X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost04.isp.att.net ([207.115.11.54] verified) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTP id 5850721 for flyrotary@lancaironline.net; Wed, 31 Oct 2012 12:03:21 -0400 Received-SPF: none receiver=logan.com; client-ip=207.115.11.54; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-98-85-148-136.mco.bellsouth.net[98.85.148.136]) by isp.att.net (frfwmhc04) with SMTP id <20121031160246H0400t6j8te>; Wed, 31 Oct 2012 16:02:46 +0000 X-Originating-IP: [98.85.148.136] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: flow path in conventional radiator Date: Wed, 31 Oct 2012 12:02:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0018_01CDB75F.A4785CA0" X-Mailer: Microsoft Office Outlook 11 Thread-Index: Ac23ePW3+XRjg77ETNWgMFHSMJ8QlAABo1ig X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 This is a multi-part message in MIME format. ------=_NextPart_000_0018_01CDB75F.A4785CA0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Ken, I am not certain that the best places for air entrance and exit on an airplane change much with speed. You need entrances in high pressure areas and exits in low pressure areas. The top of the cowl is a high pressure area and if you try to exit air there, I suspect that it will partially block the flow. While I have heard a lot of good stuff about the Paul Lamar book, I usually try to get my guidance from folks who have actually built an airplane. Bill B _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kenneth Johnson Sent: Wednesday, October 31, 2012 11:03 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: flow path in conventional radiator Tracy, Sorry to get back to you so late, but am now just getting caught up on emails. When I have free time, I am usually out in my garage working on the plane. If you have not read "How to Cool Your Wankel" by Paul Lamar, I would recommend it. It would be worth your time. The suggestion to flow air from the bottom up was not made by Paul, but was my thoughts regarding the airplane I am building. The Zenith 801 is the four passenger high wing STOL bush-type plane. It's top speed is 110 MPH. It's primary purpose is getting in and out of short, grass strips. Where engine cooling is most needed is on short runway take-off with high obstacles such as trees at the runway's end. Stall speed is about 40 MPH. This just means there is very little air flowing through the cooling system on take-off. The airplane is at a high angle of attack until obstacles are cleared. And again, at this high angle of attack, cooling flow is different and airspeed is slow. Having the cowl opening on the bottom front of the cowl where air flows directly through the radiators and having outlets on the top sides of the cowl would allow air to flow best when it is most needed to cool the engine. At flat and level flying, the air would still flow, but the higher speed would provide more cooling. What makes this plane unique is it is not an RV where one is flying at 170 knots and has a mile long runway. Please read Paul's book and give me your thoughts. Thanks for your comments. Ken Johnson _____ From: Tracy To: Rotary motors in aircraft Sent: Wednesday, October 24, 2012 12:21 PM Subject: [FlyRotary] Re: flow path in conventional radiator On Oct 24, 2012, at 10:14 AM, Kenneth Johnson wrote: > A more efficient design would have intake air entering the bottom anterior of the the cowl and to pass through the radiator. As this air is heated by the radiator it rises and should exit the top sides of the cowl. No one has done that because of the risk of engine oil on the windshield. I haven't read Paul's book but if this is an example of his suggestions, I wouldn't have much confidence in it. Two basic rules of thumb for A/C cooling systems are: 1. Turning high speed air is hard to do and loss prone energy wise. 2. The pressure represented by convection of rising hot air is not significant and can safely be ignored for our purposes. Tracy -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0018_01CDB75F.A4785CA0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Ken,

 

I am not certain that the best = places for air entrance and exit on an airplane change much with speed.  You = need entrances in high pressure areas and exits in low pressure areas.  = The top of the cowl is a high pressure area and if you try to exit air there, I = suspect that it will partially block the flow.

 

While I have heard a lot of good = stuff about the Paul Lamar book, I usually try to get my guidance from folks = who have actually built an airplane.

 

Bill B

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kenneth Johnson
Sent: Wednesday, October = 31, 2012 11:03 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = flow path in conventional radiator

 

Tracy,

Sorry to get back to you so late, = but am now just getting caught up on emails.  When I have free time, I am = usually out in my garage working on the plane.  If you have not read = "How to Cool Your Wankel" by Paul Lamar, I would recommend it.  It = would be worth your time.  

 

The suggestion to flow air from = the bottom up was not made by Paul, but was my thoughts regarding the airplane I am building.  The Zenith 801 is the four passenger high wing STOL = bush-type plane.  It's top speed is 110 MPH.  It's primary purpose is = getting in and out of short, grass strips.  Where engine cooling is most = needed is on short runway take-off with high obstacles such as trees at the = runway's end.  Stall speed is about 40 MPH.  This just means there is = very little air flowing through the cooling system on take-off.   = The airplane is at a high angle of attack until obstacles are cleared.  = And again, at this high angle of attack, cooling flow is different and = airspeed is slow.

Having the cowl opening on the = bottom front of the cowl where air flows directly through the radiators and having = outlets on the top sides of the cowl would allow air to flow best when it is = most needed to cool the engine.  At flat and level flying, the air would = still flow, but the higher speed would provide more = cooling.  

 

What makes this plane unique is = it is not an RV where one is flying at 170 knots and has a mile long runway.   

 

Please read Paul's book and give = me your thoughts.  Thanks for your comments.  =

 

Ken = Johnson

 

 

 

From: Tracy <rwstracy@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net> =
Sent: Wednesday, October = 24, 2012 12:21 PM
Subject: [FlyRotary] Re: = flow path in conventional radiator




On Oct 24, 2012, at 10:14 AM, Kenneth Johnson <kjohnsondds@yahoo.com> wrote:

> A more efficient design would  have intake air entering the = bottom anterior of the the cowl and to pass through the radiator.  As this = air is heated by the radiator it rises and should exit the top sides of the cowl.  No one has done that because of the risk of engine oil on = the windshield.


I haven't read Paul's book but if this is an example of his suggestions, = I wouldn't have much confidence in it. 

Two basic rules of thumb for A/C cooling systems are:

1. Turning high speed air is hard to do and loss prone energy wise.

2.  The pressure represented by convection of rising hot air is not significant  and can safely be ignored for our purposes. 

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

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