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Steve;
I believe the bubbles you are seeing in the line is very likely the evaporative emissions, that resulted in the development of the return-less fuel system.
I also have never seen foaming in gasoline, but diesel on the other hand, can foam easily. So unless Jet fuel is in the plans I wouldn't worry about that.
Todd
-----Original Message-----
From: Steven W. Boese <SBoese@uwyo.edu>
Reply-To: Rotary motors in aircraft <flyrotary@lancaironline.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: high/low pressure pumps question
Date: Tue, 8 Jun 2010 13:33:19 -0600
Kelly,
When the statement was made that the air would eventually be eliminated through the vent, I didn't mean to imply that it was necessary to have this happen. It would be best to avoid drawing the bubbles directly into the fuel supply line which would only happen if the fuel was returned very close to the supply inlet. On one wing tank, I have the return entering center of the root rib about a foot away from the supply inlet. For the other tank, the return outlet is next to the filler cap which is always above the fuel level and as far away from the supply inlet as is possible. No difference in operation of the two tanks has been noticed.
A reason given for returning the fuel below the liquid level has been to reduce foaming. There may be other reasons. I haven't seen much tendency for gasoline to foam under conditions present in my system.
Steve Boese
RV6A, 1986 13B NA, RD1A, EC2
From: Rotary motors in aircraft [flyrotary@lancaironline.net] On Behalf Of Kelly Troyer [keltro@att.net]
Sent: Tuesday, June 08, 2010 11:26 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: high/low pressure pumps question
Guys,
Very enlightening and truly food for thought to those of us still in the construction stage...........I have just
one more question to ask............Previous info seemed to indicate that return fuel should be entering the
fuel tank at the bottom or at least close to the bottom.............In light of Steve's observations would it
seem reasonable that air bubbles in the return fuel would be eliminated to the tank vent faster if the return
line was at the top or close to the top of the tank ??................
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold
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