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 4240023 for flyrotary@lancaironline.net; Wed, 28 Apr 2010 09:43:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.212.52; envelope-from=rwstracy@gmail.com Received: by vws10 with SMTP id 10so531755vws.25 for ; Wed, 28 Apr 2010 06:42:42 -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=77WDguSsgaFNA7j+TgXWuaP8C4pZtJOa/jGODAtuLcM=; b=kGQ/q9r5nM1+wxeCHaYtibx7qNXH8Cg+t6KEORmL6mboOTT4Aj+Q0K1cwVLToumPDO y9PZ63y1k+JaRHl0aj82h/9CZu+SPhzizw36ARNK6EpNcipCZQNOWWKcy5VgDRPofKIn h+TjUp32kZZGcVyHIX/7h4lt3e34uIXtNXFrw= 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=O2vrlK+QQAh8ol5sdO2zz7wlNbLwfZm7JY5eyB50zzWBpstVn4hMF4JBrP1wPrwXJv RwatzsALlgZrAzvrNo5vdPqzpYsOQV9+l0zOZcklEktXJ9RwVkbkXKbhAK4e18FY3Gvg UNIdxRt5qTXxnLpYVNqU4W+8hbsUxyYXJE0Gw= MIME-Version: 1.0 Received: by 10.220.62.199 with SMTP id y7mr5158311vch.200.1272462160804; Wed, 28 Apr 2010 06:42:40 -0700 (PDT) Sender: rwstracy@gmail.com Received: by 10.220.97.212 with HTTP; Wed, 28 Apr 2010 06:42:40 -0700 (PDT) In-Reply-To: References: Date: Wed, 28 Apr 2010 09:42:40 -0400 X-Google-Sender-Auth: 4c374fd6b71303b5 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=e0cb4e887f4915d0b004854c2fee --e0cb4e887f4915d0b004854c2fee Content-Type: text/plain; charset=ISO-8859-1 *"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. > > > --e0cb4e887f4915d0b004854c2fee Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable "Since the draw of air via low pressure on the output side seems t= o be=20 key, I wonder if an eductor type of scenario would work."

S= ometimes I doubt my ability to get a point across clearly :-)=A0 An eductor= can be made to help (but very hard to do as Ed pointed out)=A0 but the poi= nt I was trying to make in my original post is that the draw of air on the = low side is NOT key. =A0 You will never get a fraction of the pressure delt= a with low side help (even with an eductor) that you can with the proper in= let and diffuser.=A0=A0 This is especially true on faster airplanes.=A0 A P= ietenpol might be an exception.=A0

The inlet is what fixed my problem.=A0 This is an extreme example but w= hen I used low side help, it did cool but the drag caused the fuel consumpt= ion to increase by 50 - 60% ! at the test speed of 130 mph. =A0 That's = not a price you want to pay.

Tracy

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

Back in my Navy days, we used to use a device called an in-line eductor for= dewatering flooded spaces.=A0 Similar to a venturi, more or less, you pump= ed water through it, it created a suction, and it was designed to suck as m= uch water through it as you put into it.=A0 100 gallons per minute input wo= uld dewater at 100 gallons per minute with 200 gallons per minute flowing t= hrough the output.=A0 A representative device is here (perhaps not for flui= d 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 yo= u think?=A0 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" <eanderson@carolina.rr.com>
Sent: Wednesday, April 28, 2010 7:08 AM
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net&= gt;
Subject: [FlyRotary] Re: 20B RV-8 cooling results

Hi George,

=A0

As you know, taking heat away from your radiator co= res requires sufficient air mass flow - a number of factors affect this - o= ne of the principle factors is pressure differential across your core.=A0 N= o pressure differential =3D no flow.=A0 The primary positive pressure on th= e 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.=A0 This is= basically limited by your airspeed and efficiency of your duct/diffuser.= =A0 The back side of your core air flow (in most installations) exits insid= e the cowl.=A0 Therefore any positive pressure above ambient under the cowl= is going to reduce the pressure differential across your core.=A0 So once = you have the best duct/diffuser you can achieve on the front side of the co= re - the only thing left to increase the pressure differential is to reduce= the pressure under the cowl.

