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 2175968 for flyrotary@lancaironline.net; Fri, 13 Jul 2007 14:44:55 -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 l6DIh5x9001081 for ; Fri, 13 Jul 2007 14:43:05 -0400 (EDT) Message-ID: <003f01c7c57d$c14336e0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: Fw: [FlyRotary] Re: FW: Oil cooler air flow Date: Fri, 13 Jul 2007 14:43:50 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003C_01C7C55C.39EA0690" 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_003C_01C7C55C.39EA0690 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sorry, I made reference to your second sketch which is the wedge duct = when I meant to refer to your sketch of the vane. Ed Hi Al, I have never been able to find anything (London and Kay) on the wedge = duct for subsonic flow on the internet - there is a lot of material on = using it and shock waves for controlling flow in the transonic and = supersonic regime where it is quite efficient - but, I simply can not = find anything about it in the subsonic range. But, personally, having = the air turn 90 deg to get up into the core and then another 90 deg to = go out the back simply does not appeal to me.=20 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 But, I realize that is a lot of fiberglass work compared to making and = trying out a turning vane. So I would say try the vane - given the = relative small amount of effort required - but, to be honest, I am not = terribly optimistic about the amount it might help. Ed ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Friday, July 13, 2007 12:34 PM Subject: [FlyRotary] Re: FW: Oil cooler air flow Ed wrote: 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". I recall Tracy = Crook=20 getting 5.6" at 120 MPH in front of his core - certainly he had a = different=20 configuration, but just a data point. So your 3+" H20 is certainly a = bit on=20 the low side. So what could cause that? I see three possible causes: 1. Duct not properly shaped (but, based on your sketch it looks fine = to me) It is attempt to follow the K&W diffuser shape; but is truncated to = fit the short distance available. Perhaps that plus the turn . . . 2. Exit area insufficient (you don't mention the ratio of inlet to = exit=20 area) -=20 The ratio is about 1.6 : 1. =20 3. Boundary layer ingestion. With no standoff from fuselage for you = inlet,=20 it is possible (likely?) that a percentage of your air into the duct = could=20 be composed of the boundary layer. =20 The BL is being ingested; no doubt about that. The ram pressure I = measured at =BD" from the under-wing surface suggests to me that there = is not much of a boundary layer effect; IOW the 9 =BD" H2O represents = roughly the average velocity into the scoop - which extends to 1 =BC" = below the surface. It could well be that the BL along the surface = exacerbates the flow separation/turbulence in the duct. I'm wondering about a vane in the scoop - roughly as show in the = attached drawing. The experts on the other list are suggesting the second sketch = (attached). Al -------------------------------------------------------------------------= ----- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_003C_01C7C55C.39EA0690 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Sorry, I made reference to your second = sketch which=20 is the wedge duct when I meant to refer to your sketch of the = vane.
 
Ed

Hi Al,
 
I have never been able to find anything (London = and Kay)=20 on the wedge duct for subsonic flow  on the internet - there is a = lot of=20 material on using it and shock waves for controlling flow in the = transonic and=20 supersonic regime where it is quite efficient - but, I simply can not = find=20 anything about it in the subsonic range.   But, personally, = having the=20 air turn 90 deg to get up into the core and then another 90 deg to go = out the=20 back simply does not appeal to me.
 
Regarding your second sketch, = since you=20 do have slower moving boundary layer air moving next to the skin of the = fuselage=20 (and duct), the vane would probably help it turn around the = corner. =20 However, you are still ingesting slower moving air with less dynamic = pressure to=20 recover from it.  It is my opinion (no experience or hard data) = that moving=20 your inlet fuselage side of your inlet opening =   approx  1=20 1/2 - 2"away from the fuselage would make an=20 improvement. 
 
But, I  realize that is a lot of fiberglass = work=20 compared to making and trying out a turning vane.  So I would say = try the=20 vane - given the relative small amount of effort required - but, to be = honest, I=20 am not terribly optimistic about the amount it might help.
 
Ed
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Friday, July 13, 2007 = 12:34=20 PM
Subject: [FlyRotary] Re: FW: = Oil cooler=20 air flow

Ed=20 wrote:

 

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".  I recall Tracy Crook

getting 5.6" at 120 MPH in front of his core = -=20 certainly he had a different

configuration, but just a data point.  = So your=20 3+" H20 is certainly a bit on

the low side.  So what could cause = that?  I=20 see three possible causes:

 

1.  Duct not properly shaped (but, = based on your=20 sketch it looks fine to me)

 

It is = attempt to=20 follow the K&W diffuser shape; but is truncated to fit the short = distance=20 available.  Perhaps that plus the turn . . .

 

2.  Exit area insufficient (you don't = mention the=20 ratio of inlet to exit

area) =96

The ratio = is about=20 1.6 : 1. =20

 

3.  Boundary layer ingestion.  = With no=20 standoff from fuselage for you inlet,

it is possible (likely?) that a percentage = of your air=20 into the duct could

be composed of the boundary layer. =20

 

The BL is = being=20 ingested; no doubt about that.  The ram pressure I measured at = =BD=94 from=20 the under-wing surface suggests to me that there is not much of a = boundary=20 layer effect; IOW the 9 =BD=94 H2O represents roughly the average = velocity into=20 the scoop =96 which extends to 1 =BC=94 below the surface.  It = could well be=20 that the BL along the surface exacerbates the flow = separation/turbulence in=20 the duct.

 

I=92m = wondering about=20 a vane in the scoop =96 roughly as show in the attached=20 drawing.

 

The = experts on the=20 other list are suggesting the second sketch = (attached).

 

Al

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Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 = http://mail.lancaironline.net:81/lists/flyrotary/List.html
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