I was thinking of tinkering with a few ideas to pre-heat the primary & secondary air.
Gave it up -especially since a proper "rocket" stove sucks and roars & burns woodgas just fine without secondary air or any particular attention paid to pre-heating it, but then one day was looking online for uptake hats/spark arrestors, and on a commercial site for things for household woodstoves, ran across those little fans that you can put on top of a woodstove to push room air around.
One sort uses a sterling engine. Another used thermoelectrics to run the little fan. (=~6" diameter two bladed simple thing. The "generators" apparently were tiny. Little pictures I couldn't really see it.)
I don't know about the particulars of these little fans. I'd probably have to buy one and take it apart and see if its guts could be adapted to an intake fan, I'll look around at stores.
I could find out how to source the generators; Thomas catalog?
Just found this:
www.tegpower.com/'Below is one of our wood stove TEGs used for off-grid power, generating 75 plus watts of electrical energy 24/7 as long as the wood stove is hot."
www.tegpower.com/products.html(approx $99)
www.youtube.com/watch?v=SczCj7gilZYSpecs: Dual Power Output 4.5 VDC / 1.2 amps or 10 VDC / 125+ ma /. Can be ganged and wired together in multiples to achieve higher voltages and amperage. Life expectancy - 200,000 hrs. All aluminum construction, dimensions - 5" X 3" X 3".
2:57
www.youtube.com/watch?v=hRagQ2AZgNc&feature=player_embedded(approx $180)
Specs: The TEG Power Brick has two sets of power terminals. 1- Regulated Power: 15 VDC / 350 milliamp, enough to power most electronic devices or recharge batteries. 2- Unregulated Raw Power: 12 VDC (max) / 1.2 amps, continues operation daily output equivalent to 85 watts solar. Can be ganged and wired together in multiples to achieve higher voltages and amperage. Life expectancy - 200,000 hrs. All aluminum construction, dimensions - 8" X 4.75" X 4".
Applications: We developed this thermoelectric generator for use on rocket stoves or other bio-fuel stoves in third world countries to provide long term power and reliable battery charging. We specifically designed it first to be inexpensive and also so it can be molded in to a rocket stove when constructed or easily attached to existing ones. However, the TEG Power Brick is very versatile and easily adapted for other uses as you will see in the video
9:20
All I was thinking about, is a way to replace the battery on something like my Sierra Zip stove, or an evolved adaptation of a wood-gasifier with a complicated airflow for a pre-heat plenum for primary & secondary air.
For a tiny camp stove, if the burn tube of a rocket is 1.5"square, and the whole thing is kept to a small size for portability, it is going to get the whole body of the thing
really hot and whatever it's sitting on and 6" away from it had better not be flammable.
I had a test rig inside a coffee cans with pink fiberglass insulation, and after it'd been going for a while, I could just about light a cigar on the outside of the body. Easily a 6"tall roaring flame, when I filled the fire zone at the elbow of the rocket.
I think this small rocket can produce enough energy to heat a decent size tipi/tent, RV, or small room. Now I see these power generators, and the ideas are percolating...
