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 2177691 for flyrotary@lancaironline.net; Sat, 14 Jul 2007 15:16:38 -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 l6EJFvb9019694 for ; Sat, 14 Jul 2007 15:15:58 -0400 (EDT) Message-ID: <003301c7c64b$76f40960$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 15:16:21 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0030_01C7C629.EF830B50" 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_0030_01C7C629.EF830B50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Oops. Didn't read your question well enough, Al . But, even assuming your 9.5" of STATIC pressure (which is of course = what you are reading) is 100% of the free air stream dynamic potential = at the entrance of the inlet, you can not recover more than 84% of = whatever free air dynamic potential that 9.5" might represent inside = the duct. =20 if the free air velocity (160) converts to 12"H20 and you had a = streamline duct inlet actual had that coming in then theoretically you = could get approx 12 * .84 =3D 10.8" inside the duct. Since you measured = 3.25" static in front of the core, that would indicate a significant = lack of pressure recovery inside your duct (what ever the reason). = There are several reasons this might be happening. 1. The air flow and velocity is considerably reduced from what you are = expecting (too small opening/exit - which I don't believe to be the = case) 2. The boundary layer is a significant part of your duct total air = flow and as a consequence its lesser velocity has less dynamic pressure = potential. 3. A significant part of your duct flow is chaotic with eddies which = does not provide recoverable pressure - or it is much reduced. (The = boundary layer could be contributing to this) 4. Some combination of the above. Right, now I would suspect that the boundary layer could be the culprit = in that it can contribute to 2 and 3 above. But, as you know, this is = speculation on my part. Just throwing out some thoughts that might give = you some ideas. Best Regards 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_0030_01C7C629.EF830B50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Oops.  Didn't read your question well = enough,=20 Al
 
. But, even assuming your 9.5" of STATIC = pressure (which=20 is of course what you are reading) is 100% of the free air stream = dynamic=20 potential at the entrance of the inlet, you can not recover more than = 84%=20 of  whatever free air dynamic potential that 9.5" might = represent =20 inside the duct. 
 
if the free air velocity (160) converts to = 12"H20 and you=20 had a streamline duct inlet actual had that coming in then theoretically = you=20 could get approx 12 * .84 =3D 10.8" inside the duct.  Since you = measured=20 3.25" static in front of the core, that would indicate a significant = lack of=20 pressure recovery inside your duct (what ever the reason).  There = are=20 several reasons this   might be happening.
 
1.  The air flow and velocity is = considerably reduced=20 from what you are expecting (too small opening/exit - which I don't = believe to=20 be the case)
 
2.  The boundary layer is a significant = part of your=20 duct total  air flow  and as a consequence its lesser velocity = has=20 less dynamic pressure potential.
 
3.  A significant part of your duct flow is = chaotic=20 with eddies which does not provide recoverable pressure - or it is much=20 reduced.  (The boundary layer could be contributing to = this)
 
4.  Some combination of the = above.
 
Right, now I would suspect that the boundary = layer could=20 be the culprit in that it can contribute to 2 and 3 above.  But, as = you=20 know, this is speculation on my part.  Just throwing out some = thoughts that=20 might give you some ideas.
 
Best Regards
 
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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