X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-ma03.mx.aol.com ([64.12.206.41] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4032457 for flyrotary@lancaironline.net; Sun, 20 Dec 2009 16:59:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.41; envelope-from=SHIPCHIEF@aol.com Received: from imo-da04.mx.aol.com (imo-da04.mx.aol.com [205.188.169.202]) by imr-ma03.mx.aol.com (8.14.1/8.14.1) with ESMTP id nBKLwPHS028658 for ; Sun, 20 Dec 2009 16:58:25 -0500 Received: from SHIPCHIEF@aol.com by imo-da04.mx.aol.com (mail_out_v42.5.) id q.bb8.67343921 (43833) for ; Sun, 20 Dec 2009 16:58:20 -0500 (EST) Received: from smtprly-db03.mx.aol.com (smtprly-db03.mx.aol.com [205.188.249.154]) by cia-dc02.mx.aol.com (v126.13) with ESMTP id MAILCIADC026-5c424b2e9df3269; Sun, 20 Dec 2009 16:58:20 -0500 Received: from webmail-d053 (webmail-d053.sim.aol.com [205.188.170.229]) by smtprly-db03.mx.aol.com (v126.13) with ESMTP id MAILSMTPRLYDB038-5c424b2e9df3269; Sun, 20 Dec 2009 16:58:11 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Oil Cooling Date: Sun, 20 Dec 2009 16:58:11 -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_8CC4FD6A802B8CB_2618_50FD9_webmail-d053.sysops.aol.com" X-Mailer: AOL Webmail 30109-STANDARD Received: from 24.19.204.151 by webmail-d053.sysops.aol.com (205.188.170.229) with HTTP (WebMailUI); Sun, 20 Dec 2009 16:58:10 -0500 Message-Id: <8CC4FD6A7C9976B-2618-288DC@webmail-d053.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: SHIPCHIEF@aol.com ----------MB_8CC4FD6A802B8CB_2618_50FD9_webmail-d053.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" I've been reading everything I could on cooling after my first attempt flo= pped. Today I got my new cooling set up complete enough to ground test. I= copied (my version) from several of you, notably Dave Leonard's radiator= and Tracy's RV-4 oil cooler. Hat's off to Ed Anderson for all the under= cowl duct work on his website too.=20 I did achieve the stable temps at low power that Dave L told me are critic= al. I just now got done running my RV-8 13B turbo for over 20 minutes and= got stabilized temps of 140F water and 170F oil. Once the oil cooler ther= mostat opened, the temps dropped a few degrees. Outside air temp 53F, 81% RH. Perhaps I should have run it longer, but wor= ries about leaks, fires etc. always make inspections prudent. I suppose I have overcooled my plane, and added a big drag bucket on the= chin, but hopefully it will be safe to fly, and I can work back from 'too= cool' for more speed later. After reading Tracy's post about adding the oil cooler exit duct, and diff= erent flow resistance of the two coolers, I am glad I devided the two. What I think lead to any success I might be having, is that I devided the= air suppies and outlets. The oil cooler gets 100% of the right cowl cheek= air, and the heated air exits the right side of the cowl. The radiator ge= ts air from the highest pressure point on the airframe: under the prop spi= nner. I left out the upper lip because I believe this area has attached la= minar flow. The radiator exit air passes out the cowl bottom in the usual= way. The left cowl cheek is for Engine intake, plus surface cooling air on the= engine, turbo, & fuel system. It shares the bottom outlet with the radiat= or air. I'm still working out the this duct. . -----Original Message----- From: Tracy Crook To: Rotary motors in aircraft Sent: Sat, Dec 19, 2009 5:46 pm Subject: [FlyRotary] Re: Oil Cooling In retrospect it does seem obvious but I had never thought about matching= the airflow characteristics of the water and oil heat exchangers before.= I should know by tomorrow if this is just wishful thinking.=20 Those heat exchanger volume figures you mentioned are at best just a rule= of thumb but still useful. Other details can make a world of difference.= For example, my RV-4 has had the same cooling components since day one= but cooling on that first flight looked hopeless. Now it is fine on even= the hottest days. Heat exchanger size isn't everything. My 20B has significantly less than 1.5 times the core volume of my 13B ins= tallation. I'm hoping that better diffusers and other details will make= up for the relatively smaller heat exchangers. I can't think of any reason why the 20B would need more than 1.5 times the= 13Bs cooling requirement if all other factors are the same. That's a big= if of course. =20 Tracy On Sat, Dec 19, 2009 at 7:15 PM, George Lendich wro= te: Tracy, All that makes perfect sense and leads me to a question which has more cur= iosity value than anything else. What actual size did you settle on for th= e 20B. I'm curious to know if the 20B requires more cooling than 1.5 times= a 13B. =20 Calculating the ( rule of thumb) radiator size of approx 600 cu" for 200hp= , giving 3 cu" per HP, the size