X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-02.southeast.rr.com ([24.25.9.101] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2177668 for flyrotary@lancaironline.net; Sat, 14 Jul 2007 15:00:04 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-02.southeast.rr.com (8.13.6/8.13.6) with SMTP id l6EIwRG7009892 for ; Sat, 14 Jul 2007 14:58:27 -0400 (EDT) Message-ID: <001c01c7c649$04dccd00$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: FW: Oil cooler air flow Date: Sat, 14 Jul 2007 14:58:51 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0019_01C7C627.7D8152C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0019_01C7C627.7D8152C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sorry, Al, I left out some of the details. As you know pressure = recovery is not 100% in a duct, there is still some air velocity. The = streamline duct (according to K&W) will recover (maximum) 84% of the = free air stream dynamic pressure potential available at the inlet (turn = it into static pressure). Therefore, I took your free stream dynamic = pressure in your message the 9.5 " at the inlet and multiplied it by = 0.84 to see what a theoretically best streamline duct should give you. = Since few (if any of us) have the room for a full-length Streamline = duct, we are unlikely to get the 84% figure - but I use it as sort of a = measuring rod. This is the URL where I got the information. Apparently the author did = some research on WWII liquid cooled aircraft and obtained the = information form that material. I have no further information on it. http://www.ch601.org/resources/cooling_systems1.htm Ed ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Saturday, July 14, 2007 12:37 PM Subject: [FlyRotary] Re: FW: Oil cooler air flow Hi Al, If a "full-strength" Streamline duct were tested under the conditions = of=20 9.5"H20 at the entranced to the inlet then at the widest part of the = duct=20 you should theoretically measure 9.5*.84 =3D 7.98. Ed; Perhaps you could enlighten me on this. Where does the .84 come from? = Is this static pressure? I thought that as the air was expanded and = slowed, dynamic pressure was converted to static pressure and the value = increased. You've obviously studied this more than I. Regarding your second sketch, since you do have slower moving boundary = layer air moving next to the skin of the fuselage (and duct), the vane = would probably help it turn around the corner. However, you are still = ingesting slower moving air with less dynamic pressure to recover from = it. It is my opinion (no experience or hard data) that moving your = inlet fuselage side of your inlet opening approx 1 1/2 - 2"away from = the fuselage would make an improvement. =20 You are very right about that. Actually in the location that it is, = even an inch or less away from the surface would make a big difference. = Keep in mind that the scoop is about 23" wide with about 1 =BC" opening. = How do you get BL diversion with that configuration? Of course this = configuration began the way it did because another Velocity builder had = put his standard aircraft oil cooler (for a Lyc) in the same location, = and said it worked great without a scoop - just the differential = pressure above and below the wing was enough. Go figure. As I as looking over this diagram more carefully = (Winginstallation.jpg), it became apparent that it main point was to = show one duct installation with the inlet stand off (bottom one) and the = other without inlet stand off using a vane to assist the airflow. So, = one could draw the conclusion that you have a choice? either use inlet = stand-off OR using a vane. =20 FWIW Where did that diagram come from? Very interesting. I think that my = scoop opening is large enough, and the BL thin enough, that if I can get = effective diffusion in the duct it should work just fine. Thanks for your input on this. Al Thanks, Al ------=_NextPart_000_0019_01C7C627.7D8152C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
  Sorry, Al, I left out some of the=20 details.  As you know pressure recovery is not 100% in a duct, = there is=20 still some air velocity.  The streamline duct (according to = K&W) will=20 recover (maximum) 84% of the free air stream dynamic pressure = potential =20 available at the inlet (turn it into static pressure).  Therefore, = I took=20 your free stream dynamic pressure in your message the 9.5 " at the inlet = and=20 multiplied it by 0.84 to see what a theoretically best streamline duct = should=20 give you.  Since few (if any of us) have the room for a full-length = Streamline duct, we are unlikely to get the 84% figure - but I use it as = sort of=20 a measuring rod.
 
This is the URL where I got the = information. =20 Apparently the author did some research on WWII liquid cooled aircraft = and=20 obtained the information form that material.  I have no further = information=20 on it.
 
 
http://www.c= h601.org/resources/cooling_systems1.htm
 
 
Ed
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Saturday, July 14, 2007 = 12:37=20 PM
Subject: [FlyRotary] Re: FW: = Oil cooler=20 air flow

 

Hi Al,

 

If a "full-strength" Streamline duct were = tested under=20 the conditions of

9.5"H20 at the entranced to the inlet then = at the=20 widest part of the duct

you should theoretically measure 9.5*.84 =3D = 7.98.

 

Ed;

 

Perhaps = you could=20 enlighten me on this.  Where does the .84 come from?  Is = this static=20 pressure?  I thought that as the air was expanded and slowed, = dynamic=20 pressure was converted to static pressure and the value increased. = You=92ve=20 obviously studied this more than I.

 

Regarding your second = sketch,=20 since you do have slower moving boundary layer air moving next to the = skin of=20 the fuselage (and duct), the vane would probably help it turn around = the=20 corner.  However, you are still ingesting slower moving air with = less=20 dynamic pressure to recover from it.  It is my opinion (no = experience or=20 hard data) that moving your inlet fuselage side of your inlet = opening=20   approx  1 1/2 - 2"away from the fuselage would make = an=20 improvement. 

 

You are very right = about=20 that.  Actually in the location that it is, even an inch or less = away=20 from the surface would make a big difference.  Keep in mind that = the=20 scoop is about 23=94 wide with about 1 =BC=94 opening.  How do = you get BL=20 diversion with that configuration? Of course this configuration began = the way=20 it did because another Velocity=20 builder had put his standard aircraft oil cooler (for a Lyc) in the=20 same=20 location, and said it worked great without a scoop =96 just the = differential=20 pressure above and below the wing was enough.  Go=20 figure.

 

As I as looking over = this diagram=20 more carefully (Winginstallation.jpg), it became apparent that it main = point=20 was to show one duct installation with the inlet stand off (bottom = one) and=20 the other without inlet stand off using a vane to assist the = airflow. =20 So, one could draw the conclusion that you have a choice?  either = use=20 inlet stand-off OR using a vane. 

 

FWIW

 

Where did that diagram = come=20 from?  Very interesting. I think that my scoop opening is large = enough,=20 and the BL thin enough, that if I can get effective diffusion in the = duct it=20 should work just fine.

 

Thanks for your input = on=20 this.

 

Al

 

 

 

 

 

 

 

Thanks,

 Al

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