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 4240981 for flyrotary@lancaironline.net; Thu, 29 Apr 2010 00:24:01 -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 8767B1737FF for ; Thu, 29 Apr 2010 12:23:24 +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 A8AB2BEC00B for ; Thu, 29 Apr 2010 12:23:22 +0800 (WST) Message-ID: <4FD1AA3170904516B018B92055443BEE@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 14:23:25 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CAE7A7.87BDD480" 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_0009_01CAE7A7.87BDD480 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Tracy, Fair enough - I know where your coming from now. Your right about = concentrating on the inlet side of the rad as the highest priority. George ( down under) I was talking about the usual methods of decreasing the pressure on = backside of heat exchangers, like very large exit opening, lip on bottom = of cooling exit, cowl flaps that protrude into the slipstream, radiators = mounted naked in the slipstream, etc. I was interested in the eductor = because it was an exception. It does not increase drag if done = properly. It's hard to do properly on the rotary and still have a = reasonably quiet exhaust though.... Tracy On Wed, Apr 28, 2010 at 5:59 PM, George Lendich = wrote: 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 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. 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 ------------------------------------------------------------------------ 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_0009_01CAE7A7.87BDD480 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Tracy,
Fair enough - I know where your coming = from now.=20 Your right about concentrating on the inlet side of the rad as the = highest=20 priority.
George ( down under)
I=20 was talking about the usual methods of decreasing the pressure on = backside of=20 heat exchangers, like very large exit opening, lip on bottom of = cooling exit,=20 cowl flaps that protrude into the slipstream, radiators mounted naked = in the=20 slipstream, etc.  I was interested in the eductor because it was = an=20 exception.  It does not increase drag if done properly.  = It's hard=20 to do properly on the rotary and still have a reasonably quiet exhaust = though....

Tracy

On Wed, Apr 28, 2010 at 5:59 PM, George = Lendich <lendich@aanet.com.au> = wrote:
Tracy,
Like yourself I have been = considering the=20 benefits of an Eductor for some time, but can't understand why it = would=20 cause extra drag.
 
As a matter of fact I thought it = might decrease=20 drag by speeding up the rad exit air back up to outside air speed as = it=20 exits the cowl.
 
Can you explain the reasons = behind the=20 increased drag issues.
George (down under)
"Since=20 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."

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=20 delta with low side help (even with an eductor) that you can with = the=20 proper inlet and diffuser.   This is especially true on = faster=20 airplanes.  A Pietenpol might be an exception.  =

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

Tracy

On Wed, Apr 28, 2010 at 9:19 AM, Chris = Owens -=20 Rotary <rotary@cmowens.com> wrote:
You=20 know, I don't know if this has been discussed, but the whole = pressure=20 differential thing got me thinking of something that I'm = surprised I=20 hadn't thought of earlier.  Since the draw of air via low = pressure=20 on the output side seems to be key, I wonder if an eductor type = of=20 scenario would work.

Back in my Navy days, we used to use = a=20 device called an in-line eductor for dewatering flooded = spaces. =20 Similar to a venturi, more or less, you pumped water through it, = it=20 created a suction, and it was designed to suck as much water = through it=20 as you put into it.  100 gallons per minute input would = dewater at=20 100 gallons per minute with 200 gallons per minute flowing = through the=20 output.  A representative device is here (perhaps not for = fluid=20 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=20 you think?  I imagine it would work well for a center = mounted=20 radiator with a centerline, below-the-nose scoop, so one could = utilize=20 the cheek inlets to provide source air for the outlet=20 side.

~Chris



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

Hi=20 George,

 

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

 

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

 

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

 

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

 

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

 

Ed

 

Ed=20 Anderson

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

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

 

Ed/=20 Tracy,

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

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

George ( down=20 under)

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

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

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

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

now back to = that=20 nasty composite work to pretty up the inlets again.  They = look=20 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=20 a  Sci Fi book (Vintage Season)  meaning something = which=20 induces euphoria. =20




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