Basic Gasifier Build

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Viv
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Re: Basic Gasifier Build

Post by Viv » Mon Nov 23, 2009 4:40 pm

Hi Joe

All good comments, in light of what you say, how about swapping out the wood ash for some thing like perlite or similar commercial insulating material? faster heating and less prone to moisture issues may help out a bit

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PyroJoe
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Re: Basic Gasifier Build

Post by PyroJoe » Mon Nov 23, 2009 6:21 pm

Maybe on a more advance unit, for this one would like to keep simple enough for a beginner to build from easily obtainable supplies. Like working with ash anyhow, it has a fine structure, but is able to seal large seams. Some of the work yesterday has reinforced my affinity for the stuff.

If the ash isn't able to produce the desired resullts, will switch to perlite for PLAN B. Dry portland cement seals well but has an unfortunate characteristic of becoming "permanent". ha

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Re: Basic Gasifier Build

Post by PyroJoe » Mon Nov 30, 2009 5:10 pm

Made a run with the 1.66" dia. draft pipe, flow was still restrictive. A little frustrated, so decided to do some exploring. Used the blow pipe to slowly pick down into the fuel charge. With a little finesse was able to nudge the fuel bits to the inlet pipe, letting them drop down and out the bottom of the inlet pipe. Observed a nice char bed starting about 1/4" above the inlet pipe. Dug down to the opening of the inlet pipe. Then started noticing something different.

After picking the char out below the inlet pipe opening, the char was compacted between the inlet pipe and the flame tube! It was really packed in there. ha

Continued picking down through the 1"+ of compacted char to near the grate. The bed finally loosened up just above the grate. Its no wonder this thing has been running poorly.

After some thought(and blank stares) over a couple cups of sweet tea, decided to try some changes.
First was to not use the plunger. Second, to cut the inlet pipe at about .25" above the grate.

After starting the next run, could quickly tell things were better. As soon as the starting hot char was poured in the flame tube, there was no smoke bellowing out the top of the tube. A glance upward confirmed, the draft pipe had picked up the flow. A look down the flame tube revealed the bed in nice reddish orange glow, without the need of the bike pump.

Decided to skip the charcoal startup and just fill with raw stick fuel. The draft was strong enough to continue pulling the smoke down the flame tube. Used the cotton cloth to seal off the top of the flame tube. Used the bike pump a little to increase the heat. It wasn't long and she started responding to the bike pump. I would apply a single pump and the unit would oscillate about thirty or so times. After about the third time she just took off on her own. She was self sustaining for well over a minute! ha

That went on for some time, refueling and bringing her up to self sustain mode. Sometimes the runs were long sometimes short, something was happening in the fuel charge to bring it in or out of pulse. As the heat ramped up, noticed things where running even better.

Then to my surprise she really started up on the amplitude, housing lid started to rattle and the inlet pipe started blowing ash and loose dirt on the ground below the unit. For a few moments thought she would shake herself apart. The cotton cloth and my hand felt low pressure sucking on the flame tube. The cloth quickly began to pickup heat and was unable to hold it from the heat radiating through. As soon as I released my hand the pulse died.

A familiar smell of burnt paint arose from the lower chamber. A quick glance and pass of the hand near the surface assured that it was in familiar territory. Also the draft pipe had picked up considerable heat, not burning off the zinc, but getting close. A look down the flame tube revealed the lower 30-40% of the tube was glowing a healthy orange, with little yellow sparklers dancing off the surface of the steel.

Refilled with fuel and kept going, able to bring the "idle" mode easily. But only the stronger modes 2 more times. Had to place a steel plate atop the cotton cloth so my hand didn't take a thermal load. Portions of the cloth yielded and caught fire. Best I can tell, she likes a charge of fuel about half the volume of the flame tube. Not sure why. No condensation problems to speak of, I guess the increased flow and heat pull it through the system.

After supper that eve, Went out to haul her into the shop, but she was to hot to touch. Watched TV till about midnight and was able to put her up for the night.

