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From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-921798@logan.com>
Subject:  Re: Inserts   -   Exhaust Augmenters
Date: Mon, 2 May 2005 08:15:08 -0500
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----- Original Message ----- 
From: "Charlie England" <ceengland@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, May 01, 2005 9:36 PM
Subject: [FlyRotary] Re: Inserts


> rijakits wrote:
>
> > snipped
> >
> >Charlie,
> >
> >I suggest you look also into exhaust augmentation.
> >If you are already "skunk working" on something new and exhaust related,
you
> >might as well reap the benefits from that. It should help with cooling
> >(pulls air through the radiators/oil cooler), it would provide some kind
of
> >fairing (streamlines the cooling exit, exhaust exit and might hide any
> >muffler), it also should muffle the exhaust noise (might get away with
out
> >any muffler...). As the augmentation implies a mixing with cooler
(...than
> >exhaust) air this should muffle the noise as well. If it does not mix, it
> >will at least suround the hot exhaust gases with a mantle of cooler air -
> >muffling again. It should also increase efficiency as you have the
exhaust
> >gases do some work - should also work for a turbo (double duty!)
> >Last but not least benefit: Depending on the exhaust routing ( how early
in
> >the duct you can introduce the exhaust pipe into the cooling duct), the
> >cooler air in the duct will isolate the exhaust heat from the rest of the
> >engine compartement.
> >
> >Just a little info from this site: http://bd-4.org/cooling_nicoson.html
> >Dan Nicoson is planning a V8 installation with exhaust augmentation, so
it
> >is also liquid cooled and a lot of heat to be removed.......
> >
> >Anyway, I hope between all on this list the maximum power, lightest
weight,
> >most reliable system is found some time, so I can shamelessly copy the
> >perfect setup!! - ...sometime when I get to build:))
> >
> >Cheers,
> >Thomas Jakits
> >
>
> Thanks for the link; it's good reading. I've thought a lot about exhaust
> augmentation. The 2 downsides I've heard (2nd hand info only) is that
> they can actually increase drag at high speeds & that they usually
> *increase* noise levels. The 2nd is not too hard to understand & pilot
> opinions about certified planes using the technique seem universal that
> they are louder than similar designs w/o augmentation. The 1st is a
> little harder to understand. Maybe the augmenters draw too much air
> through the system.
>
> Are you considering a BD-4? I owned one for about a year, between two
> RV-4's.
>
> Charlie
>


I guess one could work with some kind of cowl flaps with the augmentation
idea to reduce drag (or limit the intake with flaps...)
The only airplane I ever got close to that uses augmentation was a
Twin-Bonanza, and you are eright it is failry loud. But it doesn't use any
muffler and the augmenters are not faired either, but are rather open,
pointing downwards at a rather steep angle.

If you look at Dan Nicosons drawing, the exhaust "jet" is very far forward
of from where the fairing seems to end and it points straight back.
I would hope/expect that thiswould muffle/mix the air a lot better that if
the fairing would end right at or shortly after the exhaust pipe.....

To the BD-4, see my private e-mail...

Thomas Jakits.