nozzle design and construction

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nozzle design and construction

Post by DaveLathrop57 on Thu Jun 20, 2013 1:49 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 2:16 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 8:25 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 7:12 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 10:09 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 10:49 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 11:34 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 2:16 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 4:11 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 1:16 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 3:29 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 5:13 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 5:42 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 7:18 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 9:38 pm


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Re: nozzle design and construction

Post by JJG Koopmans on Mon Jun 24, 2013 7:24 am

Dave,
The idea is to have a laser cut orifice plate, so the holes have straight sides. The centrally mounted circular disc is bolted in the middle and by choosing it smaller or larger the orifice area is increased or decreased. If you care to look in my book page 392 you will see the cast Armstrong "annular ported nozzle" with the threaded hole in the middle. My idea is that by using a "cup" with inclined sides the jets issued from the orifices should have a direction different from the vertical which makes it an experimental layout.
Btw, in the good old days they used to have summer and winter discs to cope with the demand for steam for train heating purposes.
Kind regards
Jos

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Re: nozzle design and construction

Post by DaveLathrop57 on Mon Jun 24, 2013 9:27 am

Aha - didn't make the connection between "Armstrong" and "Annular Ported." Now i think I'm better understanding you......and the disc is just a disc with the diverter on top of it, not something like an old potbelly stove draft adjuster. Varying the diameter of the disk would vary the area of all the openings......far too simple and effective for me to naturally gravitate to.  Sorry for the frustration.

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Re: nozzle design and construction

Post by Overmod on Mon Jun 24, 2013 10:38 pm

Guys, what you want is a 'forebody' -- like an inverted teardrop with both part of the bulged head and the curved top above the plane of the orifices. Or a double cone with different taper on 'top' and 'bottom'... Much thinner with better flow streamlining relative to the steam medium than the pictures drawn so far.

One of the French designers -- Lemaitre? -- experimented with this sort of thing inside a ring of more widely-spaced orifices, and I picked up on the idea for a front end that maximized the areal exposure of a given mass flow of turbulent steam, for better entrainment, wile allowing a jet of free steam 'up the middle' for lower back pressure with less effect on the draft. ISTR Thierry Stora has something like this described on his site somewhere.

I would be tempted to point out that someone, Nigel Day I think, noted that four properly-curved ducts, one from each set of ports, curving up to four nozzles, is a perfectly good approach, and involves less difficulty in casting...or fancy CNC machining at the bottom where the Goss wall is. Nigel, can you post the specific picture down into the blast stand where you flow-streamline the four tracts?

You'd have to make some sort of portable voliumetric flow bench to equalize all the cylinders, and set the valves pretty well... but hey, we'll want to do that anyway...

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Re: nozzle design and construction

Post by DaveLathrop57 on Mon Jun 24, 2013 11:47 pm

Thanks Robert, I've seen the pictures from 5AT and other sources of that design.....but Vulcan Iron Works made that choice for us in 1926, and we have what we have to work with - the common Goss wall between two converging flows merging into one common passage.

So, we can add some innards to the stand to help equalize flow across all nozzles from both sides equally, and we can design and aim the nozzles themselves once we have worked out the best proportions for everything to work well together.

The flat plate idea was to help us experiment with different sizes of openings easily. Which leaves me to wonder if we found the opening we want in a flat plate, would it be different than if we then built a set of 4 nozzles for a more Lemporish final product?

More variables to think about.......but we have time to work it out.

Dave

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Re: nozzle design and construction

Post by Overmod on Tue Jun 25, 2013 12:29 am

Is there a good, clear, bright picture down at the Goss wall and passages?  I would like to see the configuration of what is there.  I see no reason why a 'portable' multiaxis mill could not be set up over the saddle to machine better flow passage contours.  And there is always extrude-honing...

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Re: nozzle design and construction

Post by DaveLathrop57 on Tue Jun 25, 2013 10:06 am

For now, all we have is the drawing. I'll see about some photos looking down the passages. If the boiler gets off the frame, milling out the passages might be possible, but we don't want to take a lot off the old cast iron saddle since we don't know just what the quality of the metal itself is yet.

Dave

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Re: nozzle design and construction

Post by JJG Koopmans on Tue Jun 25, 2013 5:02 pm

Overmod wrote:...One of the French designers -- Lemaitre? -- experimented with this sort of thing inside a ring of more widely-spaced orifices, and I picked up on the idea for a front end that maximized the areal exposure of a given mass flow of turbulent steam, for better entrainment, wile allowing a jet of free steam 'up the middle' for lower back pressure with less effect on the draft.  ISTR Thierry Stora has something like this described on his site somewhere.
...
Robert,
The original Lemaitre had 5 angled orifices and a central adjustable one. That was in the days that they thought that such
an adjustment was a necessity. After him all orifices were fully fixed.
Kind regards
Jos

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Re: nozzle design and construction

Post by Michael Guy on Sat Aug 10, 2013 7:03 am

I took some photos inside the 110 smokebox, you can find them here: https://plus.google.com/u/0/photos/100313002764258550558/albums/5910409946290694369?authkey=CNaNlJeL__D5RA

This album also has some general shots of the firebox and burner pan with the burner visible.

The blast nozzle has a crossbar set at an angle. The short bar-like item below the crossbar is a fossilized stub of tube or pipe with no obvious function.

Michael.

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Re: nozzle design and construction

Post by Overmod on Mon Sep 09, 2013 12:09 am

Interesting. The angle faces back, toward the front tubeplate. The tube is at an angle to the divider.. I'm at a loss to guess what that tube does; if this weren't a small logging locomotive, I'd be thinking some sort of automatic draft detection system for the blower.

Here might be a good place to mention that I think the blower should be redesigned to have only four jets. That would involve fairly extensive redesign of the existing ring manifold, which would imho not be as meaningful as machining a new nozzle that would fit above the existing blastpipe... assuming we wanted to keep the blastpipe as high as it is now. And I am very sorely tempted to add that I don't think we do.

Would it be appropriate to have a top 'plate' made up so we can swap orifice configurations reasonably ceteris paribus? I was knocking around the idea of machining multiple nozzles, with a 'ball' outside profile that would allow changing the angle very precisely, and then making up a jig that would let the angle be set while brazing the balls to fix them into position.

That approach would allow relatively easy and quick comparison of non-circular cross-sectional profiles or asymmetric cross-sections for nozzles, without much expense above that of making up and finishing the nozzles themselves...

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