Ribbon Burner with 336 - 1/8" holes

[Anachronist58]

Wow. And still, only on page #1 of this thread......  a large amount of data gurging through my four stomachs.....

On 9/27/2019 at 5:09 PM, D.Rotblatt said:

First, a few people are playing with perferated ceramic tiles (one a casting filter and the other is for BBQ's I think).  Check the NA ribbon burner section or the ribbon burner section and see if you can find them.  Maybe 6 months ago? 

I will eventually hunt this down and add it to my toolbox......

I have quite a bit of heat resistant ceramic to work with. I have yet to determine its thermal conductivity.  I envision an initial test rig as perforated inconel sheet, and behind that, in full contact, a ¼" thick carbon fiber (a very poor conductor of heat) diffuser. It will be quite some time before any of this comes together - I simply wish to put that mental image out there.

D.Rotblatt, while I have not been able to absorb and catalog all of the modifications between your 125 and 336 hole burners, would you say that the hole count (flame area?) is the largest variation between the two systems, or am I once again out in the weeds?

Fascinating.

Robert Taylor

[D.Rotblatt]

7 hours ago, Anachronist58 said:

between your 125 and 336 hole burners

Two different beasts. The 122 is a NARB, while the 336 is a FARB. So the whole injector system is different. In the NARB I made the number of holes to fit the injector (standard 3/4” burner). With the FARB I figured as long as I put a large enough blower on it and the back pressure isn’t too much, it’ll work. 

Of course the number of holes is a big difference  

DanR

[Chris C]

I'm prepared to pour mine, DanR, but daily schedule is getting in the way.  Hate it when "life" does that!

I've got a Bouncy Castle blower on my line, so it definitely puts out a lot of air when unrestricted.  As I close the gate slowly, it takes the excess air and cools the motor with it.  When the gate is completely closed, all it does is revert all the air to the cooling side of the motor.  Pretty slick.  Can't wait to get my ribbon burner cast and get this whole thing set up.  I'm stoked seeing your results.

Chris

[D.Rotblatt]

14 hours ago, Chris The Curious said:

Bouncy Castle blower

More then enough air, loud though.  I'll be interested to see how yours works...when life lets you finish it!

Dan

[D.Rotblatt]

OK guys 'n gals...HELP!  

This ribbon burner works once up to heat, but takes a lot of attention and time to get up to heat and running properly - and that's a fail for me, since I don't want to sit around for 20+ minutes slowly futzing with it to get it going.  If I wanted to do that I'd use a D*#@m coal forge.  I'm getting good heats: 2325 @ 7 lbs, and 2200 at 3 lbs (the jet is two #60 or .040" holes, so that's like a 2 burner forge in gas consumption)

Problem/question:

it takes 20+ minutes of focused care to bring it up to heat.  Unless it's running very rich, it backfires.  So to get it up to heat I have to run it at high pressure (15-20 lbs propane) with the damper closed down to make it rich.  It stalls around 1600-1700, then I move the damper a hair (literally), wait as temp goes up a little, repeat until it's up over 2000, then I can slowly turn up the air and turn down the propane to around 7 lbs or so.  My take is that once the face is hot enough, the propane ignites on it before it can burn back into the tubes.

The backfiring takes on two types: one is a higher pitched organ sound where I can see the flames vibrating.  The other is a sudden drop to a lower pitch (maybe an octave down) and the flames disappear and the plenum will start to get hot.

I have tried:

-I tried blocking 3 rows of holes down the middle.  That blocked 72 holes; which reduces the # of holes by almost 1/5, but no difference.

-opening the door thinking that it's back pressure that's causing the backfiring: slight improvement but very little.

-I had put a damper in and noticed that the face of the burner under the damper was much hotter then the rest in a pattern that matched the area that would be blocked, so I cut it open and removed the damper and welded it shut again in order to even the temperature up.  No love, little difference, maybe a little worse.

-I've tries all different combinations of pressure and gas mixture: backfires at low pressures, and when neutral to lean at any pressure until it is hot enough.

