Pre Mix Systems
Pre mix refers to a class of burner where the fuel and air are pre mixed before being burned.
Many Industrial Burners and Neon Fires use premix conbustion.
The Therm people use premix systems on all of their art work.
The advatages of premix are fine control of the mix ratio and control over whether the flame is oxidizing or reducing.
I've been working with premix systems for a while as part of my neon project. I've been building up a complete neon studio. The fires use premix because it is important that the flame be oxidizing, a reducing flame causes the leaded glass to tarnish. (Lead-Oxide is reduced to lead in the surface of the glass)
Another project I've been working on is a spark machine. The idea is to spray metal and carbobn powder through a flame. Intial work with a simple 500k BTU/hr propane torch showed that adding powders caused the flame to become unstable and go out.
More work was done using a venturi to suck poweders into the flame. This worked to a point. The problem being that it was hard to feed large amounts of powder. And you need a very high flow of fuel to make it work. This is a problem because 20 gallon propane tanks can't deliver a high enough flow rate.
Thus the next attempt will be to use a premix system where the powders are sucked in through the blower and thence into the flame. Some intial work has been done using a small blower and propane. Thoughts are that the blower needs to be bigger and the flame needs to be cooler.
An interesting thought is that McCabes colored fire breathing shows a potential solution. Alcohol flames burn cooler than propane. It may be possible to design a premix system that mixes vaporized alcohol with air + powder. Hopefully the cooler flame will result in less of the material burning. (it might also be possible to add colorants to the alcohol or carbon dust to produce a colored flame with sparks.