Johannes,

(Lorn, thanks for forwarding. -perhaps Johannes can join the LML)

-a few comments and questions.

Johannes, in the way of background:  I am very interested in cooling related issues.  I went through a cowling/cooling redesign myself about two years ago.  The results were very encouraging with CHTs lower by 30 degF and cruise speed higher by 5 kts.  You can get more detail on my web site.

 

In the photos I cannot tell how, or if, the cowling inlets are sealed to the plenum chamber.  During testing, I found this sealing to be important.  There weren't any close up photos of the cowl inlet itself.  I am curious what its diameter, length and profile are.

The shape of the main diffusers appeared to have a very concave shape.  The air is most likely experiencing severe flow separation at the entrance to the diffuser.  A convex shape is more amenable to keeping flow attached over a longer period of expansion.  (see attached photo).

Regarding the flow measurements:  Measuring static pressures in a region of flow requires the use of a snubber at the measurement port.  This eliminates the accidental measurement of any dynamic contribution - positive or negative.  Any thick but porous material wrapped around the opening should work. Something like cloth, foams, or sintered metals.  Our probes at work are some kind of sintered material. 

How bad is the "cooling problem"?  I didn't see any temperatures mentioned.

What ever you do, don't give up.

Chris

 

Chris Zavatson

N91CZ

360 std.