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 5.3.6) with ESMTP id 4244405 for flyrotary@lancaironline.net; Sun, 02 May 2010 00:43:33 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=rv-4mike@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao101.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100502044252.TJEK2579.fed1rmmtao101.cox.net@fed1rmimpo03.cox.net> for ; Sun, 2 May 2010 00:42:52 -0400 Received: from willsPC ([174.66.174.143]) by fed1rmimpo03.cox.net with bizsmtp id CUig1e00D3600d204Uigq4; Sun, 02 May 2010 00:42:40 -0400 X-VR-Score: -30.00 X-Authority-Analysis: v=1.1 cv=b4II0uhcJPnwjva2/FqJSYAtAoopJitAe4Ogu0tU6w4= c=1 sm=1 a=c9VJGmjN1o4A: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=rT6EPJ7uD4Or_5Yacx4A:9 a=QkhFwE1EHUoFihvjugUA:7 a=ePe7ev_FbLtLFBRmi8-iVQJNW2AA:4 a=wPNLvfGTeEIA:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=2e8vWcZe-uw9eq0B:21 a=GH7YyXSSPKsIM5ZJ:21 a=DwdjpBgr_3_7Td2k4aUA:9 a=a0na0QIp0U8Ur1lQqaYA:7 a=dmKKvBI2i2SXPNI_i7f4swu04rMA:4 a=xxGp3PM7h1GROxI3:21 a=YZMexb9xia7R-m-F:21 a=+Wf/KPGOauV74ukzx3TzVw==:117 X-CM-Score: 0.00 Message-ID: <82282751815B40648F74743FA2295578@willsPC> From: "Mike Wills" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Augmentors (was Re: 20B RV-8 cooling results) Date: Sat, 1 May 2010 21:42:40 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0043_01CAE977.395AC330" 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_0043_01CAE977.395AC330 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, Thanks for the input - always valued. I question whether the augmentor = would help at all on the ground given the relatively low power settings. = Low exhaust flow trying to drag exit air through a constricted tube = would possibly cool worse on the ground than a conventional exit. You said "there's no question that the exhaust augmentation can work if = done properly...". If you mean there is no question that effective = cooling can be had in an installation using augmentors, I agree. Again, = C-310 and T-34 are examples. But if you mean that there is no question = that exhaust augmentation can provide effective cooling, reduce cooling = drag with a consequent increase in airplane performance, and also = reduce, not increase noise and weight, I'd ask you to cite examples. I = know of none. Mike Wills=20 From: Ed Anderson=20 Sent: Saturday, May 01, 2010 6:05 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: 20B RV-8 cooling results Hi Mike, =20 The theory indicates that once you get the inlet/diffuser combination = worked out - the inlet size should be in the range of from 25 - 40% of = core frontal area. After than, it's actually the exit conditions that = dominated the air flow through the core/cowl. A streamline duct = diffuser (K&W) is the most efficient practical diffuser (at least that I = have come across) - the theory behind it is to keep the air flow energy = (velocity) high until just before you expand the duct area in front of = the core to convert the dynamic energy to a localized pressure increase. = From what I have read, it appears that smoothness and preventing air = flow separation from the duct walls near the inlet is of major = importance. Any disturbance there creates an expanding "shadow" of = disturbed air which impinges on the core and reduces the effectiveness = of that area. So prevent flow separation is one of the key challenges. = =20 I developed my "Pinched" ducts for short run ducts (the streamline duct = requires something like 16" for cores our nominal size for optimum = performance). The ideal behind my "Pinched" ducts is to speed up the = airflow through the pinched area giving the boundary layer of the flow = more energy to stay attached to the duct walls as it makes the curve = just before the core. Any separation that does happened is much closer = to the core and generally up near the edges and corners - where the core = is not particularly effective in the first place. Been flying with them = for over 5 years and they do the job for my installation - however, just = about any, smooth flowing duct will add to cooling effectiveness - sharp = discontinuities generally do not help. =20 There is no question that the exhaust augmentation can work if done = properly, the question in my mind is whether there are easier ways to = accomplish the desired results. It's my opinion (have not tried one) is = that if it were easy to achieve success and there were major benefits, = we would be seeing them on many more installations. The one's I have = read about that seem to be successful were not what I would call simply = installations. Most have a long tunnel of some sort in which the = exhaust is directed out the end causing airflow inside the tunnel to be = accelerated and "dragged" along and out from under the cowl. In many = cowls that presents a considerable challenge to fabricate - as such = things as motor mounts and hardware have a way of getting in the = way.{:>) =20 =20 I can see that Exhaust augmentation might be advantageous for promoting = airflow during taxi and other low speed operations such as ground run up = - if other ways can not be found to do the job. But, if an installation = is not cooling at cruise - then the cooling system needs work=20 =20 Just an 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 Mike Wills Sent: Friday, April 30, 2010 10:39 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: 20B RV-8 cooling results =20 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. =20 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. =20 Mike Wills =20 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 =20 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_0043_01CAE977.395AC330 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
 
Thanks for the input - always valued. I = question whether=20 the augmentor would help at all on the ground given the relatively low = power=20 settings. Low exhaust flow trying to drag exit air through a constricted = tube=20 would possibly cool worse on the ground than a conventional = exit.
 
