Introduction: UPDATE! Backpacking Gasifier Stove
Hello, this is Quark- and I am here to show you how to make your own TLUD (Top Level Updraft gasifier stove), and you can look them up at http://www.build-a-gasifier.com/gasifier-wood-stov.... They are essentially a stove that burns the fuel not once, but twice. The base thermos holes allow air into the fuel, while the top holes allow preheated air down into the stove to basically burn the fires smoke. I recently learned about the design while looking up specification for the popular Biolite Campstove, a design which I sought to make. Only then did I learn that it was a gasifier, and the rest is history. They are often used in third world countries, due to the fact that they are incredibly cheap to manufacture and are 10x more efficient than just a plain fire. Because of the double-walled construction, it is easy to use a simple food thermos to make one of these beauties. Enough talking, Onward!
Step 1: What Does It Do?
A gasifier stove consists of two walls. The outer layer then has holes drilled along the bottom on the outside, while the inside has holes drilled in the bottom and the top. Air then flows into the bottom holes on the outside, and flow into the inner layer, into the fuel. Some air then rises between the walls, becoming heated and flowing out of the holes in the top of the inner layer, essentially becoming little jets of fire. For this project you will want a thermos, and various drill bits.
The thermos I used is: http://www.amazon.com/gp/product/B00408LQN8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Step 2: Outer Layer
First, you need to drill the outer holes. Make sure you drill these outer holes above the indentation you see about 3/4 above the bottom, as this part of the thermos is separate from the rest of the unit. I drilled on small hole, around 1/2 inch above this dent, with maybe a 1/8 bit. Then I gradually went upwards until I used a 3/8 inch drill bit. Then I took a measuring tape and used it to evenly distribute the holes along a line parallel to the base, for a total of 12 holes. This is also nice because you will inevitably push through the outer layer a little hard, and end up denting the inner layer. Don't worry this is good. YAY!
Step 3: Inner Layer
Then take a 3/16 bit and drill into the dents created by the previous layers drilling. This will leave you a straight shot from the outside into the bottom of the thermos, and an easy ventilation route for air to get in. This is probably the easiest step, and is also the fastest.
Step 4: The HARDEST Part :(
The next part is to drill the inner top holes. I really hated this part as it took forever. I used a rotary tool burr to make a small dent in the rim, and followed these small holes up with a 3/16 inch drill bit. It was easy after the initial burring to make the dent and was straightforward after that, but I ruined several burrs in the process. You want to drill these above the protruding lip, but below the threads.
Step 5: Test
I tested the stove several times without anything on it. You can see from the pictures that it quickly developed hot coals in the bottom. I filled it with some wood scraps and paper towels, and after about 2 minutes, it stopped smoking and started gassing! This process usually takes at least 1 minute, but after that it is golden. The fire eventually starts to come out of just the inner holes, and looks really cool. I prefer to light the stove through the bottom holes, as it gives me a straight shot to the fuel.
Step 6: Pot Support
For the pots, I needed some form of support. This took me a while to figure out (with my dad's help) and it worked out very well. I ended up using some 1/8 inch thick, 1 inch wide aluminum bar. They pull apart in pieces, and stack into a cross that fits neatly unto the top of the stove.
Step 7: Finished
I have yet to finally boil water in it, but I assume it would take anywhere from 6-10 minutes to boil 1 liter of water. I plan on making a fan assisted box to help move the air in the bottom, and will update when ready. I would love suggestions on how the holes could be altered to provide better gasification, or how it can be made better.
Thanks for reading until the end of my first instructable, and I would love your vote in the Make: Energy Contest, and others. Thanks, Quark-
Step 8: Thermoelectric Fan Box Update
I just couldn't wait to post. No tests have been performed, nor has the sugru even dried. For the first update, I made a thermoelectric fan box to blow air into the box and create turbulence. This should hopefully generate more of a furnace type stove and cause more efficient gasification. It functions by using a peltier element to cause a temperature differential between the side facing the stove and that facing away. Aside from the fan, it has no moving parts.
You will need:
Thermoelectric module and compound: https://www.sparkfun.com/products/10080
Aluminum enclosure: https://www.sparkfun.com/products/11735
Squirrel cage blower: http://www.amazon.com/gp/product/B008P72QYS/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
Schottky diode: https://www.sparkfun.com/products/10926
Sugru (or other method of ducting the fan): http://sugru.com
Step 9: Attaching the Fan and Copper Nipple
Firstly, drill 2 holes and position the blower in the manner mentioned above. Make sure not to attach it too well, as this is merely a testing stage. Next, drill the hole for the copper nipple, at the bottom of the box. I drilled this out with a 7/16" bit and tapped the hole, then gluing to keep it in place. For a matching hole for the nipple, make sure to drill one of the bottom 3/8" combustion holes all the way into the inside layer for additional screw space.
Step 10: Attaching Thermoelectric Module
First, drill 2 small, 1/8" holes in a spot so that the wires run directly from the module into the holes in the box. Then, run the wires into these holes and hold them at the other side. Now, attach the fan, red to red, black to black, with a Schottky diode on the red lead, white line facing towards the fan. Solder these in place, and make sure to run heat shrink over these leads before fully soldered, in order to prevent short circuits. Warm this tubing to shrink the tube over the leads, and, done! On the outside of the box, take some thermal compound and drop a little glob on the enclosure, squishing this over the cooler when you place it down. I also added little rolls of sugru around each edge of the module to keep it in place.
Step 11: Ducting Fan
Take one packet of surgu, and roll it around the copper tube in the bottom. Then, take the other packet and fold it into a small sheet, then smoothing them together and making an airtight seal.
Step 12: Adding Air Intake for Fan and Finishing Up
Simply drill a large 3/8" hole in the lid of the project enclosure in order to allow the fan to breathe and filter air. After this step, you are practically done! I would love feedback and ideas on grille shape and design, but this is what I went with. I included images of the nipple fitting into the hole I drilled in the canister, as well as it in the stored position.