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Locomotive Front End Designs

Discussion in 'Steam Traction' started by ragl, Feb 19, 2016.

  1. Jamessquared

    Jamessquared Nat Pres stalwart

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    That analogy doesn’t make any sense to me. The reason a skate moves easily over ice is that there is a pressure-induced phase change from solid ice to liquid water, and the water then acts as a lubricant. Whereas with steam flowing through a tube, there is no phase change at the boundary - it is still steam. So I don’t know what effect you are measuring, but whatever it is, the explanation sounds wrong to me.

    Tom
     
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  2. Allegheny

    Allegheny Member

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    Porta always stated that his designs were limited by what could be manufactured in his workshops. A quatrefoil bellmouth/mixing chamber sounds more difficult to make.

    I an also wondering whether, if you have a number of jets in close proximity, the draught from each one would influence the others such that they are drawn into a single jet; the Kylchap cowls would prevent this from happening. This is purely speculation though.
     
  3. class8mikado

    class8mikado Part of the furniture

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    So you are saying on the Kylchap the blasts are closely spaced, almost parallel but the stepped 'diffuser' width somehow allows the blast to tumble outwards in a sort of mushroom cloud as it progresses.... ?
    The nozzles angle outwards for the Lempor and this to me makes sense as they are generally in close proximity, and in all these systems the blast itself is divergent and therefore individual blasts will eventually coalesce Mr Day is saying that divergent nozzles into a parallel sided tube works better than parallel nozzles into a parallel sided tube ands the evidence would support this . What mr Koopmans is saying I believe is that the explanation drag caused by the mixing chamber sides causing some kind of supercharged tumbling effects doesn't make a lot of theoretical sense and that more widely spaced parallel nozzles aimed directly at the bellmouth placed at the tapered diffuser base also produces good results, in which case why is there a need for mixing chamber tubes cowls etc

    Take a circular tube of metal , hold it at one end between two shallow tapered planks and press, Rotate through 90 degrees and press again hey presto a tube that's round in cross section at one end and around cornered square at the other with a cross sectional area that is constant throughout... not a difficult job. Making the bellmouth might be a bit trickier admittedly.
     
  4. Allegheny

    Allegheny Member

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    Not really, if you consider that the pressure is lower at the centre of a group of four jets (than it is outside the group), the jets might "curve" inwards so that they merge into one.
    You could make a bellmouth out of eight individual pieces, I'm just thinking that Porta might have thought it wasn't worth the trouble.
     
  5. JJG Koopmans

    JJG Koopmans Member

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    I cannot find any reference to Mr Day's phenomena on the internet, the effect of inclined orifices should have been noted by others.
    The UK patent 452,636 of Lemaitre himself shows 6 (six) inclined orifices which he claims is a must. Question, has anyone seen a locomotive
    with such a Lemaitre chimney?
    Those who have access to a copy of Wardales book could look at fig 125 on page 305. The orifices with a 12 degree spread perform better than those
    with 18 degrees. Is 15 degrees a logical choice then? His book counts 522 pages, page 474 to 476 are devoted to the Datong tests, mainly a summary,
    so nothing can be repeated or studied as verification. Imho, inconclusive.
    That orifice inclination has an effect on the Kylpor/Lempor calculations, the physical momentum is not directed in the (vertical) direction of the
    chimney axis, the calculation assumes it does, introducing an error. I myself could not care less, imho the Lempor calculation is flawed anyway.
    For me systematic tests where the orifices were inclined in steps of say two degrees would be conclusive, not a single swing from zero to 15 degrees.
    Kind regards
    Jos Koopmans
     
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  6. class8mikado

    class8mikado Part of the furniture

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    As the splitter itself doesn't present a serious obstacle to the smokebox gases finding their way to the area between the jets I don't see that the area between the jets it at a significantly lower pressure than the areas immediately out side the jets, gases are very fluid..

    Shaping the tube and bellmouth also adds the complication that it makes accurate orientation as well as position necessary, which as you say is another layer of fuss.
     
  7. Allegheny

    Allegheny Member

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    Having looked at a couple of photographs, I would say that the splitter actually assists the gas in getting in between the jets - which is the point that I was making. In other words a multjet exhaust with a splitter is better than one without.
    Regarding manufacturing, I'm a fan of the "keep it simple" approach.
     
  8. class8mikado

    class8mikado Part of the furniture

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    Sort of with you, but a Kylchap has a single jet which the splitter ( as its name suggests) splits into 4... a Double kylchap two blast nozzles ( and two splitters)
     
  9. Allegheny

    Allegheny Member

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    Agreed, I think we are both saying the same thing. The double Kylchap has 8 jets
     
  10. class8mikado

    class8mikado Part of the furniture

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    Aye,
     
  11. Nigel Day

    Nigel Day New Member

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    Here are three files showing the area of contact and the effect I discrib on the mixing chamber.
    The second shows the aiming point of the nozzles at the top of the mixing chamber. The third is of a Lempor nozzle drawing which pre dates my work. The full set of drawrings was all I originally had to base my work on. It took quiet a while to figure out how to convert it into a working chimney espeshaly with respect to the inclination which I know to be correct from experimentation and these drawrings. image.jpeg
    image.jpeg image.jpeg
     
  12. Nigel Day

    Nigel Day New Member

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    The front of the Lempor paper and a picture of the Kylpor used to verify the theories of Kylpors and Lempors by Porta. image.jpeg image.jpeg
     
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  13. Sir Nigel Gresley

    Sir Nigel Gresley Active Member

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    Having done Kylchap etc. to death, would someone (Jos) care to comment on the various strange devices fitted to the MAV (Hungarian) Class 424?
     
  14. JJG Koopmans

    JJG Koopmans Member

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    I know nothing about the MAV 424 class. Giesl mentions in one of his books that the Hungarians used the Ister orifice which he describes as a lookalike of the american Kiesl which is a 6-slit starlike orifice with a higher backpressure than the original round orifice but increases the vacuum because it is an "in between"
    version of a single orifice and the multiple version.
    Kind regards
    Jos Koopmans
     
  15. Sir Nigel Gresley

    Sir Nigel Gresley Active Member

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    An observable characteristic of the Ister is that the exhaust ejects at about 45º to the vertical!


    [​IMG]
     
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  16. Sir Nigel Gresley

    Sir Nigel Gresley Active Member

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    This American forum has some interesting discussion concerning front ends on USA behemoths, with frequent reference to British practice.
     
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  17. Sir Nigel Gresley

    Sir Nigel Gresley Active Member

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  18. 30854

    30854 Part of the furniture

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    I've devoured the entire contents of this superb site over the past few years. Some day, I hope to be able to claim to understand rather more of some of the decidedly leftfield ideas mentioned therein!

    The link to wierd and wonderful (mostly wierd!) locos is here for your delectation:
    http://www.douglas-self.com/MUSEUM/LOCOLOCO/locoloco.htm
     
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  19. Allegheny

    Allegheny Member

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    I've just been reading through this forum. Does anyone have any information on the Jabelmann double chimney, or is it better known by some other name?
     
  20. JJG Koopmans

    JJG Koopmans Member

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    Jabelmann was the chief of the UP Big Boy designgroup, I am not aware whether the Big Boy front end was named after him. It consisted of a double chimney system with each one having an intermediate cowl in which the 4 orifices (each) exhausted.
    Kind regards
    Jos Koopmans
     
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