Another aproach in boat (and other) propulsion systems

Discussion in 'Diesel Engines' started by manolis, Nov 4, 2006.

  1. manolis
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    manolis Junior Member

    Increasing more and more the con-rod length, you finally get a harmonic or pure sinusoidal piston motion. Such a piston motion increases the constant volume portion of combustion and so increases the efficiency and the pick power at high revs. What actually the long rod makes is to keep the piston around TDC for more time. But the height of the engine would be enormous and the long con-rod would bend immediately.

    At the http://www.pattakon.com/pre/index.html it is presented the pattakon PRE engine.

    The following slide explains PRE differences from convnetional

    [​IMG]

    here they are shown the internals of a four stroke PRE (the con-rod can move without hitting the piston and the cylinder, i.e. no need for oversquare design)

    [​IMG]

    and here is a combact Junkers-PRE in section view (two stroke power concentration and at the same time four stroke lubrication, built-in scavenging pumps, four stroke like torque curve, through scavenging, improved efficiency due to the slow motion of the piston at TDC, etc). An electric power station based on this single cylinder Junkers-PRE is absolutely free from vibrations,making it ideal for Hybrid cars, Hybrid vehicles, autonomous robots etc.

    [​IMG]

    [​IMG]

    In general, to see the relevant animations enter into the http://www.pattakon.com/pre/index.html , click on an image to download the 'exe' file and then open it.



    The conventional engine offers a sub-sinusoidal piston motion around TDC. This PRE engine offers an over-sinusoidal piston motion around TDC, i.e. it increases a lot the constant volume portion of combustion. The shorter the con-rod length, the longer the time the piston stays near TDC. The PRE engine can be overquare, square or undersquare.

    In the plot below what you see is the piston travel versus the crank angle for a conventional engine, the PattakonPRE (both using conrod to stroke ratio equal to 1.65) and the Harmonic engine.

    [​IMG]


    If the conventional is revving at 1.35 times SLOWER than the PRE (for instance the conventional is revving at 5600 rpm while the PRE is revving at 7500 rpm), then around TDC the working medium (air or mixture) cannot see any difference. The orange curve in plot below is (around TDC) identical to the blue curve of the PRE.

    [​IMG]

    If the conventional is revving at 1,35 times FASTER than the PRE, then around BDC the working medium cannot see any difference again. The orange curve in the plot below is (around BDC) identical to the blue curve of the PRE.

    [​IMG]

    So the PRE as regards TDC is nothing but a conventional revving at significantly slower revs, and as regards the BDC, the PRE is nothing but a conventional revving at significantly faster revs.

    It is obvious that the valve lift profiles (if valves are used) have to be change to suit to the PRE piston motion, as well as the spark advance (or the injection advance in case of Diesel). If necessary, the PRE can use Pattakon’s Variable Valve Actuation (or VVA) system in order to optimize breathing along the whole rev range (you can see details for this breathing system at http://www.pattakon.com/ as well as the pattakon’s prototype cars).

    With a pair of opposite rotating screws/propelers, one on each crankshaft, the vibrations are completely eliminated.

    I’ll be glad to answer your questions.

    Thanks
    Manolis Pattakos
     
  2. manolis
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    manolis Junior Member

    Can a Diesel engine operate efficiently at 6000 rpm?

    When fuel is injected either into the cylinder of a conventional Diesel engine revving at 4500 rpm or into the cylinder of the Pattakon PRE Diesel engine revving at 6000 rpm, the fuel droplets cannot say (at least for the +-20% of the piston stroke around TDC) where they were injected (i.e. into the slow revving conventional or into the PRE).
    The fuel droplets see the walls of the combustion chamber and feel the existing conditions. The kinematic mechanism is invisible for the fuel droplets. All important events of Diesel combustion happen into this +-20% of piston stroke near TDC.

    The above are shown schematically in the animation
    http://www.pattakon.com/pre/droplet.exe

    So, can a Diesel engine operate efficiently at 6000 rpm?

