Baffle question

[Excaliber]

I was working on building my first ribbon burner.  I had a thought.  Instead of cutting out a hole for the 2" pipe and adding a baffle.  Could I just drill 1/4" holes where the 2" pipe was going to be welded and create a baffle that way.   

Also If I did that would adding a baffle help or hinder the fuel.  My guess is that it would all help mix and disperse the fuel.

[Chris C]

I put a baffle inside mine.  It was an upside down wide v-shaped thing...........kind of like a wing.  My understanding was it helped distribute the gas/air mixture toward both ends of the burner so the mixture didn't just go straight to the middle of the burner.  I'm no engineer, but all I can say is my burner worked flawlessly from the first firing.  Very happy with it.  This is a short video of my first firing.  So I vote for the diversion baffle inside the burner.

 

[Excaliber]

What I mean is more like instead of cutting a 2" hole for the intake of the ribbon burner can I just drill holes in that 2" circle and create an integral baffle.  Would that work.

[Chris C]

It would still allow gas and air to enter the burner box.........................but it wouldn't divert those materials towards the ends of the box to evenly distribute them to the entire burner face.   It might be over-kill, but I believe many people would agree it's important to get the entire homogenized mix out to all the holes in your plenum.  Here's a very poorly drawn sketch of what I'm talking about.  My baffle goes all the way across the box  but only covers about 2/3rds the length and is filled with random 1/4" holes.

[Frosty]

Drilling the entry point to the plenum as described won't solve either issue. First all the flow will still be entering in ONE place. Second it'll be as if not more restrictive than the ones in John's plans. 

A baffle similar to what Chris describes and illustrates is much more effective without increasing back pressure significantly. 

The plenum I experimented with using an inline inlet that worked best had a flat piece of steel about 1/2 the length of the plenum welded a little farther than 1/2 way across from the inlet. The flames on the ends were a LITTLE longer than in the center but I changed my attention to welding the inlet to the side of the plenum without a diffusion baffle at all and the flames are insignificantly longer in the center AND at both ends. 

Were I going to experiment with inline inlets again I'd make the diffusion baffle only a little wider than the ID of the inlet. So rather than 4" long the first adjusted baffle would be 3" and I'd test.

I thought about a LOT of things but lucked out and hit on one that worked well within acceptable limits for my purposes.  The ONLY things I knew for sure when I started working on NARB were: No effective burner blows dragon's breath FEET  out of the furnace openings. And, commercially made multiple outlet, naturally aspirated burners are in common use EVERYWHERE. If you have a gas range in the kitchen take a gander. 

A ribbon is only ONE shape multi outlet burner out of probably hundreds. 

Frosty The Lucky.

[Excaliber]

Thanks Chris and Frosty.  So I assuming that the ones I see online where they just put a baffle just a little bigger than the 2" would not be quite as effective.

[Chris C]

As I said, I'm no engineer.............and much of what I do when building is to over build, but I think you can't over-do on the baffle. 

[Frosty]

9 hours ago, Excaliber said:

Thanks Chris and Frosty.  So I assuming that the ones I see online where they just put a baffle just a little bigger than the 2" would not be quite as effective.

Those are too restrictive and the reason they require blowers with high static pressure and blow all the burning fuel out of the forge.

I use Ts to feed NARBs and they have hardly any static pressure. Below is my 2 NARB forge. The first pic shows the burners position on the plenum and the copper tubing propane supply from the hose connection.

The second pic shows the flames, the burner on the right still needed cleaning out a little better, the flames are much more even now. I made a number of mistakes: first was not making sure all the crud was cleaned out of the outlets and plenum. Second and worst I'll NEVER weld a burner to a forge again. NEVER.

Neither of these have a baffle.

I was concerned about the orange dragon's breath but it was the calcites in the refractory forming a surface oxide, they still burn a little orange but nothing like this. This was the first time I ran this forge for any length of time and learned not to run it at too low a pressure. Anything below 4psi and the burner blocks get hot enough they start preigniting and burn back. I ran them for almost 6 hrs straight on less than half a 20 lb. propane tank.

Frosty The Lucky.