Return-Path: Received: from mail23.syd.optusnet.com.au ([211.29.133.164] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP-TLS id 854818 for flyrotary@lancaironline.net; Mon, 04 Apr 2005 18:11:24 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.133.164; envelope-from=lendich@optusnet.com.au Received: from george (d211-31-76-250.dsl.nsw.optusnet.com.au [211.31.76.250]) by mail23.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id j34MAZrp001151 for ; Tue, 5 Apr 2005 08:10:37 +1000 Message-ID: <008d01c53963$9e981640$fa4c1fd3@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: A lot to learn Date: Tue, 5 Apr 2005 08:14:06 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_008A_01C539B7.6F9F0CA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_008A_01C539B7.6F9F0CA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, I thought necking-down like you have done would cause more of a = restriction and would result in less pressure. I thought that a more direct line of travel from the opening to the core = would give less restriction and more pressure. From what I've been told, this particular design seems to want to follow = the trumpet ( bell) shaped opening style, whereby 1.5 times the face of = the radiator, is required in the length of the duct. I don't think 6" is = enough length. What other styles of duct have you tried which are less successful than = this design. I must say it does look good but seems to fly in the face of other = previous recommendations. George ( down under) I was referring to curvature of the duct walls which should impose on = the higher pressure area in front of the core. By pushing the duct = walls into the higher pressure area in front of the core, the higher = pressure helps to keep the flow from separating as it flows along the = wall of the duct. Here are a couple of photos. One photo (MVC-033s) shows some = templates I used and shows the outline of my duct with the opening = toward the bottom and the core toward the top of the photo. Notice how = the outer walls of the template stay close to the centerline until = diverging near the core (top). The inlet is approx 6" long from inlet = to core which is too short for the Streamline duct coordinates I modeled = it on - So I try some creative things with the curve of the duct walls = which I believe worked out. I make the curvature more extreme than the = stream line duct. A second photo shows the current set of ducts I am flying with which = have a total combined opening of 28 sq inches for both cores. Here I = actually decrease the size of the duct after the opening until I expand = it before the core. My theory is that this initially accelerates the = air entering my inlet giving it higher energy which helps maintain a = higher pressure dome in front of the core> This in turn permits me to = curve the duct walls more without separation of flow. Separation of = course creates eddies which effectively blocks flow through a portion of = the core reducing your cooling effectiveness. =20 At least for the power my engine is putting out at the current time 28 = sq inches appears to be the minimum total duct opening that I can fly = with. I have tolerable temps on climbout (200F oil, 210F coolant) and = 170-180F at my nominal cruise (5600 rpm). If I go to WOT at 7500 MSL the = temps will slowly climb to the 190F range and stabilize - indicating = that I am probably about as close to the minimum cooling as advisable. = To give myself a bit more margin, I will probably open the duct area up = from the current 28 sq inch to 38 sq inch - in the future - maybe {:>) Ed ----- Original Message -----=20 From: John Slade=20 To: Rotary motors in aircraft=20 Sent: Monday, April 04, 2005 2:49 PM Subject: [FlyRotary] Re: A lot to learn The only part that really counted was understanding what was = necessary to keep air flow from separating from the walls in a diffuser. = =20 er.... what was that bit? I must have missed it. :) John -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_008A_01C539B7.6F9F0CA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
I thought necking-down like you have = done would=20 cause more of a restriction and would result in less = pressure.
I thought that a more direct line of = travel from=20 the opening to the core would give less restriction and more=20 pressure.
 
From what I've been told, this = particular design=20 seems to want to follow the trumpet ( bell) shaped opening = style, whereby=20 1.5 times the face of the radiator, is required in the length of the = duct. I=20 don't think 6" is enough length.
 
What other styles of duct have you = tried which are=20 less successful than this design.
 
I must say it does look good but seems = to fly in=20 the face of other previous recommendations.
George ( down under)
I was referring to curvature of the = duct walls=20 which should impose on the higher pressure area in front of the = core.  By=20 pushing the duct walls into the higher pressure area in front of the = core, the=20 higher pressure helps to keep the flow from separating as it flows = along the=20 wall of the duct.
Here are a couple of = photos. =20   One  photo (MVC-033s) shows some templates I used and = shows the outline of my duct with the opening toward the bottom = and the=20 core toward the top of the photo.  Notice how the outer walls of = the=20 template stay close to the centerline until diverging near the core=20 (top).  The inlet is approx 6" long from inlet to core which is = too short=20 for the Streamline duct coordinates I modeled it on - So I try some = creative=20 things with the curve of the duct walls which I believe worked = out.  I=20 make the curvature more extreme than the stream line = duct.
 
 
A second photo shows the current = set of=20 ducts I am flying with which have a total combined opening of 28 sq = inches for=20 both cores.  Here I actually decrease the size of the duct after = the=20 opening until I expand it before the core.  My theory is that = this=20 initially accelerates the air entering my inlet giving it higher = energy which=20 helps maintain a higher pressure dome in front of the core>  = This in=20 turn permits me to curve the duct walls more without separation = of=20 flow.  Separation of course creates eddies which effectively = blocks flow=20 through a portion of the core reducing your cooling = effectiveness. =20
 
At least for the power my engine is = putting out=20 at the current time 28 sq inches appears to be the minimum total duct = opening=20 that I can fly with.  I have tolerable temps on climbout (200F = oil, 210F=20 coolant) and 170-180F at my nominal cruise (5600 rpm). If I go to WOT = at 7500=20 MSL the temps will slowly climb to the 190F range and stabilize=20 - indicating that I am probably about as close to the minimum = cooling as=20 advisable.  To give myself a bit more margin, I will probably = open the=20 duct area up from the current 28 sq inch to 38 sq inch - in the future = - maybe=20 {:>)
 
Ed
----- Original Message -----
From:=20 John=20 Slade
To: Rotary motors in = aircraft=20
Sent: Monday, April 04, 2005 = 2:49=20 PM
Subject: [FlyRotary] Re: A = lot to=20 learn

The only part  that really = counted was=20 understanding what was necessary to keep air flow from separating = from the=20 walls in a diffuser.   
 
er.... what was=20 that bit? I must have missed it. :)
John
 
 
 

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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