X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop-Diagnostic: (direct reply)\eX-PolluStop-Score: 0.00\eX-PolluStop: Scanned with Niversoft PolluStop 2.1 RC1, http://www.niversoft.com/pollustop Return-Path: Received: from frontend2.cwpanama.net ([201.225.225.168] verified) by logan.com (CommuniGate Pro SMTP 4.3c4) with ESMTP id 861230 for flyrotary@lancaironline.net; Thu, 07 Apr 2005 22:21:24 -0400 Received-SPF: none receiver=logan.com; client-ip=201.225.225.168; envelope-from=rijakits@cwpanama.net Received: from [201.224.93.110] (HELO usuarioq3efog0) by frontend2.cwpanama.net (CommuniGate Pro SMTP 4.2.1) with SMTP id 38550738 for flyrotary@lancaironline.net; Thu, 07 Apr 2005 21:26:14 -0500 Message-ID: <009801c53be1$8ce81eb0$6e5de0c9@usuarioq3efog0> From: "rijakits" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: rule of thumb and RV-3 sizes- Date: Thu, 7 Apr 2005 21:20:36 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0094_01C53BB7.A3D1B250" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 This is a multi-part message in MIME format. ------=_NextPart_000_0094_01C53BB7.A3D1B250 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit MessageAl, I did mean "intake"! On both their planes, the Mustang II and the RV-4 the intake area is biiger than the exit!! As mentioned, if you need I can email the scans of the mag! You also might want to read up on: http://www.cafefoundation.org/aprs/RV-4.pdf Thomas J. ----- Original Message ----- From: Al Gietzen To: Rotary motors in aircraft Sent: Wednesday, April 06, 2005 11:29 PM Subject: [FlyRotary] Re: rule of thumb and RV-3 sizes- ..cut Note: the exhaust area requirement is greater than the inlet combination of oil and coolant due to the now considerable hotter air temperature. Rule of thumb: Coolant air inlet opening for 200 HP coolant cooled engine ~60 sq. in., oil inlet opening ~30 sq. in. equals a total opening of 90 sq. in. A good place to start with exhaust opening is 1.4 times the inlets or 126 sq. in. Close the exit area down with cowl flaps to as little as 80% of the inlet combination at cruise conditions! ...cut I do understand that an air-cooled installation is a different animal, but by the end of the day ( or at the cowl exit...for that matter) everything is air cooled. The interesting thing is that both run a intake/exit ratio of 78%, the intake (I think you meant 'exhaust) being bigger - just about confirming the above statement! Schmidtbauer mentiones the " rule of thumb" - exit about 150% of inlet. I think for our purposes, the 1.5 ratio is more applicable than 1.28. It can be lower IF you have well shaped entrance and exit ducting. Typically we focus on entry ducting, and then have rapid expansion at the exit from the core - sudden expansion pressure loss; losing all momentum and then, usually a rather sudden acceleration out a fairly small opening. Definitely less than optimum. I don't think there is a great difference on the amout of cooling necessary, as the efficiency of both engines are fairly close. So some heat goes out the exhaust and the rest has to be cooled. For sure you need different ducting, but the amount of heat energy should be about the same and you want to get rid of it with the least drag, either way. You're right. The biggest difference is the higher rejection temp, and larger delta T of the air on the air-cooled engines allows for a lower air flow rate. Al ------=_NextPart_000_0094_01C53BB7.A3D1B250 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Al,
 
I did mean "intake"!
On both their planes, the Mustang II and the = RV-4 the=20 intake area is biiger than the exit!!
As mentioned, if you need I can email the scans = of the=20 mag! You also might want to read up on: http://www.cafefound= ation.org/aprs/RV-4.pdf
 
Thomas J.
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Wednesday, April 06, 2005 = 11:29=20 PM
Subject: [FlyRotary] Re: rule = of thumb=20 and RV-3 sizes-

..cut

Note:  the=20 exhaust area requirement is greater than the inlet combination = of oil=20 and coolant due to the now considerable hotter air = temperature.  Rule=20 of thumb:  Coolant air inlet opening for 200 HP coolant cooled = engine=20 ~60 sq. in., oil inlet opening ~30 sq. in. equals a total opening of = 90 sq.=20 in.  A good place to start with exhaust opening is 1.4 times = the inlets=20 or 126 sq. in.  Close the exit area down with cowl flaps to as = little=20 as 80% of the inlet combination at cruise=20 conditions!

 

...cut

 

I do=20 understand that an air-cooled installation is a different animal, = but by the=20 end of the day ( or at the cowl exit...for that matter) everything = is air=20 cooled. The interesting thing is that both run a intake/exit ratio = of 78%,=20 the intake (I think you meant=20 =91exhaust) being bigger - just = about=20 confirming the above statement!

 

Schmidtbauer=20 mentiones the " rule of thumb" - exit about 150% of = inlet.

 

I think = for our=20 purposes, the 1.5 ratio is more applicable than 1.28. It can be = lower IF you=20 have well shaped entrance and exit ducting.  Typically we focus = on=20 entry ducting, and then have rapid expansion at the exit from the = core =96=20 sudden expansion pressure loss; losing all momentum and then, = usually a=20 rather sudden acceleration out a fairly small opening.  = Definitely less=20 than optimum.

 

I=20 don't think there is a great difference on the amout of cooling = necessary,=20 as the efficiency of both engines are fairly close. So some heat = goes out=20 the exhaust and the rest has to be cooled. For sure you need = different=20 ducting, but the amount of heat energy should be about the same and = you want=20 to get rid of it with the least drag, either way.

 

You=92re=20 right.  The biggest difference is the higher rejection temp, = and larger=20 delta T of the air on the air-cooled engines allows for a lower air = flow=20 rate.

 

Al

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