of the Mazda oil cooler then gives a .8 pe= r cu" per hp. I wondering if this holds true for the 20B and indeed the si= ngle rotor. George ( down under)=20 Just an update on my RV-8 / 20B oil cooling experiments. =20 On the theory that airflow patterns inside the cowl were blocking airflow= through oil cooler, I installed a partial exit duct behind the radiator= directing the airflow downward toward the cowl outlet. It looked very re= strictive but flight tests showed almost no affect on water cooling (which= is OK) but a significant improvement in oil cooling. I further restric= ted the airflow through the rad by putting some roof ridge vent material= inside the inlet diffuser. This gave a tiny increase in water temp but= a further improvement in oil cooling. Long story short, after several= more tests it became apparent that back pressure under the cowl was havin= g a major effect on the oil cooling. I have no idea why my instrument di= d not read the pressure correctly. It works fine on the bench and is prop= erly referenced to the static system in the plane. The temptation is to= keep changing the cooling outlet scheme until the internal cowl back pres= sure is low enough to get the cooling good enough. My belief is that this= would lead to a very high drag solution. You may remember the experiment= I did by flying with the cowl removed. The cooling was never a problem= then (except perhaps too much cooling) but the drag was enormous. The fu= el burn was 60% higher at the test airspeed of 130 mph. The conclusion I eventually came to was that the rad (because of it's rela= tively low air flow resistance) is hogging the airflow capability of the= cowl cooling outlet. (cowl flap did not have enough effect to fix the pr= oblem). Keep in mind that the oil cooler is a thick AC evaporator core= that is very restrictive. The current experiment is to replace it with= a much less restrictive (to airflow) oil cooler. I found the largest coo= ler that would fit in the same location as the AC core and I'm using the= same diffuser as before (slightly modified to fit the larger face of the= new cooler). This cooler is only 2" thick and core volume is 30% less th= an the AC core. It is slightly larger in volume than an RX-7 cooler. Wit= hout any back pressure (flying with cowl off), the AC core had way more th= an enough cooling capacity (146 F oil temp on a 93 degree day) so I'm hopi= ng that this smaller cooler will be enough. Should be ready to flight tes= t it this week. I should point out another symptom. Power setting (and therefore airspeed)= had very little effect on the cooling (i.e., it didn't get much hotter= at high power as long as airspeed went up as well. Things got hot fast= in climb however. This also indicated to me that cooling was limited by= airflow through the system rather than by the oil cooler's ability to tra= nsfer the heat to the air. If the cooler is simply too small, more airflo= w will not help much. =20 Tracy ----------MB_8CC4FD6A802B8CB_2618_50FD9_webmail-d053.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"
I've been reading everything I could on cooling after my first attemp= t flopped. Today I got my new cooling set up complete enough to ground tes= t. I copied (my version) from several of you, notably Dave Leonard's radia= tor and Tracy's RV-4 oil cooler. Hat's off to Ed Anderson for all the unde= r cowl duct work on his website too.
I did achieve the stable temps at low power that Dave L told me are= critical. I just now got done running my RV-8 13B turbo for over 20 minut= es and got stabilized temps of 140F water and 170F oil. Once the oil coole= r thermostat opened, the temps dropped a few degrees.
Outside air temp 53F, 81% RH. Perhaps I should have run it longer, bu= t worries about leaks, fires etc. always make inspections prudent.
I suppose I have overcooled my plane, and added a big drag bucket on= the chin, but hopefully it will be safe to fly, and I can work back from= 'too cool' for more speed later.
After reading Tracy's post about adding the oil cooler exit duct, and= different flow resistance of the two coolers,  I am glad I devided= the two.
What I think lead to any success I might be having, is that I devided= the air suppies and outlets. The oil cooler gets 100% of the right cowl= cheek air, and the heated air exits the right side of the cowl. The radia= tor gets air from the highest pressure point on the airframe: under the pr= op spinner. I left out the upper lip because I believe this area has attac= hed laminar flow. The radiator exit air passes out the cowl bottom in the= usual way.
The left cowl cheek is for Engine intake, plus surface cooling air on= the engine, turbo, & fuel system. It shares the bottom outlet wi= th the radiator air. I'm still working out the this duct.
.