Thoughts

Only thought I have, since it works well (though blows out at higher pressures) outside the forge, is that there is too much backpressure.  The inside is very small for a forge, only 4.5" wide x 4.5" high by 14" deep.  I'd hate to have to pull it apart and go with one layer of ceramic fiber, but that may be the next thing I try to do.  I will try taking the Mizzou shelf off with will add nougat 1/2-3/4" of depth.  That will add another 30 cu inches...but I doubt it will make much difference.

Any thoughts will help, thanks in advance!

DanR

[Frosty]

Some things aren't making much sense to me but my experience is with NARBs.

Burning back when the burner block is cool and not when it's warmed up is backwards of what I expect.

I don't think the high tone singing is burn back or the block would be getting hot faster. Could it be flames flickering at the outlets exit point, popping at high frequency? The low pitched song making the plenum hot is burning back for sure. So far that's the part that makes sense.

By damper I assume you mean a butterfly valve. Yes/no? Where in the circuit is it, between blower and fuel supply?

One thing jumps out at me that sort of explains having to turn the prop up high and damping the air till it gets warmed up enough to stay lit.

How high is the static psi at the propane jet's location? If air psi is high enough to inhibit propane delivery it could explain why you have to crank prop up and damp the air till it gets hot. I can't think of why getting hot would change the conditions so you could lower prop and open up the air and get a neutral flame. 

Frosty The Lucky.

[Buzzkill]

I'm just spitballing here, so take it for what it's worth.  In general if a flame is burning inside the plenum then there simply isn't enough FA flow through the burner head.  Propane pressure is largely irrelevant in this context since it is not used to induce air and by the time the stream reaches the plenum I'm guessing the velocity of the fuel itself is minimal.  That leaves the job of providing enough pressure in the plenum to keep the flame from burning inside up to your air source. 

I'm assuming the plenum for this burner is significantly larger by volume than any of the burners you've made in the past.  Is it possible that due to the increased volume of the plenum there is such a drop in pressure when the FA mix enters the plenum that you just aren't "filling" the plenum fast enough to create the pressure needed?   You've indicated that the fuel source is the equivalent of a 2 burner forge.  Does the mixing tube/FA delivery pipe to the plenum correspond to the increase?

I'd be curious to see how it behaves with about half the holes blocked off.  A strip of fiber blanket or maybe a piece of IFB could accomplish that without having to plug the holes individually. 

Is the thickness of the burner block roughly the same as your other burners with regard to how long the individual tubes/nozzlettes are?

Even though your forge height and width are small, if the ends are left open it shouldn't create excessive back pressure.

If you have a bunch of IFB's you may want to build a temporary brick pile forge and test some different shapes and sizes to see if there is much difference before tearing the forge apart and relining it.  I guess you could do the same thing with some rigidized fiber blanket as well.

[D.Rotblatt]

Thanks for chiming in Frosty and Buzzkill!  

1 hour ago, Frosty said:

By damper I assume you mean a butterfly valve. Yes/no? Where in the circuit is it, between blower and fuel supply?

The damper is a plate that slides over the intake in the fan.  I also have a gate just after the fan and before the propane jet.

1 hour ago, Frosty said:

I don't think the high tone singing is burn back or the block would be getting hot faster.

I agree.  When it happens I can see the flames vibrating in unison.  I think its starting to burn back, extinguishing and/or reigniting in again (perhaps by the flames next to it). There is a pattern though - clean burn with a rich flame, then as I lean out the flame (but still rich) it sings in a high pitch, then as I lean it out more it back-burns.

1 hour ago, Frosty said:

How high is the static psi at the propane jet's location? If air psi is high enough to inhibit propane delivery it could explain why you have to crank prop up and damp the air till it gets hot.

I'm using a little dayton blower, 1TDN7, about 50 cfm free flow.  Definitely not enough to inhibit the delivery of propane.

1 hour ago, Frosty said:

I can't think of why getting hot would change the conditions so you could lower prop and open up the air and get a neutral flame. 

