[Stoves] Downfeed burner student project

[Andreatta, Dale A.]

A number of people around the world have been working on downfeed rocket stoves, stoves with fuel chutes sloped at about 45 degrees but not vertical.  I believe this is a excellent basic design.   I've worked with the InStove  downfeed burners for institutional stoves and was very impressed.  Recently, a group of students at The Ohio State University worked on a project for a family size downfeed stove.

A picture is attached, as well as their final presentation.  A link to a short video is:

www.youtube.com/watch?v=VJcnp5lE_fg

The "l" above is a lower case letter ell.

Like the normal rocket stove with horizontal fuel feed, the stove is easy to light, the fire is concentrated so that the smoke had a good chance of being consumed in the fire, the insulation keeps the heat in, allowing for good combustion of wet wood and easy rekindling of the fire when it gets weak.  The downfeed burner is an improvement, I believe, because it's easy to see the fire and because the fuel sometimes self-feeds as the tips of the sticks burn away.  (This depends highly on the shape of the wood; I would hesitate to call a downfeed burner a self-feeding stove, but sometimes it self feeds.)  I did a test recently where I simmered a pot with a lid for over an hour without touching the stove at all.  Two sticks of about 5 cm diameter burned and to end, self-feeding occasionally, and even when they didn't the fire burned strongly and was pulling down the chute.  Of course, simmering with a lid is much easier than without.

The students' stove has a large diameter riser, 15 cm, which leads to high power but perhaps lower efficiency.  Time to boil 5 liters was about 20 minutes for the students, but I've been pushing the stove harder and getting 11-15 minutes.  I think more people want high power than high efficiency, so I pushed the students to use the larger riser.  Smoke seems to be minimal unless the fire is large, about like any other stove.

The students developed a unique skirt design, designed to be ideal for a large pot, but workable for any pot, with or without handles.  The fuel chute is rather large, and works for wood up to 6 cm in diameter.  Again, I pushed them to have a large fuel chute and we are perhaps sacrificing a little efficiency for usability, being able to burn larger wood.

Between tests with the InStove unit and with my students' work, the downfeed burner seems to be very good at burning wet wood, though more tests need to be done.  I intend to do these tests in the summer, and will report my findings by ETHOS-time.  I'll also try some design changes, starting with a cone-shaped pot support and a different type of skirt.  I expect to be ready to report on all this by ETHOS-time.

Dale Andreatta
dandreatta at sealimited.com<mailto:dandreatta at sealimited.com>
Mechanical Engineer and Adjunct Professor
The Ohio State University
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