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Non pulsed otto cycle engine

  1. Jul 18, 2005 #1
    Has an otto cycle engine been developed which gives a non pulsed output?
     
  2. jcsd
  3. Jul 19, 2005 #2
    What do you mean? A continuous-burn engine? That would appear to violate the definition of "Otto Cycle". That sounds more like a "Brayton Cycle" which is continuous burn. You can have a Piston Brayton Cycle engine. One of the "Mechanics " type magazines carried such an invention several years ago. If I can find it I'll let you know.

    If I'm not mistaken, some defining characteristics of an Otto Cycle are:
    1) Spark ignition.
    2) Intake, Compression, Ignition, Power generation and Exhaust all occur from the same area.
    3) Compression and Expansion volumes are the same - - - otherwise it would be Atkinson Cycle.
    4) Burn is intermittent (Pulsed?).

    FredGarvin, is this correct?

    KM
     
  4. Jul 19, 2005 #3
    I mean the ideal Otto cycle (which does not take into account the intake and exhaust strokes) which is essentially adiabatic compression, constant volume burning, adiabatic expansion and finally heat rejection at constant volume. Aside from the Wankel engine, is there any which uses this constant volume cycle and does not provide a pulsed output?
     
  5. Jul 19, 2005 #4
    surely even the wankel engine is a pulsed output?
     
  6. Jul 19, 2005 #5

    Danger

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    The only way that I can see it happening, if I'm understanding the question correctly, would be to have an essentially infinite number of combustion chambers (cylinders or lobes) firing sequentially so the explosions act like a wave. I don't think that it would fit in a Volkswagon.
     
  7. Jul 19, 2005 #6

    brewnog

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    I reckon that by definition, an Otto cycle must be used in some sort of reciprocating manner, in which case the output will always be pulsed to some extent.
     
  8. Jul 19, 2005 #7
    The Wankel, as well as the piston Otto Cycle, must have pulsating outputs from each chamber/cylinder. It goes with the sequential nature of the way each stage of the cycle occurs within the same area (chamber/cylinder). These cannot occur at the same time within this area - - - thus the output must be "pulsed". It cannot happen in any other way with this configuration.

    The same also is essentially true for the Diesel and Atkinson cycles.

    KM

    PS. Even the continuous burn Brayton cycle has some pulsation at the 'output' simply because of the presence of the 'buckets' or 'teeth', or whatever it uses to derive power. It's just a lot smoother than the others. Its burn is by definition, continuous and thus smooth (not counting internal turbulences, etc.).
     
  9. Jul 20, 2005 #8
    You're right. My bad.
     
  10. Jul 21, 2005 #9
    An electric car would have a constant energy output though wouldnt it?

    Have had quite a few lessons on automotive engineering but have never touched into electric cars.
     
  11. Jul 22, 2005 #10

    Clausius2

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    It seems any of us know what you mean by "pulsed". The pulsation in an Otto cycle engine- I will assume you are referring to something practical like an spark ignition engine- is produced by a pressure wave as exhaust valve opens. How the hell are you going to be able of not having any valve?. This would mean you have a continous combustion process while burning a continous flow of fuel as in a jet engine. If so it won't be an Otto cycle, but a Brayton one because it will be impossible the flow to be an adiabatic stream. This question makes no sense at all, but it is welcome because I made also one similar some time ago.... :biggrin: .
     
  12. Jul 22, 2005 #11

    Danger

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    Having read this post, I think that I might have misunderstood the original question. I thought that it referred to equalizing the combustion so as to eliminate the need for a flywheel, harmonic balancer, etc. in order to obtain a smooth mechanical output.
     
  13. Jul 22, 2005 #12

    Clausius2

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    Having read your post, I think that I might have misunderstood the original question too :biggrin:. I don't know what Sidgalt meant. I am not saying previous responses are wrong at all. Moreover, through our mistakens I have given Sidgalt enough information yet. :wink:
     
  14. Jul 23, 2005 #13
    Thank you all for the replies

    I was referring to an otto cycle engine which had continuous combustion like the jet engine.

