Another option has occurred to me for single house size units. Turbines
always lose efficiency as they get smaller, with a higher surface/volume
ratio. Since I'm only looking for pressures in fractions of
atmospheres, vane pumps and/or rootes blowers might be more suitable.
Could regular injections of a solvent or cleaning solution prevent
excess tar build-up?
Bob
On 17-01-03 01:39 PM, Bob Stuart wrote:
Thanks again. This has saved me a lot of trial and error.
It sounds like I should try using plenty of air to minimize CO
content, preheated for secondary combustion, and a cyclonic separator
for the ash, probably with another filter as well, perhaps
electrostatic? Air lubricated bearings seem wise as well. The
impeller case should open with the feed door, swinging a rotary wire
brush into contact with the turbo, angled to both clean and turn it
slowly. The magnet needs a strong enclosure to handle the centrifugal
force, and careful balancing.
As usual with gasifiers, price does not go down well for a
small-capacity rig, so solar may have this beat for home use now.
Maybe I've just dreamed up a good way to get forced draft on a
condensing stove using low-tech impellers. I hope someone will find
this inspiring for a larger scale unit.
Bob
On 17-01-03 12:06 PM, Doug wrote:
Hi Bob,
Coking is caused by the reversion of CO gas back to CO2 and carbon
soot, where-by the hot gas entering the turbo is over a temperature
of say 500C. If you were to first combust this gas with air so that
only CO2 hot gas drove the turbo, the problem then becomes one of ash
particle impaction onto the impeller blades. Naturally you get heaps
of waste heat, but the practicalities of cleaning the impeller daily
or after each refueling is a real party pooper! The only safe way is
to use ceramic filter candles, expensive and needing compressed air
to pulse clean.
Not sure maths is all that's required to make your idea work in the
way you perceive without adding energy. Steam and coke need the high
temperatures and pressures associated with turbo operation, but in
differing design application. I'm sure others will offer you comment
to develop this interesting concept.
Doug Williams.
On 03/01/17 12:56, Bob Stuart wrote:
Thanks, Doug.
I'd been worried about coking, so you have saved me a test setback.
Will a cyclonic separator upstream help? I've never dealt with
coking, so I don't even understand its vulnerabilities. Would a
good wire brushing with each new load of fuel do the trick? That
could be automated pretty easily.
All the ICEs have to deal with the power for a compression stroke.
I'll do the math on intake vs exhaust volume before building, of
course, to make sure the turbo efficiency is a minor fraction of the
equations. With a built-in air pump, a condensing flue is easy to
arrange, and it recaptures any heat used to burn wet wood. Would
the steam help clean coke? It eats carbon in an ICE.
From what I know about generators, a rapidly spinning magnet is
quite effective. Those little DC-DC voltage converters are
surprisingly small and efficient, running at very high frequencies.
Bob
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