FW: [TheForge] Burner angle

[Peter Fels And Phoebe Palmer]

Kathy wrote:
> 
> Pete,
> I didn't answer your question completely before; your specific concerns weren't
> answered.
  aww Mikey; Guess i'll cancel my plans to picket in front of 
your shop then.
> 
> 
> You wrote:
> I. "A natural tendency to thermosiphon would work against the inflow of air to
> mix with the fuel."
> 
> Air inflow to the burner is kept separate from the superheated forge gases by
> proper sealing of the burner collar, and also by placement far enough from the
> forge exhaust exits to permit the up-flowing exhaust gas to pass by the burner
> without entering its air intakes (as little as two inches is a perfectly
> sufficient distance from end exhausts). What does make a difference is buoyancy;
> the superheated interior gases do cause buoyancy to come into play, which does
> interfere with burner performance; in this case, the interference is used
> deliberately to slow an unnecessarily high gas exchange rate (for small parts),
> saving fuel.

The reason i brought it up is that, prior to your excellent book, 
many naturally aspirated forges have had difficulty making a high 
welding heat. Many smiths have gone for blown forges for that reason.
  I've read recommendations that owners of cool forges ( hey, 
cool forge dude) carefully polish the inside of their burners, 
fool with venturi placement and so on, all to gain some bit more 
flow.
So it always seemed to me that facing up from below would be a 
bit more efficient...one can always choke it down if it's too much.
In a related consideration, many forges pull the exhaust off the 
top, where the hottest gases hang out, spewing extra  BTUs
> 
> Any concerns about exhaust gas can be laid to rest with an easy experiment.
> Simply hold a running burner in your hand, and slowly turn it from vertical-up
> position, through the horizontal, and finally to vertical-down; as you do so,
> observe the change in flame velocity. The first surprise you will get from doing
> this experiment with any good burner is that, while flame velocity is greater in
> the vertical-up than in the vertical-down position, the difference is no where
> near so much as you had expected. The second surprise comes from finding out how
> close you can come to straight vertical-down position before the burner
> destabilizes (about five degrees). The flame starts wavering and threatening to
> go out at this point because exhaust gases begin entering the burner’s air
> intakes. When the same burner is placed within a sealed burner collar on your
> forge, exhaust gases are much further away and can do no harm even at straight
> vertical down position. 
The test, while very interesting, isn't all that relevant because 
you don't have 2000* of hot gas pushing up from below.
> 
> 2. "The greater heat of the top of the forge would cook the burner faster."
> 
> The minuet the burner is shut down, interior gases can enter the burner through
> buoyancy; this is called the "chimney effect," and is prevented by closing the
> burner's choke completely during shutdown. While running, the burner prevents
> the forge gases from entering. Refrigeration effect from the expanding fuel gas
> is sufficient to keep the burner from overheating do to conduction and
> convection gain from the forge body and nearby exhaust gas. These rules apply
> equally to top mounted burners (the overwhelmingly dominant mounting choice),
> whether they are placed at vertical down (90°) for spot heating, or 3” down from
> top dead center (on a 14" diameter forge) to create a swirl.
> 
> Finally, why is vertical down the dominate choice even for swirl effect? Because
> portable  forges use ceramic fiber for most of the interior insulation, and
> placing a burner at the forge's top allows it to be aimed directly at the
> firebrick or kiln shelf slab on the forge's bottom. Should you decide to use
> Kastolite 3000 insulating refractory for the forge's interior, instead of
> insulating fiber and a kiln shelf floor, than the burner placement can be
> changed to whatever you find most convenient. Also, solid refractory is a much
> better choice for multiple use forge/furnaces, or for a forge employed in billet
> heating. A typical five gallon cylinder with a two inch thick Kastolite 3000
> refractory lining will still be portable (approximately 65 lb.) On the other
> hand the same forge built with ceramic fiber and a kiln shelf floor can be
> lifted comfortably with two fingers; it's all a question of what features you
> find most convenient.
Perhaps a burner target  area of kastolite ( thanks for the 
reference) or kiln shelf would solve that.
Speaking of that, i got an old carbide kiln shelf i cut up for a 
floor, very durable.
Thanks Mikey...your answers are informed, considered and help a 
bunch!....pf

> 
> Mikey
> 
>  
> 
>  
> 
> 
> 
> 
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