X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from aspensprings.uwyo.edu ([129.72.10.32] verified) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTPS id 5802825 for flyrotary@lancaironline.net; Tue, 09 Oct 2012 11:08:49 -0400 Received-SPF: none receiver=logan.com; client-ip=129.72.10.32; envelope-from=SBoese@uwyo.edu Received: from ponyexpress-ht4.uwyo.edu (extlb.uwyo.edu [172.26.4.4]) by aspensprings.uwyo.edu (8.14.4/8.14.4) with ESMTP id q99F8AHE022355 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for ; Tue, 9 Oct 2012 09:08:10 -0600 (MDT) (envelope-from SBoese@uwyo.edu) Received: from ponyexpress-m10.uwyo.edu ([fe80::60dd:cb9e:6f71:3d48]) by ponyexpress-ht4.uwyo.edu ([fe80::8de7:b225:a85b:d0ee%13]) with mapi id 14.02.0318.001; Tue, 9 Oct 2012 09:08:02 -0600 From: "Steven W. Boese" To: Rotary motors in aircraft Subject: cooling airflow concepts Thread-Topic: cooling airflow concepts Thread-Index: AQHNpi/fVgp45V1lCUGM510FEAObKA== Date: Tue, 9 Oct 2012 15:08:01 +0000 Message-ID: <3E8191F276108F4481AB0721BBA9269E05DE3E47@ponyexpress-m10.uwyo.edu> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [75.196.185.255] Content-Type: multipart/alternative; boundary="_000_3E8191F276108F4481AB0721BBA9269E05DE3E47ponyexpressm10u_" MIME-Version: 1.0 --_000_3E8191F276108F4481AB0721BBA9269E05DE3E47ponyexpressm10u_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Steve, Specific details concerning Tracy's cooling setup and performance are best = obtained directly from him. I can try to relate my take on the concepts that were discussed, though: The area, cross sectional shape, location as far as practical from the cent= er of the prop, and the location close behind the prop have combined to giv= e good inlet characteristics under a wide range of conditions of airspeed a= nd angle of attack. The construction of the diffuser should result in smooth walls and avoid su= dden changes in direction of the air flowing within it. Divergence angles = greater than 7 degrees are not necessarily a pressure recovery killer. Other than the exact inlet cross sectional shape and area, the concepts jus= t mentioned follow largely from common sense. The concept that was surprising to me was that a large change in direction = of air flow from the diffuser into the core right at the face of the core i= s not necessarily a bad thing. Since the flow of the air through the core = is intended to be turbulent, the turbulence resulting from the rapid direct= ion change at the core face may actually be a good thing. In Tracy's coola= nt exchanger arrangement, the core is almost at a right angle to the direct= ion of air flow within most of the diffuser. The critical part appears to = be the shape of the interface between the core and the diffuser with the di= ffuser wall distance from the core becoming very small at the downstream en= d. The goal is to provide consistent pressure across the whole face of the= core and thus get uniform airflow through the whole core. Achieving this = goal will probably involve some experimentation and changes in the diffuser= to core transition shape for a particular installation. Making measuremen= ts of airflow through different parts of the core would be essential to ass= es the effect of changes made. Although this all sounds daunting, the free= dom resulting from the ability to change the direction of airflow at the co= re face may allow greater emphasis on the construction of a diffuser with g= ood pressure recovery within the constraints of the under cowl space availa= ble. That's just my interpretation of what I thought I heard. Someone please co= rrect me if I am mistaken. Steve Boese RV6A, 1986 13B NA, RD1A, EC2 ________________________________ From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of = Stephen Izett [steveizett@me.com] Sent: Monday, October 08, 2012 6:17 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Rotorfest 2012 photos Hi Steve Thanks for the report from the flyin, always good to get feedback and photo= s. Wish I could get to see some of the flying examples. Bit tricky being down = under. I've modelled my (Glasair SIIRG Renesis 4 port) cooling of Tracy's 8. Was t= here any thoughts - pros and cons, improvements of his setup. It would seem to be functioning very well. He has spoken previously of the importance of the diffuser shape (I am yet = to build it so am interested in his thoughts) and the difference his newer = inlets made. Much appreciated Steve Izett Perth Western Australia --_000_3E8191F276108F4481AB0721BBA9269E05DE3E47ponyexpressm10u_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Steve,

 

Specific details concerning Tracy's cooling setup and performance a= re best obtained directly from him.

 

I can try to relate my take on the concepts that were discussed, though:=

 

The area, cross sectional shape, location as far as practical from = the center of the prop, and the location close behind the prop have combine= d to give good inlet characteristics under a wide range of conditions of ai= rspeed and angle of attack.

 

The construction of the diffuser should result in smooth walls and avoid= sudden changes in direction of the air flowing within it.  = Divergence angles greater than 7 degrees are not necessarily a = pressure recovery killer.

 

Other than the exact inlet cross sectional shape and area, the concepts = just mentioned follow largely from common sense.

 

The concept that was surprising to me was that a large change in directi= on of air flow from the diffuser into the core right at the face of the cor= e is not necessarily a bad thing.  Since the flow of the a= ir through the core is intended to be turbulent, the turbulence resulting from the rapid direction change at the core face = may actually be a good thing.  In Tracy's coolant exchanger arrangemen= t, the core is almost at a right angle to the direction of air flow within = most of the diffuser.  The critical part appears to be the shape of the interface between the core and the diffuser= with the diffuser wall distance from the core becoming very small at the d= ownstream end.  The goal is to provide consistent pressure across the = whole face of the core and thus get uniform airflow through the whole core.  Achieving this goal will probably in= volve some experimentation and changes in the diffuser to core tr= ansition shape for a particular installation.  Making measurement= s of airflow through different parts of the core would be essenti= al to asses the effect of changes made.  Although this all sounds d= aunting, the freedom resulting from the ability to change the directio= n of airflow at the core face may allow greater emphasis on the constr= uction of a diffuser with good pressure recovery within the constraints of the under cowl space available.

 

That's just my interpretation of what I thought I heard.  Someone p= lease correct me if I am mistaken.

 

Steve Boese
RV6A, 1986 13B NA, RD1A, EC2

 

 

 

 

 

From: Rotary motors in aircraft [flyrotary= @lancaironline.net] on behalf of Stephen Izett [steveizett@me.com]
Sent: Monday, October 08, 2012 6:17 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Rotorfest 2012 photos

Hi Steve

Thanks for the report from the flyin, always good to get feedback and = photos.
Wish I could get to see some of the flying examples. Bit tricky being = down under.
I've modelled my (Glasair SIIRG Renesis 4 port) cooling of Tracy's 8. = Was there any thoughts - pros and cons, improvements of his setup.
It would seem to be functioning very well.
He has spoken previously of the importance of the diffuser shape (I am= yet to build it so am interested in his thoughts) and the difference his n= ewer inlets made.

Much appreciated

Steve Izett
Perth Western Australia 


 
--_000_3E8191F276108F4481AB0721BBA9269E05DE3E47ponyexpressm10u_--