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Ben, Can you discuss the long term effects of running wood gas through an engine?  RSS feed

 
Peter Hartman
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Location: springfield, MO
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Hello Ben, Good to see you on the forum. Can you discuss the life expectancy and additional maintenance on an engine that runs on wood gas?
 
Ben Peterson
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Peter:

Clean, dry woodgas that has been fully broken down from a solid into a gas (no tar) is a good fuel even for extended use. Life expectancy should not be compromised. You will get small amounts of micron size soot in the gas stream. If you quench the gas and then heat it back up this soot floats into the combustion chamber and burns beautifully. The amount of soot will depend on how tight you make your filter. You want to balance clean gas with good flow.

Aluminum parts can oxidize from the woodgas, so I try to use stainless and plastic where possible. But the thin layer of soot helps coat aluminum intakes and doesn't generally present a problem there.

You may notice your oil getting darker faster than normal from the fine soot that bonds to the cylinder oil and washes down. If your engine oil change cycle calls for 200 hours, then move the change up to 160 hours.

If you make gas that had unburned oils in it (tar) it can build up a layer on the intake valves and cause a valve to stick. Most times it doesn't cause damage, but it is inconvenient to get out the acetone and scrub the valve stems while in place. This is why machine design is so important. With good sized dry wood tar isn't something to worry about. If you aren't sure, then practice on an old engine until you feel ready to hook it up to a nicer one. User skill is important.

You may hear people talk about the hydrogen content of the gas and the chance of embrittlement of metal parts, but embrittlement is something that happens more in pressurized gases. Your gas is in a vacuum, so it's not a real concern.



 
Mat Smith
Posts: 125
Location: Gold Coast Hinterland QLD, Australia
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Ben Peterson wrote:With good sized dry wood tar isn't something to worry about.


Curious on this one - what's the standard for 'dry wood' in regard to getting a clean burn in a gasifier?
I live in the subtropics where the humidity is very high in summer. Can atmospheric humidity create problems, or once dried would the moisture content of the wood stay low enough to disregard atmospheric humidity?
Thanks
Mat
 
Ben Peterson
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Mat,

20% moisture or less is the ideal to shoot for. You have humid air, but you also have aggressive sunshine to drive the water off. I would use a moisture meter to double check the final result.

Tropical wood can be very dense so you may want to play with the chunk sizing, perhaps going smaller to compensate or boring out the jets a little bit to let in more air.

Thanks,
See you guys tomorrow
Ben
 
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