jan.mevis(at)informavia.b
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 Posted: Sun Mar 23, 2008 2:06 am Post subject: E10 fuels for radial engines |
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A lot of Yak-pilots in Europe use mogas simply because it is cheaper (1.4
euro per LITER instead of 2 euro per LITER). The Russian inspectors we asked
about this don't mind. And another argument is that the engines have to be
overhauled anyway after a few hundred hours. But with the ever higher prices
of engines ....
The newer mogas fuels with up to 10 % of Ethanol do cause problems. Ethanol
is a very good solvent, and could cause sediments in the fuel system. This
may clogg up filters etc. But the additional Ethanol is necessary to obtain
a higher octane number, since we must not use any tetraethyl lead anymore.
Thus sooner or later - when avgas will be banned by the governments - we
will have to find adequate solutions.
The problem is indeed the fact that Ethanol binds with water. It is an
efficient drying agent. This ethanol/water emulsion can phase-separate from
the gasoline if allowed to stand still, and then forms a corrosive layer on
the bottom of the fuel tank. The watermolecules form very large clusters
when they take the ethanol out of the gasoline. So they form droplets. Due
to the withdrawal of the Ethanol, the fuel's octane number might be too low.
I think a problem is, that we might not see a lot of this phase-separation
in our fuel reservoirs (especially when doing aerobatics ...). So we get
these emulsions into the fuel pump. The water comes partly in place of the
gasoline, so the pump with loose a lot of its lubrication.
A water-emulsion might raise the viscosity of the fuel - water mixture. The
combustion could be less efficient with unburnt gasoline molecules. This
causes dirty plugs and valves and so on.
Could'nt we try to de-emulgate the water? It would be better to burn
microscopically small water particles.
Just some thoughts, that may be completely wrong. I do know that this is a
very difficult subject.
Jan Mevis
YK50 RA2005K
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