X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao106.cox.net ([68.230.241.40] verified) by logan.com (CommuniGate Pro SMTP 5.3.6) with ESMTP id 4243329 for flyrotary@lancaironline.net; Fri, 30 Apr 2010 22:40:03 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.40; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao106.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100501023927.NVFP1296.fed1rmmtao106.cox.net@fed1rmimpo03.cox.net> for ; Fri, 30 Apr 2010 22:39:27 -0400 Received: from willsPC ([174.66.174.143]) by fed1rmimpo03.cox.net with bizsmtp id C2fF1e00G3600d2042fFlE; Fri, 30 Apr 2010 22:39:15 -0400 X-VR-Score: 0.00 X-Authority-Analysis: v=1.1 cv=b4II0uhcJPnwjva2/FqJSYAtAoopJitAe4Ogu0tU6w4= c=1 sm=1 a=l_ttm92naw4A:10 a=+Wf/KPGOauV74ukzx3TzVw==:17 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=8SX5LJRNrZKEco2SCvoA:9 a=AOQqQvyXihLe7QSJV2cA:7 a=s4CA3808K_dWI2qRsrTeXkGjID8A:4 a=wPNLvfGTeEIA:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=xavMt7zHiHiauaAQ:21 a=UL6lqsUr-3YQHT9I:21 a=PEmhUTj-kp42OZCsiXMA:9 a=eYuUiHYWdxyfIh2SbAcA:7 a=eow-rBCfF6gQpOGtdwZ675nM9XQA:4 a=V5HlsLBezYHnMNt4:21 a=l5rDDcAPJK7ZqxsD:21 a=+Wf/KPGOauV74ukzx3TzVw==:117 X-CM-Score: 0.00 Message-ID: From: "Mike Wills" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: 20B RV-8 cooling results Date: Fri, 30 Apr 2010 19:39:16 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0091_01CAE89C.D199F2F0" 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_0091_01CAE89C.D199F2F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Should have mentioned in my previous comment about augmentors, and = related to Ed's comments here regarding positive pressure within the = cowl impacting differential across the core. Cooling is one problem I = have not experienced. And I think part of the reason is that unlike most = of the guys currently flying tractor installations, with my radiator = under the engine, exit air has an unobstructed flow. I think I actually did a pretty lousy job of building an inlet diffuser. = I've never instrumented it and taken any measurements, but with some = tweaking I bet I could reduce the inlet size some without a negative = impact on cooling. I think it works pretty well as is in spite of the = inlet because the exit is good. Mike Wills From: Ed Anderson=20 Sent: Wednesday, April 28, 2010 5:36 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: 20B RV-8 cooling results Hi George, =20 As you know, taking heat away from your radiator cores requires = sufficient air mass flow - a number of factors affect this - one of the = principle factors is pressure differential across your core. No = pressure differential =3D no flow. The primary positive pressure on the = front side of the core comes from converting dynamic energy of the = moving air into a local static pressure increase in front of the core. = This is basically limited by your airspeed and efficiency of your = duct/diffuser. The back side of your core air flow (in most = installations) exits inside the cowl. Therefore any positive pressure = above ambient under the cowl is going to reduce the pressure = differential across your core. So once you have the best duct/diffuser = you can achieve on the front side of the core - the only thing left to = increase the pressure differential is to reduce the pressure under the = cowl. =20 An extreme example is someone who flies with an opening (such as one of = the typical inlet holes beside the prop) exposed to the air flow. In = effect this hole with little/no resistance to airflow can "pressurize" = the cowl and raise the air pressure behind the radiator cores reducing = the pressure differential and therefore the cooling. Exhaust = augmentation is theoretically a way to reduce the under the cowl = pressure by using the exhaust pulse to "pump" air from under the cowl, = thereby improving the Dp across the core and therefore your cooling. =20 While exhaust augmentation can apparently work - there was a KITPLANE = issue back several years ago on the topic showing several installations = where this was used. However, from what I read (and think I = understand), it takes some carefully planning to get an installation to = work correct and the effort is not trivial. Give the challenges you may = encounter (such as motor mount struts, etc), fabrication of the = augmentation exit, the need to have the exhaust pulse exit at or inside = the cowl (or construct an extended bottom cowl tunnel) means