X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao101.cox.net ([68.230.241.45] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036096 for flyrotary@lancaironline.net; Tue, 22 Dec 2009 22:46:42 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao101.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20091223034608.TMDN4995.fed1rmmtao101.cox.net@fed1rmimpo02.cox.net> for ; Tue, 22 Dec 2009 22:46:08 -0500 Received: from willsPC ([68.105.91.47]) by fed1rmimpo02.cox.net with bizsmtp id LTm71d00911JKxw04Tm7W3; Tue, 22 Dec 2009 22:46:08 -0500 X-VR-Score: -40.00 X-Authority-Analysis: v=1.1 cv=hBBxVKrpT8NIO1i2+E6jIs4z/JDusIBXnpwMe9ND0ls= c=1 sm=1 a=0/axarwMsD7CBOw3dIi+FQ==:17 a=3oc9M9_CAAAA:8 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=Hl1Gy0H5AAAA:8 a=pLgmBSTelCxO90o5x68A:9 a=D96kGJ7B8TgI8Cf8w78A:7 a=VF42xB5hszKkJEvdbdEnPMLXU_UA:4 a=U8Ie8EnqySEA:10 a=iVkDmfvjeKcA:10 a=EzXvWhQp4_cA:10 a=EHKEzm4Ua7S76fgqWUEA:9 a=y3sn9R95YCRY7j4L8TAA:7 a=zLNPNDopaPsxouPwpR0tLlc6eWMA:4 a=0/axarwMsD7CBOw3dIi+FQ==:117 X-CM-Score: 0.00 Message-ID: From: "Mike Wills" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Oil Cooling Date: Tue, 22 Dec 2009 19:46:06 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0DC5_01CA833F.66EE6C00" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8089.726 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8089.726 This is a multi-part message in MIME format. ------=_NextPart_000_0DC5_01CA833F.66EE6C00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Been out of the loop for about a month - computer crash. New computer = setup now and trying to catch up on 600+ emails. My take on cooling for = what its worth: 1) I like (and used) the idea of separating the cooling circuits as much = as possible. Air to oil for the oil cooler and separate inlets/ducts for = the oil cooler and radiator. That way when one or the other doesn't work = they are as isolated as possible making it easier to diagnose and fix. 2) Don't bother with trying to take advantage of any sort of thrust = recovery. As far as I can tell, thrust recovery in the P-51 is legend. = Never found anything in the way of proof that it really occurred. It's = hard enough just designing and implementing something functional. 3) Go ahead and use the theories available on proper inlet/diffuser = design, but don't get too wrapped around the axle if you cant = design/fabricate/fit the theoretical optimum. Don't fall into the Paul L = trap of designing for the rest of your life at the expense of finishing = and flying. I fell victim to this and spent a couple of years building = inlets and diffusers. 4) Oversize your inlets/exits a little beyond what you think you'll = need. Wouldn't you rather overcool on initial flights and have to figure = out how to reduce your cooling than to see oil and coolant temps = climbing through redlines at 500 AGL on your first flight? 5) If you have more room for a bigger radiator, use it. You'll pay a = weight penalty, but more core surface area has the potential to reduce = cooling drag if the diffuser/inlet is right. 6) On a tractor airplane, coolers in the front. Everyone wants to copy = the P-51 belly scoop for aesthetics, theoretical advantages (ref #2 = above), etc... Coolers in the cowl take advantage of prop blast for = better ground cooling, weigh less by eliminating long plumbing runs, and = are less subject to boundary layer effects and other air inlet = obstruction issues. 7) Copy something that works. When I started my cooling system design = there werent a lot of options, but now there are quite a few guys = flying. I like what I have (really wanted to get rid of the cowl cheeks) = but could have flown at least 3 years sooner if I'd just copied Tracy. = If building a canard I'd copy Al G's setup in a heartbeat. Just my take on it. Note that my rules arent about designing the best = system, but about trying to get something that will work first time out. = There's enough to worry about on the first flight and its nice to have a = cooling system that works from day 1. Mike Wills RV-4 N144MW=20 From: shipchief@aol.com=20 Sent: Sunday, December 20, 2009 1:58 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Oil Cooling I've been reading everything I could on cooling after my first attempt = flopped. 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 = critical. 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 thermostat opened, the temps dropped a few degrees. Outside air temp 53F, 81% RH. Perhaps I should have run it longer, but = 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 = radiator gets air from the highest pressure point on the airframe: under = the prop spinner. I left out the upper lip because I believe this area = has attached 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 with the = radiator 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 = installation. 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 = wrote: Tracy, All that makes perfect sense and leads me to a question which has more = curiosity value than anything else. What actual size did you settle on = for the 20B. I'm curious to know if the 20B requires 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 gives = a .8 per cu" per hp. I wondering if this holds true for the 20B and = indeed the single 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 restrictive but flight tests showed almost no affect on = water cooling (which is OK) but a significant improvement in oil = cooling. I further restricted 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 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 changing 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 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 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 = relatively 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 = 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 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 and = 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 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 transfer the heat to the air. If the cooler is = simply too small, more airflow will not help much. =20 Tracy ------=_NextPart_000_0DC5_01CA833F.66EE6C00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Been out of the loop for about a month - = computer crash.=20 New computer setup now and trying to catch up on 600+ emails. My take=20 on cooling for what its worth:
 
