[TheForge] burner question

[Andy Vida]

schade@acegroup.cc wrote:
> 
> Andy,
> 
> There is a drawing
> here...http://www.blacksmithsjournal.com/forgeinfo.html
> 
> There is no flare on the end of the burner that goes into the forge.

	OK, I see what you're saying.  I don't think it has to be
	present.  For a venturi to work, AFAIK, you need only a
	sufficient pressure drop across a region.  To wit:

            Burner tube          @ = turbulent air
         ______________________
         ______________________|
        |         gas          |  @
        |                    @ |     @ _____________
        |         <------------|------|_____________
        |                 @    | @           jet
        |______________________|       @
         ______________________|



	Here, the pressure drop is not sufficient to get the right
	flow going, but here:


            Burner tube          
         ______________________
         ______________________|
        |           gas        |@@@ @  @
        |                   @@@|@_____________
        |         <------------||_____________
        |                   @@@|@      jet
        |______________________|@@@ @  @
         ______________________|


	You may, assuming the ratio of the reduction in the area of the
	inlet opening to the mass flow (and therefore the resulting drop
	in pressure) is right, see a venturi effect manifested.

	Setting the jet any deeper will not help as there will be no
	further reduction in intake area.  Futhermore, you will hurt
	performance due to a lack of turbulent flow across the venturi.
	The combination of pressure drop and turbulent flow is, as far
	as I recall, what makes a venturi work. If you go too deep, the
	flow through the pipe starts to return to laminar and you lose
	the effect because all you have is a pressure drop.

	I think the bell reducer helps by increasing the pressure
	differential by a small but still significant about, and
	by furthering turbulence.  As the air enters the bell, it
	is slowed down, increasing the local pressure.  There
	is something of a ram effect and when the air passes the
	venturi point, the drop is a little more pronounced and
	the already more tubulent air becomes more violent still.


> The outside end is a piece of pipe that telescopes over the main burner
> pipe. The gas goes in the end. There are cut outs on the burner tube
> and the telescoping cap that allow for air adjustment.

	This adjusts both volume and the pressure drop.  This
	should work just fine.  Whether it is as good as a
	burner with a bell, I cannot say.  All I know is that
	bells seem to work very nicely.