ABYMC

[sylar]

I have some problems with my latest babington burner.

It's made from an Al doorknob with a diameter near to 50 mm.
First I drilled to 0.5 mm from the opposite surface with a 6 mm drill bit, then I made the blowhole by piercing the remaining material with a long thin needle. The bulge that was formed by piercing the Al was sanded smooth, the back end was drilled wider and tapped with a 1/4th pipe thread.

The air setup (regulated 0.5 to 8 bar) and heated veggie oil (at 70°C) container were used from my previous setup and the whole thing is currently in test phase. In this test phase I can't seem to get any good kind of flame from the damn thing. At first sight the fuel mist seems okay, but about 5 cm from the ball droplets are falling out. It can keep a flame when a piece of 2" tube is positioned in front of it but even then fuel is spilling out the flame.

Is it possible to have a blowhole that is too small? This ball is significantly bigger then my previous one (20 mm brass), so the fuel should disperse better (higher surface tension) at lower pressure, right?

[sylar]

I enlarged the blowhole from 0.1 mm to 0.2 mm (+/- 0.05) and it produces a much smoother flame now.

I don't want it too large to keep air consumption low, as I plan to use a fan to provide more combustion air. I was thinking about a butterfly valve setup coupled mechanicly to the position of the fuel on the ball.

I have some fears though:
-As the ball is engulfed in an air stream, won't the moving air push most of the fuel toward the front of the ball automaticly enriching the mixture?
-Fuel supply and runoff also seems like it will be somewhat affected by air currents. Perhaps these can be shielded ...

To minimise these effects a local widening of the tube encasing the ball will be needed I think. Can anyone chime in on this?
In extremis this could be much like an airbox style burner which supplies the flame with pressure buffered combustion air. See the sketch I made in ACAD below.

[sylar]

Topic resumed here:
http://backyardmetalcasting.com/forums/viewtopic.php?t=3641