Naturally Aspirated Ribbon Burner. Photo heavy.

[blacksmith-450]

2 hours ago, SaltCitySteel said:

19 holes using Wendy's straws.

 

 

They are square ??? LoL !!!

[Frosty]

Well YEAH, didn't you know that?

Looks good Mike but I think you might've shorted yourself a couple holes. Are the flames stable throughout the regulator's settings, stop to stop?

Frosty The Lucky. 

[blacksmith-450]

I am very disappointed by my first results.

The burner is fine but don't have power..., better than a BBQ but not much better.

My fan is a small fireplace blower, I have a valve for the air inlet. For gas, it's a 0.35 MIG tip.

If I want to change one thing at a time, which part should I watch first ? 

I will put a picture of the setup in a few minutes.

[jlpservicesinc]

a mixture of about 14.7/1 is about right for Gasoline..    Not sure what the exact mixture would be for propane, but finding the info would be a good place to start..  Then figure out what quantity of air you are pushing in..  Ideally being able to adjust the flame to produce the 3 different zones would come in handy.. 

[timgunn1962]

The Gasoline 14.7:1 ratio is by mass: Gasoline is usually introduced into the airstream as a liquid.

For Propane, the stoichiometric ratio is 15.67 by mass or 23.9 by volume.

I've not really found that knowing the numbers makes much difference in reality.

There are so many variables in a NA burner design that it has always been a case of taking a fairly wild guess and then making the adjustments indicated by the way the flame/forge behaves. I usually try to start with a jet that I am pretty sure is too small, then open it out in stages until it does what I want it to do. My guesses have not been too far off as a rule and the burners have tended to run too hot and too lean, but they have burned. I stop opening the gas jet up when I have reached a size which gives just a bit hotter than I will ever want, but with a rich burn (reducing forge atmosphere).

[jlpservicesinc]

I agree Timgunn1962.. But IIRC he is doing a blown forge..   Which the air to fuel can set a good place to start.. Or at least that is what I would do unless someone had some key starting points for what it is that I wanted to build.. 

Thanks for the ratio's..  I knew it was different just not by how much.. 

[blacksmith-450]

Here's my set-up : pipe 3/4... gaz jet Wig-Tip 0.35.  For the air, I have a lot of restriction to pass 2inches to 3/4 but too much air seems the problem, so... I don't think that's the problem.  I already put a pic of the burner, it's 6  X 2 inches with 15 holes.

 

[jlpservicesinc]

it might be pipe size this will increase the velocity of the air vs volume.. my blown forge had 2" id pipe X 2 outlets.. 

The smaller the pipe size the greater the velocity for a given size..  So even if you choke the air back it's still getting to a higher velocity..  Ideally a flap on the intake of the blower is a better way to do it.. The amount of turbulence going though the gate valve can be a problem on it's own..  

 

Air moves a lot like water with nearly the same flow dynamics..   In the corners there will be nearly no flow on the inside of a 90 and nearly all the air will flow the outside and then create an eddy on the down side of the bend..  

I used to wet flow the turbine exhaust systems and also the intake systems.. It's amazing how strangely the air will move even with something as simple as a reduction or enlargement, angles, adding in another pipe.. etc, etc.. 

 

For a given velocity of air traveling though a 1" straight pipe, if this opens into a 2" pipe the flow will be laminar until about 4-5" of travel unless there is a bend.. Even with being pressurized slightly this flow is about the same.. The only time this changes is when there is a valve like in an engine where it opens and closes, that closes and increases the pressure wave which will create a pressure wave back up the pipe and this way becomes a pressure sound wave..  

it can be very complex..    

Get rid of the gate valve and just use the flapper...  start the blower with the flap nearly closed with just a few CFM and then fire it up.. Opening the flapper valve till you see the pattern you are looking for..  If the flame front is way out in front of the block it's way to much air..  If the flame kernel is inside the block that is to little air.. 

you can adjust the flapper till you see the flame kernel right at the block.. Then you can adjust nozzle injector size..   A larger pipe will have a lower velocity.. Also remember that the air going though the ribbon will have a higher velocity since it is pressurized slightly..   