you would = have the bark of a rotary in front of your feet. Also, to gain maximum = advantage of these techniques, it is desirable to have the exhaust = velocity at the maximum - which implies little/no muffling. Having had = my muffler back out one time (at the cowl exit), I can tell you that you = do not want to position the pilot behind the exhaust outlet (in my = opinion). It is much quieter when you have the exhaust exit behind the = position of the pilot {:>). =20 Some few people seem to have been able to achieve some degree of = success, but even in aircraft where you have an engine without the = aggressive bark of the rotary, you seldom see it used. The basic reason = (in my opinion), is that it offers few advantages (cooling wise) that = can not be achieved easier and more reliability by other methods. For = an all out racer where noise and discomfort is secondary, it may have = some benefit. =20 Having said that, it's clear that in some installations it appears to = work well (see KITPLANE issue), but if it were the magic solution, I = think many more folks would be employing it - but, again, just my = opinion. =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 = Behalf Of George Lendich Sent: Tuesday, April 27, 2010 9:41 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: 20B RV-8 cooling results =20 Ed/ Tracy, Can't say as I understand Tracy's set- up completely, other than it's = toward the lower end of Rad sizes. I was thinking to myself how I could = create a -ve pressure in the rad outlet to create a suction on the Rad. = We all know how the exhaust augmentation works and I was wondering why = we can't do the same thing with the rad outlets by running the rad = outlets inro a larger outlet fed by outside air. At idle the air is fed = by the prop air stream and at level fight it is fed by outside air = stream. The outside air could be could controlled by a butterfly - simple = enough. I know there emphasis on using shutter /flaps to control the = cowl outlet and I believe their good at restricting air flow, but I = don't know if this equates to a good -ve pressure behind the Rad. This = presupposes the Rads are completely enclosed for both inlet and outlet = air. George ( down under) 75% of my cooling problems were solved with the oil cooler change I = did but still needed more margin for hot weather climbs. Made the = decision to not change or enlarge the cooling outlet (that adds drag) = so went ahead and butchered the pretty inlets I made. =20 Ed Anderson's spreadsheet on BTUs & CFM cooling air required was = instrumental in deciding to go this way. It showed that without = negative pressure on the back side of the rads, there would never be = enough cfm to do the job during climb at full throttle. Negative = pressure is what I had when I flew without the cowl on but oh what a = draggy condition that was.=20 The old inlets were 4.5" diameter for the radiator and 4.125" diameter = for oil cooler. New inlets are 5.190" for the rad, and 4.875" dia for the = oil. This may not sound like a lot but it represents a 36% increase in = inlet area. Results were excellent. Oil temp went down 19 degrees at the test = speed (130) and water temp dropped 9 degrees. On 80 degree day and 500 = ft msl the oil temp maxed out at 194F at 210 mph which is way faster = than I would normally go at this altitude. Temp was around 175 at 130. = Oil Temp in climb remained below redline (210) but the temperature = lapse rate today made results not very meaningful. OAT was dropping 14 = degrees a minute at 3000 fpm climb rate.=20 now back to that nasty composite work to pretty up the inlets again. = They look like large stubby pitot tubes now. I hadn't thought of a good name for the RV-8 but a friend in = California recently came up with the winning idea which fit it well. = "Euphoriac" It's a term from a Sci Fi book (Vintage Season) meaning = something which induces euphoria. =20 ------=_NextPart_000_0091_01CAE89C.D199F2F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Should have mentioned in my previous comment = about=20 augmentors, and related to Ed's comments here regarding positive = pressure within=20 the cowl impacting differential across the core. Cooling is one problem = I have=20 not experienced. And I think part of the reason is that unlike most of = the guys=20 currently flying tractor installations, with my radiator under the = engine, exit=20 air has an unobstructed flow.
 
