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Engine cooling

Paul,
Is there a readily available reference for Coanda design? Or are the particular radius and curve proportions non-critical?
 
Paul,
Is there a readily available reference for Coanda design? Or are the particular radius and curve proportions non-critical?

I wish I knew, Dan! Several years ago I spent all of an afternoon going through the Cal Poly SLO library to see if I could find a good write-up about the Coanda effect and found nothing! Cal Poly SLO has a major aero department! I haven't done a Google search lately, but ususally what I did turn up is the "spoon in the faucet" test. With the Coanda effect a major part of aero engineering, you'd think there would be gobs of info on it. What I did was make the exhaust output jet area the same as the cross-sectional area of the pipe ahead of it so as not to introduce any additional back-pressure in the exhaust. Nothing about these designs is optimum. As far as the radius, I tried to come up with a relationship between the centrifugal force of the exhaust trying to make it depart tangentially from the curve, and the force available from the airstream. This is an area that could profit enormously by some good research by a university aero department, as the intelligent application of this effect could be a major contributor to more efficient designs in the handling of airflow! There is a company, Exair, that makes use of it is in air handling nozzles that produce airflow enhancement of up to 12 times when powered from shop air. Another company makes a Coanda ceiling fan, and lest we forget, the Notar helicopter uses it to take the rotor downwash and turn it to one side to counter main rotor torque. So there are a few who understand it, but, if the literature on it is an indicator, far too few!
 
Future mod thought

If I have time before the AVC race I plan on experimenting with a fairing on the vertical support at the aft end of the lower cowl. I may make up a full size model of the lower fuselage and cooling air outlet to develop several shapes to try on the plane (RV-6A).

Bob Axsom
 
Little More Detail

This is a very informative thread and has me looking at my Europa cowl again! I think I understand the Coanda Nozzle but I'm trying to understand the variable outlets that Paul has on them. Since the exhaust flow is there too, it's not clear how to make a variable outlet that still allows the exhaust to exit. Photos or explanation would be appreciated.

Thanks

Jim Butcher
Europa XS N241BW
 
This is a very informative thread and has me looking at my Europa cowl again! I think I understand the Coanda Nozzle but I'm trying to understand the variable outlets that Paul has on them. Since the exhaust flow is there too, it's not clear how to make a variable outlet that still allows the exhaust to exit. Photos or explanation would be appreciated.

Thanks

Jim Butcher
Europa XS N241BW

I just close them up until the CHTs rise to where I like them, about 370F-390. If you contact me at [email protected] I'll send you pix of my exhaust and outlets.
 
If you'd like to see a commercial application of the Coanda effect, go to www.dyson.com and see their new Dyson Fan!

very cool...! :D

fanLargeFaceOn.jpg
 
Dyson Fan using Coanda effect

very cool...! :D

fanLargeFaceOn.jpg

I was ready to buy one of these until I saw the...gulp...price! :eek:

My wife was happy with the purchase of an iRobot Dirt Dog for my shop and hangar but I don't think she'd go for a $300 fan.

I wish I were ready to fabricate my cowling and exhaust system; this is exciting stuff. I'm just trudging away on my wing right now...getting ready to do the pro-seal thing on the tanks.
 
Massive thread resurrection!

Dan and others that contributed here - any chance you can repost some of the pictures that fell off? It was a very interesting read and I?m curious to see the drawings!
 
The best way to view photos originally posted to PhotoBucket and then linked to posts on various forums is to install an "add on" that will defeat PhotoBuckets' blocking of these photos. I know that this sort of add on is available for both Firefox and Chrome browsers. If you use Firefox, simply search for either PhotoBucket Fixer or PhotoBucket Embed Fix. Either of these will cure the issue of blocked photos.
 
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