World's first propeller with 11 blades completes first test flight

[GTX]

World's first propeller with 11 blades completes first test flight

MT-Propeller has successfully demonstrated propellers with seven and nine blade prior to this with promising results.

interestingengineering.com

 

[Grey Havoc]

I am tempted to add both the 'steampunk' and 'cyberpunk' tags to this thread.

 

[NUSNA_Moebius]

Now throw a duct over it.

 

[Michel Van]

better picture of MT propellor

 

[muttly]

Are 11 thin blades better than 5 or 6 wider ones?

 

[_Del_]

Maybe. Depends on a lot more than the number of blades (shape, chord, total area, etc).

 

[NUSNA_Moebius]

Are 11 thin blades better than 5 or 6 wider ones?

Like wing aspect ratio I figure longer thinner blades would technically be more efficient at producing “lift” but there may be speed efficiency curve issues that may limit altitude performance and max speed? Turbofan blades have moved to being wider and fewer, and even being mildly supersonic at take-off thrust but the duct and lack of pitch control creates a different working dynamic and set of requirements.

 

[martinbayer]

I would be negatively (which in my own personal worldview of being a pessimist means not really) surprised if someone had not yet developed an algorithm to determine the answer to that very exact question. It would be nice to see a big multidimensional matrix of airspeed/fuel consumption/propeller design/engine type/fuel, but then again, I'm firmly a jet/rocket guy myself - why waste any effort on open air exposed whirligigs that really have to struggle to even get to Mach 1?

 

[red admiral]

Are 11 thin blades better than 5 or 6 wider ones?

Generally no

Fewer high aspect ratio blades on as large a propellor diameter as possible should be most efficient.

But if you are limited by diameter and need to put more power through the disk then you need to increase blade area, from either more blades or wider chord blades

I wonder if noise and vibration is the real driver here. More blades shifts the tones so it might not seem as loud.

 

[1635yankee]

Are 11 thin blades better than 5 or 6 wider ones?

Generally no

Fewer high aspect ratio blades on as large a propellor diameter as possible should be most efficient.

But if you are limited by diameter and need to put more power through the disk then you need to increase blade area, from either more blades or wider chord blades

I wonder if noise and vibration is the real driver here. More blades shifts the tones so it might not seem as loud.

There's a bunch of tradeoffs (I did prop aero for several years), but generally if you spread needed blade area over more blades efficiency increases as induced losses are less. However, structural considerations will put a minimum limit on individual blade chord, hence area. Crowding between blade roots may cause shocks at high speed, reducing prop efficiency.

Noise is likely an issue, as noise increases rapidly with tip speed, but reducing tip speed means that more blade area is needed, and spreading that area over more blades tends to be advantageous.

 

[NUSNA_Moebius]

I would be negatively (which in my own personal worldview of being a pessimist means not really) surprised if someone had not yet developed an algorithm to determine the answer to that very exact question. It would be nice to see a big multidimensional matrix of airspeed/fuel consumption/propeller design/engine type/fuel, but then again, I'm firmly a jet/rocket guy myself - why waste any effort on open air exposed whirligigs that really have to struggle to even get to Mach 1?

There are basic diagrams charting engine config type with efficiency at general speed ranges. Those whirligigs remain a popular way to move aircraft and I really would love to see a prop fan make it to service. Case in which the need for turbofan-like cruise performance required swept, wide chord blades made from carbon fiber for strength at such large size and design. Those technologies did made the GE90 and many newer turbofans possible - themselves having propfan approaching efficiency.

 

[Nicknick]

So more blades, so lower the induced losses on the wingtips (as long as the other parameters haven’t changed). I guess, the reasons not to use 11 but 3 or 4 blades were mainly for mechanical reasons. The very thin and flimsy looking blades of this prop might have been impossible with traditional aluminum blades. The high damping material mix of the MT Props could be the enabler in this regard.

This design didn’t come out of nothing, MT was promoting the 5 blade props (to replace three blade props), then they tested a 7 and a nine-blade prop successfully and we might even see a 13-blade prop, who knows…

 

[sienar]

I would be negatively (which in my own personal worldview of being a pessimist means not really) surprised if someone had not yet developed an algorithm to determine the answer to that very exact question. It would be nice to see a big multidimensional matrix of airspeed/fuel consumption/propeller design/engine type/fuel, but then again, I'm firmly a jet/rocket guy myself - why waste any effort on open air exposed whirligigs that really have to struggle to even get to Mach 1?