I think I actually did a pretty lousy job of = building an=20 inlet diffuser. I've never instrumented it and taken any measurements, = but with=20 some tweaking I bet I could reduce the inlet size some without a = negative impact=20 on cooling. I think it works pretty well as is in spite of the inlet = because the=20 exit is good.
 
Mike Wills

Sent: Wednesday, April 28, 2010 5:36 AM
Subject: [FlyRotary] Re: 20B RV-8 cooling = results

Hi=20 George,

 

As you know, = taking=20 heat away from your radiator cores requires sufficient air mass flow =96 = a number=20 of factors affect this =96 one of the principle factors is pressure = differential=20 across your core.  No pressure differential =3D no flow.  The = primary=20 positive pressure on the front side of the core comes from converting = dynamic=20 energy of the moving air into a local static pressure increase in front = of the=20 core.  This is basically limited by your airspeed and efficiency of = your=20 duct/diffuser.  The back side of your core air flow (in most = installations)=20 exits inside the cowl.  Therefore any positive pressure above = ambient under=20 the cowl is going to reduce the pressure differential across your = core.  So=20 once you have the best duct/diffuser you can achieve on the front side = of the=20 core =96 the only thing left to increase the pressure differential is to = reduce=20 the pressure under the cowl.

 

An extreme = example is=20 someone who flies with an opening (such as one of the typical inlet = holes beside=20 the prop) exposed to the air flow.  In effect this hole with = little/no=20 resistance to airflow can =93pressurize=94 the cowl and raise the air = pressure=20 behind the radiator cores reducing the pressure differential and = therefore the=20 cooling.  Exhaust augmentation is theoretically a way to reduce the = under=20 the cowl pressure by using the exhaust pulse to =93pump=94 air from = under the cowl,=20 thereby improving the Dp across the = core and=20 therefore your cooling.

 

While exhaust = augmentation can apparently work =96 there was a KITPLANE issue back = several years=20 ago on the topic showing several installations where this was = used. =20 However, from what I read (and think I understand), it takes some = carefully=20 planning to get an installation to work correct and the effort is not=20 trivial.  Give the challenges you may encounter (such as motor = mount=20 struts, etc), fabrication of the augmentation exit,  the need to = have the=20 exhaust pulse exit at or inside the cowl (or construct an extended = bottom cowl=20 tunnel) means you would have the bark of a rotary in front of your = feet. =20 Also, to gain maximum advantage of these techniques, it is desirable to = have the=20 exhaust velocity at the maximum =96 which implies little/no = muffling.  Having=20 had my muffler back out one time (at the cowl exit), I can tell you that = you do=20 not want to position the pilot behind the exhaust outlet (in my = opinion). =20 It is much quieter when you have the exhaust exit behind the position of = the=20 pilot {:>).

 

Some few = people seem to=20 have been able to achieve some degree of success, but even in aircraft = where you=20 have an engine without the aggressive bark of the rotary, you seldom see = it=20 used.  The basic reason (in my opinion), is that it offers few = advantages=20 (cooling wise) that can not be achieved easier and more reliability by = other=20 methods.  For an all out racer where noise and discomfort is = secondary, it=20 may have some benefit.

 

Having said = that, it=92s=20 clear that in some installations it appears to work well (see KITPLANE = issue),=20 but if it were the magic solution, I think many more folks would be = employing it=20 =96 but, again, just my opinion.

 

Ed

 

Ed=20 Anderson

Rv-6A N494BW=20 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.r= otaryaviation.com/Rotorhead%20Truth.htm

From:=20 Rotary motors in aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of George Lendich
Sent: Tuesday, April 27, 2010 = 9:41=20 PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: 20B RV-8 = cooling=20 results

 

Ed/=20 Tracy,

Can't say as I understand = Tracy's set- = up=20 completely, other than it's toward the lower end of Rad sizes. I was = thinking to=20 myself how I could create a -ve pressure in the rad outlet to = create a=20 suction on the Rad. We all know how the exhaust augmentation works and I = was=20 wondering why we can't do the same thing with the rad outlets by running = the rad=20 outlets inro a larger outlet fed by outside air. At idle the air is fed = by the=20 prop air stream and at level fight it is fed by outside air=20 stream.

The outside air could = be could=20 controlled by a butterfly - simple enough. I know there emphasis on = using=20 shutter /flaps to control the cowl outlet and I believe their good at=20 restricting air flow, but I don't know if this equates to a good -ve = pressure=20 behind the Rad. This presupposes the Rads are completely enclosed for = both inlet=20 and outlet air.

George ( down=20 under)

75% of my cooling problems were solved with = the oil=20 cooler change I did but still needed more margin for hot weather = climbs.=20   Made the decision to not change or enlarge the cooling outlet = (that=20 adds drag)  so went ahead and butchered the pretty inlets I = made. =20
Ed Anderson's spreadsheet on BTUs & CFM cooling air required = was=20 instrumental in deciding to go this way.   It showed that = without=20 negative pressure on the back side of the rads, there would never be = enough=20 cfm to do the job during climb at full throttle.  Negative = pressure is=20 what I had when I flew without the cowl on but oh what a draggy = condition that=20 was.

The old inlets were 4.5" diameter for the radiator and = 4.125"=20 diameter for oil cooler.
New inlets=20 are        5.190" for the = rad,  and=20   4.875" dia for the oil.

This may not sound like a lot = but it=20 represents a 36% increase in inlet area.

Results were = excellent. =20 Oil temp went down 19 degrees at the test speed (130) and water temp = dropped 9=20 degrees.  On 80 degree day and 500 ft msl the oil temp maxed out = at 194F=20 at 210 mph which is way faster than I would normally go at this=20 altitude.  Temp was around 175 at 130.    Oil Temp in = climb=20 remained below redline (210) but the temperature lapse rate today made = results=20 not very meaningful.  OAT was dropping 14 degrees a minute at = 3000 fpm=20 climb rate.

now back to that nasty composite work to pretty up = the=20 inlets again.  They look like large stubby pitot tubes = now.

I=20 hadn't thought of a good name for the RV-8 but a friend in California = recently=20 came up with the winning idea which fit it well. "Euphoriac"  = It's a term=20 from a  Sci Fi book (Vintage Season)  meaning something = which=20 induces euphoria. =20

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