[blacksmith-450]

Thanks a lot. I will look at that one thing a the time.

[timgunn1962]

Sorry, I'd missed the blown thing. I'd lose the .035 mig tip first. 

The mig tip is appropriate for a NA burner, less so for a blown burner. The gas velocity changes with the square root of the pressure across the jet (until the flow "chokes" when the velocity reaches the speed of sound: this happens somewhere around 30 PSI in "our" application).

NA burners need the gas velocity to entrain air. Blown burners do not. You do need to be able to control the gas flow adequately and this can be done with a gas jet and variable pressure, or a needle valve, which is essentially a variable-area orifice, at a fixed pressure.

On Ron Reil's site, there is a link to an orifice flow calculator. An .035" mig tip will probably have a hole diameter of around .042". You can plug in some pressures and see the flows. Note that the flow changes as the square root of the pressure. To double the gas flow, you need 4 times the pressure. To halve the gas flow, you need one-quarter the pressure.

I'd use the calculator to determine a jet size that, at 30 PSI, gives about the maximum BTU value you think you might need, based on the forge volume and whichever BTU/cu.in. value you feel comfortable using. Drill out the mig tip to that size (or the next available drill size up). The mig tips make nice gas jets largely because the hole has a lead-in taper (to help center the wire) that just happens to have really good gas flow characteristics. The default Discharge Coefficient of 0.75 in the BTU calculator should be about right for a drilled-out mig tip.

This should give adequate control of the gas feed with the regulator adjustment.

Alternatively, just take out the mig tip altogether and fit a needle valve.

[blacksmith-450]

Thanks again. I supposed that the problem was with the jet size.  I'll start from there. 

[jlpservicesinc]

Timgunn1962 the needle valve is really the best idea for the blown setup as then one can create just about any air flow rate to fuel mixture..

 

Blacksmith 450...  try the flapper fisrt as it looks like it is already setup that way..  its an easy test and you can fine tune from there..

 

Making to many untested changes at once can have you chasing your own shadow..

Make on change, note the results..  the 0.035 size with the flapoer will work, it just wont offer full advantage as you will max out fuel flow  

 

But test it with different air flows so you set a base line of understanding.   Then change 1 thing.  And test again..   needle valves are rated in flow and volume..  i have a vernier needle valve with 100 turns for gas mixing for scuba diving and would not be the best choice for what you would want...  

[SaltCitySteel]

On 5/26/2018 at 1:37 AM, Frosty said:

 

Looks good Mike but I think you might've shorted yourself a couple holes. Are the flames stable throughout the regulator's settings, stop to stop?

Frosty The Lucky. 

Frosty,

thanks and yea stable from 4-20psi.  I just get a lot of dragons breath past 10psi.  Running a little rich but I'd prefer that for forge welding anyway.  Thanks again.

-Mike B

 

[blacksmith-450]

I removed the Mig Tip and I got a better result.  With a needle valve, I think that I have it !  Thanks everyone.

[blacksmith-450]

I removed the valve on the air line. I added a neddle valve on the gas line. I am able to have a bright orange forge at 15psi but it is not yellow.

To get  a few more degrees of heat is it that I put my jet of gas farther to mix in the tube longer would help? Also my holes in the casting are made with straws. To enlarge slightly to remove some restriction would that help too ? Thank you

[Buzzkill]

Take this with a grain of salt because I'm not sure how well it translates into your setup.  My NARB has 14 holes of 9/32" diameter. It's fed by a 1/2 inch Frosty T, and that gets a freon tank sized forge to welding temperatures at around 20 psi.  You've said you have 15 holes using straws in the mold.  I don't know what the diameter of those straws happens to be, but it occurs to me that you may not have enough (or big enough) holes to get enough gas/air mixture through at that pressure in order to bring your forge to your desired temperature.