You said "there's no question that the exhaust = augmentation can work if done properly...". If you mean there is no = question=20 that effective cooling can be had in an installation using augmentors, I = agree.=20 Again, C-310 and T-34 are examples. But if you mean that there is no = question=20 that exhaust augmentation can provide effective cooling, reduce cooling = drag=20 with a consequent increase in airplane performance, and also reduce, not = increase noise and weight, I'd ask you to cite examples. I know of=20 none.
 
Mike Wills 

Sent: Saturday, May 01, 2010 6:05 AM
Subject: [FlyRotary] Re: 20B RV-8 cooling = results

Hi=20 Mike,

 

The theory = indicates=20 that once you get the inlet/diffuser combination worked out =96 the = inlet size=20 should be in the range of from 25 =96 40% of core frontal area.  = After than,=20 it=92s actually the exit conditions that dominated the air flow through = the=20 core/cowl.  A streamline duct diffuser (K&W) is the most = efficient=20 practical diffuser (at least that I have come across) =96 the theory = behind it is=20 to keep the air flow energy (velocity) high until just before you expand = the=20 duct area in front of the core to convert the dynamic energy to a = localized=20 pressure increase.  From what I have read, it appears that = smoothness and=20 preventing air flow separation from the duct walls near the inlet is of = major=20 importance.  Any disturbance there creates an expanding = =93shadow=94 of=20 disturbed air which impinges on the core and reduces the effectiveness = of that=20 area.  So prevent flow separation is one of the key = challenges. =20

 

I developed = my=20 =93Pinched=94 ducts for short run ducts (the streamline duct requires = something like=20 16=94 for cores our nominal size for optimum performance).  The = ideal behind=20 my =93Pinched=94 ducts is to speed up the airflow through the pinched = area giving=20 the boundary layer of the flow more energy to stay attached to the duct = walls as=20 it makes the curve just before the core.  Any separation that does = happened=20 is much closer to the core and generally up near the edges and corners = =96 where=20 the core is not particularly effective in the first place.  Been = flying=20 with them for over 5 years and they do the job for my installation =96 = however,=20 just about any, smooth flowing duct will add to cooling effectiveness = =96 sharp=20 discontinuities generally do not help.

 

There is no = question=20 that the exhaust augmentation can work if done properly, the question in = my mind=20 is whether there are easier ways to accomplish the desired = results.  It=92s=20 my opinion (have not tried one) is that if it were easy to achieve = success and=20 there were major benefits, we would be seeing them on many more=20 installations.  The one=92s I have read about that seem to be = successful were=20 not what I would call simply installations.  Most have a long = tunnel of=20 some sort in which the exhaust is directed out the end causing airflow = inside=20 the tunnel to be accelerated and  =93dragged=94 along and out from = under the=20 cowl.  In many cowls that presents a considerable challenge to = fabricate -=20 as such things as motor mounts and hardware have a way of getting in the = way.{:>) 

 

I can see = that Exhaust=20 augmentation might be advantageous for promoting airflow during taxi and = other=20 low speed operations such as ground run up =96 if other ways can not be = found to=20 do the job.  But, if an installation is not cooling at cruise =96 = then the=20  cooling system needs work

 

Just an=20 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 Mike Wills
Sent: Friday, April 30, 2010 = 10:39=20 PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: 20B RV-8 = cooling=20 results

 

Should have mentioned in = my=20 previous comment about augmentors, and related to Ed's comments here = regarding=20 positive pressure within the cowl impacting differential across the = core.=20 Cooling is one problem I have not experienced. And I think part of the = reason is=20 that unlike most of the guys currently flying tractor installations, = with my=20 radiator under the engine, exit air has an unobstructed=20 flow.

 

I think I actually did a = pretty=20 lousy job of building an inlet diffuser. I've never instrumented it and = taken=20 any measurements, but with some tweaking I bet I could reduce the inlet = size=20 some without a negative impact on cooling. I think it works pretty well = as is in=20 spite of the inlet because the exit is = good.

 

Mike=20 Wills

 

From: Ed=20 Anderson

Sent:=20 Wednesday, April 28, 2010 5:36 AM

To: Rotary motors in = aircraft=20

Subject:=20 [FlyRotary] Re: 20B RV-8 cooling=20 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 = completely,=20 other than it's toward the lower end of Rad sizes. I was thinking to = myself=20 how I could create a -ve pressure in the rad outlet to create a = suction on=20 the Rad. We all know how the exhaust augmentation works and I was = wondering why=20 we can't do the same thing with the rad outlets by running the rad = outlets inro=20 a larger outlet fed by outside air. At idle the air is fed by the prop = air=20 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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