Return-Path: Received: from fed1rmmtao12.cox.net ([68.230.241.27] verified) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 359849 for flyrotary@lancaironline.net; Tue, 10 Aug 2004 14:00:44 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.27; envelope-from=daveleonard@cox.net Received: from davidandanne ([68.111.224.107]) by fed1rmmtao12.cox.net (InterMail vM.6.01.03.02.01 201-2131-111-104-103-20040709) with SMTP id <20040810180011.PUKY19941.fed1rmmtao12.cox.net@davidandanne> for ; Tue, 10 Aug 2004 14:00:11 -0400 From: "DaveLeonard" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Re: returnless fuel system Date: Tue, 10 Aug 2004 11:00:17 -0700 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0056_01C47EC9.3850C440" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0056_01C47EC9.3850C440 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit MessageAl, I don't believe that what I am seeing is mostly vapor (although there is possibly some). If your theory is correct then lowering the pressure at the regulator would decrease the pressure drop and less vapor would be made and the return flow would decrease. This is opposite what I have found. Also, my totalizer obviously cannot be used to account for my total fuel, but it is a very useful reminder for fuel management. I start a flight with the totalizer set to say 40gal. So after about an hour it beeps to remind me to switch tanks. But since all my return flow goes to the left tank, switching to the right tank effectively transfers fuel from the right to left tank. When I switch I set the totalizer to remind me when a particular quantity of fuel has been transferred to the left tank, usually about 5 gal. It then beeps again in a few min. to remind me to switch back to the left tank. I find these transferred quantities to be very representative of the amount of gas I know to be in the right tank. The ratings on those pumps are probably for max fuel consumption. They would need to make this number conservative given the variability in flow depending on fuel pressure and other factors. Also, even if it is mostly bubbles (foam), there is still 40-80 gal/hr of something going through that return line so it should be big enough to handle it. Dave Leonard That may be what the meter is reading, but (I believe) not representative. I don't have the data handy, but I once pulled up some specs on the pump (or equivalent) that I got from Tracy, and I think about 30 gph was max, and maybe less at 40psi. One reason for exceptional high readings from a Floscan type meter downstream from a pressure regulator is there are almost always bubbles in the fuel as some low vapor pressure fractionates flash due to the sudden pressure drop, especially if there has been some heating as the fuel traversed the fuel rails. Al Wow, is that true Dave? That seems high, but I have no way of measuring it. I run both pumps all the time (aside from testing them individually during preflight), so I guess my fuel stays pretty well stirred :-) Rusty (yes I know you don't need to run both all the time) ------=_NextPart_000_0056_01C47EC9.3850C440 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
Al, I=20 don't believe that what I am seeing is mostly vapor (although there is = possibly=20 some).  If your theory is correct then lowering the pressure at the = regulator would decrease the pressure drop and less vapor would be made = and the=20 return flow would decrease.  This is opposite what I have=20 found.
 
Also,=20 my totalizer obviously cannot be used to account for my total fuel, but = it is a=20 very useful reminder for fuel management.  I start a flight with = the=20 totalizer set to say 40gal.  So after about an hour it beeps = to remind=20 me to switch tanks.  But since all my return flow goes to the left = tank,=20 switching to the right tank effectively transfers fuel from the right to = left=20 tank.  When I switch I set the totalizer to remind me when a = particular=20 quantity of fuel has been transferred to the left tank, usually about 5=20 gal.  It then beeps again in a few min. to remind me to switch = back to=20 the left tank.  I find these transferred quantities to be very=20 representative of the amount of gas I know to be in the right=20 tank.
 
The=20 ratings on those pumps are probably for max fuel consumption.  They = would=20 need to make this number conservative given the variability in flow = depending on=20 fuel pressure and other factors.
 
Also,=20 even if it is mostly bubbles (foam), there is still 40-80 gal/hr of = something=20 going through that return line so it should be big enough to handle=20 it.
 
Dave=20 Leonard
 

That may = be what=20 the meter is reading, but (I believe) not representative.  I = don’t have=20 the data handy, but I once pulled up some specs on the pump (or = equivalent)=20 that I got from Tracy, and I think about 30 gph was max, and maybe = less at=20 40psi.  One reason for exceptional high readings from a Floscan = type=20 meter downstream from a pressure regulator is there are almost always = bubbles=20 in the fuel as some low vapor pressure fractionates flash due to the = sudden=20 pressure drop, especially if there has been some heating as the fuel = traversed=20 the fuel rails.

 

Al

 

Wow, is=20 that true Dave?  That seems high, but I have no way of = measuring=20 it.  I run both pumps all the time (aside from testing them=20 individually during preflight), so I guess my fuel stays pretty = well=20 stirred :-)

 

Rusty=20 (yes I know you don't need to run both all the = time) 

------=_NextPart_000_0056_01C47EC9.3850C440--