One of these days I'll get around to casting a NARB to be fed by a 3/4" Frosty T and my plan is to start with 25 holes of 9/32" diameter for that one and plug as needed until I find the sweet spot.   Since you're using a blower it shouldn't be as critical.  However, if you took it to the extreme and had only 15 pin holes in your burner I think you can surmise that it's not likely you could ever get to forge welding temperatures at any reasonably attainable pressure.  Just my opinion and food for thought.

[blacksmith-450]

Finally, I got it !....  Larger holes and more power in the air line.  The fan was too weak...  

I'll start a new thread and stop hijacking the NARB one...

 

[Daguy]

Question for Frosty(or any other experienced curmudgeon): 

I have access to a couple of old Propane tanks that are the same diameter as the one I'm using for my forge shell.  What are your thoughts on cutting the bottom of the mold out of one of them, then building the form in such a way that I can intruduce the ribbon burner to the heat chamber at a 15 - 20 degree angle  with a closely matching surface geometry to encourage a vortex within the heat chamber? Would you expect that to be a good angle, or should I go more? 

I also want the feed end of my burner to be lower than the flame discharge so it doesn't heat up after shutdown, thermocycling the equipment unecessarily.  I figure this will be safer.  Safe enough to use a stainless clad rubber hose to feed the NARB rather than copper tubing.  Am I overthinking / worrying too much?  I'd just expirement, but I only bought enough refractory to make one or two burners so I thought I'd get input from the brain trust.

Are there any other considerations thatoccur to any of you that I should be thinking about?

 

Daguy

Forgot to mention I plan to side mount it.

[Frosty]

That should be okay depending on the details. Just don't get the burner too far into the forge, overheating the burner block makes them burn back. 

I make mine so the T inducers are horizontal off the back to prevent inducing exhaust. I'm waiting for one of the guys in the club to make an updraft ribbon. 

Frosty The Lucky.

[Daguy]

4 minutes ago, Frosty said:

I'm waiting for one of the guys in the club to make an updraft ribbon. 

By this do you mmean what I was describing?

Daguy

[Frosty]

12 minutes ago, Daguy said:

By this do you mmean what I was describing?

Daguy

An updraft burner has the outlets aimed upwards in the forge usually but not always through the floor. I put that in as an example of an orientation that may seem extreme but turns out to work well. It's not critically important how you aim soft flame burners like a ribbon. I like a vortex in the forge chamber for even heat, just don't expect a dramatic one with a ribbon, they have a low velocity flame.

Frosty The Lucky.

[Daguy]

OK, so we're thinking along the same lines.  I'll try to remember to take pictures as I build and upload results and photos.  I've got most of what I need to build. Wayne has shipped some castable refractory, all I need is some  hydrophillic fumed silica and I'm ready to start.   Thanks for the input and, "xxxx the torpedoes, full steam ahead". 

You know, once the silica gets here and I get enough time to devote to the project.

Yada, yada, yada, the thing, the thing, the thing.

 

BTW, I just think bringing the burner in from the side angled up will make it look kinda sexy.  If I'm gonna build it, I kinda want it to look good as long as it doesn't negatively effect how it works.

 

Daguy

[Frosty]

Looking sexy is good. That should've been DANG the torpedoes. If you have time still editing it out yourself would be a good thing saves Admin from xxxing it and explaining. Keeping on Admin's good side is a happy making thing. 

Gotta go scout a camp ground where the local club is holding a hammer in camp out next weekend. can't be scratching Deb's new RV. 

Frosty The Lucky.

[Daguy]

My apologies to everyone.  as it was a quote,it didn't even occur to me to edit/censor. You'd have thought after my earlier "occurence" I'd have been more  aware.

[Frosty]

We all slip up now and then so don't sweat it. Just be careful is all they ask, we want the forum to be the kind of place you'd let a toddler surf without worrying about having to explain adult things.

Roll on Brother.

Frosty The Lucky.