Talk:Toroidal propeller

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Picture?

To better understand the design a picture would be very helpful. 2001:A61:2ABB:D901:3083:7064:924A:B882 (talk) 07:57, 30 June 2023 (UTC)[reply]

Yes it would. We would love to have one for this article. Do you have one that can be uploaded under a free licence? - Ahunt (talk) 12:13, 30 June 2023 (UTC)[reply]

I made this simple model, hope this helps. Sauer202 (talk) 17:52, 15 March 2024 (UTC)[reply]

Simple 3 blade toroidal propeller

Dubious sources

We have sources on this of claims in patent filings, articles by media, broken links, and a few manufacturers who's marketing teams always bend the truth. Like the noiseless propellers statement on one source that is definitely false. Where is a scientific study or credible source? One of the pages shows MIT designs, but all that is discussed is noise. Whoever did that work, probably has some decent information about their findings.

In air there are several reasons why this is likely to be less efficient. It has twice as many blades. More blades create more turbulence in the air around the prop. This means more turbulent air strikes the blade and turbulent flow over the blade develops faster. Turbulence is wasted energy.

The parasite drag is higher as the total surface area moving through the air is greater.

Induced drag is a bit trickier. It is usually the larger drag component as well. The lead blade is not an ideal shape and actually pushes air off the blade which is less efficient. The inside blade will tend to hold the air on the blade keeping it from slipping outward radially.

Are the induced drag modifications enough to overcome all the other negative effects? None of the sources appear to say so, or in a credible manner. Milgaco (talk) 04:23, 12 February 2024 (UTC)[reply]

I agree that this article is currently quite lacking in its sources, and it would be useful to have some more impartial and academic references on the benefits/drawbacks of this propeller shape. So far I have not been able to find much in this regard, which could simply be the academic literature using a different term for the same phenomenon or because it is actually a topic that has not been studied much. Whatever research the people at MIT and Sharrow may have performed, they don't appear to have published it anywhere.

However, I wouldn't be so skeptical of some of the claims presented here and by the manufacturers. In air at least, much of the noise in a propeller or rotor is generated due to blade vortex interaction. Closed-wing/annular designs are known to reduce the shedding of tip-vortices, and designs that reduce tip-vortices are known to reduce the noise (e.g. fenestrons or ducted fans).

Regarding the induced drag, this is indeed the larger component of power when hovering or in low-speed flight. I'm not sure what you've written is accurate regarding the efficiency here though. In fixed-wing aircraft, closed-wing designs are well-known to be the most efficient in terms of induced drag due to the reduction in wing-tip vortices that is achieved. This could very well also be the explanation for why this blade could be efficient. Also note that the MIT researchers are fairly careful to claim that their design is more efficient than the conventional, leaving it out of the press release at least.

I can't say much about the specifics about the Sharrow propeller because I don't know enough about hydrodynamics. But it's a commercial product and there are plenty of reviews available, for example on YouTube, that discuss and confirm that it is also less noisy and more fuel efficient.

Swaggernagger (talk) 19:07, 23 April 2024 (UTC)[reply]

Small-scale testing (in terms of size and quantity of tests) indicate reduced efficiency over standard props, but do indicate greatly reduced sound. [1]https://www.youtube.com/watch?v=kyjCwyfnrU8 TeflonTrout (talk) 14:18, 17 July 2024 (UTC)[reply]