propane baffle plate

[Karl_Losely]

Greetings All:

I have a 1.6 scale Hudson that I normally fire with coal but am converting to propane firing for the trip to TM. The firebox is about 9x14 with an arch. I am using 45 Marty burners on a 3 tube and 2 tube manifold. The manifold is made of 1 inch square tube with 1 inch between tubes I have made baffle that fits between the air intake holes and the burner heads which is a tight fit on the burners and the bottom of the firebox in accordance with what I have read about firing a locomotive on propane which is basically that all the air entering the firebox should come through the burners.

I did a test fire today with the manifold outside the firebox. I could only fire 3 or 2 tubes at a time as I did not have the needed plumbing to fire all 5 together. I had lots of yellow flame reaching up to 4 feet above the burner assembly depending on pressure except at the very lowest which gave only little nubs of blue flame from the burners. The flames would lean from the outside toward the center indicating a lot of air being pulled toward the center of the assembly. The assembly was making a lot of heat.

Based on what I observed with the test fire it seems to me that there is insufficient air available for combustion,especially toward the interior of the burner assembly, so this is my question.

Do I need to put some holes in the baffle plate to allow for secondary combustion air or when the burner assembly is installed in the firebox and subject to draft from the blower or exhaust will enough air be drawn through the burners for a more normal flame?

Thanks for sharing your knowledge.

Karl

[bcody]

Karl:

It is probably a T&E situation. I would install the propane burners in your engine and run it on the track like you normally would. At your home track would be the place to test your set-up, not at TM.

I run a Bill Conner 4+4 Beam Engine with a 12" diameter boiler fired with propane that (10" diameter x5" high fire box) is totally open on the bottom. My burner is 5.5" in diameter and I don't think I have a problem with excess air. Always have a good flame color and never want for adequate firing/steam.


Bill

[vtgrwood]

Hello,

I remember a few threads on this site discussing this topic. I would search and see if you can find them. Here is one off the top of my head.

http://www.chaski.org/homemachinist/vie ... r&start=12

George

[Bill Shields]

Karl:

you don't say what pressure you are running to the burners, but my guess is that you have entriely too many burners and too much pressure.

you probably have something like this:



consider a 2" bloom from each burner, you should recalculate and respace.

at most, you should think of 24 burners in that box (give or take a couple), not

putting the burners any closer than this is a total waste and will lead to incomplete combustion.

Air into the boiler should only equal the air drawn in by the burners, no more.

Additional air only COOLS the total.



as you can see, I have 20 burners and believe me, it makes MORE than enough heat for the 10 x 10 firebox at 1 psi. Most of the time I run on 10 burners and RARELY turn on the other 10 for a 'quick makeup' of pressure.

you don't need a manifold anwhere near the size you are quoting to supply gas to the burners. Add up the total area of the orifices (orifii?) in use, and that is the total cross section needed for a manifold.

Mine is 1/2" square only to allow the correct size mounting fittings. otherwise, smaller would be ok.





It isn't so much trial and error, but understanding the basics of combustion and following them.

[Lovesthedrive]

When I had the Marty burners in my mogul. I found the need of a 1/4" set screw through the top of the burner to act as a mixer in the burner. The flame would not sit on the burner.

just my 2 pennies, sorry no pics avail.

[ccvstmr]

I have a 1.6 scale Hudson that I normally fire with coal but am converting to propane firing for the trip to TM. The firebox is about 9x14 with an arch. I am using 45 Marty burners on a 3 tube and 2 tube manifold. The manifold is made of 1 inch square tube with 1 inch between tubes I have made baffle that fits between the air intake holes and the burner heads which is a tight fit on the burners and the bottom of the firebox in accordance with what I have read about firing a locomotive on propane which is basically that all the air entering the firebox should come through the burners.

I did a test fire today with the manifold outside the firebox. I could only fire 3 or 2 tubes at a time as I did not have the needed plumbing to fire all 5 together. I had lots of yellow flame reaching up to 4 feet above the burner assembly depending on pressure except at the very lowest which gave only little nubs of blue flame from the burners. The flames would lean from the outside toward the center indicating a lot of air being pulled toward the center of the assembly. The assembly was making a lot of heat.

Based on what I observed with the test fire it seems to me that there is insufficient air available for combustion,especially toward the interior of the burner assembly, so this is my question.

Do I need to put some holes in the baffle plate to allow for secondary combustion air or when the burner assembly is installed in the firebox and subject to draft from the blower or exhaust will enough air be drawn through the burners for a more normal flame?Karl

Hello Karl,

Lots of item to take into consideration here. I did a quick layout of a 9x14 firebox and pretty much filled the area with (35) burners. I used a 1.75" diameter flame front for each burner. Five rows, 7 burners each. Burners in rows #2 and #4 were staggered with respect to the burners in rows #1, 3 & 5. As Bill's photos show...you want a complete bed of flame...and certainly no "holes" around the perimeter of the fire box and lastly, no yellow flame. You didn't say what kind of pressure you were running your fuel at.

Using an arch...good for you. This creates a "long path" to hopefully give you complete combustion of the fuel before the air flow reaches the flues. Have you considered turbulators for each flue? Steel strips will work. Stainless even better. Round the edges over so they don't scrape the insides of the flues (in particular if you've got copper flues). To fabricate...put one end of the metal strip in a lathe chuck and clamp the other end to the tool post holder. Turn by hand. Probably shoot for one complete turn of the turbulator for each 6-7" of flue length.

