of the article, I see nothing connecting the 15% figure to efficiency.

Static thrust is plausibly measured with the airplane sitting still on the ground - which is helpful at the start of your take-off run, but probably not a metric that's worth any optimization.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#69

Post by [deleted] »

rbanffy wrote: post #60
vlovich123 wrote: post #29

Earlier quoted context omitted.

Would that change when using an electric motor?

I'd say the most favorable arrangement for noise would be a pusher configuration, with the engines close to the back of the plane instead of a tractor config on the front. This is done on the Piaggio Avanti. Not sure how well it works, but it looks like a spaceship. Eviation electrical plane recently changed their pusher design to a tractor, but kept the engines on the back (IIRC, they started with a central big one…

[deleted]

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#70

Post by xplanephil »

rbanffy wrote: post #60
vlovich123 wrote: post #29

Earlier quoted context omitted.

Would that change when using an electric motor?

I'd say the most favorable arrangement for noise would be a pusher configuration, with the engines close to the back of the plane instead of a tractor config on the front. This is done on the Piaggio Avanti. Not sure how well it works, but it looks like a spaceship. Eviation electrical plane recently changed their pusher design to a tractor, but kept the engines on the back (IIRC, they started with a central big one…

The problem with pusher configuration is that the prop operates in turbulent air, that has already ben disturbed by going around the rest of the airplane. Whereas in tractor configuration, the prop grabs "clean" air. This is traditionally cited as the reason why pusher prop planes are louder (from the outside). In fact, one of the noisiest GA planes is the Cessna 337, which is a pull-push twin configuration.

The advantage of the Piaggio Avanti is that you can do away with the prop heat completely, as the hot exhaust from the turboprop engine simply blows on the blades. Which makes for a very nice anti-ice system.

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