X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 1 [X] Return-Path: Sender: To: lml Date: Tue, 05 Dec 2006 16:49:01 -0500 Message-ID: X-Original-Return-Path: Received: from [68.98.211.24] (HELO systems3.net) by logan.com (CommuniGate Pro SMTP 5.1.3) with ESMTP id 1643919 for lml@lancaironline.net; Tue, 05 Dec 2006 15:30:43 -0500 Received-SPF: none receiver=logan.com; client-ip=68.98.211.24; envelope-from=cberland@systems3.net Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C718AC.35BB487A" Subject: RE: [LML] Friction loss X-MimeOLE: Produced By Microsoft Exchange V6.5 X-Original-Date: Tue, 5 Dec 2006 13:30:31 -0700 X-Original-Message-ID: <87C33F695961494D886EB3B6C8A476511670F1@s3server.Systems3.local> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Friction loss Thread-Index: AccYnGtk25sDP14wR2G2KToFLm28GQADhnpw From: "Craig Berland" X-Original-To: "Lancair Mailing List" This is a multi-part message in MIME format. ------_=_NextPart_001_01C718AC.35BB487A Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Paul, All dyno testing of automotive engines I have done suggests that friction is linear relative to rpm as you suggest. That is of course unless you deprive a sliding surface of lubrication. All friction studies I have done were on "motoring" engines therefore any added ring drag due to compression loads were not comprehended. On the relatively constant speed of our aircraft engines, I can't imagine it would have any proportional effect. I suspect prop effientcy and other similar factors are bigger guns on reducing bsfc numbers that the internal engine parts when it comes to minor engine speed changes. Certainly timing would be a factor on naturally aspirated engines at altitude. Craig Berland ________________________________ From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Paul Lipps Sent: Tuesday, December 05, 2006 11:37 AM To: lml Subject: [LML] Friction loss Friction or Coulomb* loss is independent of sliding rate. However, the friction loss in pounds, when multiplied by rate, yields hp. As rpm goes up, so does the friction hp. Also, as rpm goes up, engine power, at a given MEP, also goes up proportionatly. It would seem that the friction hp would maintain a certain percentage of the overall power input, and I'm not sure how this would cause a change in SFC. Also, I'm not sure of the effect of increased MEP on the coefficient of friction. Does it go up with the increased pressure of the rings against the cylinder walls at higher MEP? Keeping MEP max certainly cuts down on pumping loss! I seek enlightenment! =20 *Charles Augustin de Coulomb ------_=_NextPart_001_01C718AC.35BB487A Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Paul,

All dyno testing of automotive engines I have = done suggests=20 that friction is linear relative to rpm as you suggest. That is of = course unless=20 you deprive a sliding surface of lubrication. All friction studies = I have=20 done were on "motoring" engines therefore any added ring drag due to = compression=20 loads were not comprehended. On the relatively constant speed of our = aircraft=20 engines, I can't imagine it would have any proportional effect. I = suspect=20 prop effientcy and other similar factors are bigger guns on reducing = bsfc=20 numbers that the internal engine parts when it comes to minor = engine speed=20 changes. Certainly timing would be a factor on naturally aspirated = engines=20 at altitude.

Craig Berland

From: Lancair Mailing List=20 [mailto:lml@lancaironline.net] On Behalf Of Paul = Lipps
Sent:=20 Tuesday, December 05, 2006 11:37 AM
To: lml
Subject: = [LML]=20 Friction loss

Friction or Coulomb* loss is independent of = sliding rate.=20 However, the friction loss in pounds, when multiplied by rate, = yields hp.=20 As rpm goes up, so does the friction hp. Also, as rpm goes up, engine = power, at=20 a given MEP, also goes up proportionatly. It would seem that the = friction hp=20 would maintain a certain percentage of the overall power input, and I'm = not sure=20 how this would cause a change in SFC. Also, I'm not sure of the effect = of=20 increased MEP on the coefficient of friction. Does it go up with = the=20 increased pressure of the rings against the cylinder walls at higher = MEP?=20 Keeping MEP max certainly cuts down on pumping loss! I seek=20 enlightenment!

*Charles Augustin de = Coulomb

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