The only thing I can think of is that it is igniting the FA mix at the exit of the nozzles and preventing it from burning back in.  If that's the case, I simply have insufficient pressure in the plenum (which gets to Buzzkills thoughts).

1 hour ago, Buzzkill said:

I'm assuming the plenum for this burner is significantly larger by volume than any of the burners you've made in the past.  Is it possible that due to the increased volume of the plenum there is such a drop in pressure when the FA mix enters the plenum that you just aren't "filling" the plenum fast enough to create the pressure needed?   You've indicated that the fuel source is the equivalent of a 2 burner forge.  Does the mixing tube/FA delivery pipe to the plenum correspond to the increase?

I made the jets the size of 3/4" burners because I wanted to compare consumption. I figured I could just crank it up to what I needed.  You are right, the pressure is purely provided by the air source.  The 2 jets are able to provide plenty of propane, with the blower wide open I can run a very rich flame.

The plenum is significantly larger then my other two ribbon burners, but I don't think its the size of the plenum, rather the size of the openings that would reduce pressure.  Either way it has nearly 3 times more holes then my little NARB with 1/8" holes which is powered by a single 3/4" burner.  But this is a FARB, so I figured the blower would keep it pressurized enough.  

The mixing tubes are much larger; 3" or over I think.  The idea was to provide less restriction for air flow.  I pulled this blower assembly off my regular Wayne Coe style ribbon burner, and it worked fine on that (though I have changed the jet size, but I should be able to just run it at higher pressure).

It is possible that the burner is just way oversized for the forge and blower, and I'm trying to run it at pressures that are too low.  I just did a quick calculation: I'll have to check to be sure, but if I remember right about the number of holes in my old Wayne Coe burner, the area of the holes in this new ribbon burner I made are about 3x the area of opening. about 6" area for the old one, and 17" area for this new one.  

1 hour ago, Buzzkill said:

I'd be curious to see how it behaves with about half the holes blocked off.  A strip of fiber blanket or maybe a piece of IFB could accomplish that without having to plug the holes individually.

I think I'll have to block off about 2/3 of the holes and see what happens.  The thickness and construction of the block is identical to the NARB, only width, length and number of holes are different.

I'll also first try putting on a blower I have that is more powerful running full open and see if that makes a difference.

 

OK!  Thanks both of you!  I have a direction and a working theory.  

 

Side note to Frosty: the last layer of refractory I put on (which would be the face inside the plenum) was sifted Mizzou with no aggregate in it.  It is powdery and has no strength, just turns to powder if scratched.  The rest of the head, where I put aggregate (even if it was crushed and small), has plenty of strength so far.  

 

DanR

[Buzzkill]

7 hours ago, D.Rotblatt said:

It is possible that the burner is just way oversized for the forge and blower, and I'm trying to run it at pressures that are too low.

That's pretty much what I was thinking too. If that's the case then blocking off 1/2 to 2/3 of the holes should make a significant difference.  Although a forced air burner should be a little bit more forgiving than a NARB regarding the exact number of holes that works, there has to be some practical limits in both directions on what will produce a functioning burner at a given pressure and FA mix.

[D.Rotblatt]

On 10/3/2019 at 7:56 AM, Buzzkill said:

there has to be some practical limits

Some success:

First: I put replaced the dayton with a larger blower.  Put up the psi to 30lbs and opened her up at full throttle.  As I turned up the needle valve it ignited, running lean as starving marathon runner. No dragons breath, but a blast of hot air that was hair singeing from 4 feet from the door.  No singing until I started to close the gate a bit.  Turns out there's a range somewhere near neutral that it did sing, but not backfire.  Just a sound like blowing across a bottle...but lots of bottles at the same pitch.  Flame was way off the burner head.  Upshot is that more back pressure prevented backburn (as expected).

Second: I ran a piece of tape across the middle 6 rows of holes (lengthwise, each row is 24, so I had 192 holes open) and covered the tape with refractory mortar.  I hooked up the the dayton blower.  Same thing, sang around neutral but didn't really back-burn and ran at lower temperatures.  It only worked for 30 seconds or so and the mortar warped and exposed/opened the middle rows of holes.

