X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-vw0-f52.google.com ([209.85.212.52] verified) by logan.com (CommuniGate Pro SMTP 5.3.6) with ESMTP id 4240774 for flyrotary@lancaironline.net; Wed, 28 Apr 2010 21:09:58 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.212.52; envelope-from=rwstracy@gmail.com Received: by vws10 with SMTP id 10so1032965vws.25 for ; Wed, 28 Apr 2010 18:09:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:content-type; bh=gFVIvz/Y716ue9DpOT8WzGjGwUT3eEnHqRD1HswmtD8=; b=lgnsp9y9FzvqfteqxX3e7OAjy+aWKAfXA14PeWsRgKF5QjqCI7kP4jrsEK2Wg3wvuC clT5OIKFsSrWc/8mZWwfJdTEHhNEvl63zKK/Y+9vh3gxOHWFrlhQzHpdeHjm3eiT1u02 +iuBKmVXf6NUVMZ7yJrO3aTS22Z6gmaMTdHoM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=fc/cCy1mv6A9t8aRsC5N7XcMvor+GDaJ1tPQljkHGO3e7OPKDohH3KDo4QlFkuique fIKbGkwkK6Yeo+M9vjMLkKO6xuGm1sa1HDO7cNCQzyUl6CJ+Z29gz3jEvo6evSiduj8b rwb1d9tGO9d64qGsFF1NG7yRM1Y8RaHe2obGI= MIME-Version: 1.0 Received: by 10.220.60.13 with SMTP id n13mr5970036vch.238.1272503362676; Wed, 28 Apr 2010 18:09:22 -0700 (PDT) Sender: rwstracy@gmail.com Received: by 10.220.97.212 with HTTP; Wed, 28 Apr 2010 18:09:22 -0700 (PDT) In-Reply-To: References: Date: Wed, 28 Apr 2010 21:09:22 -0400 X-Google-Sender-Auth: 0ae7770090ed5211 Message-ID: Subject: Re: [FlyRotary] Re: Eductor scavenging of radiator outlet, WAS 20B RV-8 cooling results From: Tracy Crook To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=e0cb4e887527e86ff1048555c62f --e0cb4e887527e86ff1048555c62f Content-Type: text/plain; charset=ISO-8859-1 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. > > 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. > > 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 >> = 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. >> 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. >> >> 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. >> >> 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. >> >> >> > --e0cb4e887527e86ff1048555c62f Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable I was talking about the usual methods of decreasing the pressure on backsid= e of heat exchangers, like very large exit opening, lip on bottom of coolin= g exit, cowl flaps that protrude into the slipstream, radiators mounted nak= ed in the slipstream, etc.=A0 I was interested in the eductor because it wa= s an exception.=A0 It does not increase drag if done properly.=A0 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 <lendich@aanet.com.au> wrote:
Tracy,
Like yourself I have been considering = the benefits=20 of an Eductor for some time, but can't understand why it would cause ex= tra drag.=20
=A0
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 exi= ts=20 the cowl.
=A0
Can you explain=A0the reasons behind t= he=20 increased drag issues.
George (down under)
"Since t= he=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 doub= t my=20 ability to get a point across clearly :-)=A0 An eductor can be made to he= lp=20 (but very hard to do as Ed pointed out)=A0 but the point I was trying to= =20 make in my original post is that the draw of air on the low side is NOT k= ey.=20 =A0 You will never get a fraction of the pressure delta with low side hel= p=20 (even with an eductor) that you can with the proper inlet and=20 diffuser.=A0=A0 This is especially true on faster airplanes.=A0 A=20 Pietenpol might be an exception.=A0

The inlet is what fixed my=20 problem.=A0 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%= ! at=20 the test speed of 130 mph. =A0 That's not a price you want to=20 pay.

Tracy

On Wed, Apr 28, 2010 at 9:19 AM, Chris Owens -= Rotary=20 <rotary@cmowens.com> wrote:
You know, I=20 don't know if this has been discussed, but the whole pressure diffe= rential=20 thing got me thinking of something that I'm surprised I hadn't = thought of=20 earlier.=A0 Since the draw of air via low pressure on the output side= =20 seems to be key, I wonder if an eductor type of scenario would=20 work.

Back in my Navy days, we used to use a device called an in= -line=20 eductor for dewatering flooded spaces.=A0 Similar to a venturi, more or= =20 less, you pumped water through it, it created a suction, and it was des= igned=20 to suck as much water through it as you put into it.=A0 100 gallons per= =20 minute input would dewater at 100 gallons per minute with 200 gallons p= er=20 minute flowing through the output.=A0 A representative device is here= =20 (perhaps not for 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?=A0 I imagine it would work well for a center mounted radiator wi= th=20 a centerline, below-the-nose scoop, so one could utilize the cheek inle= ts to=20 provide source air for the outlet side.

