On 04/27/2012 04:53 AM, klinefelter.kevin@gmail.com wrote:
> If the return fuel enters the top of the tank (under a little pressure) and
> expands
while falling to the level of fuel in the tank,
Fuel is not compressible.
However boiling temperature decreases with lower pressure. So if the
fuel is hot, the free fall will promote evaporation of the fuel due to
the sudden drop of pressure.
So, the only way to release hot fuel properly is to release it below the
fuel level.
> This also does away with any need for a second fuel valve and it's weight and
complexity in an emergency.
Well, a one-way-valve is a low weight and low complexity solution. Fuel
can only flow into the tank but never out of it.
Even when you have the fuel return in the top of the tank, I would still
advise a one-way valve. Fuel fumes also burn excepionally well, and of
course it is always possible that you end up inverted.
I recall the story of one Europa-flyer (I believe it was PH-ZZZ ) who
had an emergency and ended up unharmed but inverted. The doors where of
course blocked, and fuel started dripping on the trapped pilot. Luckily
a fire was not started and he was rescued in time.
So for this reason I don't want any port in the tank where fuel can
escape. This includes the sight gauge. I have consequently scrapped the
sight gauge.
Frans
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