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Date: Thu, 11 Feb 2010 10:29:52 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Flywheel turbo
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Al Gietzen wrote:
> I'm taking the intake air from around the side of the gearbox, through 
> its mounting plate.  The flywheel will have an impeller attached to it.  
> I built a fiberglass shroud to enclose the area between the gearbox 
> mounting plate and the engine.  Intake air is taken from this 
> centrifugal pump.
>
> I admire the creativity and effort, but I see big question marks. My only
> point of reference is a large furnace type centrifugal blower which
> generates maybe 1/2" HG pressure.   And how is this approach going come
> close to the efficiency of a well designed supercharger.
>
> I've been wrong before; so go ahead - shoot me.
>
> Al
>
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
>   
I ain't claiming to be right until my engine runs, but...

The research I've done leads me to believe that a centrifugal pump can
give you pressure or volume.  The 1/2" HG may be all that was needed to
get the volume of airflow the designers wanted?  I'm trying to remember
the numbers off the top of my head, so please forgive me if I'm way off,
but with the approximately 11" diameter of the flywheel spinning between
6000 and 6500RPM, the equations said I would get 2lbs of pressure
increase.  2lbs of pressure translates into somewhere around 20Hp.  I
tested the static pressure of my electric leaf blower. Labeled to spin
at 9000RPM with a 6" impeller.  I got over 9" of static pressure. That
was enough incentive for me to give it the old college try.

If you look at the numbers for "high efficiency" vs a round plate with
perpendicular vanes bolted to it, the efficiency drops from the mid-90s
to the mid-80s.  Quite a lot of specialized engineering goes into
squeezing out that last 10 points.  I don't yet have the environmental
data or skills to design or manufacture what would be needed to get that
last 10 points.  Sooo .... I'll see what I can get with what I can do,
and then decide if I should expand on what I can do.  I've attached a
OpenOffice document dealing with the design of centrifugal compressors
for your reading pleasure. (EDIT:  My mail bounced because the document 
was to big.  If you want it, I'll email it to
you directly.)

My engine has not run yet.  This may be a complete waste of time.
YMMV.  Not applicable outside of the continental United States.
Franchisees are individual owners and may not participate in this
promotion. etc....

Lynn, I gave some consideration to the multiple stage idea.  The leading
scenario would be to have a two piece shroud.  An impeller would be
attached to the engine shaft, then the first shroud would be bolted to
the engine.  Then the flywheel mounted, followed by the front impeller,
followed by the second shroud.  The two big problems were the complexity
of all the clearances needed, and, more importantly, the counterweight.
There simply wasn't enough room to get enough flow.  You need
significantly more pump volume than needed for the intake in order to
develop rated pressure.