Then, since it was moving in the right direction, I plugged 4 rows of holes with the mortar and gave it a try. But at 240 holes open, it's still too much.  A bit of improvement though.  It seems 336 holes is way too much.  Probably half that, 175 plus or minus should work. I'll plug a row at a time (24 holes) and see what the results are this weekend.

DanR

On 10/2/2019 at 10:29 PM, Frosty said:

I can't think of why getting hot would change the conditions so you could lower prop and open up the air and get a neutral flame.

Frosty: Might be a miscommunication on my part here.  I was running a very rich flame to keep it from backfiring because every time I adjusted it to neutral or lean when it was cool it sang and backfired.  Once it heated up, I was able to reduce the propane pressure to get a neutral flame.

 

[Frosty]

On 10/2/2019 at 11:21 PM, D.Rotblatt said:

I'm using a little dayton blower, 1TDN7, about 50 cfm free flow.  Definitely not enough to inhibit the delivery of propane.

It's still making pressure and the propane delivery rate depends on differential between the regulator and psi outside jet's orifice. The only real way to know what the blower's static pressure is and where is with a gauge.

On 10/2/2019 at 11:21 PM, D.Rotblatt said:

The only thing I can think of is that it is igniting the FA mix at the exit of the nozzles and preventing it from burning back in.  If that's the case, I simply have insufficient pressure in the plenum (which gets to Buzzkills thoughts).

I don't think burning back is the problem until you reach the low toned song, the signs don't seem to be there. Igniting off the outlets is how I THINK the high tone song is generated. The flames are basically sputtering at high rate, once hot they stay lit and without sputter, no song. 

6 hours ago, D.Rotblatt said:

Frosty: Might be a miscommunication on my part here.  I was running a very rich flame to keep it from backfiring because every time I adjusted it to neutral or lean when it was cool it sang and backfired.  Once it heated up, I was able to reduce the propane pressure to get a neutral flame.

That's about what I thought you meant and it still does't make a lot of sense, unless my above surmise is in the ball park. 

I'm thinking there is a lot more to making multiple outlet burners this size than we thought. Some things just don't scale up so easily, the variables don't seem to change consistently. 

Frosty The Lucky.

[Old Crew]

Dan

I have been watching your posts and appreciate how you approach building and testing your ribbon burners. Hopefully I can learn from your documented experimentation.

I have been working on a drilled brick NARB.  I was somewhat happy with version 1 and am still in the testing phase of version 2 but both have exhibited some of the harmonics you are experiencing .

Version 1 would sing at different pitches until it got up to heat it had 136   1/8 inch holes and was very stable.  Version 2 has 163 of the 1/8 holes and seems less stable so far. As of yet I don't have a completed forge to fully test my burners in , but I am getting closer to completing it. Please continue to let us newbies learn from your Tinkering!

Thanks

David

[D.Rotblatt]

Okay....new wrinkle; back-firing (not back burning).  So I blocked off all but 8 rows of holes with mortar (that left 192 holes open).  I had to do a little bit of adjusting while it got up to heat, but it meant startup would be a tweak and walk away for a few minutes and tweak again kind of thing.  So I get it going and I adjust the pressure to 10 lbs or so, and the damper to about 3/4.  Took about 10 minutes to heat up.  So it's nice and hot, up in the 2250F range running even and beautiful.  So I walk away to let it run and see where the temperature will settle and suddenly "POP" big back-fire.  Wasn't looking at it, so I wait a minute or two and "POP"  it does it again.  So I shut it off, and that's where I stand.

I did have one problem before this that might effect things, the burner cracked around the seam between the cast head and the metal shell when I cut it open and pulled out the baffle. All the vibrations of cutting cracked the seal I think.  I sealed it back up with my zircon/colloidal silica mix and some mortar.  Didn't see any leak when I started it up, but wasn't looking too hard so maybe there was in the back and it heated the shell.  Honestly, I was just so freaked out by the backfire that I forgot to check if the shell was hot.