1) I like (and used) the idea of separating = the cooling=20 circuits as much as possible. Air to oil for the oil cooler and separate = inlets/ducts for the oil cooler and radiator. That way when one or the=20 other doesn=92t work they are as isolated as possible making it = easier to=20 diagnose and fix.
2) Don=92t bother with trying to take = advantage of any=20 sort of thrust recovery. As far as I can tell, thrust recovery in the = P-51 is=20 legend. Never found anything in the way of proof that it really = occurred. It's=20 hard enough just designing and implementing something = functional.
3) Go ahead and use the theories available on = proper=20 inlet/diffuser design, but don=92t get too wrapped around the axle if = you cant=20 design/fabricate/fit the theoretical optimum. Don=92t fall into the Paul = L trap of=20 designing for the rest of your life at the expense of finishing and = flying. I=20 fell victim to this and spent a couple of years building inlets and = diffusers.
4) Oversize your inlets/exits a little beyond = what you=20 think you'll need. Wouldn=92t you rather overcool on initial flights and = have to=20 figure out how to reduce your cooling than to see oil and coolant temps = climbing=20 through redlines at 500 AGL on your first flight?
5) If you have more room for a bigger = radiator, use=20 it. You'll pay a weight penalty, but more core surface area has the = potential to=20 reduce cooling drag if the diffuser/inlet is right.
6) On a tractor airplane, coolers in the = front. Everyone=20 wants to copy the P-51 belly scoop for aesthetics, theoretical = advantages=20 (ref #2 above), etc... Coolers in the cowl take advantage of prop blast = for=20 better ground cooling, weigh less by eliminating long plumbing runs, and = are=20 less subject to boundary layer effects and other air inlet obstruction=20 issues.
7) Copy something that works. When I started = my cooling=20 system design there werent a lot of options, but now there are quite a = few guys=20 flying. I like what I have (really wanted to get rid of the cowl cheeks) = but=20 could have flown at least 3 years sooner if I'd just copied Tracy. If = building a=20 canard I'd copy Al G's setup in a heartbeat.
 
Just my take on it. Note that my rules arent = about=20 designing the best system, but about trying to get something that will=20 work first time out. There's enough to worry about on the first = flight and=20 its nice to have a cooling system that works from day 1.
 
Mike Wills
RV-4 N144MW 

Sent: Sunday, December 20, 2009 1:58 PM
Subject: [FlyRotary] Re: Oil Cooling

I've been reading everything I could on cooling after my first = attempt=20 flopped. Today I got my new cooling set up complete enough to ground = test. I=20 copied (my version) from several of you, notably Dave Leonard's radiator = and=20 Tracy's RV-4 oil cooler. Hat's off to Ed Anderson for all the under cowl = duct=20 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 = minutes and=20 got stabilized temps of 140F water and 170F oil. Once the oil cooler = thermostat=20 opened, the temps dropped a few degrees.
Outside air temp 53F, 81% RH. Perhaps I should have run it longer, = but=20 worries about leaks, fires etc. always make inspections prudent.
I suppose I have overcooled my plane, and added a big drag bucket = on the=20 chin, but hopefully it will be safe to fly, and I can work back from = 'too cool'=20 for more speed later.
After reading Tracy's post about adding the oil cooler exit duct, = and=20 different flow resistance of the two coolers,  I am glad I devided = the=20 two.
What I think lead to any success I might be having, is that I = devided the=20 air suppies and outlets. The oil cooler gets 100% of the right cowl = cheek air,=20 and the heated air exits the right side of the cowl. The radiator gets = air from=20 the highest pressure point on the airframe: under the prop spinner. I = left out=20 the upper lip because I believe this area has attached 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=20 engine, turbo, & fuel system. It shares the bottom outlet with = the=20 radiator air. I'm still working out the this duct.
.

