nozzle design and construction

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nozzle design and construction

Post by DaveLathrop57 on Thu Jun 20, 2013 12:49 pm

I think we all understand the basic nozzles as used on probably 95% of the locos we run - one big hole set atop a conically narrowing cavity. Some of us even explored the multiple orifice designs such as Goodfellow, linear designs like Geisl, and all manner of bridges and dividers.......and the "classic" Lempor style with 4 diagonally divergent pipes.

So, for the sake of efficient experimenting....I'm interested in a nozzle for a Lempor style design that can be installed  on top of the stand like the old school type, but is easily adaptable to varying angles of divergence and diameters of bore. Would a flat plate with the openings laser-cut through it suffice? How thick would it need to be? Would the holes need to converge and then diverge withn the thickness of the pipe? Does the bottom facing the stand need to be conically designed?

Seems that as many variations of a flat plate with holes in it as you want to try could be inexpensively made, and very quickly changed in the field.

Dave

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Re: nozzle design and construction

Post by Low_Water_Odom on Thu Jun 20, 2013 1:16 pm

Dave,

Your inquiry immediately made me think "what's the maximum thickness of material that can be laser-cut?".  A google search turned up this page:

http://www.teskolaser.com/waterjet_cutting.html

Apparently lasers can do stock from 0.12 to 0.4 inches depending on the material, and water jets can do 0.4 to 2 inches.  Using thick stock (if we went to water jet cutting), you could conceivably even do convergent-divergent nozzles in a solid plate.  We might want to do some hand-blending of the inlets using a die grinder, but I'd think this would work well, certainly well enough for test purposes.

Hugh

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Re: nozzle design and construction

Post by DaveLathrop57 on Thu Jun 20, 2013 7:25 pm

Fire, water, earth or air,
how we cut it I don't care.
Eye of newt and polecat's penis
guide the hand of our machinists,
And by Brigid and Hephaestus
may we all create the bestest
front end that will still fit in
to the old stack on 110.

Dave

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Re: nozzle design and construction

Post by JJG Koopmans on Fri Jun 21, 2013 6:12 am

Dave,
For the experimental period I would like to repeat the advice I gave to the good people of the Southern Railways 401, try a Sweney/Armstrong type orifice. Flat plate with petal flower pattern with a bolted disc in the centre that can be changed easily.
It works perfectly and the 401 is also an oil burner.
For a final design I would suggest some sophistication since you want a Kordina plus orifices with a minimal effect on the blast pressure.
Kind regards
Jos

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Re: nozzle design and construction

Post by Low_Water_Odom on Fri Jun 21, 2013 9:09 am

Jos,

That's a story I hadn't heard before.  Can you tell us any more about the exhaust work on Southern 401?

Hugh

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Re: nozzle design and construction

Post by DaveLathrop57 on Fri Jun 21, 2013 9:49 am

Yes, please...sounds like we need to get in touch with somebody up there.

Kordina....I associate them with the part of the saddle below the stand where the exhaust streams from both cylinders combine, not with the nozzle on top of the stand. I'm sure it all works together...but I'm not sure just how. Please explain more fully if you can - we just have the common Goss arrangement in the saddle to join the exhaust streams.

Dave

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Re: nozzle design and construction

Post by JJG Koopmans on Fri Jun 21, 2013 10:34 am

Mr Kordina used some streamlining down below between the front and back blastchannels from the cylinder. Goss used a separation between the left and right flows. The problem is that if the blast orifice is down below, like Porta uses, and I
end up with right now, you have to do some flow guiding to prevent the exhaust flows to choose a preferred orifice of the four.
As for the 401, please get in touch with the Monticello people. The locomotive was reboilered, changed from coal to oil, restaured and steamed right away with the original stack and redesigned front-end components. It had a Sweney/Armstrong type blast cap, a proper distance to the throat and the original petticoat was changed to an internal chimney/mixing chamber. Since they were ready back in 2010 they should have some experience by now.
Kind regards
Jos

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Re: nozzle design and construction

Post by DaveLathrop57 on Fri Jun 21, 2013 1:16 pm

Email off to a RyPN correspondent from Monticello.

OK, looks like we need to include innards of the stand to the nozzle design under discussion here.....How can we optimize flow across the entire nozzle within the stand above the Goss wall in the saddle?

Dave

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Re: nozzle design and construction

Post by JJG Koopmans on Sat Jun 22, 2013 3:11 pm

Fwiiw, today I was driving back home from a very frustrating ride with my absolute standard 3,5 in. Tich who refused to make proper steam, when it dawned on me that one of the possibilities of testing orifice incline was by mounting an upside down/inverted cone below the Sweney/Armstrong orifice and continue that with a truncated (?) cone made from plate steel on top of the centre disc, (a kind of straightforward teacup Smile)
Imho this would suffice to guide the exhaust jets in any wanted direction, but of course I bow to superior knowledge
Kind regards
Jos

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Re: nozzle design and construction

Post by DaveLathrop57 on Sun Jun 23, 2013 12:16 pm

Is this what you were describing?

http://i82.servimg.com/u/f82/18/31/23/40/scanco10.jpg


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Re: nozzle design and construction

Post by JJG Koopmans on Sun Jun 23, 2013 2:29 pm

Dave,
The bottom part is ok, on top of the orifices there should be a disc that can cover the orifice holes for sizing orifice area. If you consider those discs as the bottom of a teacup is should be more clear. The upper cone starts at the inside of the remaining holes and not on the outside as drawn. Sorry for my unclarity, as you know I am not a native speaker!
Kind regards
Jos
Jos

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Re: nozzle design and construction

Post by DaveLathrop57 on Sun Jun 23, 2013 4:13 pm

I'm not a native listener either......half deaf from a misspent youth of loud music and louder machinery. I'll try again, I think I understand you.

If the inner cone actually evenly disperses steam to all 4 holes.....what do we need the upper cone for?  

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Re: nozzle design and construction

Post by JJG Koopmans on Sun Jun 23, 2013 4:42 pm

Dave,
The upper cone is the guide for an inclined jet! Did you not ask for a simplified test layout to simulate proper orifices?
Kind regards
Jos

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Re: nozzle design and construction

Post by DaveLathrop57 on Sun Jun 23, 2013 6:18 pm

Yes, i think it would be a good thing to do......I'm having a hard time envisioning it. Hope what i learn from the Southern 401 people (if I ever hear from them) will help.

Dave

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Is this more like it?

Post by DaveLathrop57 on Sun Jun 23, 2013 8:38 pm


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