I'm not giving up, but I am stumped right now, except to check if there is a leak in the shell/face.  Hate to have to start over....

_______

 

14 hours ago, Frosty said:

It's still making pressure and the propane delivery rate depends on differential between the regulator and psi outside jet's orifice. The only real way to know what the blower's static pressure is and where is with a gauge.

True.  Taking a quick google trip: this blower puts out 18 cfm at .5" sp.  .5 inches static pressure = .0181 psi.  So if I figured that right (which is no certainty), that's not going to make much difference from a high pressure propane jet.

15 hours ago, Frosty said:

I don't think burning back is the problem until you reach the low toned song, the signs don't seem to be there. Igniting off the outlets is how I THINK the high tone song is generated. The flames are basically sputtering at high rate, once hot they stay lit and without sputter, no song. 

I'm game.  What it looks like is the flames go from a normal non-moving cone when not singing, to seeming to vibrate in unison side to side at an incredibly fast rate.  There are times when it will sing, stop, sing, stop, etc, so it's easy to watch them.  Quite mesmerizing.  It could be jumping off the end of the burner then reigniting from the flames next to them, or....?????  Either way, the hot face seems to stabilize them.

15 hours ago, Frosty said:

I'm thinking there is a lot more to making multiple outlet burners this size than we thought. Some things just don't scale up so easily, the variables don't seem to change consistently.

Yup!  I thought when I got my NARB mod to work so easily the first time, that this would go easily too.  But it's not looking like that. This back-firing is really bothering me.  I thought I had it worked out too  

4 hours ago, Old Crew said:

I have been watching your posts and appreciate how you approach building and testing your ribbon burners.

Thanks!  Glad it's helpful.  I'm interested in the drilled brick faces.  I assume you are using IFB's.  Seems an easy way to make them.  I have a pile of IFB bricks, but they just don't hold up in the forge.  They always crack.  I know Frosty and Mikey recommend a particular brand and I may get some of those.  I have a CNC mill, so it's easy to set up and drill stuff.  Love to see how your's work in the forge!  It's a different animal.  I did test mine using Frosty's method of drilling a board as a face.  You get around 30 seconds before it starts to burn, but you can see if it will work.  That's how I came to around 125 holes as working best for my NARB.

DanR

[D.Rotblatt]

After sleeping on it, I had one other thought on the back firing. I put a thin coat of mortar over the holes to seal them. In the hole behind the mortar is gas/air mix...maybe when the mortar on the holes is hot enough it’s igniting the gas in the plenum and “POP”!

Dan

[Anachronist58]

That is certainly a variable that ought to be eliminated.

That stagnant fuel air mix would be just waiting to ignite.

Since you have an nc mill, the quickest way to find a hole count sweet spot would be to drill test blocks with systematically increasing hole counts, since plugging seems to be problematic.....

Do you have a good idea of what to use for drilling? No reason I can see that the drilling would be difficult/expensive........

Robert Taylor

[D.Rotblatt]

1 hour ago, Anachronist58 said:

Do you have a good idea of what to use for drilling? No reason I can see that the drilling would be difficult/expensive........

For an IFB probably a carbide tipped masonry bit. An IFB is so soft it’s just about clearing the debris from the hole so it doesn’t break out the brick. I’d do a peck drill routine. Could  also just use an old carbide end mill. 

Dan

[Anachronist58]

Yep. I would use reasonably sharp carbide (not so much radius on the cutting edge), since "IFB is so soft".

Robert Taylor

[Buzzkill]

When I "drilled" the holes in an IFB for my current burner I just used a piece of 1/8" welding rod that I ground  bevels in.  It drills very easily if you lift the bit and clear the debris from the holes a few times.  The key is very low pressure.  They will crack if you try to force the drilling at all.  I didn't have a masonry bit that small.  It would probably work.  However, IFB's will dull a "standard" drill bit fairly quickly.

[D.Rotblatt]

13 hours ago, Buzzkill said:

However, IFB's will dull a "standard" drill bit fairly quickly

Yup, I figured that was the case.  Masonry bits are carbon tipped and cheap, plus the tip is larger then the shank so debris will not get caught up as easy.  I've used a piece of welding rod for a drill before too  Use what ya got!

