Steam exhaust nozzle

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jscarmozza
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Steam exhaust nozzle

Post by jscarmozza »

What type of steam exhaust jet should I be trying to develop, should it be a narrow concentrated stream directed through the center of the petticoat and stack or should it be a broad spray like stream that fills the stack? I made two conical nozzles, one concentrating and the other expanding, both do the job based on the cigar smoke test. The concentrating nozzle focuses the smoke into a pencil diameter stream that stays concentrated for about 12", the expanding nozzle creates an ever expanding conical stream. Which exhaust jet should I be using?
318J
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Re: Steam exhaust nozzle

Post by 318J »

There was a lengthy thread (24 pages long...) about the exhaust nozzle design, stack arrangement, ect. some time ago. Worth a good read.

http://www.chaski.org/homemachinist/vie ... =8&t=82682
-Sam
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jscarmozza
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Re: Steam exhaust nozzle

Post by jscarmozza »

Thanks for directing me to that thread.
Glenn Brooks
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Re: Steam exhaust nozzle

Post by Glenn Brooks »

The thread mentioned above is pretty invigorating at times. Dr. Koopmans is an acknowledged expert on front end design, and published a really superb book based on his doctoral thesis. - “The Fire Burns Brighter”. It’s out of print, but I found an unread used on copy on line a few years ago.

The thread boils down to two choices: use the old style, 1890’s Master mechanics Association single stack blast nozzle, or replace with Eng. Portia’s multi- port, two chamber blast nozzle ‘system’ (multi port nozzle, and properly dimensioned stack).

My personal experience is the multi-port Lempor nozzle I built for my 12” gauge coal fired Ottaway did exactly what all the international prototype studies have shown over the years. My steam production, draw bar capacity, and operating performance went through the roof. Easily got the expected 25% performance improvement, all the national railway systems of old experienced, when they made this modification.

I would recommend you at least explore this option. You would be building the most advanced and efficient front end design ever produced for steam engines. It’s biggest draw back is it came to late in steam locomotive design, to make the impact it deserves. So these multi port systems are not well known as they could be. Nevertheless, I have a second steam locomotive to restore, and plan on replacing the old existing style single stack nozzle with the Lempor design.

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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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cbrew
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Re: Steam exhaust nozzle

Post by cbrew »

i will, fuel type will drive the design also, Propane tend to require a lazy draft vs oil and coal can demand a strong to very strong draft.
If it is not live steam. its not worth it.
steamingon
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Re: Steam exhaust nozzle

Post by steamingon »

Hello, the book “The Fire Burns Brighter” by Dr. Koopmans is STILL AVAILABLE from Camden Miniature Steam Services.

https://www.camdenmin.co.uk/collections ... late-april

also available from https://www.advanced-steam.org/books-fo ... ch-better/
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Highiron
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Re: Steam exhaust nozzle

Post by Highiron »

I am a fan of the single nozzle Master mechanics front end design Dr coopman's information and thesis are very well noted and work in Minneapolis I felt for my Hudson and my Northern as well as some of the other engines that I have built that the single nozzle design worked best with what we have to work with in our small scale live steamers I use a calculation based on the information found in the master Mechanics for an end I'm also a fan of a modified nozzle both of my engines have a single nozzle shaped like a kaisal star they work extremely well produce phenomenal stack talk and a violent exhaust with great vacuum putting draft on the Fire one of the keys here is to make sure that your steam cone upon exiting your nozzle expand to the point where it touches the inside diameter of your stack one and one half inches down from the top if you're working in 1.5 inch scale this will create a seal thus giving you good vacuum and draft on your fire

If you want to hear and see the results of this do a YouTube search on Lackawanna 1637 and watch some of the videos of my Northern and Hudson in action
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NP317
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Re: Steam exhaust nozzle

Post by NP317 »

I've been wondering how to measure the conical dispersion of the steam from the exhaust nozzles in our 1/8th scale locomotives, to achieve that upper stack seal, as described.
I'm looking for continued eduction...again.
RussN
Last edited by NP317 on Thu Aug 18, 2022 1:24 am, edited 1 time in total.
jscarmozza
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Re: Steam exhaust nozzle

Post by jscarmozza »

Like most things in this hobby there's more to it than meets the eye, and the more you learn the clearer things become. I'm inconsistent with the type of fuel I use and get erratic performance as a result, didn't think it mattered that much but apparently it does. Still trying to grasp everything in the referenced thread, not only for my projects but also to improve the performance of my engines. Because I have LE boilers fabricated with Sil-fos I rarely use coal in my engines, I usually use charcoal and once in the while wood, never gave a thought to the exhaust nozzle or grates and that all these things need to be coordinated. Thanks for the education guys!
jscarmozza
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Re: Steam exhaust nozzle

Post by jscarmozza »

Having read through the referenced thread on this matter, which was a very comprehensive discussion, I concluded that the 1:6, 1:3 and 1/7 rules will suffice for my 1" steamers. That being said, now I find that my stack is too short or too big in diameter for the expanding steam cone to intersect with it before exhausting to the atmosphere. Should I place a liner in the stack to reduce the ID so that the 1:6 cone intersects the stack below the rim, how do I go about correcting this?

Looking back on the operation of this engine, I've had to run with continuous blower to maintain steam and even then after once around the track I have to stop and re-stoke the fire, I always thought it was because of the fuel that I was using. Curiously, at the end of last season it was steaming nicely for the last couple of runs. When I cleaned and winterized it, I noticed a 3/16" thick layer of crud had deposited on the inside of the stack reducing its diameter, maybe it was trying to tell me something.
jscarmozza
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Re: Steam exhaust nozzle

Post by jscarmozza »

As a follow up, I made a steel liner to reconfigure the stack dimensions in my 1" LE Atlantic to the 1:3 and 1:6 proportions referenced above and got excellent performance as a result. Yesterday I ran continuously for four hours, plenty of steam and no blower except when I stopped moving. Along with the greatly improved performance I got a nice little exhaust 'bark' that wasn't there before. Thanks to all here and to my live steam buddies that helped with information and advice. This is a modification that is well worth the effort.
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Bill Shields
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Re: Steam exhaust nozzle

Post by Bill Shields »

the science of steam expansion angles through a round orifice to create a vacuum is pretty well fixed -> and has NOTHING TO DO with being in the smokebox of a loco.

as you can see, making the stack smaller is not necessarily a bad thing.

another bit to try is to just put some small pieces of rod (or music wire depending on the scale) in an X across the top of the blast pipe. (which is exactly what HighIron is doing with the 'star'....).

with very little work, you can see what a simple change can do to (or for) the draught of the loco.
Too many things going on to bother listing them.
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