X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036462 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 08:18:12 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.0 c=1 a=0aLk6q_wiroA:10 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=3oc9M9_CAAAA:8 a=ZZNEH-WgAAAA:8 a=5kgCHx-JAAAA:8 a=3T_JeE6tAAAA:8 a=nUuTZ29dAAAA:8 a=ztcgZFkk88gJPzf-UX8A:9 a=4wE-Q2xUNKPZmA9xJRYA:7 a=h_zZqLWjVH2BwQseVYqb2iI3plIA:4 a=puYnZ-EecwQA:10 a=782tgarBYgIA:10 a=8BQgeFA2TAwA:10 a=dBnkUEi4Sm4A:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=U8Ie8EnqySEA:10 a=BPCOYmGL8QAA:10 a=niKeoH4w14CIEyG0:21 a=DmgdiXnG0Ehh4HyZ:21 a=SSmOFEACAAAA:8 a=KvCz95cOQgmIzWGvi64A:9 a=Sj5hI60WH7ev8CpwXXMA:7 a=-C3BMldwFoyue8WUzrpvoiwfaVcA:4 a=92DAUPwbGLd-cc3s:21 a=fB6qy1ga86IeUba8:21 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:1318] helo=computername) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 92/C4-01470-F68123B4; Wed, 23 Dec 2009 13:17:37 +0000 From: "Ed Anderson" Message-ID: <92.C4.01470.F68123B4@cdptpa-omtalb.mail.rr.com> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Question Date: Wed, 23 Dec 2009 08:17:44 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001B_01CA83A8.6767F110" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcqDeqTx+waz0jLbT8u4Bf3brPDT1QAVgHsg In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_001B_01CA83A8.6767F110 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Neat looking installation. Seeing the turbo, I think you were wise to go to a larger core than the 1.8 ratio would indicate. That is the trouble with a "rule of Thumb" - it may not apply if your installation is different than that for with the rule was derived - or depending on your design point selection. Theory is a starting point - as pointed out by several, deviation from the "perfect" system almost always happens in the "real world". Finding a similar (successful ) installation to copy is not a bad approach. Air up near the prop end of the cowl is turbulent to say the least - for that reason it is likely that not using a more "optimum inlet" to keep out the boundary layer, may not have that much (if any) adverse affect. The main thing is to get sufficient air mass flow through the core, if you do that it will cool (assuming the core is adequate). Looking forward to hearing how the system performs in the air. The most frustrating thing I encountered back many years ago was what seemed to work and cool well on the ground - didn't in the air and vice versa. But, finally got it sorted out. 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 shipchief@aol.com Sent: Tuesday, December 22, 2009 9:49 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Mereidth effect: [FlyRotary] Re: Air Flow Question Yes; Thanks Ed. I went out to the garage and looked at my chin scoop radiator. 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. The Horse Power target is 200, so the 1.8 cubic inch core volume to HP = 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 = 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 = 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 - 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_001B_01CA83A8.6767F110 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Neat looking installation.  = Seeing  the turbo, I think you were wise to go to a larger core than the 1.8 ratio = would indicate.  That is the trouble with a “rule of Thumb” = – it may not apply if your installation is different than that for with = the rule was derived – or depending on your design point = selection.

 

Theory is a starting point – = as pointed out by several, deviation from the “perfect” system almost = always happens in the “real world”.  Finding a similar = (successful ) installation to copy is not a bad approach.

 

Air up near the prop end of the = cowl is turbulent to say the least – for that reason it is likely that not = using a more “optimum inlet” to keep out the boundary layer, =  may not have that much (if any) adverse affect.  The main thing is to = get sufficient air mass flow through the core, if you do that it will cool (assuming the core is adequate).

 

Looking forward to hearing how the = system performs in the air.  The most frustrating thing I encountered back = many years ago was what seemed to work and cool well on the ground – = didn’t in the air and vice versa.  But, finally got it sorted = out.

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of shipchief@aol.com
Sent: Tuesday, December = 22, 2009 9:49 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Mereidth effect: [FlyRotary] Re: Air Flow Question

 

Yes;

Thanks Ed. I went out to the = garage and looked at my chin scoop radiator.

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.

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.



-----Origina= l 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 = Question

Thanks for = the links Ed.<= /span>

It looks = like I have some reading to do!<= /span>

 

 

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

 <= /o:p>

 

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.<= /span>

 

 

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

 

 

 

 

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.  <= /span>

 

 

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.<= /span>

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.<= /span>

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.<= /span>

 

Ed<= /span>

 

Ed = Anderson

Rv-6A N494BW = Rotary Powered<= /span>

Matthews, = NC

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<= /span>

 <= /o:p>

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

 

Ed”<= /span>

 

 

That is = the plan Ed. <= /span>

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=

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