I am not recommending a six inch diameter tail pipe but three inches
sounds about right. The ratio of the areas are obviously important.

Furthermore the gas velocity flowing past the end of the inner pipe
will have high velocity and consequently considerable inertia.
Exhaust gas velocity can be 1300 to 1700 ft per second. Exhaust gas
has mass. For every pound of fuel burned there is 10 to 15 pounds
of air burned. This forms a powerful jet of exhaust gases.
The total energy (heat and inertia) in the exhaust in terms
of HP is more than what comes of of the e-shaft and the cooling
system combined.

Due to the Coanda effect a jet of fluid tends to entrain fluid
surrounding it and drag it along with the main jet. In this case
the main jet of exhaust gas is hollow so any air introduced in
the the center of the jet will be entrained.

Another fact is a tangential muffler is a vortex generator.
This vortex is forced to flow aft out of the can due to exhaust
gas pressure build up in the front of the can.

At the center of every gas vortex the pressure is much lower than it
is at the periphery of the vortex due to centrifugal forces on
on the gas molecules. As the vortex flows past the end of the
inner pipe this low pressure will further help draw air out of
the center cooling pipe.

I think this thing is going to work great. We need to come up with
a catchy name for it :)

BTW There is a pretty good book on this subject that I highly recommend.
Scientific Design of Exhaust and Intake Systems P.Smith and J. Morrison
Robert Bently publisher. ISBN 0-8376-0309-9 Lots of experimental
work was reported.

Paul Lamar

Paul,
Vortex Augmentation Muffler or VAM for short.
George (down under)

 
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