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Peppie

Flared Ribbon Burner Ports?

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Hi David,

My burner is a drilled-IFB NARB, so no blower. 

I am using an AMAL 3/4" Propane injector, which is a very efficient Fuel/Air mixer and is very adjustable, so I do get a nice hot flame, and a very even heat.

Tink!

 

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It's looking good David, maybe close enough just don't paint yourself into the getting it "RIGHT" corner. I've been putting forges together for decades and haven't gotten one "right" yet. They just keeping better and that's good.

I'm sure it needs a little fine tuning but it's good enough to start practicing with now. Use Dan's kiln wash, it's not what I make but he has years more experience with the stuff, I'm a recent zirconia kiln wash home brewer.  NO ITC-100! it is formulated for furnaces and kilns but not to do what we need it to. Worse it's CRAZY expensive.

I can't comment on your tapered outlets, I've lost track of which direction the taper is pointed when you say in or out. That's okay, I'm letting other folk experiment with tapered outlets.

You're doing good, no go have some fun with it for a while. Then make some mods if you think they'll help, you'll have a better idea of what to do and why. Hmmm?

Tink: Your AVATAR makes me laugh every time I see it. Thank you.

Frosty The Lucky.

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Hi everyone, 

If you look back thru that behemoth of the original robbon burner thread, you will see that I was the first one to post about drilling IFB.  My first block with 16 +/- holes had flared ends just because that's what I was used to with single port burner forges and I had a cute little countersink I'd never used begging to be useful.  Don't take my post as scientific experimentation!

 Please note.  I'm a profesional architectural smith and when my forges are running I want them HOT for production work.  I rarely run my forges at low psi.

In my main forge, I average 12 psi with a single Amal injector (thanks to Tim for turning me onto these years ago!) in a 400 cu.in. forge.  The first burner block with nozzles that tapered larger towards the flame face worked very well.  After seeing all the posts of more/smaller ports I drilled another block without flares but with more, smaller ports.  It also performs very well, no noticeable difference between the two except the slightly quieter noise of the smaller port burner.  

There might be slight performance differences in tapered/straight/reverse tapered nozzles.  I have not noticed if there is one.  Seems to me that we are splitting hairs here, after all sometimes a good old-fashioned coal fire is the most economical fire for certain operations!

 

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2 hours ago, Frosty said:

I've lost track of which direction the taper is pointed

If I'm right about our conversation, with tapers inside the forge like a single burner, the IFB got hotter then the tapers on the plenum side.  This was because the flame ignited inside the taper rather then outside the nozzle.

1 hour ago, Judson Yaggy said:

There might be slight performance differences in tapered/straight/reverse tapered nozzles.  I have not noticed if there is one.

I think the issue we are trying to solve doesn't affect you since you run at high pressures.  At low pressures (under 4 or 5 lbs) the flame back-burns after the nozzle block gets hot (after an hour or so).  For heat treating, etc, this is not ideal.  In my experience, even when working on a knife I like to go with a lower pressure since the steel is so thin and I don't want it to overheat.  I've had back burn under these circumstances and had to turn up the pressure.  Small holes seem to make a big difference preventing back burn.  It's also an even quieter burner.

Dan R

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19 hours ago, D.Rotblatt said:

with tapers inside the forge like a single burner, the IFB got hotter then the tapers on the plenum side.

My problem is, tapers go two directions and I'm not sure if you're referring to the wide or narrow end.

I'm sure I'd know if I'd followed more closely but I don't keep things straight so well sometimes. I think I can follow knowing how the mix moves but I'm never sure.

I've been of mixed minds about running the same basic multiple outlet as the NARB or messing with 1/8" outlets. I think the new idea will work better with a faster flame though. 

Frosty The Lucky.

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I necked down the crayons on my burner block.  Narrow side is at the plenum.  Still full crayon diameter at the flame face of the block.  This is one of the test crayons.

  IMG_7079.jpg.6d5e21053c3c73e7b6dbe88074ace9bd.jpg

In theory it should help keep a higher velocity by the plenum so no back burn.  Downside is that there is more restriction so need better blower pressure.  Gas pressure is all relative to what size orifice there is.  I can run mine 1PSI (probably lower) through a 1/16" orifice but I only have a 9-hole burner block.  .. Again, no other blocks to compare it to.  It was my first and I was curious how it would be.

