Toroidal propeller

A toroidal propeller is a type of propeller that is ring-shaped. Toroid propellers are significantly quieter (especially at audible frequencies, which lie between 20 Hz and 20 kHz) and are claimed to be more efficient than traditional propellers both in air and water. Toroidal propellers are promising for their potential to reduce noise pollution through quieter aviation and maritime transport, but they have always been difficult to manufacture and therefore very expensive.

History

The torus marine propeller, then described as one featuring "double blades", was invented in the early 1890s by Charles Myers from Manchester[1] (related Canadian patents also feature others[2]) affiliated with Fawcett, Preston and Company.[3] The design was successfully trialed on several English steam tugboats and passenger ferries at the time.[4] Frenchman Joseph Ganio and Spaniard Jose Fola also patented similar designs during the 1900s.[5]

In the 1930s, Friedrich Honerkamp patented a toroidal fan,[6] and Rene Louis Marlet patented a toroidal aircraft propeller.[7] The marine propeller was patented again in the late 1960s by Australian engineer David B. Sudgen affiliated with Robbins Company of Seattle.[8][9] Overall, the relevant Cooperative Patent Classification category, B63H1/265 Blades each blade being constituted by a surface enclosing an empty space, e.g. forming a closed loop, features over 150 patents in 120 years worldwide as of 2022.[10]

In 2013, Sharrow Marine applied for a patent for a toroidal propeller[11] and developed propellers for use in boats. They claim that the benefits of lower fuel consumption (higher efficiency) and reduced noise are even greater in water.[12]

In 2017, the design was brought up to date again when Massachusetts Institute of Technology (MiT) applied for a patent for the toroidal propeller, and in 2020 the application was granted.[13] In 2022, Lincoln Laboratory was awarded the R&D 100 Award for making the toroidal propeller available.[14][15]

Design and function

The design distributes vortices generated by the propeller along the entire shape of the propeller, which means that noise is distributed and damped more quickly.[16][17] The propeller design has similarities with the closed wing, which is annularly shaped and therefore distributes the vortices generated along the entire shape instead of just at the tip.

Drone propellers made according to this principle have been shown to emit a frequency between 1 and 5 Hz,[18] which is outside the audible spectrum for humans.

See also

References
  1. U.S. Patent 467322A
  2. CA 37791A, CA 39504A
  3. Marine Engineer and Motorship Builder. 1892. p. 241. Retrieved May 8, 2023.
  4. Proceedings. Institution of Mechanical Engineers. 1892. p. 546. Retrieved May 7, 2023.
  5. FR 339176A, FR 357655A
  6. U.S. Patent 2273756A
  7. FR 808801A
  8. Engineering Heritage Western Australia. "Sugden, David". ehwa.wikidot.com.
  9. U.S. Patent 3504990A
  10. https://www.patentguru.com/search?q=cpc=B63H1/265
  11. Sharrow, Gregory Charles (September 7, 2016). "Propeller". EP2941539A4. Retrieved May 1, 2023. {{cite journal}}: Cite journal requires |journal= (help)
  12. "Toroidal propellers: A noise-killing game changer in air and water". January 27, 2023. Retrieved April 30, 2023.
  13. Sebastian, Thomas; Strem, Christopher (November 17, 2020). "Toroidal propeller". US10836466B2. Retrieved April 30, 2023. {{cite journal}}: Cite journal requires |journal= (help)
  14. "Toroidal Propeller". Retrieved April 30, 2023.
  15. "Six Lincoln Laboratory inventions win R&D 100 Awards | MIT Lincoln Laboratory". Retrieved April 30, 2023.
  16. Blain, Loz (January 27, 2023). "Toroidal propellers: A noise-killing game changer in air and water". New Atlas. Retrieved January 29, 2023.
  17. US US10,836,466B2, Sebastian, Thomas, "TOROIDALPROPELLER", published 2020
  18. designboom, lea zeitoun I. (January 27, 2023). "toroidal propellers turn your drones and boats into noiseless machines". Retrieved April 30, 2023.
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