Return-Path: Received: from corpprd-pxy2.canfor.ca ([198.162.160.3] verified) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 753299 for flyrotary@lancaironline.net; Mon, 21 Feb 2005 16:35:16 -0500 Received-SPF: none receiver=logan.com; client-ip=198.162.160.3; envelope-from=Steve.Bartrim@canfor.com Received: from canformail1.canfor.ca (canformail1.canfor.ca [199.60.193.29]) by corpprd-pxy2.canfor.ca (Build 103 8.9.3p2/NT-8.9.3) with ESMTP id NAA08107 for ; Mon, 21 Feb 2005 13:34:29 -0800 X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C5185D.1F59DF28" Subject: RE: [FlyRotary] For Todd "Vena Contracta" was Re: Returnless Fuel System - Fuel Cooler Date: Mon, 21 Feb 2005 13:34:28 -0800 Message-ID: <091A2D42FAF91A41B84750D269FC97E72B3115@canformail1.canfor.ca> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [FlyRotary] For Todd "Vena Contracta" was Re: Returnless Fuel System - Fuel Cooler Thread-Index: AcUV/U2TdKws6PvFSbG+Cv/vz+cG+QCVgmig From: "Bartrim, Todd" To: "Rotary motors in aircraft" This is a multi-part message in MIME format. ------_=_NextPart_001_01C5185D.1F59DF28 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hi Leon; I'm a little late responding as I spent the weekend rebuilding my dirt bike with one of them ole fashioned piston engines what go up & down to make something go round 'n round? What a goofy idea! Anyways, back to the subject at hand. Pressure recovery ?... so what? Well without pressure differential there is no flow. None. I realize that jets are used to meter flow and that a restriction is an impediment to flow, however my point was that if the EFI pump has an outlet of say 1/8" into a 3/8" line (or in Bob's case, his 1/4" return line) it does not have the equivalent flow of a 1/8" line. While it will not have full flow of an unrestricted line due to permanent pressure loss, it will recover much of its pressure resulting in a much greater flow than would be provided by a 1/8" tube. To calculate this the Beta ratio of the "orifice" is required, however it really isn't that important. Besides, I can't find right now the required formula. I should get back to studying this as I return to school for 4th year in 2 months and I can be assured that there will be at least one twisted question concerning this on the incoming exam. Someone had mentioned drilling out the pump outlet to reduce this restriction, but that would be a really bad idea. The pump outlet is usually sized smaller than the pipe that it is sized for in order to provide adequate back pressure to the pump to prevent cavitation. If you drill out this outlet, then bubbles can/will form in the impellor and the resulting cavitation will result in less flow and quite possibly the vapour lock that we are trying to avoid. This restriction does not diminish the requirement for a proper sized tube to be plumbed to it in order to achieve rated flow. Just my 2 bits worth Cheers Todd So I just can't see what the size of an attached pipe has to do with the flow rate through a "vena contracta" ("vena constricta"??). You also say "but much of this pressure is recovered downstream" Hmmmmmm, ... I say "so what"??. We aren't interested in pressure drops or pressure recovery, ... it's flow rates that are the SOLE issue, and the capacity of an open flow 1/4 inch line to get rid of the fuel dumped by the regulator. =20 =20 =20 Leon =20 ------_=_NextPart_001_01C5185D.1F59DF28 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable RE: [FlyRotary] Returnless Fuel System - Fuel = Cooler
Hi Leon;
    I'm a little late responding as I = spent the=20 weekend rebuilding my dirt bike with one of them ole fashioned piston = engines=20 what go up & down to make something go round 'n round? What a goofy=20 idea!
    Anyways, back to the subject at = hand. Pressure=20 recovery ?... so what? Well without pressure differential there is = no flow.=20 None. I realize that jets are used to meter flow and that a restriction = is an=20 impediment to flow, however my point was that if the EFI pump has an = outlet of=20 say 1/8" into a 3/8" line (or in Bob's case, his 1/4" return line) it = does not=20 have the equivalent flow of a 1/8" line. While it will not have = full flow=20 of an unrestricted line due to permanent pressure loss, it will recover = much of=20 its pressure resulting in a much greater flow than would be = provided by a=20 1/8" tube. To calculate this the Beta ratio of the "orifice" is = required,=20 however it really isn't that important. Besides, I can't find right now = the=20 required formula. I should get back to studying this as I return to = school for=20 4th year in 2 months and I can be assured that there will be at least = one=20 twisted question concerning this on the incoming = exam.
    Someone had mentioned drilling out = the pump=20 outlet to reduce this restriction, but that would be a really bad idea. = The pump=20 outlet is usually sized smaller than the pipe that it is sized for in = order to=20 provide adequate back pressure to the pump to prevent cavitation. If you = drill=20 out this outlet, then bubbles can/will form in the impellor and the = resulting=20 cavitation will result in less flow and quite possibly the vapour lock = that we=20 are trying to avoid. This restriction does not diminish the requirement = for a=20 proper sized tube to be plumbed to it in order to achieve rated=20 flow.
    Just my 2 bits = worth
Cheers
Todd

So I just can't see what the = size of an=20 attached pipe has to do with the flow rate through a  "vena = contracta"=20 ("vena constricta"??).  You also say "but much of this pressure = is=20 recovered downstream"  Hmmmmmm, ... I say "so what"??.  We = aren't=20 interested in pressure drops or pressure recovery, ... it's flow = rates=20 that are the SOLE issue,  and the capacity of an open = flow 1/4=20 inch line to get rid of the fuel dumped by the regulator.  =
 
 
Leon  =
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