X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.6) with ESMTP id 4241950 for flyrotary@lancaironline.net; Thu, 29 Apr 2010 17:31:46 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id 7DFCC173845 for ; Fri, 30 Apr 2010 05:31:05 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id BDCEFBEC079 for ; Fri, 30 Apr 2010 05:30:27 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Eductor scavenging of radiator outlet, WAS 20B RV-8 cooling results Date: Fri, 30 Apr 2010 07:30:30 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0013_01CAE837.0334D5C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 100429-1, 04/29/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0013_01CAE837.0334D5C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, I finally got to read all those web sites and discussions, There seems = to be a consensus that there are advantages, highly dependent upon = configuration - it will require more thought to the process, however = that's why I put it up in the first instance. A lot of discussion was concentrated on exhaust augmentation and I = was considering more in line of outside air augmentation - airspeed = driven by the prop and flight speed. I'm still concentrating on the problems associated. George ( down under) Hi George, =20 You may have missed the e mail where Tracy described his "Eductor" = experiment - one reason his drag was so high was he was flying without a = cowl - or part of one. In any case, cooling was great but drag was = horrendous. You could certainly do better on drag if you designed and = build a slightly more "sophisticated" one than Tracy quickly came up = with. However, the question still remains as to whether the benefits vs = cost equation is on the right side of the line using an eductor as = opposed says to larger inlet opening? Its not a question of can it be = done - its been done, the real question is if it offered some cost = effective benefit why are not more folks using it? =20 I've attached a couple of discussions links related to augmentation = that you might want to read. Basically, it appears that the reason most = folks are not using them more are due to it simply not being worth the = effort - unless you are an all out air racer. That's my take on it. =20 http://aafo.com/racing/news/98/intrepid.htm =20 = http://www.homebuiltairplanes.com/forums/firewall-forward-props-fuel-syst= em/395-exhaust-augmenter-cooling-system.html =20 = http://www.homebuiltairplanes.com/forums/design-structures-cutting-edge-t= echnology/4897-exhaust-augmentoed-cooling.html =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: Wednesday, April 28, 2010 6:00 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Eductor scavenging of radiator outlet, WAS = 20B RV-8 cooling results =20 Tracy, Like yourself I have been considering the benefits of an Eductor for = some time, but can't understand why it would cause extra drag.=20 =20 As a matter of fact I thought it might decrease drag by speeding up = the rad exit air back up to outside air speed as it exits the cowl. =20 Can you explain the reasons behind the increased drag issues. George (down under) "Since the draw of air via low pressure on the output side seems to = be key, I wonder if an eductor type of scenario would work." Sometimes I doubt my ability to get a point across clearly :-) An = eductor can be made to help (but very hard to do as Ed pointed out) but = the point I was trying to make in my original post is that the draw of = air on the low side is NOT key. You will never get a fraction of the = pressure delta with low side help (even with an eductor) that you can = with the proper inlet and diffuser. This is especially true on faster = airplanes. A Pietenpol might be an exception. =20 The inlet is what fixed my problem. This is an extreme example but = when I used low side help, it did cool but the drag caused the fuel = consumption to increase by 50 - 60% ! at the test speed of 130 mph. = That's not a price you want to pay. Tracy On Wed, Apr 28, 2010 at 9:19 AM, Chris Owens - Rotary = wrote: You know, I don't know if this has been discussed, but the whole = pressure differential thing got me thinking of something that I'm = surprised I hadn't thought of earlier. Since the draw of air via low = pressure on the output side seems to be key, I wonder if an eductor type = of scenario would work. Back in my Navy days, we used to use a device called an in-line = eductor for dewatering flooded spaces. Similar to a venturi, more or = less, you pumped water through it, it created a suction, and it was = designed to suck as much water through it as you put into it. 100 = gallons per minute input would dewater at 100 gallons per minute with = 200 gallons per minute flowing through the output. A representative = device is here (perhaps not for fluid use, but the concept is similar): http://www.1877eductors.com/eductor_gas_dimensions.htm I presume a similar approach could be taken with a radiator setup, = would you think? I imagine it would work well for a center mounted = radiator with a centerline, below-the-nose scoop, so one could utilize = the cheek inlets to provide source air for the outlet side. ~Chris =20 -------------------------------------------------------------------------= --- From: "Ed Anderson" Sent: Wednesday, April 28, 2010 7:08 AM To: "Rotary motors in aircraft" 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 =20 =20 ------=_NextPart_000_0013_01CAE837.0334D5C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
 Ed,
I finally got to read all those web = sites and=20 discussions, There seems to be a consensus that there are advantages, = highly=20 dependent upon configuration - it will require more thought to the = process,=20 however that's why I put it up in the first instance.
 
 A lot of discussion was = concentrated on=20 exhaust augmentation and I was considering more in line of outside air = augmentation - airspeed driven by the prop and flight speed.
I'm still concentrating on the = problems=20 associated.
George ( down under)
 

Hi=20 George,

 

You may = have missed=20 the e mail where Tracy described his =93Eductor=94 = experiment =96=20 one reason his drag was so high was he was flying without a cowl =96 = or part of=20 one.  In any case, cooling was great but drag was = horrendous.  You=20 could certainly do better on drag if you designed and build a slightly = more=20 =93sophisticated=94 one than Tracy quickly came up with.  = However,=20 the question still remains as to whether the benefits vs cost equation = is on=20 the right side of the line using an eductor as opposed says to=20   larger inlet opening?  Its not a question of can it = be done =96=20 its been done, the real question is if it offered some cost effective = benefit=20 why are not more folks using it?