    BTW, are the 2 stroke, 4 stroke and Wankel engines the only implementation of the Otto Cycle


    edit: One more question, during the downward stroke of the piston in a piston engine, does the car feel an upward force?
     
    Last edited: Jul 23, 2005
  15. Jul 23, 2005 #14
    [


    As several of us have said, no. Any ICEs that have continuous combustion like a jet engine, also like a jet engine are Brayton cycle engines. To date that is the definition of Brayton Cycle (Who knows, in the future there may be a new ICE cycle discovered that is also continuous burn ), and it is the main differentiator from the timed-combustion engines, like the Otto and Diesel cycles.

    Basically yes, but it's a bit more complex than that. For example, the Wankel Otto cycle can also be 2 stroke or 4 stroke. Or, You could make a piston or Wankel Brayton Cycle engine. (It's not the "shape" of the engine's parts that make the difference, but how you use them. This determines their thermodynamic characteristics.) For that matter, even the Brayton Cycle (At least piston versions) could have 2-cycle or 4-cycle equivalents. It appears to me however that 2-cycle equivalent might be less efficient, but then I could be wrong about that.


    No! Whereas the detonation pushes upwardly on the head, it also pushes equally down on the piston and thus the crankshaft. Both of these forces go equally into the block, thus cancelling any net translative forces, though they'll twist and vibrate the engine like mad.

    KM
     
  16. Jul 23, 2005 #15

    Danger

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    Right... I misunderstood. What you're asking about is impossible within the parameters of an Otto cycle.

    No. The only other one that comes to mind immediately, because I love the thing, is the 'K-cycle'. It was developed in Saskatchewan or Manitoba by a fellow in his home shop, and I don't know if it ever went into commercial production. It was based upon sets of counter-acting pistons angled something like 160º from each other and pushing on a swash plate between them. What made it especially peculiar was that the pistons remained essentially where they were and the block rotated around them. It was all housed within a case that looked a lot like 2 small garbage cans fastened together at an angle. It would burn just about any fuel, and the one demonstrated was producing approximately 500hp from 350ci. Tonnes of torque too, if memory serves.

    Shouldn't, I suspect, because the downward force is still contained within the physical limitations of the vehicle. With it being an enclosed system, the forces should balance out.
     
    Last edited: Jul 23, 2005
  17. Jul 23, 2005 #16
    I should point out, that though these are the only commercial implementations of the Otto cycle, they are not by any means the only possibilities of it. For example, there is the (in development) Veselovsky Rotary engine, and several past designs (most of which had pistons of some type).

    KM
     
  18. Jul 23, 2005 #17
    There have been several similarly intriguing designs. They have all suffered from the same flaw, the NIH factor! Another particular example is the Bricklin-Turner Rotary Vee engine.
     
  19. Jul 24, 2005 #18

    Danger

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    That is exactly the motor that I was reffering to, which was called the 'K-cycle' when I saw it. Since the report was on CBC or CTV national TV here, and the production facilities were here, I misunderstood and thought that the motor itself was developed here. Thanks for the link!
     
  20. Aug 19, 2005 #19
    What's the NIH factor
     
  21. Aug 20, 2005 #20

    NIH means "Not Invented Here". It refers to the dismissive reception that anything not designed within a company (or even within a particular division or section of a company) virtually always gets within the organization. In the past this attitude always puzzled me, I couldn't see why people would always look for fault in a new concept, even when it could bring big profits.

    Now I think that I'm beginning to understand the politics of the matter, and why this destructive trend is so prevalent in America, and far less so in Far East countries (Europe, I don't know, though I suspect British behavior is similar to that in America.)

    KM

    PS: This has been around and discussed for decades, and probably throughout the twentieth century, so it's not new.
     
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