Hi Paul,

In my glass goose, I plan to have both upper wing tanks draining into
a common header tank under the engine.  The header tank will contain
twin submersible Walbro pumps, with appropriate check valves,
filters, etc., leading to the fuel rail.  Due to space limitations,
this tank can only hold about 3 gallons.

I can route the return fuel directly back into this tank or to the
inboard fuel sending towers in each wing tank. With the latter, I
don't have a good way to assure equal return flow to both wing tanks,
and the rapid flow might disturb the fuel level sensors.

My question is whether the fuel in a 3-gal tank might get too hot
after being continually cycled through the engine?  If that is
likely, I could probably squeeze in a small fuel cooling radiator
prior to returning to the header tank.

Thanks,

Scott Gettings

That is a good question Scott. At high power the return flow is
less. The thing to do is install some way to measure the temperature
in there and let the engine idle. That will be a worse case scenario.

By sending the fuel back to only one of the main tanks you risk a fuel
transfer problem. Airplanes have crashed because of this. They selected
one tank and it ran out of gas much faster than expected.

Paul Lamar

Scott,
I have test flown two GlaStars with a system similar to what you are
describing.
One had a 1 litre 3rd tank behind the seats and the other had a 1 gallon
tank
under the cowl.  I wasn't able to get the aluminum 3rd tank to feel
warmer than
my hands skin temperature. I don't think you need to worry, but as Paul
suggests try it and monitor the situation.

John  Rogi

A few years ago I started working on an exact solution for this situation.  The physics of this setup is not simple.  As I was developing the equations, I made some estimates of the heat flows and it became evident that the heat flow back to the sump tank was not enough to cause an alarming temperature rise in the sump.  So, I decided to devote my time toward other things and abandoned the effort on the exact solution.

There would, of course, be variations in different installations, but, it is unlikely the sump temperature will rise much.

Aubrey Thompson

I suspect how much fuel is returned is a function of the size of the injectors
you use. We have 4 very large injectors on the time to climb so
at the lower power levels a lot of fuel is returned.

If you have 4 staged injectors like Tracy used (we do not) at cruise
power you might be able to turn 2  off. I don't recall exactly when or what MAN
pressure or RPM that happens in Tracy's set up.

The RX8 uses six. I assume they too are staged.

Paul Lamar

The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove  you.  ACRE NL web
site. http://www.rotaryeng.net <http://www.rotaryeng.net/>You Tube http://tinyurl.com/beqqxas
Copyright 1998-2017 All world wide rights reserved.