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 4240079 for flyrotary@lancaironline.net; Wed, 28 Apr 2010 10:16:01 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.212.52; envelope-from=rwstracy@gmail.com Received: by vws10 with SMTP id 10so556420vws.25 for ; Wed, 28 Apr 2010 07:15:25 -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=Rg4McxZ1hIPGIAZElJbro3G2BCOiC7uZcw9cUHEieXk=; b=Mbztt7D/5cHO3ZTyuwrmaIc/DiVQbOIvPPggmzkb8zYQYVbzOiiE+yYYz4sTHFVfk6 4v5Nrm68eKRbAFfGFBMCPVnN8mwlgt2saPx1wK0EtHEzEPDA5LI2g4hKOwqB5Ji4PpXf r+B1Rba+Mim0o7E0zMYEtSzD3n24zfDNSGBIc= 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=cwFtEnh/y6f4R2ZzmkbE+cj6VhKy9J5B5zokWCJXdhEZ4ZTLo9gxQJWDLxW15iJPeL 9gZSxF1XguBy2T0JZXstG70hZF1clpMoQv44vWSmVOXICyI651T70pAAgeBcwqvJuoS5 IeNVo2V9/5T/mnsrIVnlVeMRPt3k1zisEMElg= MIME-Version: 1.0 Received: by 10.220.123.67 with SMTP id o3mr5290463vcr.176.1272464124431; Wed, 28 Apr 2010 07:15:24 -0700 (PDT) Sender: rwstracy@gmail.com Received: by 10.220.97.212 with HTTP; Wed, 28 Apr 2010 07:15:24 -0700 (PDT) In-Reply-To: References: Date: Wed, 28 Apr 2010 10:15:24 -0400 X-Google-Sender-Auth: b57f14d3b024ea20 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=00504502eca0204ff904854ca4c0 --00504502eca0204ff904854ca4c0 Content-Type: text/plain; charset=ISO-8859-1 No need to hold back Chris, all comments welcome here. I was just struck that most comments on the thread were reactions to the low side pressure where there isn't much to be gained other than a lot of drag. I will admit to giving a lot of thought to eductor systems though. Tracy On Wed, Apr 28, 2010 at 9:48 AM, Chris Owens - Rotary wrote: > Thanks for the thoughts, Tracy. Wasn't picking on your aircraft > specifically, just speaking out loud in general. And I guess I should more > thoroughly read through other contributors' info before I offer up my own > questions. There has been plenty of information disseminated here on the > topic, eductors or not, and so I'll be more diligent in my reading. > > ~Chris > > > ------------------------------ > *From*: "Tracy Crook" > *Sent*: Wednesday, April 28, 2010 8:43 AM > > *To*: "Rotary motors in aircraft" > *Subject*: [FlyRotary] Re: Eductor scavenging of radiator outlet, WAS 20B > RV-8 cooling results > > > *"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. >> >> >> > > --00504502eca0204ff904854ca4c0 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable No need to hold back Chris, all comments welcome here.=A0 I was just struck= that most comments on the thread were reactions to the low side pressure w= here there isn't much to be gained other than a lot of drag.=A0 I will = admit to giving a lot of thought to eductor systems though.=A0

Tracy

On Wed, Apr 28, 2010 at 9:48 AM= , Chris Owens - Rotary <rotary@cmowens.com> wrote:
T= hanks for the thoughts, Tracy.=A0 Wasn't picking on your aircraft speci= fically, just speaking out loud in general.=A0 And I guess I should more th= oroughly read through other contributors' info before I offer up my own= questions.=A0 There has been plenty of information disseminated here on th= e topic, eductors or not, and so I'll be more diligent in my reading.
~Chris


From: "Tracy Crook" <tracy@rotaryaviation.com>
Sent: Wednesday, April 28, 2010 8:43 AM

To: "Rotary motors in aircraft" <flyrotary@lancaironline.net&= gt;
Subject: [FlyRotary] Re: Eductor scavenging of radiator outlet= , WAS 20B RV-8 cooling results


<= i>"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 :-)=A0 An educto= r can be made to help (but very hard to do as Ed pointed out)=A0 but the po= int 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 del= ta with low side help (even with an eductor) that you can with the proper i= nlet and diffuser.=A0=A0 This is especially true on faster airplanes.=A0 A = Pietenpol might be an exception.=A0

The inlet is what fixed my problem.=A0 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. =A0 That's not = a price you want to pay.

Tracy

On Wed, Apr 28, 2010 at 9:19 AM, Chris Owens - R= otary <rotary@cmowens.com> wrote:
You know, I don= 9;t know if this has been discussed, but the whole pressure differential th= ing got me thinking of something that I'm surprised I hadn't though= t 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 would 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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