[Stoves] gas wick, first try

David Young dyoung at pobox.com
Fri Apr 4 11:20:12 CDT 2014


On Thu, Mar 27, 2014 at 12:16:31PM -0400, Jock Gill wrote:
> I really hope others will try this FXJ burner design and see what it
> can do for them.  Have any of you seen a burner like this before?

Jock,

You have inspired me to try a gas wick.

In the FXJ burner, I'm not sure that I understand how the shape and
materials in the I-shaped member made of washers and copper pipe affect
the burn, but this is my working theory: the lower washer concentrates
the wood gas and secondary air into a smaller area and increases the
speed of their ascent.  The lower washer may also act as a bluff body,
adding some turbulence: as the gases pass the lower washer, the opening
up of the combustion chamber will cause eddies to form on top of the
washer.  The eddies will help to mix the air with the fuel.  The copper
pipe confines the combustion somewhat.  The top washer concentrates the
flame & hot air on your pot for better heat transfer.

Does that make any physical sense?  Is it what you were going for?

I decided that my old burner deserved another try, so I have put aside
the burner made of 18-ounce beverage cans.

I added some more primary air holes to the old burner.  I added a third
row of 1/8-inch secondary air holes, and I widened the top two rows to
3/16 inches.  With these changes, I got more blue flame than before,
long yellow tips, less red-orange flame licking the top of chimney with
or without a pot installed.  That is without the gas wick.

I tried to create some turbulence by putting a fan-shaped insert at the
bottom of the primary air can, like the Vesto stove does, but I could
not tell you for certain that that made a difference.  Sometimes the
flames swirled slightly.  That is also without the gas wick.

Last night I left out the fan-shaped insert.  I inserted a "gas wick"
made from a small (10-ounce?) tomato-paste can.  The bottom of the wick
is at the level of the bottom row of secondary-air holes, and the top
extends into the chimney by a few inches.  I saw a similar effect as
Jock did with his new design: short blue flames, short yellow tips, much
less flame crawling up the chimney.  Some flame did crawl up the wick,
but only on one side of the burner.

I was able to start the burner with the wick in place, wood gas
generation began, but the flame went out after a while.  I was able to
restart the wood gas after I removed the chimney and the wick.  I let
the stove burn for a while, and then I gradually lowered the wick into
the flames and pressed it into place.  Then I reinstalled the chimney.

I have a couple of guesses about what was going on with the wick last
night.  First, the wick is too cold at start, and it quenches the
flames.  I should probably raise the wick.  Second, the burner is very
sensitive to the wick position: it has to be centered and level or else
it doesn't shape the flames properly and they will be high on one side.
I need a better scheme for suspending the wick in the proper alignment.

I have attached a top view of the blue flame.  Some 1/8-inch steel rod
steadies the gas wick in the chimney.  It is glowing red hot!

Dave

-- 
David Young
dyoung at pobox.com    Urbana, IL    (217) 721-9981
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