-----Original Message-----
From: Tracy Crook <tracy@rotaryaviation.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sat, Dec 19, 2009 5:46 pm
Subject: [FlyRotary] Re: Oil Cooling

In retrospect= it does seem obvious but I had never thought about matching the airflow= characteristics of the water and oil heat exchangers before.  I shou= ld know by tomorrow if this is just wishful thinking.

Those heat exchanger volume figures you mentioned are at best just a rule= of thumb but still useful.  Other details can make a world of differ= ence.  For example, my RV-4 has had the same cooling components since= day one but cooling on that first flight looked hopeless.  Now it is= fine on even the hottest days.  Heat exchanger size isn't everything= .

My 20B has significantly less than 1.5 times the core volume of my 13B ins= tallation.  I'm hoping that better diffusers and other details will= make up for the relatively smaller heat exchangers.

I can't think of any reason why the 20B would need more than 1.5 times the= 13Bs cooling requirement if all other factors are the same.  That's= a big if of course. 

Tracy


On Sat, Dec 19, 2009 at 7:15 PM, George Lendich= <lendich@aanet= .com.au> wrote:
Tracy,
All that makes perfect sense and leads me= to a question which has more curiosity value than anything else. What act= ual size did you settle on for the 20B. I'm curious to know if the 20B req= uires more cooling than 1.5 times a 13B.
 
Calculating the ( rule of thumb) radiator= size of approx 600 cu" for 200hp,= giving 3 cu" per HP, the size of the Mazda oil cooler then give= s a .8 per cu" per hp. I wondering if this holds true for the 20B and inde= ed the single rotor.
George ( down under) 

Just an update on my RV-8 / 20B  oil cooling experiments. 

On the theory that airflow patterns inside the cowl were blocking airflow= through oil cooler, I installed a partial exit duct behind the radiator= directing the airflow downward toward the cowl outlet.  It looked ve= ry restrictive but flight tests showed almost no affect on water cooling= (which is OK)  but a significant improvement in oil cooling. &n= bsp; I further restricted the airflow through the rad by putting some roof= ridge vent material inside the inlet diffuser.  This gave a tiny inc= rease in water temp but a further improvement in oil cooling.  = Long story short,  after several more tests it became apparent that= back pressure under the cowl was having a major effect on the oil cooling= .   I have no idea why my instrument did not read the pressure= correctly.  It works fine on the bench and is properly referenced to= the static system in the plane.   The temptation is to keep cha= nging the cooling outlet scheme until the internal cowl back pressure is= low enough to get the cooling good enough.  My belief is that this= would lead to a very high drag solution.  You may remember the exper= iment I did by flying with the cowl removed.  The cooling was never= a problem then (except perhaps too much cooling) but the drag was enormou= s.  The fuel burn was 60% higher at the test airspeed of 130 mph.

The conclusion I eventually came to was that the rad (because of it's rela= tively low air flow resistance) is hogging the airflow capability of the= cowl cooling outlet.  (cowl flap did not have enough effect to fix= the problem).   Keep in mind that the oil cooler is a thick AC evapo= rator core that is very restrictive.   The current experiment is= to replace it with a much less restrictive (to airflow) oil cooler. = I found the largest cooler that would fit in the same location as the AC= core and I'm using the same diffuser as before (slightly modified to fit= the larger face of the new cooler).  This cooler is only 2" thick an= d core volume is 30% less than the AC core.  It is slightly larger in= volume than an RX-7 cooler.  Without any back pressure (flying with= cowl off), the AC core had way more than enough cooling capacity (146 F= oil temp on a 93 degree day) so I'm hoping that this smaller cooler will= be enough.  Should be ready to flight test it this week.

I should point out another symptom. Power setting (and therefore airspeed)= had very little effect on the cooling  (i.e., it didn't get much hot= ter at high power as long as airspeed went up as well.   Things= got hot fast in climb however.  This also indicated to me that cooli= ng was limited by airflow through the system rather than by the oil cooler= 's ability to transfer the heat to the air.  If the cooler is simply= too small, more airflow will not help much. 

Tracy

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