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 4240633 for flyrotary@lancaironline.net; Wed, 28 Apr 2010 18:11:26 -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 8B46D1738FE for ; Thu, 29 Apr 2010 06:10:49 +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 B19BDBEC00C for ; Thu, 29 Apr 2010 06:10:48 +0800 (WST) Message-ID: <73DD60C7BB774BB1A2EF2ABD8FB26E1F@ownerf1fc517b8> 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: Thu, 29 Apr 2010 08:10:51 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0033_01CAE773.7BCFED40" 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 100428-1, 04/28/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0033_01CAE773.7BCFED40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris, Never heard of the term eductor before, so I've learnt something today, = but Ernest is right that's the same as exhaust augmentation, I guess you = could say exhaust augmentation by way of using an eductor. Seems like thinking along these lines is logical but is limited in it's = effectiveness - but I'm still unsure why. Thanks for your input, at least I wasn't out on a limb by myself and it = looks like Tracy went and tried it already. George (down under) 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 -------------------------------------------------------------------------= ----- 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, 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. 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. 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 {:>). 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. 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. Ed 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 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_0033_01CAE773.7BCFED40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Chris,
Never heard of the term eductor before, = so I've=20 learnt something today, but Ernest is right that's the same as exhaust=20 augmentation, I guess you could say exhaust augmentation by way of using = an=20 eductor.
Seems like thinking along these = lines is=20 logical but is limited in it's effectiveness - but I'm still unsure=20 why.
Thanks for your input, at least I = wasn't out=20 on a limb by myself and it looks like Tracy went and tried it=20 already.
George (down under)
You know, I=20 don't know if this has been discussed, but the whole pressure = differential=20 thing got me thinking of something that I'm surprised I hadn't thought = of=20 earlier.  Since the draw of air via low pressure on the output = side seems=20 to be key, I wonder if an eductor type of scenario would = work.

Back in=20 my Navy 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 = through=20 the output.  A representative device is here (perhaps not for = fluid use,=20 but the concept is similar):

http://ww= w.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 a=20 centerline, below-the-nose scoop, so one could utilize the cheek = inlets to=20 provide source air for the outlet side.

~Chris



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

Hi=20 George,

 

As you = know,=20 taking heat away from your radiator cores requires sufficient air mass = flow -=20 a number of factors affect this - one of the principle factors is = pressure=20 differential across your core.  No pressure differential =3D no = flow. =20 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=20 increase in front of the core.  This is basically limited by your = airspeed and efficiency of your duct/diffuser.  The back side of = your=20 core air flow (in most installations) exits inside the cowl.  = Therefore=20 any positive pressure above ambient under the cowl is going to reduce = the=20 pressure differential across your core.  So once you have the = best=20 duct/diffuser you can achieve on the front side of the core - the only = thing=20 left to increase the pressure differential is to reduce the pressure = under the=20 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 some=20 carefully planning to get an installation to work correct and the = effort is=20 not 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=20 the exhaust velocity at the maximum - which implies little/no = muffling. =20 Having had my muffler back out one time (at the cowl exit), I can tell = you=20 that you do not want to position the pilot behind the exhaust outlet = (in my=20 opinion).  It is much quieter when you have the exhaust exit = behind the=20 position of the pilot {:>).

 

Some few = people=20 seem to have been able to achieve some degree of success, but even in = aircraft=20 where you have an engine without the aggressive bark of the rotary, = you seldom=20 see it used.  The basic reason (in my opinion), is that it offers = few=20 advantages (cooling wise) that can not be achieved easier and more = reliability=20 by other methods.  For an all out racer where noise and = discomfort is=20 secondary, it may have some 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=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: Rotary=20 motors in aircraft = [mailto:flyrotary@lancaironline.net]=20 On Behalf Of George=20 Lendich
Sent: = Tuesday, April=20 27, 2010 9:41 PM
To:=20 Rotary motors in=20 aircraft
Subject: [FlyRotary] Re: 20B = RV-8 cooling=20 results

 

Ed/=20 Tracy,

Can't say=20 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 all=20 know how the exhaust augmentation works and I was wondering why we = can't do=20 the same thing with the rad outlets by running the rad outlets inro a = larger=20 outlet fed by outside air. At idle the air is fed by the prop air = stream and=20 at level fight it is fed by outside air 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=20 completely enclosed for both inlet and outlet air.

George (=20 down under)

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

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

This may not = sound like=20 a lot 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 oil=20 temp maxed out at 194F at 210 mph which is way faster than I would = normally=20 go at this altitude.  Temp was around 175 at 130.    = Oil Temp=20 in climb remained below redline (210) but the temperature lapse rate = today=20 made results not very meaningful.  OAT was dropping 14 degrees = a minute=20 at 3000 fpm climb rate.

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

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


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