Basic Gasifier Build

Moderator: Mike Everman

Post Reply
PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Mon Oct 26, 2009 3:33 pm

Currently formulating a starting procedure and how to best bundle the fuel/sticks. Also need to construct a swirl burner/flame holder apparatus on top of the draft pipe.

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Sat Oct 31, 2009 12:29 am

Flame holder constructed, like this better than the swirl burners. It is just a large pipe with the exhaust pipe inserted into the lower end of the FH pipe. A mesh wire is placed near the center of the FH pipe.
Attachments
FH.jpg

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Sat Oct 31, 2009 12:35 am

3 fuel bundles created. Labor involved, quickly reveals why a chipper/shredder is a gasifiers best friend.
Attachments
3bundles.jpg
Last edited by PyroJoe on Sat Oct 31, 2009 2:19 am, edited 1 time in total.

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Basic Gasifier Build

Post by Viv » Sat Oct 31, 2009 1:10 am

And there was me thinking you knew some thing I didn't ;-) I always thought an auger feed was the way to go

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Sat Oct 31, 2009 1:13 am

Starting procedure was to create a fire in a metal BBQ and transfer the burning wood into the flame tube, filling the lower section of the tube up to the rim of the intake pipe. This worked fine. Used a bicycle pump to bring the embers up to a nice glow before dropping in the first bundle of fuel.

Blew into the top of the flame tube to start the flow up the draft pipe, only worked so-so. At this time plenty of smoke was flowing out the top of the FT. Placed my hand on the tube to seal it up and maybe start the draft process on its way. Started getting some light feedback pulses. They were strong and audible, but weaker than a biggish snorkler. The pulses stopped after I placed the plunger in (this starting process was the only time pulses where observed).

After some minutes could quickly judged the resistance of gas flow through the fuel was creating problems, the smoke stayed thick and would not light at the exhaust. Began using the bicycle pump to speed up the flow and increase the burn temperature. The plunger was lacking a side seal to the flame tube, so was observing considerable blow-by smoke. this was easily stopped with a old piece of cotton cloth placed around the top of the FT.

Placed the second fuel bundle in and started into steady control of process. After some practice, could use the bicycle pump to control the burn rate to produce a healthy flame at the exhaust with no observable smoke. The draft pipe would actually sustain this condition for a short time, maybe a minute or so, before it would need more bike pump. The flame was clean and clear, to clear really, had to use shadow to see it well, as there was no tinge of orange or blue that was distinguishable in daylight. It was very easy to see when the exhaust was lit, the smoke would just completely disappear. This went on for some time, I guess with the slower flow/burn rates meant that each bundle was lasting considerably longer than the 10 minutes planned.

Started removing the plunger to see if anything strange was occuring in the second fuel bundle, mostly just checking there wasn't a early burn through. The cotton cloth felt a little damp, then when I pulled the plunger I noticed a un-imagineable amount of moisture on the plunger and flame tube. Looked like someone had sprayed it with a garden hose.

So I left the plunger out for several seconds, hopeing to see the inner flame tube burn off the excess moisture, well, it didn't burn off. After determined there was nothing that could be done about the pesky water on this run, added the third bundle and reinserted the plunger. Continued work on controlling the process, and would only stop to agitate the grate or plunger and pull the plunger to check the moisture build up. The moisture didn't subside, I can tell it will probably become a problem.

At the very last of the third bundle, pulled the plunger and let the fuel have a slight run-away burn and cooked the moisture off.

Joe
Attachments
BLOWBY.jpg
smoke.jpg
LASTFUEL.jpg
Last edited by PyroJoe on Sat Oct 31, 2009 2:08 am, edited 6 times in total.

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Basic Gasifier Build

Post by Viv » Sat Oct 31, 2009 1:32 am

Hey congrats!

She makes gas ;-) pretty good result for a first go from paper to metal build

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Sat Oct 31, 2009 2:18 am

Thanks Viv,
Was very happy to make gas on the first run. I thought it may take several runs to get to that stage.
Joe

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Basic Gasifier Build

Post by Viv » Sat Oct 31, 2009 2:47 pm

Hi Joe

The moister problem is an interesting development but highlights the starting moister content of the wood, a basic rule of thumb for drying green wood is one year per inch of wood thickness to bring it to the average ambient moisture content, obviously it changes a bit depending on prevailing conditions but people working in the trade use that as a rough guide, so with that said even after a good summer your cut wood at best still be over 30% moister content (best) in comparison good quality kiln dried lumber may be around 12% to 15%.

A fix may be to just insulate the exit pipe so its above the condensation point?

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Sat Oct 31, 2009 4:59 pm

Here are some shots of the internals. The plunger and bottom side of the lower plate look like they have been nicely painted with a gloss black paint. The FT has the most telling display.

Only the lower half of flame tube achieved high heat. The highest heat started 4 inches from the bottom of the flame tube (where the inlet pipe opened). The highest temp zone appears to extend about 3 inches above the intake opening.

Just looking at this I think the top of the intake pipe can be trimmed by 2.25 inches, considerably reducing the flow resistance. Maybe the higher flow rate will carry more of the moisture and reduce the build up.

