X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-da04.mx.aol.com ([205.188.105.146] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036062 for flyrotary@lancaironline.net; Tue, 22 Dec 2009 21:50:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.146; envelope-from=SHIPCHIEF@aol.com Received: from imo-da03.mx.aol.com (imo-da03.mx.aol.com [205.188.169.201]) by imr-da04.mx.aol.com (8.14.1/8.14.1) with ESMTP id nBN2nKSo016269 for ; Tue, 22 Dec 2009 21:49:20 -0500 Received: from SHIPCHIEF@aol.com by imo-da03.mx.aol.com (mail_out_v42.5.) id q.c0a.6e4f70b8 (43830) for ; Tue, 22 Dec 2009 21:49:18 -0500 (EST) Received: from smtprly-ma02.mx.aol.com (smtprly-ma02.mx.aol.com [64.12.207.141]) by cia-dc02.mx.aol.com (v126.13) with ESMTP id MAILCIADC023-5c4e4b31852529c; Tue, 22 Dec 2009 21:49:18 -0500 Received: from webmail-m055 (webmail-m055.sim.aol.com [64.12.158.155]) by smtprly-ma02.mx.aol.com (v127.6) with ESMTP id MAILSMTPRLYMA024-5c4e4b31852529c; Tue, 22 Dec 2009 21:49:09 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Question Date: Tue, 22 Dec 2009 21:49:09 -0500 X-AOL-IP: 24.19.204.151 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: shipchief@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CC5191A2E18CA9_350_8334B_webmail-m055.sysops.aol.com" X-Mailer: AOL Webmail 30109-STANDARD Received: from 24.19.204.151 by webmail-m055.sysops.aol.com (64.12.158.155) with HTTP (WebMailUI); Tue, 22 Dec 2009 21:49:09 -0500 Message-Id: <8CC5191A2AACCF2-350-41A5F@webmail-m055.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: SHIPCHIEF@aol.com ----------MB_8CC5191A2E18CA9_350_8334B_webmail-m055.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Yes; Thanks Ed. I went out to the garage and looked at my chin scoop radiator.= =20 It fails to conform to the shape reccomended in the article. :( But it does cool well in ground testing so far. I leaned heavily toward pr= essure recovery from the supposed bow wake effect, and can't verify if I= get any diffuser effect because of the slope of the cooler core. I know= this is not optimal, but I wanted greater core area and less core depth= so air would pass thru the core with a lower differential pressure. Here is a link to my EAA Capter's site, direct to my pictures: http://gal= lery.eaa326.org/members/semery/ Constructive comments are always welcome. I did try to keep external drag to a minimum, and have an Inlet area of ab= out 52 In Sq, over a Core face area of 306 In Sq. for a intlet / core ratio 17 % which seems small for the core.=20 The Horse Power target is 200, so the 1.8 cubic inch core volume to HP =3D= 360 cubic inches. My core is 2" thick for 612 cubic inches. So I theoreti= cally only require 59% of my existing core volume. 180 square inches of 2= inch thick core. My inlet opening =3D 29% of that, so I'm close to optimum on inlet opening= area. As I continue to test, and eventually fly, I could change to a smal= ler cooler, which could set it more 'normal' to the air flow, while also= moving it aft allowing a longer diffuser. The side mounted oil cooler was not a matter of choices. The Mazda cooler= comes in one size, so does the cowl cheek opening. I just measured my dif= fuser inlet, 24.8 In Sq. The cooler face: 87.75 In Sq. Ratio =3D 28%. I th= ink that's pretty good considering the airflow must turn 90 degrees to pas= s thru the core, then get sucked out thru surface louvers on the cowl side= . Here's hoping for the best, and trying again if it doesn't work. -----Original Message----- From: Thomas Mann To: Rotary motors in aircraft Sent: Mon, Dec 21, 2009 6:01 pm Subject: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Questio= n Thanks for the links Ed. It looks like I have some reading to do! =20 =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Be= half Of Ed Anderson Sent: Monday, December 21, 2009 7:19 PM To: Rotary motors in aircraft Subject: [FlyRotary] Mereidth effect: [FlyRotary] Re: Air Flow Question =20 =20 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 sh= ort article =20 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 unfortunatel= y the most frequently botched by homebuilders. =20 http://contrails.free.fr/engine_aerodyn_radia_en.php =20 Also note his comment about how to control airflow once your intake is 30-= 50% of your core area =E2=80=93 may surprise you. =20 =20 http://contrails.free.fr/tunnel_en.php =20 =20 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= =E2=80=93 but, most agree whether it did produce significant thrust or no= t the cooling drag was probably close to an optimum minimum. =20 =20 http://contrails.free.fr/refroid_meredith_en.php =20 You are right, there is always trade offs. You can certainly put an oil= cooler in front of your radiator =E2=80=93 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 =E2=80=93 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 simil= ar 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 =E2=80=9Cbleeding=E2=80=99=E2=80=9D cooling air from the oth= er. 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 possi= ble and there are always space constraints in our vehicles) and also keepi= ng their air flow separate is generally the best course of action to get= the best cooling. But, compromises are frequently necessary, in which ca= se you simply have to try and figure out the possible interaction and effe= cts. =20 Ed =20 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 Be= half Of Thomas Mann Sent: Monday, December 21, 2009 6:17 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Air Flow Question =20 =E2=80=9CStick with this group, we=E2=80=99ve all been there and have conq= uered the cooling beast =E2=80=93 well, at least tamed it a bit. =20 Ed=E2=80=9D =20 =20 That is the plan Ed.=20 I=E2=80=99m trying to figure out how much radiator I can fit into my confi= guration. I=E2=80=99m running the numbers and drafting it out in AutoCAD. =20 I=E2=80=99m hoping that I can cash in on the Meredith Effect in my design.= I=E2=80=99m planning on an adjustable exhaust opening much like the P-51s= had. I=E2=80=99m not sure if I need it or not but it=E2=80=99s easier to= not use it vs. add it later. =20 Question: If I use a separate oil cooler, can I place it in front of the= radiator?=20 I=E2=80=99ve seen some installations like this but it seems to me that the= re is a cost involved. =20 T Mann __________ Information from ESET NOD32 Antivirus, version of virus signatu= re database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ----------MB_8CC5191A2E18CA9_350_8334B_webmail-m055.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Yes;
Thanks Ed. I went out to the garage and looked at my chin scoop radia= tor.
It fails to conform to the shape reccomended in the article. :(
But it does cool well in ground testing so far. I leaned heavily towa= rd pressure recovery from the supposed bow wake effect, and can't verify= if I get any diffuser effect because of the slope of the cooler core. I= know this is not optimal, but I wanted greater core area and less core de= pth so air would pass thru the core with a lower differential pressure.
Here is a link to my EAA Capter's site, direct to my pictures: = http://gallery.eaa3= 26.org/members/semery/
Constructive comments are always welcome.
I did try to keep external drag to a minimum, and have an Inlet area= of about 52 In Sq, over a Core face area of 306 In Sq.
for a intlet / core ratio 17 % which seems small for= the core.
The Horse Power target is 200, so the 1.8 cubic inch core volume to= HP =3D 360 cubic inches. My core is 2" thick for 612 cubic inches. So I= theoretically only require 59% of my existing core volume. 180 square inc= hes of 2 inch thick core.
My inlet opening =3D 29% of that, so I'm close to optimum on inlet op= ening area. As I continue to test, and eventually fly, I could change to= a smaller cooler, which could set it more 'normal' to the air flow, while= also moving it aft allowing a longer diffuser.
The side mounted oil cooler was not a matter of choices. The Mazda co= oler comes in one size, so does the cowl cheek opening. I just measured my= diffuser inlet, 24.8 In Sq. The cooler face: 87.75 In Sq. Ratio =3D 28%.= I think that's pretty good considering the airflow must turn 90 degrees= to pass thru the core, then get sucked out thru surface louvers on the co= wl side.
Here's hoping for the best, and trying again if it doesn't work.