-----Original=20 Message-----
From: Tracy Crook = <tracy@rotaryaviation.com>
To: Rotary=20 motors in aircraft <flyrotary@lancaironline.net>
Sent: Sat, Dec = 19,=20 2009 5:46 pm
Subject: [FlyRotary] Re: Oil Cooling

In = retrospect it does=20 seem obvious but I had never thought about matching the airflow = characteristics=20 of the water and oil heat exchangers before.  I should know by = tomorrow if=20 this is just wishful thinking.

Those heat exchanger volume = figures you=20 mentioned are at best just a rule of thumb but still useful.  Other = details=20 can make a world of difference.  For example, my RV-4 has had the = same=20 cooling components since day one but cooling on that first flight looked = hopeless.  Now it is fine on even the hottest days.  Heat = exchanger=20 size isn't everything.

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

I=20 can't think of any reason why the 20B would need more than 1.5 times the = 13Bs=20 cooling requirement if all other factors are the same.  That's a = big if of=20 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=20 question which has more curiosity value than anything else. What = actual size=20 did you settle on for the 20B. I'm curious to know if the 20B requires = more=20 cooling than 1.5 times a 13B.
 
Calculating the ( rule of thumb) = radiator size of=20 approx 600 cu" for 200hp, = giving 3 cu" per=20 HP, the size of the Mazda oil cooler then gives a .8 per cu" = per hp.=20 I wondering if this holds true for the 20B and indeed the single=20 rotor.
George ( down = under) 

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

On the theory that airflow = patterns=20 inside the cowl were blocking airflow through oil cooler, I installed = a=20 partial exit duct behind the radiator directing the airflow downward = toward=20 the cowl outlet.  It looked very restrictive but flight tests = showed=20 almost no affect on water cooling (which is OK)  but a = significant=20 improvement in oil cooling.   I further restricted the = airflow=20 through the rad by putting some roof ridge vent material inside the = inlet=20 diffuser.  This gave a tiny increase in water temp but a further=20 improvement in oil cooling.   Long story short,  after = several=20 more tests it became apparent that back pressure under the cowl was = having a=20 major effect on the oil cooling.   I have no idea why my = instrument=20 did not read the pressure correctly.  It works fine on the bench = and is=20 properly referenced to the static system in the plane.   The = temptation is to keep changing the cooling outlet scheme until the = internal=20 cowl back pressure is low enough to get the cooling good enough.  = My=20 belief is that this would lead to a very high drag solution.  You = may=20 remember the experiment I did by flying with the cowl removed.  = The=20 cooling was never a problem then (except perhaps too much cooling) but = the=20 drag was enormous.  The fuel burn was 60% higher at the test = airspeed of=20 130 mph.

The conclusion I eventually came to was that the rad = (because=20 of it's relatively low air flow resistance) is hogging the airflow = capability=20 of the cowl cooling outlet.  (cowl flap did not have enough = effect to fix=20 the problem).   Keep in mind that the oil cooler is a thick AC = evaporator=20 core that is very restrictive.   The current experiment is = to=20 replace it with a much less restrictive (to airflow) oil cooler.  = I found=20 the largest cooler that would fit in the same location as the AC core = and I'm=20 using the same diffuser as before (slightly modified to fit the larger = face of=20 the new cooler).  This cooler is only 2" thick and core volume is = 30%=20 less than the AC core.  It is slightly larger in volume than an = RX-7=20 cooler.  Without any back pressure (flying with cowl off), the AC = core=20 had way more than enough cooling capacity (146 F oil temp on a 93 = degree day)=20 so I'm hoping that this smaller cooler will be enough.  Should be = ready=20 to flight test it this week.

I should point out another = symptom. Power=20 setting (and therefore airspeed) had very little effect on the = cooling =20 (i.e., it didn't get much hotter at high power as long as airspeed = went up as=20 well.   Things got hot fast in climb however.  This = also=20 indicated to me that cooling was limited by airflow through the system = rather=20 than by the oil cooler's ability to transfer the heat to the = air.  If the=20 cooler is simply too small, more airflow will not help much. =20 =

Tracy

 ------=_NextPart_000_0DC5_01CA833F.66EE6C00--