Thanks for the suggestion Viv, I think will move the exhaust pipe inboard of the housing and use the ash insulation to see if it will help.

vturbine is likely correct in the notion that these things can be made very small.

As a side note there was maybe 6 or so cups of char left in the bottom of the chamber.
Attachments
disassembled.jpg

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Mon Nov 02, 2009 4:42 pm

Made some changes, cut a little over 40% of the upper flame tube, and 5 inches off the housing. The idea
was to illiminate the dead cool space that was accumulating the moisture. The last fuel bundle in que would have had a problem of basically being bathed in moisture. This is a very, very bad condition, because not only are you cooking of the moisture the first time, it recondenses and will be cooked off a second, or third time and so on. Very wasteful. The disadvantage in doing this is the fuel hopper/storage is basicallly gone, but with the time frames involved it is of
little importance.

One goal of the new setup was to force the moisture into the heat/flow process.

(included is a picture of the stick harvester, with a calibrated measure welded to the pruners.)
Reduced the fuel bundle sizes down to 5" in length, as it is much easier to harvest straight sticks of
5" length than 6", this also reduced the flame tube length needed to load 2 bundles. This basically
places both bundles in a well heated environment. So far this has worked well and the moisture problem
was very minor in last nights run.

Moving the exhaust pipe inboard to insulate helped a great deal also. Thanks again Viv for the input.
So far these changes have nearly doubled the lengths of time that the unit produces burnable gas,
without aid of the bike pump.

Noticed the best volumes and quality of gas occured when the draft pipe was at a relatively high heat,
nearly to hot to touch. When the pipe was cold it tended to condense the moisture and reduce the gas
temp. to a critical point that combustion could not be supported. Will insulate the rest of the draft
pipe up to the flame holder before the next run.

Estimate the intake pipe probably needs a small trim also, but this unit is very close to making gas in a continous self sustaining mode.

A very fortunate incident led to a pulse jam-jar mode for over 3 minutes. Not sure about the gas output
at that time, was to busy trying to sustain the mode. Not the typical jam jar or draft engine mode.
Sounded about as healthy as a snorkler, with some distinct differences. Surprising as the main chamber
actually has very poor Helmholtz dimensions. Very interesting stuff!

The run went into the night, so was able to see the type of flame that was created, it was mostly orange
with some brief periods of yellows and hints of blue.

The new dimensions appear that the unit could be made from a reasonably standard propane tank. Will
release the dims after some more testing and fine tuning.
Attachments
trimmed.JPG
trimmed2.JPG
harvester.JPG

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Basic Gasifier Build

Post by Viv » Mon Nov 02, 2009 5:17 pm

Hi Joe

Got to say I love this thread and way we are all learning at the same pace ;-) makes it full fun! and only we I suppose would try to make a gasifier pulse ;-) (I still think a reed valve on the inlet could be fun) and so the partial pulse combustion wood gasifier is borne!

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Mon Nov 02, 2009 9:01 pm

Here is my guess at how this thing is pulsing. There is a deflag event above the fuel in the flame tube which creates enough pressure to push the air downward to have a deflag event beneath the fuel. This makes a sustaining oscillation through the fuel between the two chambers (of course the draft pipe adds needed flow and some inertial pumping). Wouldn't have dreamt it would pulse like that, but it seems to do just fine.

The incident I mentioned earlier was that the plunger had a piece of bark wedged between it and the flame tube wall and had become stuck leaving a large part of the flame tube to act as a chamber. after the plunger was free and dropped to the top of the fuel bundle, the pulsing stopped. Will try next weekend to video it pulsing.
Attachments
CYCLE.JPG

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Mon Nov 09, 2009 4:28 pm

The new mods are taking longer than anticipated. It has taken careful consideration on the mods of the intake pipe, after the last run I notice there is a significant amount of char that is passing though the grate, and not utilized.

After some thought I decided to drill 4 holes (1/8" dia.) in the intake pipe, just below the opening. Reasoned that the char is not seeing a significant amount of oxygen after it falls below the end of the intake pipe. The holes should provide a secondary oxygen supply for the char and maybe boost the temperature in the area, as well as slightly reducing the resistance to flow. (also cut 3/16" off the intake pipe length, "baby steps")

The insulating jacket for the draft pipe is constructed, all that remains is to fill with ash and attach the flame holder.

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Tue Nov 10, 2009 5:21 pm

illust.
Attachments
holes.JPG
holes.JPG (8.97 KiB) Viewed 2053 times

PyroJoe
Posts: 1743
Joined: Wed Aug 29, 2007 5:44 pm
Antipspambot question: 125
Location: Texas

Re: Basic Gasifier Build

Post by PyroJoe » Thu Nov 12, 2009 4:00 pm

One good feature of this unit is the 3 support legs. As many designers know, 3 legs give support without the rocking effect that is often observed with 4 legs.

The three legs have also helped in the ash clean out operation, tilting it in three directions will empty the lower chamber relatively easy and quickly, a task that I thought would be a pain in the arse, turned out to be not so bad.
Attachments
tilt.JPG
tilt.JPG (9.03 KiB) Viewed 2016 times
Last edited by PyroJoe on Thu Nov 12, 2009 7:53 pm, edited 1 time in total.

Post Reply