    Thanks
    Manolis Pattakos
     
  3. manolis
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    manolis Junior Member

    It is also the piston speed

    Think also about the piston and the piston ring speed of the Junkers PRE.
    Given the cylinder dimensions, for instance 700 mm Stroke and 400 mm Bore, the Junkers PRE has two opposite moving piston with 350 mm stroke each. I.e. in Jubkers PRE two "short" stroke pistons form a long stroke cylinder.
    This means that the best economy engine speed is significantly increased or doubled. Doesn't it?

    Thanks
    Manolis Pattakos
     
  4. manolis
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    manolis Junior Member

    Good-by

    It was a very nice "discussion".

    Thank you
    Manolis Pattakos
     
  5. Guillermo
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    Guillermo Ingeniero Naval

    manolis,
    how does this engine compare in specific fuel consumption, performance, reliability and endurance with a similar powered light duty marine engine?
    Cheers.
     
  6. yipster
    Joined: Oct 2002
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    yipster designer

    must have missed this post a few days ago so here my 2 cents
    nice animations and you and Guillermo have valid points
    junkers was a fine sample but R&D against 100 years otto aint easy
    have seen somehow similar designs for hydrogen combustion engines
    that also need other cycles for H flame point duration etc.
     
  7. manolis
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    manolis Junior Member

    Guillermo

    A Junkers-PRE prototype is under construction, but not yet ready, so only theoretically I can talk.

    (Before making the Variable Valve Actuation prototype cars, shown at www.pattakon.com web site, we had to talk only theoretically for the Pattakon VVA, but for a long time now they are on the roads competing the best mass production engines).

    So theoretically talking:

    As long as the PRE engine keeps longer the “good conditions” for combustion, everything is improved (especially the fuel consumption). And there is more.

    Suppose you have a 200 mm stroke conventional engine revving at 1500 rpm (i.e. mean piston speed 10 m/sec). A Junkers-PRE needs only 100 mm piston stroke to make a 200 mm “cylinder stroke”, i.e. at 1500 rpm the Junkers-PRE has half the piston speed of the conventional. Looking at from another point of view: revving at 3000 rpm the Junkers-PRE has the same mean piston speed to the conventional revving at only 1500 rpm. Think about this (in terms of performance, reliability and endurance). Junkers PRE has no other parts to suffer from high revs like popet valves, camshafts, valve springs etc.

    It is also the absolute balance. When a pair of counter-rotating screws/propellers is used or when a pair of counter-rotating electric generators, in case electric power plant, is used, the basis of the engine does not transfer vibrations – neither inertia, nor combustion – to the boat (or vehicle) body.

    _____________________


    Yipster,

    The Jubkers-PRE is an evolution of the known Junkers engine (used as Diesel on aircrafts during the 2nd world war).
    The Junkers-PRE compared to the typical Junkers engine, has:
    1. far shorter distance between the two crankshafts, for the same piston stroke (think what this means)
    2. far slower piston near TDC (think about its ability to operate at revs until now unreachable for Diesels)
    3. built in scavenging pumps
    4. far more compact design.

    If you know some similar design, please let me know.

    The Pulling Piston Engine (PPE) is the father of the Pulling Rod Engine (PRE).
    When you get the chance, take a look at the Pattakon’s US patent 6,062,187 (for PPE) and then at the four year later HONDA’s endeavour on the same exactly problem with the US patents 6,763,796 and 6,786,189 (at http://www.uspto.gov/patft/index.html). Spot on the complication of each solution.
    Honda’s patents start with “In order to increase thermal efficiency by increasing the constant volume portion of combustion, it is proposed . . . “

    Thanks
    Manolis Pattakos
     
  8. Guillermo
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    Guillermo Ingeniero Naval

    Thanks, manolis.
    I'd like to know specific consumption charts, whenever possible.
    I liked your "Libellula" idea. You should be developing a prototype! :)
    http://www.pattakon.com/fly/index.html

    Cheers
     

  9. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

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