Bill Jepson wrote:
Paul, The attached jpeg is a variation on the tangental muffler
theme.
The intent is to cool the exhaust system using the exhaust energy. A
outside air source is provided near the front. The design could also
be
inverted, (exhaust inside the the can), if the inside tube wouldn't
provide enough cooling. The tail pipe mixing should also make it a
bit
quieter. comments? Bill Jepson
That is a really great idea Bill. I really like it. I think it is
THE soluttion.
Paul Lamar
Al Gietzen wrote:
What am I missing here? It seems quite apparent that the exhaust will
come out both ends. The pressure at the 'back' end of the inner tube
will be quite high.
Al
It depends on the area ratio of the concentric space to that of the tail
pipe area. It should work like a thrust augmentor. There may be a slight
design change required to get a venturi shape around the cooling pipe
exit.
Dynamic pressure could also be fed in at the front to enhance the flow.
Paul Lamar
Al Gietzen wrote:
Go ahead and prove me wrong; but . . ., IMHO it can only work if the
outer pipe exit ended at about the same place as the inner pipe, or you
had very much higher pressure on the inner pipe than you would ever get
from the dynamic pressure at the speeds we go; OR, possibly if you had
the exhaust going on the inner tube and the air going through the
annulus.
Al
I always look at the limits or in this case the extremes. If the tail
pipe is the same diameter as the can (six inches) and the cooling pipe
one inch in diameter obviously the sudden increase in pipe area as the
exhaust gases pass the end of the inner pipe would reduce the pressure
in the center pipe.
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
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