Propane Front End Design

[Bill Shields]

Actually....an extension on that idea... a thermocouple in the smokebox in the hot gas path is very helpful. It lets you see real time what things are doing while you are running. Too much air and the temperature comes down...which is exactly the opposite of a coal fire.

[Glenn Brooks]

Based on this thread, I am beginning to wonder if the lempor, or multiple Port blast nozzle approach might be an advantage for propane?

Lempor and other multi port nozzles all exhibit substantially larger blast oriface surfaces than single blast pipes. The result is substantially reduced velocity out the stack, which I assume lowers the vacuum. Also properly done, multi port nozzles reduce back exhaust from the cylinders. So You get improved air flow with much a much smoother, less violent exhaust. Seems like this would be beneficial for propane combustion. In fact, the highest efficiency Lempor front ends are reported to have little more than a slight puff of exhaust- almost completely quite. Yet with full replacement of combustion air.

Am I on the right track with this?

Glenn

[NP317]

I went through quite a lot of changes to my 2-6-0 to get it to work. I ended up with a conventional smoke box arrangement. An arch (re-bent more than once to get it right), and no baffle plate on the Locoparts burner is what made it work. Get a infrared thermometer and aim it at the stack to see what the exhaust temperature is.

When I built my Allen Ten Wheeler, using a LocoParts burner, I initially made the recommended baffle plate to block "excess" air flow up past the burners.
I ended up removing it so I could get a more complete gas burn. The arch was added after several test runs, and greatly increased the burn efficiency in the firebox.
My sense of smell and stinging eyes (from unburned propane) were my test devices.
Otherwise, the smokebox end is per the Allen design, with the cast petticoat as part of the smoke stack.

My new Mikado, also a propane burner, has a separate petticoat that leaves a gap at the top, as recommended.
I've not yet had the opportunity to really test this locomotive. Covid-19 factor...
RussN

[Bill Shields]

Single blast stack would be my first choice.

The system I use works well with restricted air flow input to the firebox.

There is no one absolute answer..you have to understand what is happening and choose wisely

[Santafescotty60]

Hi Dave, Could you tell me the heat range that the stack puts out, best, highest and simmer or when you take a break as you stretch and have a snack or drink...... LOL

[PRR G5s]

Great responses!

Marty, when basing the stack ID off of the flue area, do you use 25% as for coal, or have you found something larger or smaller works better?

Same goes for the 1/7 ratio for the blast orifice, something larger or smaller?

Keep the replies coming!

Thanks!

Eric L.

[Marty_Knox]

Great responses!

Marty, when basing the stack ID off of the flue area, do you use 25% as for coal, or have you found something larger or smaller works better?

Same goes for the 1/7 ratio for the blast orifice, something larger or smaller?

Keep the replies coming!

Thanks!

Eric L.

I would use the 25% for the inside area of the stack. I would adjust the size of the blast nozzle to get the results I want.

[Dave_Johnson]

Hi Dave, Could you tell me the heat range that the stack puts out, best, highest and simmer or when you take a break as you stretch and have a snack or drink...... LOL

It has been a few years since I went through the process, and I didn't write anything down. But I do recall that once I got the best results, I was pulling about 400-430 or so degrees at the stack while running the loco. I don't recall what I measured when it was idling, but it was lower than when I was running the locomotive.

[Berkman]

I would think using turbulators would be a fairly painless way to realize max heat transfer

[Greg_Lewis]

Back about 18 years ago I ran a very unscientific check of stack temps. Anyone with a science background would recognize the flaws in the test, but here is a link to the results anyway:
http://www.chaski.org/homemachinist/vie ... box#p16207

[Bill Shields]

I would think using turbulators would be a fairly painless way to realize max heat transfer

They can help...and usually do

[sky]

Not sure if I am in the right spot for this post. I am a novice on getting things to work. But I am trying to get my 3/4 scale Kozo's Pennsylvania A3 Switcher to run on Propane. I need a burner design. I have it running on air and just a few decorative parts left to make. I have read every post I can find on burners, but can't figure out what they all mean. As they say, a picture is worth a thousand words, especially if you are new to all the terminology and a dimensioned drawing priceless. Have been working on it for 4 yrs.
sky