-----Original Message-----
From: Thomas Mann <tmann@n200lz.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, Dec 21, 2009 6:01 pm
Subject: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Questio= n

Thanks for the links Ed.
It looks like I have some reading to do!=
 
 <= /A>
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Monday, December 21, 2009 7:19 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Mereidth effect: [FlyRotary] Re: Air Flow Ques= tion
 
 
Thomas, Here is probably the best, most und= erstandable (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 crit= ical part, and unfortunately the most frequently botched by homebuilders.<= /I>
 
http://contrails.free.fr/engine_aero= dyn_radia_en.php
 
Also note his comment about how to control= airflow once your intake is 30-50% of your core area =E2=80=93 may surpri= se you.
 
 
http://contrails.free.fr/tunnel_en.php<= /div>
 
 
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 =E2=80=93 but, most agree whether it di= d produce significant thrust or not the cooling drag was probably close to= an optimum minimum. 
 
http://contrails.free.fr/refroid_meredit= h_en.php
 
You are right, there is always trade offs.  You can certai= nly put an oil cooler in front of your radiator =E2=80=93 in effect you ar= e just making a thick radiator as far as airflow is concerned.  Obvio= usly you will have hotter air flow through the part of your radiator behin= d 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 th= rough the other part of the radiator core =E2=80=93 due to its less air re= sistance.
Placing them side by side (or top bottom) is another approach.&= nbsp; However, it is my opinion that unless your oil cooler and radiator= core have similar air flow characteristics or great care is taken in desi= gning your ducts to each, that air will take the route of least resistance= .  So one  core could end up =E2=80=9Cbleeding=E2=80=99=E2=80=9D= cooling air from the other.  Similarly, the exit pressure of one (ge= nerally 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 se= parate (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 nec= essary, 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
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
 
=E2=80=9CStick with this gr= oup, we=E2=80=99ve all been there and have conquered the cooling beast =E2= =80=93 well, at least tamed it a bit.
 
Ed=E2=80=9D
 
 
That is the plan Ed.=
I=E2=80=99m trying= to figure out how much radiator I can fit into my configuration. I=E2=80= =99m running the numbers and drafting it out in AutoCAD.
 
I=E2=80=99m hoping= that I can cash in on the Meredith Effect in my design. I=E2=80=99m plann= ing on an adjustable exhaust opening much like the P-51s had. I=E2=80=99m= not sure if I need it or not but it=E2=80=99s easier to not use it vs. ad= d it later.
 
Question: If I use= a separate oil cooler, can I place it in front of the radiator?
I=E2=80=99ve seen so= me installations like this but it seems to me that there is a cost involve= d.
 
T Mann


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