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Re: Basic Gasifier Build

Post by PyroJoe » Tue Dec 01, 2009 4:35 am

Sound quality is poor and the frame is from the side, but was able to capture the idle mode.
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Re: Basic Gasifier Build

Post by PyroJoe » Tue Dec 01, 2009 4:45 am

vid2
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Re: Basic Gasifier Build

Post by PyroJoe » Fri Dec 04, 2009 7:32 pm

Well, thinking about the design, could use interchangeable intake pipe lengths and have the same platform serve two design paths. The first as a basic gasifier as the topic was intended, the second continued under the topic: Wood Fueled Pulse Combustor

The gasifier would have the longer intake pipe extending up into the flame tube, resulting in wood gas production. The combustor would have the short intake pipe, as it is configured at present.

A third intermediate option may be to produce low level pulse combustion, and produce wood gas.

So many options. ha

Its raining here, and will most likely continue through the weekend.
Have another project that will be coming online in the 2 weeks, so the advances will be slow.

As a side note I tested sticks cut to approx. 2" and used them directly without tieing them into bundles. Seemed to work as good if not better than the bundled fuel charges.

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Re: Basic Gasifier Build

Post by Viv » Fri Dec 04, 2009 7:44 pm

Hi Joe

I must say you are running a very nice little project here and all by your self, its a pleasure to follow your progress, keep it up

the idea of running two paths is also good I think as both offer some real scope for experimentation, personally I would love to see the gasifier configured as a sealed Helmholtz chamber and then connected directly to the CC as a tuned component, there is plenty of excess air in a pulse jet CC so it will be forced in to the gasifeir as it pulsates.

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Re: Basic Gasifier Build

Post by PyroJoe » Mon Dec 14, 2009 2:29 pm

Well, in a poor weather pattern for a second weekend, little progress.

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Re: Basic Gasifier Build

Post by PyroJoe » Wed Dec 23, 2009 3:23 pm

Looking at ways of shaving some volume from the CC. Swapping back to the smaller ID draft pipe, as I think the big one creates a condition that the fuel is consumed to quickly. Also with the harder swings from the big draft pipe I think a fraction of exhaust gas is blowing channels through the ash nearest the housing, weakening the cycle. Perlite is probably far to light and fluffy. Need to apply a cone transition between the draft pipe and the CC, so more pressure will be directed into draft pipe, the last hard run looked like the intake was expelling the highest volume.

Don't know if she can reach a lock in but maybe something close.

Ignition has been a little puzzling on this one, not sure how it runs with fuel, air and ignition source located directly above the intake. Usually the fuel/air mix will need to traverse the CC before ignition. And why does it like the dead space above the fuel? If I could eliminate that dead space, I would say she is running exactly like a draft engine, except for the ignition.

Tempted to test dry pasture grass soon.

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Re: Basic Gasifier Build

Post by Viv » Wed Dec 23, 2009 5:22 pm

Hi Joe

Maybe that dead space is acting as a kind of gas spring? maybe altering its size will let you tune its pulsation?

Viv
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Re: Basic Gasifier Build

Post by PyroJoe » Wed Dec 23, 2009 7:11 pm

If I can make it seal correctly, will try a glass pyrex bowl over the flame tube to see WTH is going on in there. At times I wish this thing was constructed of quartz. (taking a page out of Marks book, ha)

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Re: Basic Gasifier Build

Post by PyroJoe » Mon Dec 28, 2009 7:46 pm

The next round of mods are done. Reduced about 5 cubic inches of CC volume. Shaped a long transition cone from the CC to the tailpipe. Most of the transition cone is buried in the ash. Normally I wouldn't use such a long transition cone, but it seems to fit this particular device.

Today will purchase high temp., RTV silicone to adhere cork/rubber gasket material to the Pyrex. Fuel gathered for next run.

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Re: Basic Gasifier Build

Post by PyroJoe » Thu Dec 31, 2009 10:56 pm

Pyrex pan with gaskets:
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Re: Basic Gasifier Build

Post by PyroJoe » Thu Dec 31, 2009 11:05 pm

vid1:
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Re: Basic Gasifier Build

Post by PyroJoe » Thu Dec 31, 2009 11:19 pm

vid 2:
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