X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036998 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 16:21:33 -0500 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id 6CE46173B4A for ; Thu, 24 Dec 2009 05:20:56 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id 87347BEC009 for ; Thu, 24 Dec 2009 05:20:53 +0800 (WST) Message-ID: <6B766BBCB7E545859E6ED70682398D54@ownerf1fc517b8> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Question Date: Thu, 24 Dec 2009 07:20:53 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CA8469.A065A950" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 091223-0, 12/23/2009), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0009_01CA8469.A065A950 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable I don't know where that 1.8cu" for each hp rule of thumb came from, but = I do know that the 3 - 3.5 cu"per hp came from and for 200 hp that's 600 = cu" - so 612cu" is good. I thought that the inlet area was a minimum of 30% of the core surface = area and the outlet was 1.5 - 1.7 of the inlet. Therefore opening would = be 91sq" and exit 136.5 sq"- 154.7 sq". Your oil inlet at 28% appears close enough. George ( down under) 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 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 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://gallery.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 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.=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 = theoretically 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 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 = cooler 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 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 = Question Thanks for the links Ed. It looks like I have some reading to do! From: 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 = Question 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 =E2=80=93 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 =E2=80=93 but, most agree whether it did produce significant = thrust or not the cooling drag was probably close to an optimum minimum. = =20 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 =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 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 = =E2=80=9Cbleeding=E2=80=99=E2=80=9D 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 =E2=80=9CStick with this group, 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.=20 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 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. 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 = 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_0009_01CA8469.A065A950 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
 I don't know where that 1.8cu" = for each hp=20 rule of thumb came from, but I do know that the 3 - 3.5 cu"per hp came = from and=20 for 200 hp that's 600 cu" -  so 612cu" is good.
 
I thought that the inlet area was a = minimum of 30%=20 of the core surface area and the outlet was 1.5 - 1.7 of the inlet. = Therefore=20 opening would be 91sq" and exit 136.5 sq"- 154.7 sq".
 
Your oil inlet at 28% appears close=20 enough.
George ( down under)
 
 
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=20 pressure recovery from the supposed bow wake effect, and can't verify = if I get=20 any diffuser effect because of the slope of the cooler core. I know = this is=20 not optimal, but I wanted greater core area and less core depth so air = would=20 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.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=20 about 52 In Sq, over a Core face area of 306 In Sq.
for a intlet / core ratio 17 % which seems small = for the=20 core.
The Horse Power target is 200, so the 1.8 cubic inch core volume = to HP =3D=20 360 cubic inches. My core is 2" thick for 612 cubic inches. So I = theoretically=20 only require 59% of my existing core volume. 180 square inches of 2 = inch thick=20 core.
My inlet opening =3D 29% of that, so I'm close to optimum on = inlet opening=20 area. As I continue to test, and eventually fly, I could change to a = smaller=20 cooler, which could set it more 'normal' to the air flow, while also = moving it=20 aft allowing a longer diffuser.
The side mounted oil cooler was not a matter of choices. The = Mazda cooler=20 comes in one size, so does the cowl cheek opening. I just measured my = diffuser=20 inlet, 24.8 In Sq. The cooler face: 87.75 In Sq. Ratio =3D 28%. I = think that's=20 pretty good considering the airflow must turn 90 degrees to pass thru = the=20 core, then get sucked out thru surface louvers on the cowl = side.
Here's=20 hoping for the best, and trying again if it doesn't work.



-----Original=20 Message-----
From: Thomas Mann <tmann@n200lz.com>
To: = Rotary=20 motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, = Dec 21,=20 2009 6:01 pm
Subject: [FlyRotary] Re: Mereidth effect: [FlyRotary] = Re: Air=20 Flow Question

Thanks=20 for the links Ed.
It=20 looks like I have some reading to do!
 