If I can get a better blower and get the forge to weld temp then there won't be a need to modify.  Thought was that I could just drill it out straight through with a carbide bit if it was an issue.  Mizzou seems to be extremely hard so I'm not sure how clean the inside of the hole would be.

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4 hours ago, Frosty said:

My problem is, tapers go two directions and I'm not sure if you're referring to the wide or narrow end.

Ah!  Position A has the "taper" on the hot face; the "taper" is actually a widening of the hole like a 1:12 tapered nozzle on a single burner forge (wider on the face, narrower inside the block).  To see the difference between a taper and no taper, Old Crew just flipped the block putting the "taper" on the plenum side.  Of course, if I got it wrong, then my whole discussion with Old Crew is all screwed up...been there and done that before!  Very embarrassing!

Dan R

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Got it. You're using "taper" to describe the large or "flared" end of the outlet. I just needed to know how you were using the term.

I've always used "flare". Flare towards the plenum should result in a faster flow with flames more likely to lift off the block. Flare out is slower flame perhaps burning inside the outlet. Yes?

Funny thing about the 1:12 ratio I got that originally from a number of sales pamphlets for air inducers. A coffee shop friend was always looking for application patent ideas and dumping stuff on my to brainstorm. His idea was to  make a tire inflator using a jet ejector and CO2 capsule for primary pressure. Nothing we could pull off jet ejectors are transparent air movers, the more you restrict them the weaker they are.

Anyway, of the useful things I learned from that box was the basic ratios to make the T and other burners work effectively. You know them, throat dia. x 8 = mixing tube length. Air intake ports minimum 2x area of throat. The last ratio you just don't see in home built burners and heck most commercial ones is the max 1:12 tapered mixing tube. This about triples induction and stability. Unfortunately it requires tooling, screwing plumbing fittings together don't.

1:12 Is the greatest increase or decrease a fluid flow will remain laminar. Less if fine but greater induces turbulence that disrupts the flow.

It's not the best for a given purpose say fire hose nozzle, those are more acute for acceleration. A wider taper is used for dispersion say fire extinguishers. 

I picked up on it because it was mentioned in almost every pamphlet as a given for induction devices. One of these days I'll run across that box and will share some manufacturers and specifics.

Frosty The Lucky.

 

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7 hours ago, Frosty said:

1:12 Is the greatest increase or decrease a fluid flow will remain laminar. Less if fine but greater induces turbulence that disrupts the flow.

Aerodynamicist commonly use 6° expansion as the limit, which is a little more aggressive than 1:12. But in that range. 

https://www.grc.nasa.gov/www/k-12/WindTunnel/windtunnel_report.html

Look at figure 9 here (5-6° for optimal pressure recovery); pretty interesting study: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720020645.pdf

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On 6/1/2019 at 9:17 PM, Frosty said:

I've always used "flare". Flare towards the plenum should result in a faster flow with flames more likely to lift off the block. Flare out is slower flame perhaps burning inside the outlet. Yes?

Yes.  That's right.  And the results work in accordance with what you've said.  My take is:  On a ribbon burner we don't want the flare out since that pulls the flame into the block and heats the block more, resulting in easier blowback.  At the same time, without a flare there is not a problem with the flames trying to blow away from the block because the multiple nozzles ignite each other to prevent it from going out, plus we want the block to be cooler.  In a single burner it is the opposite: a flare out holds the flame to the nozzle and prevent it from blowing out (in the forge this is not an issue because the heat of the forge walls keep the flame ignited).

18 hours ago, jwmelvin said:

Look at figure 9 here (5-6° for optimal pressure recovery); pretty interesting study

JW; these articles are way beyond me, the terminology alone would take me quite awhile to wade through.  Thanks god we have someone here who can translate!

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We're on the same page Dan, thanks. 

JW: The 1:12 ratio is from sales pamphlets given to me maybe 30 years ago. Exceeding the ratio has inhibited induction in my experience so I go with it as max. Outside of following the basic ratios as departure points I don't calculate anything when making a burner. NARB was strictly trial and error with wooden outlet blocks before I crossed my fingers and cast one fro refractory. The basic ratio dropped function on me like it was dodging monkey poop at the zoo.

I can't comment on your figures, I can barely do basic algebra. 

Frosty The Lucky.

 

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