Mailing List flyrotary@lancaironline.net Message #38735
From: Al Gietzen <ALVentures@cox.net>
Subject: RE: [FlyRotary] Re: bench flowtest
Date: Thu, 26 Jul 2007 07:17:45 -0800
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>

Subject: [FlyRotary] Re: bench flowtest

 

WRJJRS@aol.com wrote:

Kevin,

With rotaries they have found that a constantly expanding exhaust helps keep the pulse moving. It also keeps the LOUD moving.

Okay,  This brings to mind a question: how fast are those pulse moving?
It's pretty easy to figure out how long between pulses for any given
RPM, but it would be nice to know how far down the pipe a puff of
exhaust gets before the next one starts chasing it.  Anyone here already
know this?  (Yes, I know I can search for it on the net - well, this is my
first attempt.)
Best Regards,
Dale R.

Dale;

I may have missed if someone answered this already; the shock wave travels at the speed of sound in the air at EG temps – that would be about 2700 fpm.

(http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html). Since it is traveling in a gas that has an average velocity of some number depending on the volume of exhaust and the diameter of the pipe; add that on.

Al

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