Naturally Aspirated Ribbon Burner. Photo heavy.

[Frosty]

[cleatusj]

Found this thread while waiting for materials to come in to build a 20 pound propane forge. I decided first to build in an old 2 gallon gas can and use a NARB. My NARB is 1 1/2 x 6 with 63 .143 size holes, these were cast with greased 12 penny nails. Tried firing  with a 1/2 " frosty tee but the flames just lifted off. Then a new Frosty with a 1/2" cross, all 4 sides 1/2", this worked a charm, for keeping the flames on the Narb.

When the forge finishes curing in a couple days, i'll test in the forge.

[Another FrankenBurner]

Both of the burners are not Frosty Ts.  Unless a burner is built to the specs in Frosty's instructions, it is not a Frosty design.  You have two of your own design which are Frosty T inspired.  Nothing wrong with that, we all learn from new designs.  You just have more of your own figuring to do.

That said, your first picture of the first burner (if the orifice is the same) is showing a more powerful inducer.  Your flames are lifting because they are lean.  Look at the deep blue color of the flames.  You are inducing more air.

Lean flames are thinner and don't hold as well.   If it were mine, I'd enlarge the orifice on the first burner to see if it would prevent lifting without going to greenish flames.  Unless you have a positionable orifice, then I would try sliding it in and out first because it's easier.

Either way, they are looking good.  Nice job.

[cleatusj]

Frosty T inspired would be the best description. Both have a positionable orifice and using .023 mig tips. Sliding the tip only seems to make a difference without the NARB. 

I will try another tip after dark tonight.

[cleatusj]

With the fact that all nails pulled out easy from the Kast-o-lite, I thought I would explain how it was done.

First was drilling a piece of 1/2" lexan and coating it and the nails with petroleum jelly and axle grease. Wrapped the sides of the form with clear packing tape, before coating with the grease. Each piece of the form was removable, encase it stuck.

I

 

I swifted the KoL thru some window screen, until there was 1/2 cup of cement, that was added into more KoL for the cast. This left a smooth finish when removed from form.

[Another FrankenBurner]

I am inexperienced with the NARBs.  I was speaking about what I saw in the flames and extrapolating.  I probably should have refrained.  Now that you mentioned it, I recall someone else on the forum saying the same thing about orifice position not changing much on their NARB as well.

Where the first burner is running lean outside of the forge, I wonder if forge back pressure will reduce enough induction to run nicely.

[cleatusj]

3 minutes ago, Another FrankenBurner said:

 I recall someone else on the forum saying the same thing about orifice position not changing much on their NARB as well.

That was why I threw together the second burner, with the 1/2" pipe size inlets instead of the 3/4" openings, to slow the induction. 

With the adjustable depth tip, i release set screw and move to the other tee and tube.

[Another FrankenBurner]

That works just fine.  I am always after more potential output and what I said was based on that. By enlarging the orifice instead of throttling the air, you increase burner output.  Both ways work and you don't need to chase more to get the job done.  I tend to forget that.

[cleatusj]

All our minds work a little differently, so at any given time anyone could trigger another different way of doing something. I like getting feedback.

[Another FrankenBurner]

Yeah, this forum and others like it are wonderful for getting all kinds of minds together.  

[cleatusj]

Here's a pic of the one with larger intake with the .035 tip.

 

And the one with the smaller intakes.

[cleatusj]

Went back and ran the burner with the 1/2" intakes with a .035 tip. First is at 1-2 psi and then at 5 psi.

[Marcus_Aurelius]

ITS ALIVE!

Finally after many hours researching and seeing Lou's NARB in person, I have built up the nerve to give the NARB a go. This is the third Gasser I have made and my first attempt at a NA burner. So far it has gone swimmingly, except for one fact, its not quite at the temperatures I have hoped for. It reaches around 2000 degrees (just a guess) but I was hoping for forge welding temps.

The forge is ~340 cubic inches with 2 inches of kaowool and about 1/2 of kastolite-30. It is about 10" long, 8" wide, and 5" tall. While I was casting the refractory, some of the wool was compressed and created a section that is closer to an inch of kastolite (originally I was worried that the extra hard refractory was to much for my burner to get to temps).

