Paul and group,

I'm plannning on a 2.5 gallon header tank for my Glass Goose, with
in-tank Walbro pumps.  The header tank is planned to be gravity-fed from
BOTH high-wing tanks to keep things simple. Ideally, the fuel return
should come back to the header.

An issue that has been discussed is the potential heat generated by the
pumps and the engine recirculation.

I tested a 2 gallon tank with one 190lph high-pressure Walbro in-tank
pump running against a 60 psi fuel pressure regulator in a closed system.

I found that there was a 8-10 degree F temperature rise over 15 minutes
with one pump running.  The pump also started at about 6.2 amps current
draw and gradually rose to 7.4 amps as the temperature rose.

This was a pure recirculating system, with no incoming fuel to cool the
pump.  This should give a higher-than-expected temperature rise.
Factors making the temp lower than in real operation include: no
incoming heat from the fuel rail return, and no heat from the backup
pump running during takeoff and landing.

Is this degree of heat buildup a potential problem?

If it is important to minimize heat buildup, I might be able to make the
header tank a little larger.  Adding a fuel cooling radiator for the
return fuel is another possibility.

Yet another possible mitigation would be to return the fuel to the wing
tanks, but I know from previous threads that it is difficult or
impossible to assure an even return. Using an Andair valve to fill the
header from one wing tank and return fuel to that same tank would remove
some of the simplicity and safety of a BOTH always-on system that keeps
the header full at all times.

In the BOTH position and about 6" of head pressure, I get 72 gph of
gravity flow through my fuel valve. This drops to 42 gph in the right or
left-only position.   If uneven fuel return to wing tanks might be an
issue in this scenario, I could easily add a separate 3/8"
interconnecting tube  between the two tanks to help keep them
equilibrated if the fuel needs to return to the wing tanks.

Comments or suggestions?

Scott Gettings
BTW, thanks for the suggestions on the radiators!
I'll submit drawings for these in the near future.




The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.