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From: "Michael Burke" <mburke@southernphone.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-853297@logan.com>
Subject: Re: [FlyRotary] Cooling -Learned a lot
Date: Mon, 4 Apr 2005 16:47:22 +1000
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Ed is this book the"Holy Grail" on liquid cooled aircraft engines. Is it
still available from book stores, if not where can it be purchased.
Many Thanks,
Rotary Newbie,
Michael.

----- Original Message ----- 
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, April 04, 2005 12:14 AM
Subject: [FlyRotary] Cooling -Learned a lot


> Too right, Jerry
>
> My  first 40 hours or so were in the marginal cooling zone. {:>).  As
other
> things in this hobby, there are so many variables that interact, that what
> may appear simply at first, is almost always a bit more complex.  I
> say(Cooling Axiom 1) if you have enough cooling surface area and air mass
> flow then it WILL cool.    However, you may incur a high penalty in
cooling
> drag - which may not be as important for draggy airframes (such as
biplanes)
> as it is to sleeker airframes.   Also a system that adequately cools an
> engine producing  150 HP may not cool an engine producing 180 HP.  Picking
> your cooling design point is important.  Optimizing for cruise and your
will
> be less than optimum for take and climb.  Optimize for climb and you will
> probably have more cooling drag than required at cruise.  Compromise,
> compromise - cowl flaps are sometimes used to try to have the best of both
> worlds.
>
> Some folks advocate a thinner, larger surface area core -which is great
for
> slow moving automobiles stuck in traffic with low dynamic pressure
> potential, but I think is not the optimum for most aircraft.  Once you
trip
> the airflow and turn it turbulent you have incurred most of the drag
> penalty.  Larger surface area cores disrupt a larger airstream and incur
> more drag.  Yes, thicker cores produce a bit more drag than the SAME
frontal
> area thinner cores.  But, with a thicker core you can use a core with
> smaller frontal area.
>
>   The NASCAR radiator's average 3" thick and on the long tracks where
speeds
> are higher some even go up to 7" thick.  My contention is their operating
> environment is more akin to ours than regular automobiles moving at slower
> speeds.  You know that the NASCAR folks will spend $$ for just a tiny
> advantage - so clearly they don't use thick cores because it is a
> disadvantage. But, some folks will continue to point to the large thin
> radiators designed for environments with much lower dynamic pressure as
> being the way to go.  Will it cool? sure it will (Cooling axiom 1 above).
> Is it the lowest drag option for an aircraft of the RV/TailWind type, I am
> convinced it is not.
>
> The diffuser makes a considerable amount of difference and can made the
> difference between a system that cools adequately and one which does not.
> The biggest culprit that lessens cooling effectiveness is turbulent eddies
> that form inside the duct due to flow detachment from the walls.  These
> eddies in effect act to block effective airflow through part of the core.
> So keeping the airflow attached to the sides of the diffusers is crucial
for
> good cooling from two standpoints. A good diffuser will reduce airflow
> velocity through the core which will reduces cooling drag.  Pressure
across
> the core is increased which further enhances cooling.
>
> I have gone from a total of 48 sq inches opening (total) for my two GM
cores
> and that provided marginal cooling - down to 28 sq inches (total) with
> adequate cooling with an engine now producing more HP.  Experimenting with
> the diffuser shape made the difference.
>
> The K&W book (Chapter 12) really provided the insight to how and which
> diffuser shapes provided the better dynamic recovery.  The Streamline duct
> was shown to be able to provide up to 82% recovery of the dynamic
pressure.
> Some folks reading the chapter misinterpreted the chart to show only 42%
> recovery where there chart was actually only showing the pressure recovery
> contribution due to the duct walls and did not include the contribution
due
> to the core.  On the same chart, an equation (which apparently gets
ignored)
> clearly shows that the TOTAL  pressure recovery is 82%.
>
> I have taken the Streamline duct as a starting point, but since I do not
> have the space to provide the 12-14" for a proper Streamline duct, I did
> some "creative" things to try to insure that there was no separation even
> though my walls diverge more rapidly than the Streamline duct.  Won't
claim
> mine are as good as a Streamline, but they clearly are much better than
the
> previous design which basically just captured the air and forced it
through
> the cores.
>
> FWIW
>
> Ed Anderson
> RV-6A N494BW 275 Rotary Hours (Plugs Up)
> Matthews, NC
> eanderson@carolina.rr.com
>
>
> ----- Original Message -----
> From: "Jerry Hey" <jerryhey@earthlink.net>
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Sent: Sunday, April 03, 2005 9:27 AM
> Subject: [FlyRotary] Re: phase I flight restrictions was:N19VX flys
>
>
> > It was not long ago that "cooling" was the major issue.  Now it seems
> > that we have learned enough to make several different configurations
> > work.   I can't lay my finger on what it is we have learned but my
> > recommendation is to use smaller radiators and EWPs.   Jerry
> >
> >
> >
>
>
>
>
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