BZN 3000f IFB

[Frosty]

Try different nozzle shapes is what I'd do. Something simple and disposable at first. The first couple Ts I made didn't have any kind of flare. I put thread protectors on them as a screw on mounting bracket more than as a large nozzle The threads let me dip them in a kiln wash and prolong the life considerably. 

I get 3/4" thread protectors from the plumbing HVAC supply up the road. Last time I asked they gave me a bucket with maybe 50 and tossed in a bunch of 1" and 1/2" thread protectors too. 

When I was messing with a fan nozzle I tried a few things like flattening a thread protector (T P) [not to be confused with Thomas Powers in his TP guise!]

I was less than thrilled and started futzing with a ribbon instead, NARB.

For a needle nozzle I'd make a paper pattern and roll one out of an old steel can or similar, it wouldn't need to last long 30 seconds should be plenty to tell if it's worth trying something more durable. The wooden ribbon burner test blocks lasted 10-15 seconds before they were unreadable. A little practice and you can tell if a flame nozzle is worth developing further right away.  

The screens and perforated plates on Fisher and Bunsen burners are commonly referred to as "flame holders," they control the flame: shape, position, complete combustion and probably a raft of other things. That type structure on a T burner really reduces efficiency for questionable results. A T burner is nowhere as low velocity a burner as a Fisher or bunsen.

 Frosty The Lucky.

 

[deepwater]

Frosty, as always that's a nice bit of useful info.  Thank you! 

I hadn't considered that the Fisher and Benzomatic type burners were dealing with different velocity gas.  Makes sense with the Fisher /bunsen style (thinking back to my chemistry lab days) but I thought the smaller propane torches were basically operating at tank pressure, at least when wide open. I thought the smaller flames were a byproduct of a smaller orifice plus associated burner tubes and air holes. 

OK, let's say I want to experiment with a tapered cone (smaller at tip than at burner tube) or a flattened flare on a 1/2"T.   Seems I'd still want an initial step bigger from the tube, then a chamber of sorts to give the fuel/air mix a place to slow its velocity and ignite, then my cone or flattened flare.  Is that right? If so how big should that chamber be? I feel like a straight sleeve of a "flaree" seems to like about 1" of length on these to give what I think is the best flame.  Will a shaped flare to concentrate the flame rewrite a similar sized chamber? 

[Frosty]

Oh no, Bernzomatic torches are high velocity multi outlet burners depending on the burner tip in use of course.

I was referring to the Bunsen and Fisher lab burners, those are low velocity and normally natural gas rather than propane. There is an adjustment screw on the bottom of the Fisher so you can tune the jet to burn propane. I picked up several Fishers at a yard sale free box a couple years ago. I don't know about Bunsen though, I haven't seen one in years. 

I didn't like my first few attempts at making a flare nozzle so I can't say what your best departure point would be. My experimentals all had a step as they were attached to a thread protector. Who knows about a step, I don't.

A reducing taper should follow the 1:12 ratio or it will produce BAD turbulence and inhibit the burner's induction. Forget the step a reducing taper WILL accelerate the flow at the square of the area reduction. for example if the outlet of the nozzle is 1/2 the diameter of the mixing tube it will have 4x the area and maybe 8x(?) the velocity. Maybe only 4x V, I don't recall  and I don't have my book at hand.

Again, NO you do NOT want the flame burning inside  the burner, you want ignition at the tip or it will melt it. 

 Frosty The Lucky.

 

[ThomasPowers]

I was thinking of using pipe and crushing it to an oval---trying to keep the same total area, but changing the shape.  If it works you may want to try to duplicate it in stainless.   (Inconel would be even better but you could probably buy another O-A set up or two or three for the cost of making it in Inconel.)

[Frosty]

That was my first thought and experiment too Thomas. I ended up rolling one from 14 ga. with 2x the cross section and it still didn't work very well. I experimented with casting a flare nozzle into the forge's refractory with 4x the area, it was working marginally and I went with the NARB when I looked at the ribbon burner plans posted by ABANA and eslewhere. 

I wanted to see if I could make a flame curtain across the opening in the forge for more localized heat and scrubbed the plans as above my level. 

Frosty The Lucky.

[deepwater]

Thanks Thomas and Frosty! 

So, how to little plumbers torches and bigger O2/fuel systems get that sharp pencil like flame?  On systems using oxy is it a byproduct of the higher pressure oxygen?  Small naturally aspirated benzomatic style hand torches still achieve this concentrated tip though.  That's really what I want, for use outside the forge as a bigger hand torch.  I know the easy and likely best solution is an O/A or O/P rig but those are not feasible for me at this time.  I have propane and a forge, seems to me I should be able to come up with a solution to make a larger naturally aspirated hand torch that will spot heat a couple inch length of 1/4" or 3/8" round or square stock to to bend at my vice, or to tweek already shaped pieces that will no longer fit in my forge, like the 12" dinner triangle I was making yesterday. 

Is it as simple as scaling up the tip /flare design of a smaller benzomatic style torch or does that idea go out the window as you get bigger? 

[Frosty]

Oxy fuel torches are low velocity because the oxidizer is NOT mixed 30:70 with nitrogen. Nitrogen takes a lot of energy to get very hot. Using straight oxy the temp and BTU output is about 2.5x higher. 

How the pros at Bernzomatic, etc, get their burners to perform is well above my level of competence. 

Frosty The Lucky.

[deepwater]

2 hours ago, Frosty said:

How the pros at Bernzomatic, etc, get their burners to perform is well above my level of competence. 

I might as well just give up then if it's above you, hahaha! 

But seriously thanks for the air VS oxygen reminder. 

[Frosty]

That's why I gave up, I'm as competent as I want to be now.

Sure, I explain the nitrogen heat sink thing every now and then otherwise it's pretty easy not to think about.  

Frosty The Lucky.