 

I=92ve = attached a=20 couple of discussions links related to augmentation that you might = want to=20 read.  Basically, it appears that the reason most folks are not = using=20 them more are due to it simply not being worth the effort =96 unless = you are an=20 all out air racer.  That=92s my take on = it.

 

http://aafo.com/raci= ng/news/98/intrepid.htm

 

http://www.homebuil= tairplanes.com/forums/firewall-forward-props-fuel-system/395-exhaust-augm= enter-cooling-system.html

 

http://www.homebu= iltairplanes.com/forums/design-structures-cutting-edge-technology/4897-ex= haust-augmentoed-cooling.html

 

Ed=20 Anderson

Rv-6A = N494BW Rotary=20 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 = [mailto:flyrotary@lancaironline.net] On=20 Behalf Of George Lendich
Sent: Wednesday, April 28, 2010 = 6:00=20 PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: = Eductor=20 scavenging of radiator outlet, WAS 20B RV-8 cooling=20 results

 

Tracy,

Like yourself I have = been=20 considering the benefits of an Eductor for some time, but can't = understand why=20 it would cause extra drag.

 

As a matter of fact I = thought it=20 might decrease drag by speeding up the rad exit air back up to outside = air=20 speed as it exits the cowl.

 

Can you explain the = reasons=20 behind the increased drag issues.

George (down=20 under)

"Since the=20 draw of air via low pressure on the output side seems to be key, I = wonder if=20 an eductor type of scenario would work."

Sometimes I=20 doubt my ability to get a point across clearly :-)  An eductor = can be=20 made to help (but very hard to do as Ed pointed out)  but the = point I=20 was trying to make in my original post is that the draw of air on = the low=20 side is NOT key.   You will never get a fraction of the = pressure delta=20 with low side help (even with an eductor) that you can with the = proper inlet=20 and diffuser.   This is especially true on faster = airplanes. =20 A Pietenpol might be an exception. 

The inlet is what = fixed my=20 problem.  This is an extreme example but when I used low side = help, it=20 did cool but the drag caused the fuel consumption to increase by 50 = - 60% !=20 at the test speed of 130 mph.   That's not a price you want to=20 pay.

Tracy

On Wed, Apr 28, 2010 at 9:19 AM, Chris = Owens -=20 Rotary <rotary@cmowens.com>=20 wrote:

You know, I don't know = if this=20 has been discussed, but the whole pressure differential thing got me = thinking of something that I'm surprised I hadn't thought of = earlier. =20 Since the draw of air via low pressure on the output side seems to = be key, I=20 wonder if an eductor type of scenario would work.

Back in my = Navy=20 days, we used to use a device called an in-line eductor for = dewatering=20 flooded spaces.  Similar to a venturi, more or less, you pumped = water=20 through it, it created a suction, and it was designed to suck as = much water=20 through it as you put into it.  100 gallons per minute input = would=20 dewater at 100 gallons per minute with 200 gallons per minute = flowing=20 through the output.  A representative device is here (perhaps = not for=20 fluid use, but the concept is similar):

http://www.1877eductors.com/eductor_gas_dimensions.htm

I=20 presume a similar approach could be taken with a radiator setup, = would you=20 think?  I imagine it would work well for a center mounted = radiator with=20 a centerline, below-the-nose scoop, so one could utilize the cheek = inlets to=20 provide source air for the outlet=20 side.

~Chris

 

From: "Ed=20 Anderson" <eanderson@carolina.rr.com>
Sent: Wednesday, April 28, = 2010 7:08=20 AM
To: = "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: 20B = RV-8=20 cooling results

Hi=20 George,

 

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

 

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

 

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

 

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

 

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

 

Ed

 

Ed=20 Anderson

Rv-6A = N494BW Rotary=20 Powered

Matthews, = NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html<= FONT=20 face=3DArial size=3D2>

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

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

 

Ed/=20 Tracy,

Can't=20 say as I understand Tracy's set- up completely, other = than it's=20 toward the lower end of Rad sizes. I was thinking to myself = how I could=20 create a -ve pressure in the rad outlet to create a suction on the = Rad. We=20 all know how the exhaust augmentation works and I was wondering why = we can't=20 do the same thing with the rad outlets by running the rad outlets = inro a=20 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=20 outside air could be could controlled by a butterfly - simple = enough. I=20 know there emphasis on using shutter /flaps to control the cowl = outlet and I=20 believe their good at restricting air flow, but I don't know if this = equates=20 to a good -ve pressure behind the Rad. This presupposes the Rads are = completely enclosed for both inlet and outlet=20 air.

George (=20 down under)

75% of my=20 cooling problems were solved with the oil cooler change I did but = still=20 needed more margin for hot weather climbs.   Made the = decision to not=20 change or enlarge the cooling outlet (that adds drag)  so = went ahead=20 and butchered the pretty inlets I made. 
Ed Anderson's=20 spreadsheet on BTUs & CFM cooling air required was = instrumental in=20 deciding to go this way.   It showed that without = negative=20 pressure on the back side of the rads, there would never be enough = cfm to=20 do the job during climb at full throttle.  Negative pressure = is what=20 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, =20 and   4.875" dia for the oil.

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

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

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

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

 

 

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