=A0

An extreme example is someone who flies with an ope= ning (such as one of the typical inlet holes beside the prop) exposed to th= e air flow.=A0 In effect this hole with little/no resistance to airflow can= "pressurize" the cowl and raise the air pressure behind the radi= ator cores reducing the pressure differential and therefore the cooling.=A0= Exhaust augmentation is theoretically a way to reduce the under the cowl p= ressure by using the exhaust pulse to "pump" air from under the c= owl, thereby improving the Dp across the core and therefor= e your cooling.

=A0

While exhaust augmentation can apparently work - th= ere was a KITPLANE issue back several years ago on the topic showing severa= l installations where this was used.=A0 However, from what I read (and thin= k I understand), it takes some carefully planning to get an installation to= work correct and the effort is not trivial.=A0 Give the challenges you may= encounter (such as motor mount struts, etc), fabrication of the augmentati= on exit, =A0the 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.=A0 Also, to gain maximum advantage of th= ese techniques, it is desirable to have the exhaust velocity at the maximum= - which implies little/no muffling.=A0 Having had my muffler back out one = time (at the cowl exit), I can tell you that you do not want to position th= e pilot behind the exhaust outlet (in my opinion).=A0 It is much quieter wh= en you have the exhaust exit behind the position of the pilot {:>).

=A0

Some few people seem to have been able to achieve s= ome degree of success, but even in aircraft where you have an engine withou= t the aggressive bark of the rotary, you seldom see it used.=A0 The basic r= eason (in my opinion), is that it offers few advantages (cooling wise) that= can not be achieved easier and more reliability by other methods.=A0 For a= n all out racer where noise and discomfort is secondary, it may have some b= enefit.

=A0

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

=A0

Ed

=A0

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net= ] On Behalf Of George Lend= ich
Sent: Tuesday, April 27, 2= 010 9:41 PM
To: Rotary motors in aircr= aft
Subject: [FlyRotary] Re: 2= 0B RV-8 cooling results

=A0

Ed/ Tracy,

Can't say as I understand Tracy's set- up completely, other than i= t's toward the lower end of Rad sizes. I was thinking to myself how=A0I= could create a -ve pressure in the rad outlet to create a suction on the R= ad. 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 outl= ets 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.<= /p>

The outside air could be=A0could 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 t= his equates to a good -ve pressure behind the Rad. This presupposes the Rad= s are completely enclosed for both inlet and outlet air.

George ( down under)

75% of my cooling problems were solved with the oil cooler chang= e I did but still needed more margin for hot weather climbs. =A0 Made the d= ecision to not change or enlarge the cooling outlet (that adds drag)=A0 so = went ahead and butchered the pretty inlets I made.=A0
Ed Anderson's spreadsheet on BTUs & CFM cooling air required was in= strumental in deciding to go this way.=A0=A0 It showed that without negativ= e pressure on the back side of the rads, there would never be enough cfm to= do the job during climb at full throttle.=A0 Negative pressure is what I h= ad 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" dia= meter for oil cooler.
New inlets are=A0=A0=A0=A0=A0=A0=A0 5.190" for the rad,=A0 and =A0 4.8= 75" dia for the oil.

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

Results were excellent.=A0 Oil temp went down 19 degrees at the test speed = (130) and water temp dropped 9 degrees.=A0 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.=A0 Temp was around 175 at 130. =A0=A0 Oil Tem= p in climb remained below redline (210) but the temperature lapse rate toda= y made results not very meaningful.=A0 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.=A0 The= y 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&= quot;=A0 It's a term from a=A0 Sci Fi book (Vintage Season)=A0 meaning = something which induces euphoria.=A0



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