Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 351530 for flyrotary@lancaironline.net; Wed, 04 Aug 2004 07:16:25 -0400 Received-SPF: none receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from EDWARD (cpe-069-132-183-211.carolina.rr.com [69.132.183.211]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i74BFrNs018766 for ; Wed, 4 Aug 2004 07:15:54 -0400 (EDT) Message-ID: <002701c47a14$6db99530$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: May not work above 8000 MSL was [FlyRotary] Re: Oil injection, and more Date: Wed, 4 Aug 2004 07:16:02 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0024_01C479F2.E67CED90" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0024_01C479F2.E67CED90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable You may be correct, Al. Without testing it would be hard to say.=20 No question my theory could be wrong - but as you say something must = have made Atkins come to the conclusion that the metering pump does not = work above 8000. If his claim is valid - then there must be some cause = related to altitude. The only part of the fuel metering system that = would be affected by altitude that I can see is the oil feed from the = shaft boss to the pump. =20 We know that as pressure changes across an aperture will cause the flow = rate to change - whether (as you point out) the difference due to = altitude is significant enough to account for any lessening of oil flow = is the question. Whether or not a few pi would ensure adequately flow = sufficient CCs of oil will depend on the size of the orifice through = which the oil flows. I agree if the aperture is sufficiently large = then a few PSI change in pressure will make little (if any) difference = in flow. However, if the orifice is small and the flow barely adequate = to meet the needs say at 14.7 psi then 11 psi could lessen the flow. = Not claiming that flow would cease, but it may well be diminished. My 0.02 Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, August 04, 2004 1:07 AM Subject: [FlyRotary] Re: May not work above 8000 MSL was [FlyRotary] = Re: Oil injection, and more Subject: [FlyRotary] May not work above 8000 MSL was [FlyRotary] Re: = Oil injection, and more Dave may be correct, Perry. Here is what I think could occur. First, The oil meter pump itself = is a positive displacement pump.=20 Therefore, from the standpoint of the pump it will always disperse any = oil fed to it into the injectors and combustion chamber under some = amount of pressure. However, the shaft opening that drives the pump = also provides for the oil flow from inside the Engine Front mount into = the metering pump. There is a hole in the boss of the metering pump = shaft (on the inside of the front housing) that is open to the = atmosphere. At sea level of course this hole in the boss results in 14.7 psi of = pressure on the oil in the meter shaft. So as the positive displacement = pump opens a chamber - the oil flows into the chamber with the help of = this 14.7 (or what ever the differential between the pressure in the = pump chamber and the atmosphere- it will something less than 14.7 but = probably greater than 12?) and gets "squirted" toward the injectors = underpressure. Ed; I hear what you're sayin', but I really don't think so. How much = pressure does it take to make hot oil flow through a short length of = tube (or a port in the pump) at a VERY low flow rate? Very little. = We're talking a few cc/min; and I'd guess even a couple of psi, would do = the job nicely. And at 8000 ft we still have; what, about 11 psi. As we go to higher altitudes it is probably more likely that we'd get = vapor lock upstream from the fuel pump before we stop getting oil from = the metering pump.=20 This is just off the top of my head, so, you know, maybe there is = something I overlooked. The question is: what phenomenon was Atkins = observing? He obviously had some reason for his statement. Al ------=_NextPart_000_0024_01C479F2.E67CED90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
You may be correct, Al.  Without = testing it=20 would be hard to say. 
 
 No question my theory could be = wrong - but as=20 you say something must have made Atkins come to the conclusion that the = metering=20 pump does not work above 8000.  If his claim is valid - then = there=20 must be some cause related to altitude. The only part of the fuel = metering=20 system that would be affected by altitude that I can see is the oil feed = from=20 the shaft boss to the pump. 
 
We know that as pressure changes across = an=20  aperture will cause the flow rate to change - whether (as you = point out)=20 the difference due to altitude is significant enough to account for any=20 lessening of oil flow is the question.  Whether or not a few pi = would=20 ensure adequately flow sufficient CCs of oil will depend on the size of = the=20 orifice through which the oil flows.   I agree if the aperture = is=20 sufficiently large then a few PSI change in pressure will make little = (if any)=20 difference in flow.  However, if the orifice is small and the = flow =20 barely adequate to meet the needs say at 14.7 psi then 11 psi could = lessen the=20 flow.  Not claiming that flow would cease, but it may well be=20 diminished.
 
My 0.02
 
Ed
 
 
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Wednesday, August 04, = 2004 1:07=20 AM
Subject: [FlyRotary] Re: May = not work=20 above 8000 MSL was [FlyRotary] Re: Oil injection, and more

Subject:=20 [FlyRotary] May not work above 8000 MSL was [FlyRotary] Re: Oil = injection, and=20 more

 

Dave may be correct,=20 Perry.

 

Here is what I think = could=20 occur.  First, The oil  meter pump itself is a positive = displacement=20 pump.

 

Therefore, from the = standpoint of=20 the pump it will always disperse any oil fed to it into the injectors = and=20 combustion chamber under some amount of pressure.  However, the = shaft=20 opening that drives the pump also provides for the oil flow from = inside the=20 Engine Front mount into the metering pump.  There is a hole = in the=20 boss of the metering pump shaft (on the inside of the front housing) = that is=20 open to the atmosphere.

 

  At sea level of = course this=20 hole in the boss results in 14.7 psi of pressure on the oil in the = meter=20 shaft.  So as the positive displacement pump opens a = chamber  - the=20 oil flows into the chamber with the help of this 14.7 (or what ever = the=20 differential between the pressure in the pump chamber and the = atmosphere- it=20 will something less than 14.7 but probably greater than 12?)  and = gets=20 "squirted" toward the injectors underpressure.

 

Ed;

 

I hear = what you=92re=20 sayin=92, but I really don=92t think so.  How much pressure does = it take to=20 make hot oil flow through a short length of tube (or a port in the = pump) at a=20 VERY low flow rate?  Very little.  We=92re talking a few = cc/min; and=20 I=92d guess even a couple of psi, would do the job nicely.  And = at 8000 ft=20 we still have; what, about 11 psi.

 

As we go = to higher=20 altitudes it is probably more likely that we=92d get vapor lock = upstream from=20 the fuel pump before we stop getting oil from the metering pump.=20

 

This is = just off=20 the top of my head, so, you know, maybe there is something I = overlooked.=20  The question is: what phenomenon was Atkins observing?  He=20 obviously had some reason for his statement.

 

Al

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