Theodorsen pretty much solved propellers. Unfortunately it came right on the tail end of piston engine aircraft. I'd guess that the few companies who really need high performance props with big turboprops have done what you've asked, but they aren't sharing their methods.

This looks more like a PR stunt than anything else to me. Its hard to see how 11 blades would be worth it, even if the prop diameter is really constrained.

 

[Nicknick]

MT is a company which knows what they are doing. The video sound might not be 100 % accurate, but the plane is totally missing the familliar propeller sound. It is very reasonable to believe, that they really archieved a very great noise reduction.

MT also mentioned 15 % higher trust at zero speed, this is nice to have, but the efficiency at cruise speed would be of intrest...

 

[1635yankee]

MT is a company which knows what they are doing. The video sound might not be 100 % accurate, but the plane is totally missing the familliar propeller sound. It is very reasonable to believe, that they really archieved a very great noise reduction.

MT also mentioned 15 % higher trust at zero speed, this is nice to have, but the efficiency at cruise speed would be of intrest...

A good chunk of a propeller's blades are stalled during takeoff. This prop may have more unstalled regions than their baseline or it has too much area for optimal cruise performance

 

[Nicknick]

I think, the noise reduction is the driving force behind it. Many users (e.g. in Switzerland) will surly accept even a slightly lower cruise effeciency if they can use more airfields in exchange.

 

[NUSNA_Moebius]

I would be negatively (which in my own personal worldview of being a pessimist means not really) surprised if someone had not yet developed an algorithm to determine the answer to that very exact question. It would be nice to see a big multidimensional matrix of airspeed/fuel consumption/propeller design/engine type/fuel, but then again, I'm firmly a jet/rocket guy myself - why waste any effort on open air exposed whirligigs that really have to struggle to even get to Mach 1?

Theodorsen pretty much solved propellers. Unfortunately it came right on the tail end of piston engine aircraft. I'd guess that the few companies who really need high performance props with big turboprops have done what you've asked, but they aren't sharing their methods.

This looks more like a PR stunt than anything else to me. Its hard to see how 11 blades would be worth it, even if the prop diameter is really constrained.

There's alot of complexity in having that many pitchable blades in such a small package but we have many newer technologies to produce more complexity for a given cost. This could be a real game changer for STOL planes really needing that 15% extra thrust as Nicknick mentioned in post #14, but such civil platforms are cost constrained from the get-go by operators. Producing 9 and 11 blade props needs to be affordable for the market that needs it most. Otherwise this really could just be a PR exercise or a showcase for potential military ops.

 

[TomcatViP]

Don't forget that power on wing is increasing due to market demand while the overall volume available for a prop is generally constant. Also, new props will spend a higher time at increased speed (faster cruise speed) and higher power ratio (better climb performances).

Blades have then to be made stronger and still transform more power into momentum.

A good way to do this is to reduce the blade span and reduce the blade lift (higher nbr per rotor of equal diameter).

Availability of better Sciences at lower cost (CFD tools and newly formed engineers with overall knowledge of how to use them) make it a very efficient road to keep up with market requirements. The bonus is the retrofit market that makes those new rotors immediately cost efficient by spreading tooling and r&d costs.

 

[publiusr]

I am tempted to add both the 'steampunk' and 'cyberpunk' tags to this thread.

“Thus Returns Hartmann The Anarchist:”
an AIR WONDER story.

“And I thought Freddy Krueger was scary!”

Or maybe he just really hates his mechanic…or vice versa. “Designed by Slender—something…”

As for the prop itself—call it Maximilian.

 

[southwestforests]

I wonder if noise and vibration is the real driver here.

I'd say most likely yes, given this from the attached article,

MT-Propellers' five-bladed propellers have lower noise and vibration levels and have quickly become the industry standard. They are used on a wide range of aircraft, such as the Cessna 425 Series, Piper Cheyenne PA31T and T1, Piper Cheyenne PA42-1000, and Cessna 208 Caravan aircraft.

 

[Scott Kenny]

This looks more like a PR stunt than anything else to me. Its hard to see how 11 blades would be worth it, even if the prop diameter is really constrained.

This is all about noise reduction, though a 15% boost in takeoff thrust is a very nice bonus.

 

[stealthflanker]

I can see possibility of having this propeller in Loitering munitions, especially those using electric motor like Switchblade and Lancet.