----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Friday, April 08, 2005 2:09 PM

Subject: [FlyRotary] Re: Ed Anderson Cooling System

Hi Doug,

 

No doubt when you have different (higher?) standards they can be tougher to meet {:>).

 

  I agree with you assessment about a "reverse venturi" duct.  I have a larger "capture area" before the one duct necks down to 10 sq inches and the other to 18 sq inches.  My theory was that would increase the velocity (dynamic pressure potential) to help maintain that higher dome of pressure in front of the core that my radical curved duct walls infringe on.  My inlet is 6" long on one side and 3" long on the other, so did not have a lot of room to play duct with.

 

I flew a max power/climb take off two days ago with the ground OAT was 85F, by the time I hit 3000 MSL the oil temp was up to 210F and the coolant to 220F (my personal maxs for short duration).  I then leveled off and let the cooling system catch up with heat load.  So it does appear that for mid summer operation a bit more inlet area is called for.  I intend to open up the 10sq inch side (which is on my hottest radiator - first in the series) to 18 sq inches as well.  That will provide a bit more margin on those hottest days.  My personal experience with the 91 turbo block and the Teflon coat silicon coolant "O" rings that even coolant temps of 240F for short periods do not appear to have done any harm - as you say, coolant and combustion chamber are still separate.

 

But, I am please with the experiment in that I believe for my HP engine (I estimate 175-180HP) I have found a "lower" limit on duct size.  Although perhaps with "exhaust augmentation" it could be made to work fine in hotter days - much easier just to open one duct up a bit.

 

I total agree, when approaching trees or a ridge line - who cares about the temps - can always replace the engine (if necessary) provided you clear the tree line.

 

It always a personal pleasure to exchange ideas, experiences and theories with people of the calibrate we have on this list.  I always report my happenings - even when they are a bit embarrassing at times.  I seem to have had an unusually assortment of events happen.  I was awarded the Rotary Round Up "Lightening strikes six times (or more) award which lists a litany of things from oil pump key drop out, front tire gauges on both sides by the bolts holding on the wheel pant when I screwed them in a bit too much and then planted the front tire a bit hard causing it to balloon out and catch the bolts, flop tube drop off resulting in a 12 miles engine out glide, etc, etc. 

 

But one of the main reasons I share -  is life is too short to make all the mistakes yourself, so my objective is IF you are going to make mistakes - advance the state of the art and make one I haven't - we already know how those turned out{:>).

 

Thanks for the comments, Doug.  We try our best - and what's great is when you're wrong, folks will bring it to you attention - in a pleasant manner.

 

Tomorrow I launch (weather permitting) heading down to join Tracy Crook and on to Lakeland, Fl for Sun & Fun hope to see a bunch of your folks down there.

 

Best Regards

 

Ed

 

----- Original Message -----

From: Shearbond@aol.com

To: Rotary motors in aircraft

Sent: Friday, April 08, 2005 11:05 AM

Subject: [FlyRotary] Ed Anderson Cooling System

In a message dated 4/4/05 6:05:09 PM Mountain Daylight Time, eanderson@carolina.rr.com writes:

There were those who claimed that there was no way that would work.  Well, I reduced my inlet area from 48 sq inch to 28 and it works just fine thank you.  Tracy Crook can vouch that I have flown with the small openings for well over a year and he has never seen steam or smoke coming from my engine - yet {:>).

Hey Ed...that was probably me!  All my analysis uses Military Air outside conditions (+40 deg F over standard conditions), are climbing at 100 mph TAS (near max rate of climb) and assumes that you are actually generating 200 HP.  At 2,000 ASL and +40 deg F over standard....I suspect you are not generating 200HP and if you are indeed capable of 200 HP probably do not maintain that operating condition sufficiently long (at 100 mph) to reach steady state conditions which my rules of thumb consider. 

 

Hopefully if you ever are approaching the trees on T/O under the more severe conditions you can tolerate 245+ deg F engine out coolant temperature.  Been there done that with the Mooney.  You know what?  The throttle stayed in WOT and no leaves on the belly!  It defined "pucker" for me.  So you'll have to forgive me if I size my inlets just a little bit larger for our 95 deg summer days.  (Military Air at sea level is 99 deg F)...WOT...generating 200 HP for an extended period!!  Do what Tracy "noodles" and spray water on the heat exchangers!!  Of course you have to carry that two gallons of water around for the inevitable situation :>).  Sort of like a "gear up...not if, but when...if one flys enough.

 

Incidentally we unavoidably reached those 245 deg F engine out temperatures while developing my friends system without "apparent" ill effects.  He does not have sufficient hours to determine if there were long term effects, but water and oil are still separate!  Being a little experienced with automotive tests I would estimate that short of rapid temperature "shock" at those temperatues, no damage was done.  Note:  one of the OEM Automotive tests of heads/head gaskets is to dump just above freezing water into the engine inlet side of the waterpump while running at full tilt!!  That is thermal stress!

 

SWAG (valuable engineering tool), I believe you have what is almost a reverse venturi duct and your "effective" inlet area is actually larger than 28 sq. in. which is probably your smallest area in the inlet duct.  I have "noodled" (another valuable engineering tool!) that what you are doing might very effectively compensate for a very short inlet duct....but probably is a small detriment to cooling drag.  Too small to matter IMO.

 

Hey, you are a terrific experimenter and an invaluable Hummmmmer flyer who is willing to share even at the risk of us "still building" asking questions trying to understand what is happening in the Big RW.  It is terrific you share so we can consider what you have done and if we are smart....will try to implement same in our own builds.

 

I truly appreciate your combination of theory, practical application and ability to write!!  Thanks!

 

Doug in CO