ArtMetal

Nelson,

There are so many variables in any given burner design that you could spend countless hours experimenting. You might come up with something new that works better.

 One reason that some people use the reducing tee for the venturi is that certain tees have a nearly perfect taper where they change size, resulting in a more efficient Bernoulli (venturi) effect. The Ward brand reducing tee is one that is very good, while most of the cheap Chinese and Thai tees that I've seen had an almost hemispherical reduction step, or a very short ramp, either of which is far less efficient than the longer ramp of the Ward tees. I get my Ward tees, and a number of other burner parts, from Larry Zoeller, by the way.  Good guy to do business with.

I'm dubious about the success of using a "Y" instead of the tee, as they don't have the right configuration to create a good venturi.  The venturi area is the place where you do want everything to be shiny and smooth, and the gases traveling quickly and with little turbulence.  Taking a few minutes with a die grinder and shining up the ramp in your reducing tee is one way to improve the efficiency of the burner.

Including a mixing chamber in the burner tube is not a new idea, and it is one that has some real merit.  You 'll probably want to bring the tube back down to the original diameter after the mixing chamber, to get the gas flow to the right speed for proper flame control.

Keep in mind, too, that backpressure in the forge chamber itself has an effect on burner performance.  Too little backpressure and the burner is running too quickly and may not retain the flame at its end, as well as running too lean due to inducing too much air.  Too much backpressure and the burner is choked, just as if you restrict the intake side of the burner.  That can cause backfires and too rich a mixture.

Forge and burner design are an art as much as a science.  It takes a lot of experimentation andsome good luck to end up with a forge that works really well, particularly when you're using venturi burners.  With blown burners youcan get away with a lot more errors in design, since you can adjust both the air and gas to overcome problems.  I'm about to have to build a new forge for the shop and it will most likely be a blown burner design, because I need to have a lot of featuers in the forge that will make it impossible to have just one burner design that will work with all the different configurations that the forge will be capable of.  Blown burners will solve that issue easily and simply.  The only drawback of blown burners is that they don't readily lend themselves to the use of an "idle" circuit to conserve fuel.  Our fuel here is not cheap, so that is a consideration I'm trying to work out a way around.