Re: GAS-L: can't get my gas to light!

[Joacim Persson <joacim@ymex.net>]

On Sat, 17 Feb 2001, Arnt Karlsen wrote:

> ..you use an heat exchanger to heat up primary air going 
> into the gasifiers combustion zone?  (The right thing to do.)

An external heat exchanger, yes.  I decided to have no outer mantle on the
gasifier, so I had to pre-heat the air some other way. It's not very
optimal though. I built it for the first car originally, and had to trade
off some effciency to get it compact enough to fit in. (33 2cm diameter
pipes in three rows, ...55cm long, I think. Should make about one square
meter, but a heat exchanger should be long and lean rather than short and
wide to be efficient, and this one is too chubby. It's a choice between
cost in pressure drop and heat transfer efficiency too of course.)

> ..I used stripped down vacuum cleaner motor fans, sealing 
> all leaks, they lift water about 2 meters up.  Most are 
> rated to about 100°C, so, you will want to either cool 
> your gas or drive your fan some other way.  
> I have observed life spans from 2 to 20 hours on 
> 200°C dry gas, and within 5 minutes on waterbubbled 
> tarry gas, rather spectacular deaths.  ;-)

I can imagine a couple of seconds, if I forget to close the secondary air
valve at the gas mixer. ;)   I have a homebuilt fan in metal (which isn't
dimensioned right for that fairly low rpm, but powerful enough motor; a
cooler fan motor from a Saab 99), attaeched to the main gas pipe via a back
valve made from tube rubber. I've already managed to fry two back valves by
forgetting to close the mixer valve: the flame disappears down the test
flame pipe...oops Sometimes there's just a bang and the flame goes out, but
sometimes the flame find a new stable point just before the fan. After
watching a friends plastic fan melting in an instant for the same reason, I
decided I didn't want a plastic fan, not if it's mounted permanently
anyway.  If it's `hand held' I can pull it off the pipe if the flame
backfires, but it takes a little longer to dive into the car and shut the
mixer handle. The back valve is easy to replace though. I could add another
back valve on the gas pipe from the fan to the mixer to avoid the risk of
frying the fan, but then I'd get a permanent extra pressure drop across it.

I do have a 12V vacuum cleaner too, my first fan, which still works I
think, although rather clogged up by now. I just sealed it and attached a
couple of tube stubs to each end, all using silver tape, a fine invention
indeed. (the tape, that is. The fan looks terrible.)


Joacim
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