[Stoves] iCan w/ Deflectors @ 20 minutes

[Crispin Pemberton-Pigott]

Dear Jonathan

The video you sent shows a TLUD gasifier with a 'bluff body' in the
combustion zone. The reason you find it helpful is the same reason the
'concentrator disk' is used. It helps maintain the flame when disturbed or
uneven in any manner. As a flame is self-disturbing they always assist.
There are many variations on the theme. They all work.

There are other ways to use the function provided by a bluff body. I have
used a central one with a circular space around it, spraying paraffin at the
middle of the disk and using the bluff body as a flame retaining impediment
to gas and air flow. The advantage of such a system is that when the central
disk is removed (falls off because the stove tips over) the fire
self-extinguishes immediately.

I found out today that gas water heaters that have concentric direct intake
and vent pipes (no fan on the exhaust). When the pipe is less than 30 inches
long, a bluff body is placed across the vent to create a slight
back-pressure to stabilise the natural gas flame. It is no more than a
rectangular strip and two screws.

If you were to reduce the amount of secondary air I think your can stove
would have a more stable flame. It runs at a very low power and would
benefit from a small air supply. This sort of thing is very difficult to
tune precisely without a combustion analyser because you need to watch the
CO/CO2 ratio while reducing the air, to the point where the CO/CO2 ratio
starts to increase. There is no magic number to seek - I find all sorts of
inflection points. You can, without any instruments, tweak the air closed
until your eyes water when placed in the gas stream. Eyes are pretty
sensitive!  It has a lot (or everything) to do with the layout of the parts.

Thanks for sharing
Crispin


Subject: iCan w/ Deflectors @ 20 minutes

Flame action in combustion zone