 
From: Rotary = motors in=20 aircraft [mailto:flyrotary@lancaironli= ne.net]=20 On Behalf Of Ed Anderson
Sent: Monday, December 21, = 2009 7:19=20 PM
To: Rotary motors in aircraft
Subject: = [FlyRotary]=20 Mereidth effect: [FlyRotary] Re: Air Flow = Question
 
 
Thomas,=20 Here is probably the best, most understandable (without a lot of math) = on the=20 cooling challenge that I have come across.   You might want = to check=20 it out.   Here is one of the statements you will find in = this short=20 article
 
It has been shown that the diffuser = efficiency is key=20 in the reduction of the overall radiator drag. It is the most critical = part,=20 and unfortunately the most frequently botched by = homebuilders.
 
http://contrails.free.fr/engine_aerodyn_radia_en.php<= /SPAN>
 
Also=20 note his comment about how to control airflow once your intake is = 30-50% of=20 your core area =E2=80=93 may surprise you.
 
 
http://contrails.free.fr/tunnel_en.php
 
 
Here=20 is a summary by Meredith on the effect.  There is still some = debate about=20 whether the P-51 cooling system actually resulted in a net thrust = =E2=80=93 but, most=20 agree whether it did produce significant thrust or not the cooling = drag was=20 probably close to an optimum minimum. 
 
http://contrails.free.fr/refroid_meredith_en.php
 
You=20 are right, there is always trade offs.  You can certainly put an = oil=20 cooler in front of your radiator =E2=80=93 in effect you are just = making a thick=20 radiator as far as airflow is concerned.  Obviously you will have = hotter=20 air flow through the part of your radiator behind the oil cooler so = its=20 cooling effectiveness will be reduced.  Also, you may find that a = lot of=20 the air in their common duct may want to go through the other part of = the=20 radiator core =E2=80=93 due to its less air resistance.
Placing=20 them side by side (or top bottom) is another approach.  However, = it is my=20 opinion that unless your oil cooler and radiator core have similar air = flow=20 characteristics or great care is taken in designing your ducts to = each, that=20 air will take the route of least resistance.  So one  core = could end=20 up =E2=80=9Cbleeding=E2=80=99=E2=80=9D cooling air from the = other.  Similarly, the exit pressure=20 of one (generally the one with the least air resistance) will be = higher than=20 the one with less resistance. So this can cause airflow problems under = the=20 cowl as well.
Its my=20 opinion that keeping  your oil and coolant cores separate (if = possible=20 and there are always space constraints in our vehicles) and also = keeping their=20 air flow separate is generally the best course of action to get the = best=20 cooling.  But, compromises are frequently necessary, in which = case you=20 simply have to try and figure out the possible interaction and=20 effects.
 
Ed
 
Ed=20 Anderson
Rv-6A=20 N494BW Rotary Powered
Matthews,=20 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=20 aircraft [mailto:flyrotary@lancaironli= ne.net]=20 On Behalf Of Thomas Mann
Sent: Monday, December 21, = 2009 6:17=20 PM
To: Rotary motors in aircraft
Subject: = [FlyRotary] Re:=20 Air Flow Question
 
=E2=80=9CStick=20 with this group, we=E2=80=99ve all been there and have conquered the = cooling beast =E2=80=93=20 well, at least tamed it a bit.
 
Ed=E2=80=9D
 
 
That is the plan = Ed.=20
I=E2=80=99m = trying to figure out how=20 much radiator I can fit into my configuration. I=E2=80=99m running the = numbers and=20 drafting it out in AutoCAD.
 
I=E2=80=99m = hoping that I can cash=20 in on the Meredith Effect in my design. I=E2=80=99m planning on an = adjustable exhaust=20 opening much like the P-51s had. I=E2=80=99m not sure if I need it or = not but it=E2=80=99s=20 easier to not use it vs. add it later.
 
Question: If I = use a=20 separate oil cooler, can I place it in front of the radiator? =
I=E2=80=99ve = seen some installations=20 like this but it seems to me that there is a cost = involved.
 
T = Mann


__________ Information from ESET NOD32 = Antivirus,=20 version of virus signature database 3267 (20080714) = __________

The=20 message was checked by ESET NOD32 Antivirus.

http://www.eset.com
 ------=_NextPart_000_0009_01CA8469.A065A950--