I was thinking about casting or drilling a new burner head, being that the seal cracked on it and it's got "troubles".  But that's a lot of work. So now I'm rethinking about taking the time to fill those holes up deeper.  Maybe a mix of zircon/bentonite clay would work better and fill the hole deeper.  I played with making a few mixes and they are strong and stable under heat and smooth enough so they can probably be pushed pretty far into the holes. 

I'll get this thing to work if it kills me!

DanR

[Frosty]

Dan: I think the big bang is the result of FAM building up in the outlet holes and the burner block reaching ignition temp. I'd be thinking of pushing Kaowool into the holes till it's blocked closer to the plenum but ceramic blanket can be infiltrated by the FAM so ramming hard refractory to plug them is probably what you'll need to do.

I've made drill bits out of small rod by giving the end a smack to flatten it slightly then grinding to an edge. It makes an old style spade bit sort of. If it's large enough I can grind obtuse edges that come to an obtuse point but I've never tried 1/8". For that small I've had luck with a little creative dyke work but you still need to make the point pretty obtuse or it wobble in the hole and you end up with a triangular or square hole. Might not matter though.

Frosty The Lucky.

[bubba682]

Dan i've been following this thread and i have the same noise coming out of my ribbon burner with the same blower my burner is not like yours though ,i went and talked to the guys on the homebuilt forge site on facebook.Their opinion and mine for me is not enough airflow  so i got a bigger blower comin if ya got one thats bigger try it. That noise is a definite fail for me and im only able to get to 2050 deg hopefully the blower solves the problem.I went cheap on the ribbon burner its a 2'' coupler with a 1/4 '' plate welded on and drilled with 25  1/4'' hole for the first experiment into ribbon burners.I

 

[D.Rotblatt]

1 hour ago, bubba682 said:

so i got a bigger blower comin if ya got one thats bigger try it.

Agreed.  I did put a larger blower on it, and it worked.  Still made an organ sound at the right mixes when not hot, but at the same time the flame was blown 1-2" of the head - so it wasn't backfiring, just resonance. The flame was so strong I was running at 30 lbs (two .040 holes), it was lean, and the  heat shooting out the door kept me several feet away. There's a different sound that's lower and the flames disappear, that's the back-firing - the flame burning back into the holes.  Then there's the infamous "POP" - which is a backfire.  This burner has now seen them all!

6 hours ago, Frosty said:

I think the big bang is the result of FAM building up in the outlet holes and the burner block reaching ignition temp.

Yup, I concur! Maybe zircon soaked ceramic fiber pushed deep into the holes will do it.  It should form a solid plug.  I'll play and see...it'll either work or it won't.  Either way we'll get more data!  Thanks for the thoughts!

DanR

[bubba682]

Thats alot off pressure lol the noise is beyond though its loud i just wanna get to welding temp and no noise so i hope the stronger blower does the trick.Mine hasn't bachfired yet but i only ran between 3/10 psi .

[D.Rotblatt]

2 hours ago, bubba682 said:

the noise is beyond though its loud i just wanna get to welding temp and no noise so i hope the stronger blower does the trick.

My normal ribbon burner (with 1/4" holes) makes some sound at first sometimes, but slight mixture adjustments stop it.  It does take my larger blower to get to welding heat, the little Dayton 50 CFM blower is fine for forging but not for welding.  A stronger blower will probably work.  You're 1/4" plate is also much thinner then cast faces, so I don't know what effect that will have.  It will also heat up and may backfire if it gets too hot - hopefully not.  You'll have to see.

DanR

[bubba682]

 I ran the new forge for an hour as hot as i could get it no backfires i took the temp of the burner were its tacked to the body it was under 200 deg once i get the bugs out i'll probably replace the plate with something more suited for heat like chrome i can't find no cast around here.I'M not lookin forward to the big bang lol...The burner is a gas miser that is something i like and if it works the way they say for welding it'll be worth it.