Not enough air for combustion is similar to too much fuel. You may be choking out the air with all those burners. With your 45 burner set up...try removing every other burner...plug the holes and light 'er off again to see what happens. 1" square tube is probably more than you need. In particular if you're dividing the manifold into "2 circuits" each with it's own fuel feed and flow control.

Baffles...I tried solid plate baffles and was not satisfied with the performance. Once the holes were punched...it was difficult to go back and change the size. I wasn't sure what size gap to leave around the burner stem. Instead, I used perforated alum screen material. I was happy with the first piece I used...never changed it after that. No, the heat does not melt the aluminum...as long as ambient air is being drawn up from underneath...this keeps the baffle screen cool. Kind of like boiling water in a paper cup over an open fire. As long as there's water in the cup...the cup will only burn down to the water line. Just make sure your baffles are above the primary air inlet holes in the burners as already noted. You don't want any restrictions for your primary combustion air source. The baffle is restricting the air available for secondary combustion at the burner tip. On my manifold, I welded some "Vee" brackets to the top to hold the screen above the primary air holes.

I'll attach a few pix for reference. These are from my Allen 10 Wheeler. This set up has worked extremely well for the last 11 years...but like any "system"...there are lots of little items to consider. Hope this helps you. Carl B.

[KidAmato]

Karl:

you don't say what pressure you are running to the burners, but my guess is that you have entriely too many burners and too much pressure.

you probably have something like this:



consider a 2" bloom from each burner, you should recalculate and respace.

at most, you should think of 24 burners in that box (give or take a couple), not

putting the burners any closer than this is a total waste and will lead to incomplete combustion.

Air into the boiler should only equal the air drawn in by the burners, no more.

Additional air only COOLS the total.



as you can see, I have 20 burners and believe me, it makes MORE than enough heat for the 10 x 10 firebox at 1 psi. Most of the time I run on 10 burners and RARELY turn on the other 10 for a 'quick makeup' of pressure.

you don't need a manifold anwhere near the size you are quoting to supply gas to the burners. Add up the total area of the orifices (orifii?) in use, and that is the total cross section needed for a manifold.

Mine is 1/2" square only to allow the correct size mounting fittings. otherwise, smaller would be ok.





It isn't so much trial and error, but understanding the basics of combustion and following them.

Karl,
Bill is bringing up very good points... Beleive it or not, its not really calculations. It's more trial and error than anything. Sorry Bill, I'm not trying to contradict you or anything of that nature . Bill's baffle plate looks great for the burner set up. I would reccomend copying his. The only thing I could suggest for a burner based on YOUR dimensions of your firebox would probably be... A 4 row burner having 7 tulip burners per row. This would leave you at 28 burners. Like bill said "give or take a couple". You would probably want to space the insides of each row about 2" to 2.5" apart just to allow the burners to burn independently and to allow good air flow between each flame to provide a "proper combustion". I hope my limited knowledge will help you out on your project. Please post photos of your progress. I'm pretty sure that most if not everyone on this forum would love to see it for refrence use. Possibly for their own projects? Good luck!

Best wishes,
Nico Amato

[Harlock]

You don't want the baffle a tight fit around each burner, you need to leave a little hole for secondary combustion and for draft to prevent the fire from sucking out under heavy throttle. Bill's photos show a good gap around the burners.

Nico's comments on the spacing between burners also applies. If they are too close they can 'eat each other's lunch'.

On smaller engines with tiny boilers such as my Chloe, I have found that no baffle is the way to go as just about any baffle will cause the fire to be sucked out under throttle. On your Hudson adding a baffle as Bill Shields has done should help your fuel efficiency and keep unnecessary cool secondary air out. On mine it just doesn't matter, I only have six burners. One BBQ tank will last for 1 1/2 meets heavy running, typically.

I've noticed the Marty burners do not produce as clean of a flame as the commercial SolarFlo burners. It's either not making much flame or there's some yellow in it, at least on a friend's engine that has them. But I only have experience with Marty Burners from that one engine, it may not be set up optimally. Despite this, is does deliver heat to the engine very well and the engine fires just fine.

Since you have so many burners, you don't need to run them at very high pressure. Turn it down and see if you can get the flame to go mostly blue. This will also have the added benefit of giving you a quiet firebox.

Track testing will show you what they need to run at to maintain steam with your engine and train, given a particular grade.

Also, the recommendation for turbulators is a good one. I have them in the Chloe and they appear to make a significant difference, slowing down the gasses to give them more time to heat exchange through each tube. The exhaust is much cooler than when I ran without them, meaning less wasted heat.

-Mike

[Phil Tucker]

The “Baffle Plate” may be the most appropriately-named device to be found anywhere, as I have been baffled by these on more than one occasion. My solution, at present, is simply to do without them. I find that any incremental gains in thermal efficiency are far outweighed by problems with poor combustion.

[cp4449]

I have wire turbulators from this company:

http://www.ormiston-wire.co.uk/products ... lators.php

They are in my 1" 0-6-0, and I must say they helped a lot. The burner I have is a slot burner, and run about 5-8 pounds, with a small opening for air. I would like to change to a Locoparts burner, but have not got the time to roll the beast over to take out the old burner, and measure the fire box. (Unless someone out there has ordered a burner from Locoparts and knows the dimensions)

I also have thought of a arch also.

My .02

[Bill Shields]

I won't run without an arch or baffle plate.

my first plate had 3/16" clearance around the firebox, and ran too cold, no matter what I did.

I stuffed fibrefrax around the gap, and temps came right up.

made new plate that fits snug and all is well.