Farymann

[Islander]

The Farymann range of engines look quite good for conversion from diesel to wood gas. Does anyone have experience of these units? See http://www.farymann.de/43w.aspx

[Jumper]

It is very difficult to convert this engine, the compression 19.5 : 1 is much to high for woodgas. I think woodgas could handle max. 14:1 or something like that. so you will need another piston and of course you have to find a spark plug that fits into the whole of the "glow plug" ...
Good luck and keep us up to date !

[Islander]

It is very difficult to convert this engine, the compression 19.5 : 1 is much to high for woodgas. I think woodgas could handle max. 14:1 or something like that.

I disagree. I have never run wood gas on a CR of less than 16.5:1 and usually choose 18-19:1. There are studies from IISC in Bangalore that show wood gas is fine up to 22:1 but I have never tried this. The problem with low compression ratios is that efficiency falls off and so, because the gas is already weak (say 5-6MJ/Nm3) the power available from the engine is downrated quite a lot. A 30% engine downrating is the same as a 30% price increase for your generator!

Engine knock (pre-detonation) can be a problem with some wood gas producers where the hydrogen content is high, but this is best dealt with by changing the spark timing rather than lowering the CR.

So I think 19.5:1 from Farymann is fine. As to the problems of converting to spark, you may be right. Has anyone tried this engine? (I have only done Perkins before).

[Islander]

Jumper

Here is a link to one of the interesting IISc papers on producer gas engines: http://eprints.iisc.ernet.in/11164/1/record168.pdf

The part about carburettors is not interesting but the analysis of compression ratios and ignition timing is well worth reading.

[Jumper]

Oh, I am very sorry about this wrong information
But there are still two things:
Woodgas is not normed ... Peters gasifier produces another gas than Pascals.
And of course the Problem with the spark plug. There you could ask some farmers with biogas motors, they had this problem too.

[Islander]

Woodgas is not normed

Very true. A "Drizzler" set-up produces much more hydrogen than an ascending co-current. And even the same gasifier produces very different gas at different times: wood moisture, air humidity, lots of variables ...... but who said this was easy?