Anyways, the burner was constructed in the methods explained originally by frosty. I made the burner head with 19 holes but instead of using crayons as per Frosty, I decided on some straws, they are a tad smaller then the crayons, but I had enough of them. I figured that if the holes where to small it would be simple enough to drill them bigger. When I first lit the burner, it looked great (I believe it is fairly well tuned) but upon closer inspection I noticed lift-off on the outer holes. The combustion was not at the beginning of the hole but rather about an inch and a half above. I believe this is the trouble I am having with not getting the forge hot enough (forge-welding temps).

Here is the burner running at 8 PSI

From the side, it is obvious of the incomplete combustion on the side.

and finally at about 2.5 psi (anything higher and there is burner lift-off)

 

Here are a couple of pictures with the burner in the forge right after it was lit (at 8 PSI). Note that with the 'doors' completely closed it seems that the flames are combusting properly on the holes, I believe this is from the internal pressure pushing back from the forge, it is hard to see but I tried to get a picture (at least it looks cool). When the forge is at a higher temps, say a nice orange. The problem comes back, as the burner block heats up and increases the FA mixture speed. Thankfully there are no issues with the burner blowing out.

 

 

So there you go, the burner is not getting up to temps, and any help on the situation is appreciated.

I know you guys do not need my help to figure out the issue, but I figure I'll give it a go based upon my own experiences and research:

From what I have observed I believe there is to much velocity from the FA mixture, this in-turn causes the burner lift off. When in the forge, the back-pressure corrects this issue (so maybe its not the reason I am getting to temps.) Considering I used a smaller diameter on the burner holes I believe that there is not enough friction to slow down the fuel air mix, in turn there is to much forward velocity. The simple solution would be to open up the holes, which I want to be sure before I do. This would allow for more friction to slow down the mixture, and bang a better torch. 

Overall, I am really happy with the forge and consider it a big upgrade from my last one, which was obnoxiously loud. I put it through its paces over the last week by forging a couple of top tools. It gets the 1" 1045 stock quickly up to temps, which is why I don't think the extra hard refractory is the issue.

If you got this far thanks for looking, and hats off to Frosty for this gnarly invention.

 

- Mark

 

 

 

 

[Frosty]

I haven't been online for a long weekend walking on the beach and campground roads with the dogs. Getting away from news and politics was the best decompressor.

Anyway, I skimmed some of the other guys threads ad have some input but a little later.

Mark: I answered your question about "lift off" by another name in my original NARB posts. Remember why I settled on 19 crayons and why 18 or 20 weren't optimum? 20 orifices burnt back as the flow velocity was less than the rate of propagation or flame front velocity. 18 orifices lifted off because the flow velocity was too much greater than the rate of propagation and so blew off the burner block. 

Using smaller orifices means you need more to balance flow and rate of propagation. It has NOTHING to do with friction in the channels slowing the flow down. 

No, I don't know how many straws you should've used, I only messed with them once, even packed with sand then tended to bend and crush packing the Kastolite between them. 

If you wish to find out how many, use the same method I did originally, make a plenum that can be screwed to a piece of lumber, drill the test number of orifices in the block and give it a try. A few seconds will tell you if the flames are lifting off. 

You might as well start drilling holes in that one or you'll have to de-tune the induction device considerably. Drill more holes ONE AT A TIME AND TEST before drilling another!! 

More holes will probably help lean the flame out without having to do more tuning on the inducer.

These are just minor things, you're doing well. Keep it up.

Frosty The Lucky.

[cleatusj]

Being new and diving in with a lot of reading, I miss comprehend and have to back track. I've choose to try several different lengths of pipe  and sizes and the one that seems to work best is the 8" with the 1/2" cross.

Here's a pic of the pipes and the cross. The .023 tip and valve are still on the hose. The best burn and after shut off.

[Frosty]

I've never had much luck using a cross but I only tried a few times. 8" is 2x as long as the mixing tube should be. Try a 1/2" x 4" nipple for the mixing tube. 

Can you take a pic through the air intakes of the burner with the mig tip in place so I can get an idea of where it is? 

Where is the inducer mounted to the plenum?

Frosty The Lucky.

[Marcus_Aurelius]

Thanks for the response Frosty, your logic and solution make a lot more sense. To clarify, does the 'rate of propagation' refers to the flame front, or the speed at which the gas burns? I forged out a hammer yesterday with the forge, still a champ, but I definitely want to get it hotter, I'll take you advice and get drilling.