~Chris



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

Hi=20 George,

=A0

As you=20 know, taking heat away from your radiator cores requires sufficient air= mass=20 flow - a number of factors affect this - one of the principle factors i= s=20 pressure differential across your core.=A0 No pressure differential =3D= no=20 flow.=A0 The primary positive pressure on the front side of the core=20 comes from converting dynamic energy of the moving air into a local sta= tic=20 pressure increase in front of the core.=A0 This is basically limited by= =20 your airspeed and efficiency of your duct/diffuser.=A0 The back side of= =20 your core air flow (in most installations) exits inside the cowl.=A0=20 Therefore any positive pressure above ambient under the cowl is going t= o=20 reduce the pressure differential across your core.=A0 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.

=A0

An extreme=20 example is someone who flies with an opening (such as one of the typica= l=20 inlet holes beside the prop) exposed to the air flow.=A0 In effect this= =20 hole with little/no resistance to airflow can "pressurize" th= e cowl and=20 raise the air pressure behind the radiator cores reducing the pressure= =20 differential and therefore the cooling.=A0 Exhaust augmentation is=20 theoretically a way to reduce the under the cowl pressure by using the= =20 exhaust pulse to "pump" air from under the cowl, thereby impr= oving the=20 Dp across=20 the core and therefore your cooling.

=A0

While=20 exhaust augmentation can apparently work - there was a KITPLANE issue b= ack=20 several years ago on the topic showing several installations where this= was=20 used.=A0 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.=A0 Give the challenges you may encounter (such a= s=20 motor mount struts, etc), fabrication of the augmentation exit, =A0the= =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.=A0 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.=A0 Having had my muffler back out one= =20 time (at the cowl exit), I can tell you that you do not want to positio= n the=20 pilot behind the exhaust outlet (in my opinion).=A0 It is much quieter= =20 when you have the exhaust exit behind the position of the pilot=20 {:>).

=A0

Some few=20 people seem to have been able to achieve some degree of success, but ev= en in=20 aircraft where you have an engine without the aggressive bark of the ro= tary,=20 you seldom see it used.=A0 The basic reason (in my opinion), is that it= =20 offers few advantages (cooling wise) that can not be achieved easier an= d=20 more reliability by other methods.=A0 For an all out racer where noise= =20 and discomfort is secondary, it may have some benefit.

=A0

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

=A0

Ed

=A0

From: 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 motor= s in=20 aircraft
Subject:= =20 [FlyRotary] Re: 20B RV-8 cooling results

=A0

Ed/=20 Tracy,

Can't=20 say as I understand Tracy's set- up completely, other than it's= toward the=20 lower end of Rad sizes. I was thinking to myself how=A0I could create a= =20 -ve pressure in the rad outlet to create a suction on the Rad. We all k= now=20 how the exhaust augmentation works and I was wondering why we can't= do the=20 same thing with the rad outlets by running the rad outlets inro a large= r=20 outlet fed by outside air. At idle the air is fed by the prop air strea= m and=20 at level fight it is fed by outside air stream.

The=20 outside air could be=A0could 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 thi= s 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 neede= d=20 more margin for hot weather climbs. =A0 Made the decision to not chan= ge=20 or enlarge the cooling outlet (that adds drag)=A0 so went ahead and= =20 butchered the pretty inlets I made.=A0
Ed Anderson's spreadsh= eet on=20 BTUs & CFM cooling air required was instrumental in deciding to g= o=20 this way.=A0=A0 It showed that without negative pressure on the back= =20 side of the rads, there would never be enough cfm to do the job durin= g=20 climb at full throttle.=A0 Negative pressure is what I had when I fle= w=20 without the cowl on but oh what a draggy condition that was.

= The=20 old inlets were 4.5" diameter for the radiator and 4.125" d= iameter for oil=20 cooler.
New inlets are=A0=A0=A0=A0=A0=A0=A0 5.190"=20 for the rad,=A0 and =A0 4.875" dia for the oil.

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

Results were excellent.=A0 Oil temp went down 19 degrees= =20 at the test speed (130) and water temp dropped 9 degrees.=A0 On 80=20 degree day and 500 ft msl the oil temp maxed out at 194F at 210 mph w= hich=20 is way faster than I would normally go at this altitude.=A0 Temp was= =20 around 175 at 130. =A0=A0 Oil Temp in climb remained below redline=20 (210) but the temperature lapse rate today made results not very=20 meaningful.=A0 OAT was dropping 14 degrees a minute at 3000 fpm climb= =20 rate.

now back to that nasty composite work to pretty up the= =20 inlets again.=A0 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 Califo= rnia=20 recently came up with the winning idea which fit it well.=20 "Euphoriac"=A0 It's a term from a=A0 Sci Fi book (Vinta= ge=20 Season)=A0 meaning something which induces euphoria.=A0=20




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