X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4034332 for flyrotary@lancaironline.net; Mon, 21 Dec 2009 20:19:01 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.0 c=1 a=Az3EmYMNpQcA:10 a=3T_JeE6tAAAA:8 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=nUuTZ29dAAAA:8 a=Gt2CEEc3HLBMUt0NY7sA:9 a=6_PCExmnu4zm7LEJRKwA:7 a=nkAUla2xUkuqCP5eDqda7rVW0GgA:4 a=782tgarBYgIA:10 a=8BQgeFA2TAwA:10 a=dBnkUEi4Sm4A:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=Y2VNeNrzAAAA:8 a=yMhMjlubAAAA:8 a=TW66zc2HAAAA:8 a=SSmOFEACAAAA:8 a=HQ31llbKAAAA:8 a=_8T02d2IFJn98Y307XUA:9 a=xnw73XJuGnXHlEOM9cEA:7 a=1FjaO6NCx0U1nGHB4SB4W449eYsA:4 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:2681] helo=computername) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id CB/4E-01567-16E103B4; Tue, 22 Dec 2009 01:18:26 +0000 From: "Ed Anderson" Message-ID: To: "'Rotary motors in aircraft'" Subject: Mereidth effect: [FlyRotary] Re: Air Flow Question Date: Mon, 21 Dec 2009 20:18:32 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0022_01CA827A.C44B4A50" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: Thread-Index: AcqCk8KXjskV0t5MRgm+9NZKSJhgygADXOmA This is a multi-part message in MIME format. ------=_NextPart_000_0022_01CA827A.C44B4A50 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Thomas, Here is probably the best, most understandable (without a lot of math) on the cooling challenge that I have come across. You might want to check it out. Here is one of the statements you will find in this short article It has been shown that the diffuser efficiency is key in the reduction of the overall radiator drag. It is the most critical part, and unfortunately the most frequently botched by homebuilders. http://contrails.free.fr/engine_aerodyn_radia_en.php Also note his comment about how to control airflow once your intake is 30-50% of your core area - may surprise you. http://contrails.free.fr/tunnel_en.php Here is a summary by Meredith on the effect. There is still some debate about whether the P-51 cooling system actually resulted in a net thrust - but, most agree whether it did produce significant thrust or not the cooling drag was probably close to an optimum minimum. http://contrails.free.fr/refroid_meredith_en.php You are right, there is always trade offs. You can certainly put an oil cooler in front of your radiator - in effect you are just making a thick radiator as far as airflow is concerned. Obviously you will have hotter air flow through the part of your radiator behind the oil cooler so its cooling effectiveness will be reduced. Also, you may find that a lot of the air in their common duct may want to go through the other part of the radiator core - due to its less air resistance. Placing them side by side (or top bottom) is another approach. However, it is my opinion that unless your oil cooler and radiator core have similar air flow characteristics or great care is taken in designing your ducts to each, that air will take the route of least resistance. So one core could end up "bleeding'" cooling air from the other. Similarly, the exit pressure of one (generally the one with the least air resistance) will be higher than the one with less resistance. So this can cause airflow problems under the cowl as well. Its my opinion that keeping your oil and coolant cores separate (if possible and there are always space constraints in our vehicles) and also keeping their air flow separate is generally the best course of action to get the best cooling. But, compromises are frequently necessary, in which case you simply have to try and figure out the possible interaction and effects. Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Thomas Mann Sent: Monday, December 21, 2009 6:17 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Air Flow Question "Stick with this group, we've all been there and have conquered the cooling beast - well, at least tamed it a bit. Ed" That is the plan Ed. I'm trying to figure out how much radiator I can fit into my configuration. I'm running the numbers and drafting it out in AutoCAD. I'm hoping that I can cash in on the Meredith Effect in my design. I'm planning on an adjustable exhaust opening much like the P-51s had. I'm not sure if I need it or not but it's easier to not use it vs. add it later. Question: If I use a separate oil cooler, can I place it in front of the radiator? I've seen some installations like this but it seems to me that there is a cost involved. T Mann __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0022_01CA827A.C44B4A50 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

 

Thomas, Here is probably the best, = most understandable (without a lot of math) on the cooling challenge that I = have come across.   You might want to check it out.   Here is = one of the statements you will find in this short = article

 

It has been shown that the = diffuser efficiency is key in the reduction of the overall radiator drag. It is = the most critical part, and unfortunately the most frequently botched by = homebuilders.

 

http://cont= rails.free.fr/engine_aerodyn_radia_en.php

 

Also note his comment about how to = control airflow once your intake is 30-50% of your core area – may = surprise you.

 

 

http://contrails.free.fr/= tunnel_en.php

 

 

Here is a summary by Meredith on = the effect.  There is still some debate about whether the P-51 cooling = system actually resulted in a net thrust – but, most agree whether it did produce significant thrust or not the cooling drag was probably close to = an optimum minimum. 

 

http://contrail= s.free.fr/refroid_meredith_en.php

 

You are right, there is always trade offs.  You = can certainly put an oil cooler in front of your radiator – in effect = you are just making a thick radiator as far as airflow is concerned.  = Obviously you will have hotter air flow through the part of your radiator behind = the oil cooler so its cooling effectiveness will be reduced.  Also, you may = find that a lot of the air in their common duct may want to go through the = other part of the radiator core – due to its less air = resistance.

Placing them side by side (or top bottom) is another = approach.  However, it is my opinion that unless your oil cooler and radiator core = have similar air flow characteristics or great care is taken in designing = your ducts to each, that air will take the route of least resistance.  So one =  core could end up “bleeding’” cooling air from the = other.  Similarly, the exit pressure of one (generally the one with the least air = resistance) will be higher than the one with less resistance. So this can cause airflow = problems under the cowl as well.

Its my opinion that keeping  your oil and coolant = cores separate (if possible and there are always space constraints in our = vehicles) and also keeping their air flow separate is generally the best course of = action to get the best cooling.  But, compromises are frequently = necessary, in which case you simply have to try and figure out the possible = interaction and effects.

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary = Powered

Matthews, NC

eanderson@carolina.rr.com=

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.r= otaryaviation.com/Rotorhead%20Truth.htm

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Thomas Mann
Sent: Monday, December = 21, 2009 6:17 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Air Flow Question

 

“= Stick with this group, we’ve all been there and have conquered the cooling beast – well, at least tamed it a = bit.

 

Ed”

 <= /o:p>

 <= /p>

That is the plan Ed. =

I’m trying to figure out = how much radiator I can fit into my configuration. I’m running the numbers = and drafting it out in AutoCAD.

 <= /p>

I’m hoping that I can = cash in on the Meredith Effect in my design. I’m planning on an adjustable = exhaust opening much like the P-51s had. I’m not sure if I need it or not = but it’s easier to not use it vs. add it = later.

 <= /p>

Question: If I use a separate = oil cooler, can I place it in front of the radiator? =

I’ve seen some = installations like this but it seems to me that there is a cost = involved.

 <= /p>

T Mann



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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