you want to adjust the water flow of your gasifier with a gasoline engine carburetor?
it seems like a great idea. Is this your idea or this design has already been tested?
Do you think that the internal temperature of the gasifier could be automatically controlled in this way?
a central nozzle vs several concentric air jet which advantages?
I have been thinking about that idea for a while now. Very interesting to me. I would aim the sensor from one of those new pistol type color temperature thermometers directly into a nozzle, and use the signal to add more or less EGR or water.
no, it was not my idea. Max Gasman suggested this in the Seat thread of Kristijan more than three years ago:
(See this post and the ones following)
Anyway, I think no one really tested it this way.
I just try to absorb all good ideas “as a sponge” and then try to combine it. I hope that I can control the internal temp with this, as the water-air-mixture should be more or less constant at the generator inlet for different loads instead of a water drip.
Advatages of a central nozzle:
Easier to built and if the Lighting port is directly above (as in my scetch) easy to look directly into the burning hearth of the gasifier. -> Easier to check reaction temp (white glowing char or orange glowing)
Easier to replace or try a different design/material of the nozzle.
For the reaction there should be no big difference. With a central nozzle, the danger of a channel is burned down through the char to the grate (bridging) could be higher. Also the reaction zone could be more centralised and longer (more space between nozzle and grate needed). A design like Krisitjans last one can be more compact.
I thought about this, too. Gary Gilmore is doing this according to the colour of the reaction zone in his simple-fire-gasifiers: White glowing char = too hot, red glowing char = too cool, organge glow is about right.
In numbers: About 900 °C (centigrade) is the optimum point for EGR or added steam: With this temp, the best equilibrium of the reaction is reached: Most of the added EGR or steam is cracked and there is not much CO2 in the gas. With lower temps in the reaction, the amount of CO2 in the gas raises, with hihger temps you waste the surplus heat of the reaction.
Note: the hotter the primary air plus steam, the more steam can be added and the richer the gas.
summary very interesting. I suppose you build a down current generator (coal) for the same reason as Kristijan? (ie to avoid the problems of imperfectly carbonized and wet coal). Do you think that under our temperate climate, the coal exposed for some time to the atmospheric air is very wet for a Gilmore style?
Yes, that’s the reason. Kristijan reported problems with his updraft system with not totally charred coal.
For the same reason, updraft gasifiers were not very popular during WW2, especially at the early years before strict quality standards of car-charcoal were established.
Charcoal can absorb quite a lot of moisture, but it depends on how you store it (warm dry place against a cool moist one) and if it is in a breathable bag or a sealed barrel.
If the char is too wet, you will get a lot af condensation in your cooler and filter. But maybe someone with more practical experneice can give some advice here?
I think I have seen a graph of how much moisture the char can absorb at different air humidities. I will try to find it.
here is the promised information: This graph is from an old book written in German. Its the equilibrium of the moisture of the charcoal with the relative humidity of the surrounding air.
“% relative Feuchtigkeit” means relative humidity of the air
“Wassergehalt in %” means % moisture of the charcoal
The graph is an average, you can see that different samples can differ quite a bit.