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Wankel Rotary Engine

  1. Jun 24, 2007 #1

    baywax

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    Is there a reason we don't see the Wankel rotary engine being used more as an alternative to the piston engine? I've heard different reasons but there must be a reason that its not used in every engine today.

    http://auto.howstuffworks.com/rotary-engine.htm

    I see that it was first used as an aircraft engine shortly before WW1 and later Norton Motorcycles gave it a "whirl".
     
  2. jcsd
  3. Jun 25, 2007 #2

    russ_watters

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    That article lists several reasons. Low efficiency is a biggie.
     
  4. Jun 25, 2007 #3

    HallsofIvy

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    It is interesting that the Wankel engine was orginally marketed as being both more efficient and less poluting than piston engines- apparently the reasoning was that those are both weak areas for piston engines and since the Wankel was not piston it must be better! Objective testing showed that it was worse than piston engines in both categories.
     
  5. Jun 25, 2007 #4

    baywax

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    Ah ha. I can see that being a problem. No way to compartmentalize the thing?
     
  6. Jun 25, 2007 #5

    Integral

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    The rotor seal is a problem, the article says that due to gearing the rotor runs slower, but it has a much higher average speed then a piston. A piston stops at top dead center and bottom dead center, while the rotor of a Wankel is continuous high speed motion. This poses a real materials problem for the seals.
     
  7. Jun 26, 2007 #6

    baywax

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    If there were a more efficient seal developed for this purpose could the low compression problem be reduced if the size of the combustion chamber was reduced by using more than one rotary? So that there would be more than one rotary chamber and they would be smaller sizes? (more moving parts of course)
     
  8. Jun 27, 2007 #7

    brewnog

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    That said, the Mazda RX7 and RX8 have both been very successful, even if the service intervals and fuel economy are more like an American car than a Japanese one.
     
  9. Jun 27, 2007 #8

    Danger

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    I'm not entirely sure, but I think that you've hit on the idea behind the quasiturbine.
    http://auto.howstuffworks.com/quasiturbine.htm
     
  10. Jun 27, 2007 #9

    NateTG

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    Actually, sealing issues are made worse by having smaller rotors because the losses at the seal go as the linear dimension of the rotor, while power and energy production go as the cube of the linear dimension of the rotor. (There is a similar scaling factor for piston engines, and piston rings - the seals - are a very heavily developed and studied technology.)

    The Mazda engines do use multiple rotors (IIRC three of them), and have had a number of racing successes. Rotary engines are also still somewhat popular in airplanes.
     
  11. Jul 2, 2007 #10

    baywax

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    Thanks Danger and Nate TG

    I guess this one has been figured out:redface:

    Its so predictable that someone would tell me "the rotary engine isn't mass produced because its too efficient and doesn't sell enough gas". What website or planet were they on?

    Was the rotary developed as an alternative to the piston engine or was this a case of parallel inventions?

    Thanks again
     
  12. Jul 3, 2007 #11
    wankel rotary was much later,
    1960's first use in a NSU car vs 1880 for the early crude piston engine
    mazda started in the 70's to build them
    some use in bikes and other stuff

    lite and compact but uses more fuel per HP, way more
    maybe cheaper to build
    but needs a rebuild at less miles then a piston engine
     
  13. Jul 4, 2007 #12

    baywax

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    I found some different data on the inception of the rotary engine... used first in aircraft engines before 1918

    From the first post in the thread.
     
  14. Jul 4, 2007 #13
    thats an aircraft piston motor that spins in pre 1918 form
    it is mostly an aircooling trick setup but still a normal piston motor
    not anything like a wankel
    there are many kinds of rotarys
     
  15. Jul 4, 2007 #14

    Integral

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    LOL!
    There is little connection between the WWI aircraft rotary engine and a Wankel. The crankshaft of the WWI era engine was rigidly attached to the airframe. Conventional pistons provide the power to spin a massive cylinder head with the propeller attached around the crankshaft. The moment of inertia of the huge cylinder head was a major factor in the handling of the aircraft and therefore in the tactics employed during aerial combat of the era. Both of the commonly known planes of the era, the English Sopwith Camel and the German Fokker Dr1 (The triplane) were powered by rotary engines.
     
  16. Jul 5, 2007 #15

    baywax

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    And so when we say "damn you Red Baron" it is in regard to his disregard of fuel efficency..... among other atrocities.(?)
     
  17. Jul 8, 2007 #16

    wolram

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    The Wankel is still improving.

     
    Last edited by a moderator: Sep 25, 2014
  18. Jul 12, 2007 #17

    baywax

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    Cool! This also brought the idea of the Magnetic Rotary Engine to my attention but the video was about 36 seconds long.

    Here's a slightly better look at a Multiple Magnet Engine concept.

    http://www.youtube.com/watch?v=So8mhc40pZQ&NR=1
     
    Last edited by a moderator: Sep 25, 2014
  19. Jul 25, 2007 #18
    Wankel engines suffer because there isn't a large interest in developing them and therefore little money for R&D. Wankels are interesting because they have fewer moving parts and the manner in which they rotate cause little mechanical stress, but suffer horrible efficiency and emissions. Maybe one day, I love an engine that can rev.
     
  20. Jul 31, 2007 #19
    So whats the main advantage of a wankel? Is it more balanced in terms of vibration than a reciprocating piston engine?
     
  21. Aug 10, 2007 #20
    no they donot rev very high do to vibration problems
    but as they have three lobes they trippel the real RPM reading
    IE A WANKEL AT 2000 RPM READS 6K ON THE TACH

    THE MAIN ADVANTAGE IS LOW WEIGHT
    it is a lite simple motor
    and weight is about 1/2 a normal piston motor of equil power
     
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