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Circular engines

  1. Jul 27, 2009 #1
    Is there any circular engine (or any engine in general) which exhibits almost full time combustion?

    Leave alone turbine engines...that's too much of a hassle when implemented on automobiles (or is it?).

    Nope...no propulsion systems (like ramjet).
     
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  3. Jul 27, 2009 #2

    negitron

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    By definition, a gas turbine engine is the only type which meets your requirements: i.e., rotary and continuous combustion. A Wankel is also rotary but is an impulse combustion type like the ordinary Otto engine we're all familiar with.
     
  4. Jul 27, 2009 #3

    minger

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  5. Jul 27, 2009 #4

    russ_watters

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    From what I've read, the Chrysler Turbine was feasible, but just not marketable. One of the priimary reasons being people just didn't like the way it sounded. But with hybrids and electrics catching on, that shouldn't be so much of an issue anymore. And one of the maini drawbacks, a long warm-up time, could be worked-around via making it a hybird. I'm not sure if anyone is researching them now, but it seems to me that they'd be a great idea.

    Righ now, gas turbine->electric is used for ships and trains. Perhaps it will trickle down to trucks and cars.
     
  6. Jul 27, 2009 #5
    I dont really see gas turbines being used for cars, they are rather costly and inefficient for the stop start of a typical town driver, as far as I can remember (not done anytheing about gas turbines in a bit).

    I can see them being more suitable for a truck as once they are up to to power they are more efficient and you wouldnt have packaging issues in an enormous truck.

    Due to the higher shaft speeds and less vibration I suppose the perfect mate would be some kind of CVT box.

    EDIT: Just read about the gas turbine -> electric. Making the above not terribly relevant.
     
  7. Jul 27, 2009 #6
    Only 325 BHP with a turbine?...man!...it's a shame!

    Ok so...a almost full time combustion 'single stroke' engine is very much desirable and will be a replacements for such hybrids. I mean combustion + suction + exhaust + power at the same time @ efficiency of a 4 stroke.


    :rofl: No doubt.



    We have many circular engine designs right?...so none of them exhibit almost full time combustion?
     
  8. Jul 27, 2009 #7

    russ_watters

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    For a 3 litre engine? That's not half bad...
    Not quite sure what you're getting at there. The fact that the parts of the cycle are separated in time in a piston engine is not a big source of inefficiency. The main reasons a turbine engine is more efficient are compression ratio, combustion temp, and the deceleration of the pistons.
    I don't know that there are that many - there really aren't that many ways to generate mechanical work from fire. Reciprocating engines and turbine engines are about it. Even a Wankel rotary engine is basically a reciprocating engine.
     
  9. Jul 27, 2009 #8
    Modern reciprocating formula 1 engines work at 2.4 liters and on the verge of hitting 1000+ hp.

    So the F1 authority has posed a cap of around 700hp on the cars...since every time they reduce the engine capacity, the engineers do figure a way out to get 700+HP.

    You know they also posed an RPM limit...I think it was 19000 RPM.


    No I mean, I know if we incorporate all the strokes in one go, it wont pose that much of an advantage in efficiency; the advantage lies in the power in a unit volume.

    Most of the energy goes out in exhaust right?

    There's a 'tommy lee' circular engine but I could not get it's working.

    It produced 65 ps with the size of almost a fist.

    IRIS engine too is a very innovative way...very different.
     
  10. Jul 28, 2009 #9
    You've also got to remember that an F1 engine has to do no more than (approx) 2000 - 3000KM in its life and a grand prix distance (300km) at any 1 time. They are also silly money.


    I think I remember seeing this at the time, but I also remember something not being quite 'right' about it. His calculations and figures just seemed a little bit off, to be honest I dont think it worked the way it should anyway. As far as I can remember it worked in a silmlar way to a rotary vane compressor.
     
  11. Jul 28, 2009 #10

    minger

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    Right, that turbine in the Howmet TX only weighed 170 lb and while only put out 325 bhp, it put out 650 ft-lb of torque. Remember, this engine was not designed for the race car, it was designed for rotorcraft.
     
  12. Jul 28, 2009 #11

    brewnog

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    I saw (and heard) the Howmet TX at Le Mans last year, the thing was just awesome when up against GT40s and Daytonas.
     
  13. Jul 28, 2009 #12
    There have been several designs of rotary engines, but most have not been the continuous-burn types that you ask about. The main reason for this seems to be more lack of imagination than non-feasibility. Look at "www.starrotor.com"[/URL] design. (Russ, you ought to remember this one.) There are basically three types of internal combustion engines in use today, these being the Otto Cycle (ie. the standard automobile engine of choice), the Diesel Cycle and the Brayton Cycle. Any use (V8 piston design, for example) that can be designed as an Otto or Diesel engine can (with modification) be made as a Brayton Cycle engine. Most people don't know it, but George Brayton's original conceptualization is of a piston engine design, not a turbine design. The reason turbine (or other Brayton cycle) engines are a hassle on cars is simply because almost no-one has bothered to devote time and money to their development and we're all poorer for it.

    KM
     
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  14. Jul 28, 2009 #13
    That's not a very good indictment of the human race. The (beloved?) pop-pop engine sound of today is nothing more than a speed-up of the "chugga-chugga" of the engines of yesteryear.

    Re: the usefulness with hybrids - - - I couldn't agree more, in addition to being cleaner and ultimately more efficient, turbines have much higher RPM, which makes them ideal for use with the smaller and lighter 400 Hz alternators. A fellow several years ago used this combination to make a very efficient hybrid prototype. If I can find reference to it I'll put it in here. BTW, I think he is still around - - - in Florida somewhere.

    There was another objection people had to the GT engine - - - its slow acceleration/deceleration (this would be of no consequence in a hybrid). We should understand the reason for turbine lag - - - is, its a big flywheel. Actually, the cars themselves could smoke anything on the road - - - if you didn't mind the chance of launching the clutch and transmission. Simply run the engine up at a stop light - then pop the clutch. Chrysler definitely frowned on this.

    Rumor has it that the real reason for the GT being dropped was that Chrysler had just been bailed out, and the Government said "no new experimental designs". Take that for whatever it is worth.

    KM
     
  15. Jul 28, 2009 #14
    And that exhaust "blowdown" is one of the inescapable disadvantages of the Otto/Diesel Cycle engines relative to the Brayton Cycle. Actually, this can probably be better realized in an engine like a Brayton Cycle piston engine than a turbine. In the "pop-pop" engines, because intake, compression, ignition, expansion and exhaust all take place in the same chamber - - the hot gasses can only expand the amount they were compressed. Thus, a lot of expansion is wasted, and must be dumped out. Turbocharging helps a little. The Brayton cycle engine doesn't have this limitation since all these phases occur in different places.

    KM
     
  16. Jul 28, 2009 #15
    I saw the Howmet turbine many years ago, at a track that no longer exists. It ate all the other cars alive.

    Remember, there was also a gas turbine car entered one year in the Indianapolis 500, driven by Parnelli Jones. It got a couple laps ahead of everything else - - - when about five miles from the finish - - - it blew out the transmission. It apparently couldn't take the torque. The next year Indy essentially outlawed it.

    KM
     
  17. Jul 29, 2009 #16
    Woo hoo!...ok now that's good!
    Thanks for that info.

    So it's still the turbine sort of.

    The Kinetic energy in the gassed.

    I heard gas turbines had a major problem with this...~60% of power went out though this K.E.

    Yeah...I was thinking about that...thanks for confirming.
     
  18. Jul 29, 2009 #17

    minger

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    Here's a great read about the car and race.

    http://www.autopuzzles.com/Indy1967.htm
     
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