Chris,

Good luck searching the archives. Topic drift is driving = me nuts as I try to find a response Tracy sent me long ago regarding m= y program knob not responding. Perhaps it is the program button, but&= nbsp;the button is working ok as a primer button, but I can't get the MAP to change and my engine stalls when I take it out of M= ode 0. Thought it was fixed with its latest trip to FL a = few months ago, but alas, no joy. Seems he said it may be a ground...= .so the search continues

I did mount my turbo today. It is not yet plumbed to the intake = yet, but just the turbo by itself takes a lot of the rotary bark away....mo= stly prop noise now. But, kinda moot with out bein= g able to tune properly...due to the program knob glitch.

Not sure of how to test if the knob or button are working and it is a = problem somewhere else. <sigh>

My cooing seemed pretty good with the turbo. Oil was a bit highe= r than water. The turbo IS a wet housing, but it did not seem to be a= n issue around idle in Houston...pretty mild day in the 80's .=

All the best,

Chris Barber

Houston, GSOT

From: Rotary motors in aircraft [flyrotary= @lancaironline.net] on behalf of Tracy Crook [tracy@rotaryaviation.com]
Sent: Wednesday, April 28, 2010 8:09 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Eductor scavenging of radiator outlet, WAS = 20BRV-8 cooling results

I was talking about the usual methods of decreasing the pressure on ba= ckside of heat exchangers, like very large exit opening, lip on bottom of c= ooling exit, cowl flaps that protrude into the slipstream, radiators mounte= d 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 = <lendich@aanet= .com.au> 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 behin= d the increased drag issues.

George (down under)

"Since the draw of air via low pressure on the output side seems to b= e key, I wonder if an eductor type of scenario would work."

Sometimes I doubt my ability to get a point across clearly :-) An edu= ctor 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 educ= tor) that you can with the proper inlet and diffuser.   This is e= specially true on faster airplanes. A Pietenpol might be an exception= .

The inlet is what fixed my problem. This is an extreme example but wh= en I used low side help, it did cool but the drag caused the fuel consumpti= on to increase by 50 - 60% ! at the test speed of 130 mph. That's no= t a price you want to pay.

Tracy

On Wed, Apr 28, 2010 at 9:19 AM, Chris Owens - R= otary <rotary@cmowens.= com> wrote:

Yo= u know, I don't know if this has been discussed, but the whole pressure dif= ferential thing got me thinking of something that I'm surprised I hadn't th= ought 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 p= umped water through it, it created a suction, and it was designed to suck a= s much water through it as you put into it. 100 gallons per minute input would dewater at 100 gallons per mi= nute with 200 gallons per minute flowing through the output. A repres= entative device is here (perhaps not for fluid use, but the concept is simi= lar):

http://www.1877eductors.com/eductor_gas_dimensions.htm

I presume a similar approach could be taken with a radiator setup, would yo= u think? I imagine it would work well for a center mounted radiator w= ith a centerline, below-the-nose scoop, so one could utilize the cheek inle= ts 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,

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 fr= om 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 b= ack side of your core air flow (in most installations) exits inside the cow= l. Therefore any positive pressure above ambient under the cowl is go= ing to reduce the pressure differential across your core. So once you have the best duct/diffuser you can achieve o= n 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 openin= g (such as one of the typical inlet holes beside the prop) exposed to the a= ir flow. In effect this hole with little/no resistance to airflow can "pressurize" the cowl and raise the ai= r pressure behind the radiator cores reducing the pressure differential and= therefore the cooling. Exhaust augmentation is theoretically a way t= o reduce the under the cowl pressure by using the exhaust pulse to "pump" air from under the cowl, thereby improvi= ng 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 i= nstallations where this was used. However, from what I read (and think I understand), it takes some carefully plannin= g to get an installation to work correct and the effort is not trivial.&nbs= p; 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 co= nstruct 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 thes= e 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 t= he aggressive bark of the rotary, you seldom see it used. The basic reason (in my opinion), is that it off= ers few advantages (cooling wise) that can not be achieved easier and more = reliability by other methods. For an all out racer where noise and di= scomfort is secondary, it may have some benefit.

Having said that, it's clear that in some installation= s it appears to work well (see KITPLANE issue), but if it were the magic so= lution, 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, 20= 10 9:41 PM
To: Rotary motors in aircra= ft
Subject: [FlyRotary] Re: 20= B RV-8 cooling results

= Ed/ Tracy,

= Can't say as I understand Tracy's set- up completely, other than it's towar= d the lower end of Rad sizes. I was thinking to myself how I could cre= ate 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 runni= ng 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 enou= gh. I know there emphasis on using shutter /flaps to control the cowl outle= t and I believe their good at restricting air flow, but I don't know if this equates to a good -ve pressure behind t= he Rad. This presupposes the Rads are completely enclosed for both inlet an= d 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 inlet= s I made.
Ed Anderson's spreadsheet on BTUs & CFM cooling air required was instru= mental in deciding to go this way.   It showed that without negat= ive 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 wha= t 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        5.190" for th= e rad, and 4.875" dia for the oil.

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

Results were excellent. Oil temp went down 19 degrees at the test spe= ed (130) and water temp dropped 9 degrees. On 80 degree day and 500 f= t 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 redli= ne (210) but the temperature lapse rate today made results not very meaning= ful. 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 rec= ently 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.