<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Me too. Co-gen; Heat and Stove design.<br>
<br>
My thoughts are that fuel needs to flow. If you have flow
problems, you might consider adding an air nozzle or two pointing
horizontal, or down along the slope, at the base of the vertical
wall at the back of the bin. If the fuel at base of the grate
burns out before it is replenished then to much air may bypass the
fuel. In that case you may need to create separate air supply
zones under the grate and have some control, perhaps reducing the
air to that portion. <br>
<br>
Only one way to find out.<br>
<br>
Good luck,<br>
Alex<br>
<br>
On 19/10/2012 9:28 PM, Darren wrote:<br>
</div>
<blockquote cite="mid:5081FE42.9030300@vegburner.co.uk" type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<div class="moz-cite-prefix">Its getting cold again, so I'm making
time for the stove again.<br>
<br>
First refinement on my list is to try to provide a fuel / hopper
combination that will not 'bridge' jamming in the hopper causing
the fire to die back for a while until fuel finally falls onto
the grate giving poor combustion for a time.<br>
<br>
My plan is to modify the hopper adding two walls to either side
of the grate (shown in red on the plan) so the hopper is only as
wide as the grate and the mouth through into the combustion
chamber.<br>
<br>
I've got a load of ash branches that I'm going to chop into
short lengths (10cm, as wide as the grate) so that they can be
stacked into the hopper in an orderly pile (see side view)<br>
<br>
I am hoping this will help the burner to operate without
requiring frequent grate rattling to get the fuel to self feed
onto and down the grate.<br>
<br>
Anyone got any thoughts on this?<br>
<br>
<br>
<img src="cid:part1.09000408.02080007@kingston.net" alt=""><br>
<br>
Drawing was made using QCad on Linux Mint. <br>
<br>
<br>
<br>
On 23/03/12 17:34, Darren wrote:<br>
</div>
<blockquote cite="mid:4F6CB413.5020900@vegburner.co.uk"
type="cite">Finally got a chance to write up my further
experiences... <br>
<br>
I replaced the broken glass in the door into the combustion
chamber and I added the shakable grate on top of the original
grate. In order to make this work without some very tricky
welding I had to also install the parts to make the hopper taper
from three sides towards the bridge (and onto the part of the
grate inside the bottom of the fuel hopper), rather than from
just one side as it was previously. With the current design the
extra two sloping sides of the hopper act to keep the shakable
grate on top of the original grate and hold the third sloping
side in place. <br>
<br>
I chopped some very dry recycled pieces of pine timber into
approximately inch by inch and a half 'cubes' and ran the stove
with this. This worked quite well. Approximately every 15
minutes I could see the fire beginning to die back
considerably. I would then shake the grate and it would flare
up again. From my observations it looked as if this might in
part be due to the fire having burnt back up the grate so that
there were only embers on the part of the grate under the hopper
or possibly because the fuel was bridging in the hopper -
shaking the grate also moves the tapered sides of the hopper and
is likely to encourage any fuel bridge in the hopper to
collapse. I noticed after this die back, once shaken and the
fire started to flare up again that there would be a
considerable amount of visible smoke from the chimney for some
time. This led me to believe that I was getting bridging in the
hopper. <br>
<br>
Next I cut a piece of plate metal to sit on the back part of the
grate and cover about half of the part of the grate that is
under the combustion chamber. I also extended the chimney from
2 meters to 3 meters. <br>
<br>
I ran the stove again a couple more times, these times the wood
was probably 2 inch by inch and a half 'cubes'. I had not
intended to cut the wood bigger but preparing the wood was time
consuming and once I had finished I noticed that the 'cubes'
were consistently bigger than on the previous occasion. <br>
<br>
On both these burns the stove appeared to run similar to the
previous occasion. <br>
<br>
Next I managed to get my hands on some recently cut ash
branches. Ash has a very low water content and burns reasonably
when freshly cut. I put these branches through a tree surgeons
wood chipper. I loaded the hopper with this and started the
fire on the combustion chamber side using small 'cubes' of dry
pine and paper. <br>
<br>
I ran the stove like this on three occasions. The stove
appeared to 'work' reasonably well. It gave a higher heat
output and did not require shaking, although I did notice at
times the fire would die back a bit, but it would self remedy.
I think that this was probably fuel bridging that would collapse
by itself. I did notice that at times there would be visible
smoke from the chimney - I'm guessing this was after fuel
bridging collapse. <br>
<br>
Burning the chip was however providing a much higher heat output
than I require. I'm not sure how best to try to reduce this
output and keep the stove burning efficiently. <br>
<br>
I think I need to try and address fuel bridging but I'm not sure
how best to do this - nor am I sure what type of fuel is going
to work best. <br>
<br>
I can get lots of wood chip although generally the water content
is likely to be too high - and I cant think of an easy way to
dry the wood chip. <br>
<br>
I was thinking about laying up a lot of 1-2 inch diameter
branches to season that I could then saw to 1 inch lengths. I
could get some seasoned wood and put it through a wood chipper -
although I do not always have access to a chipper and would
prefer not to be dependant on access to such a machine for my
fuel. <br>
<br>
I was wondering how best to modify the hopper design. As the
sloping sides guide the fuel onto the grate, if they were not
there I'm thinking that they would, in effect, be replaced by
unburnt fuel as air will not be flowing through these areas???
Unless I reduce the hopper area so that it has upright sides
going straight up from the grate. This would however seriously
reduce the amount of fuel that the hopper holds (and would be
somewhat disappointing) <br>
<br>
The stove was getting through the fuel more quickly than I
expected - I guess that I can address this by reducing the burn
rate (and the output) which would be a double win for me, as
long as the stove would still burn efficiently. <br>
<br>
I currently have a butterfly valve in the primary air inlet -
can block the secondary air inlets (although this appears to
have limited effect on combustion) I intend to fit some kind of
valves to these. I also intend to add a butterfly valve in the
bottom of the chimney. <br>
<br>
I wont be able to do any more testing/make more refinements for
a while but thought I would give a (late) update before the
details had escaped me. <br>
<br>
Best <br>
<br>
Darren <br>
</blockquote>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Stoves mailing list
to Send a Message to the list, use the email address
<a class="moz-txt-link-abbreviated" href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a>
to UNSUBSCRIBE or Change your List Settings use the web page
<a class="moz-txt-link-freetext" href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a>
for more Biomass Cooking Stoves, News and Information see our web site:
<a class="moz-txt-link-freetext" href="http://www.bioenergylists.org/">http://www.bioenergylists.org/</a>
</pre>
</blockquote>
<br>
</body>
</html>