Gavin Phillips wrote:Michael Scott,
Am I correct in thinking you want to quantify the thrust ( is that in Newtons?) of your rocket stove? And to predict its thrust under varying parameters of fuel load and fuel moisture content?
To be able to predict would be a big deal; I'll put it on my wish list, but I am not specifically working towards it.
I do want to compare.
The bare J stove I am prototyping in my back yard can burn a lot more wood with a small drop in ambient temperature.
Right now I have two data points. At +30dF it can burn 1.0 pound of wood in about 18 minutes. This is with a good hot burn, eye clean smoke, and the rocket noise telling me it has all the fuel it can handle.
Second data point, at +1dF the stove burnt 2.0 pounds of wood in 17:37 and was running like it wanted more fuel. I switched to a denser wood, loaded 2.5# without filling the feed tube and got back to the sound of the stove having all the fuel it could handle. Burn was 19:09.
Air density change from +30dF to +1dF was only about 6%.
I don't see how I can get good numbers without knowing how much air is getting sucked through the stove. Weighing and storing atmospheric air by mass is well beyond my budget, which has me looking at handheld anemometers. The other good thing about an anemometer is I could -probably- claim exemption from EPA (USA Environmental Protection Agency) regulation if I can prove my air to fuel ratio (by mass) is more than 50 parts air to 1 part fuel.
If anyone knows the specific heat of wood smoke I would be glad to know it- butI think I still need to know how much atmospheric air is in there with the wood smoke to get meaningful data out of velocity squared is equal twice the difference between h4 and h5.
I am also looking at data loggers, the kind that take industry standard temperature probes and O2 sensors and so forth. I found a two channel one yesterday for about US$400 with two temperature probes that will read up to +2500dF - but the operating range in the user manual is +32 to +122dF, so I couldn't count on it if I take it out in my yard at -25dF.
I will be watching for a 4 channel today if I have any free time. An O2 sensor to demonstrate free oxygen in the stove exhaust, coupled with a CO sensor to demonstrate the absence of CO in an eye clean burn will go a long way towards convincing someone at the university with a chromatograph to look for 2.5 micron particles in my exhaust stream.