- Mark

[Frosty]

I believe "rate of propagation" fits what I mean better than flame front in this circumstance. They're almost synonymous and are often used interchangeably. Flame front is appropriate in more circumstances than rate of propagation. 

Yes, I'm referring to the velocity the mixture burns. The only one I recall is oxy acet with a rate of propagation of 24,000 ft/sec. Nearly orbital velocity.  I just spent WAY too long trying to find a graph or simple information regarding the rate of propagation of air propane flame and all I've come across so far are scientific papers and most targeted at internal combustion engines. 

I did discover what I THINK covers one bit of confusion between the two terms under discussion right now. I believe the term that best fits our usage is, "Flame Front Propagation Rate."

Anyway, back to the real point of making a multiple outlet burner work properly. The velocity of the mixture flowing through the outlets must be greater than the mixture's rate of propagation. This prevents the flame from burning back into the plenum or in the case of single outlet burners like the basic Mikey or T burning back into the mixing tube. Flame Front Propagation Rate fits the conditions perfectly.

The other thing I saw, without seeing what I was looking for is the leaner the flame, the higher the: Rate Of Propagation, explosive energy and temperature. Mike was exactly right of course, even if I didn't have my head wrapped around it in the right direction. I'm just not sure how a high Flame front propagation rate effects the flame velocity at the burner outlets. Cool, I have some head wrapping for today's cognitizing.

Getting the flow rate matched to the Flame Front Propagation Rate is a matter of controlling the pressure in the plenum. The higher the pressure the faster the flow velocity. The lower the pressure the slower the flow. 

I balanced the two by the # of outlets, crayons. Bear in mind every T is a home made device so is an individual critter, I've been making T burners for a few decades now and every single one is a little different. Almost any of them works well on MY NARBs. Don't know about yours.

Frosty The Lucky.

 

[cleatusj]

Frosty, I'm working my way shorter, as I test, to try and learn the affects. With this cross starting with 12" ,  then 8" and down to 6".

I increased every other hole to 1/8 inch, as the flames were lifting.  It got a lot better, so I went to 5" and it still improved.

It enters the NARB at 85 deg. 

I used a cut down hydraulic fitting, screwed to a close nipple. The fitting had a 3/8" hole that accepted the 1/8" sch 80 nipple for adjustment.

This is the 5" pipe at 15 psi after 3 minuets. I'll try a 4" after it cools down outside to 90.

[Marcus_Aurelius]

On 8/20/2020 at 3:01 PM, Frosty said:

Flame Front Propagation Rate

I like the new term, thanks for clarifying. The propagation rate has always been a road block for me trying to understand burner physics. Your last two posts have been very enlightening and I believe I am more capable to tackle the burner and I understand the term a lot better now. I am going to hold off on the modification for a tad, there are some things I want to hammer on before I decommission the forge for a while.

From a little research through the interwebs I believe the scientific term for 'Flame Front Propagation Rate' is simple 'Flame Speed'. Flame speed  is defined as how rapidly the flame travels from an absolute reference point. A little more searching brought up a graph for the flame speed of propane at different percents of propane.

A lot of the graphs I found from a quick search require a lot of eye scrubbing to comprehend. This is one of the simpler ones.

cool stuff

-Mark

[Frosty]

There ARE a lot of different terms for the rate of propagation, often depending on which university or country the article originates. Introducing more terms for exactly the same thing can only add to the confusion.. I have to translate to common terms and names all the time, here and at meetings so I don't have to keep explaining what I meant. It's the purpose of craft a jargon. 

Frosty The Lucky.

[jt0119]

Hey guys, I'm getting ready to cast the refractory for mine and wanted to check how important the alignment is on the dowels I'm using for the holes. Is it just as long as they don't touch each other at the top, or do they need to be as straight as possible?

[Frosty]

No they don't need to be straight, though it doesn't hurt. Not touching is much more important. Enough space between so enough refractory can fit to make a strong burner block is important.

Frosty The Lucky.

[jt0119]

Well, I was going to post about being concerned with how quiet it is, but after reading the thread some more and watching a few videos, it seems like that's pretty standard. I think my first NARB might have been a success! I'll get some pictures tomorrow once I'm done adapting my forge to accept it. "Stoked" doesn't even begin to describe how excited I am to put it through its paces.

[jt0119]

I knew this was going too smoothly. I don't feel like it's working nearly as well as it should be. This is it running from about 5psi up to 20. Toying with the idea of side mounting it to see if that helps.