[TheForge] burner question

[Andy Vida]

Dave Brown wrote:
> 
> At 08:11 12/01/03, you wrote:
> 
> >I guess the question (is a reducer needed?) is answered by the fact that
> >this burner works. Why did everyone use a reducer? (me too)
> 
> Bob,
> 
> I believe that the Venturi effect works whether you have the bell reducer
> or not.  The stream of fast moving propane will drag air along with it
> regardless of whether there is a reducer there or not. 

	This should be correct.  The Bernoulli effect is operating
	as there is a pressure drop across the inlet where the gas
	is crossing at high speed, and therefore low pressure.  The
	ambient air will naturally try to fill the "vacuum".

> But I've always
> been under the impression that the bell reducer improved the flow of the
> entrainment air so that it actually dragged in more air that way.

	Well, this is an interesting thing.  When NJBA built their
	gas forges, we built no flare into the burner.  Mine worked
	wonderfully at first, and then for some mysterious reason it
	stopped holding flame when cold.  I fiddled with it interminably
	in an attempt to get it to hold flame in a cold forge, but to
	no avail.  What changed, I cannot say.  The only possibility
	was the jet depth (we built adjustable venturis), but no matter
	how I messed with it, it would not hold a stable flame while
	cold.  I had to change tactics and place a ball of paper into
	the forge, light it, and then turn on the gas.  Pretty lame, I
	admit, but it was the best I could achieve at that time.  I
	did put a flare on the end and that fixed the problem, but it
	would not fit into the tube in the forge body, so I was SOL.

> Maybe it works, but I can't help but wonder if the commercially produced
> burners (look in your gas furnace at home, or gas water heater, or gas
> stove) know something that Jerry Hoffman doesn't know.  There's got to be a
> reason that they use the bell shape on the inlet side of the burners.

	Tapering down as the gas travels, or opening up?

	-Andy