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----- Original Message -----
From: "Jim Sower" <canarder@frontiernet.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, September 21, 2003 10:58 PM
Subject: [FlyRotary] Re: DIE Power Calculations
Ed,
<... The sound of speed (of the wave) is of course dependent on the
density of
the medium it is traveling through ...>
Actually, the speed of sound in a gas is varies only with Temperature.
Not with
density. You look at the formula for determining the speed of sound in a
particular gas, and the only variable is Ta (Absolute Temperature). The
speed
of sound also stabilizes at 575 kts (or whatever) at all "attainable"
altitudes
above tropopause (36089' (standard day)).
Anyway, turbocharging increases the local speed of sound only to the
extent that
it raises the temperature of the air charge. If you start at 60 deg air,
turbocharge it to 60" MAP, could intercool it back to 60 deg, the local
speed of
sound doesn't change. Intercooling would therefore help you with
stabilizing
DIE, and you would want to tune your runners to the temperature downstream
of
the butterfly valve that you anticipate encountering most often in cruise.
Weird but true .... Jim S.
Ok, Jim
Must have been asleep in that part of class. I knew that in the atmosphere
the density is dependent on the air temperature and the speed of sound is as
well. I guess I am still somewhat surpised that if you pressurized a gas
say to 10-20 atmospheres that speed of sound would not be increased (even
after you let it cool off from the compression heating). But, you live and
learn every day.
I agree that having the intercooler before the throttle body would eliminate
it from any possible disruption of the DIE FAW. Also agree that anything
you do to stabilize intake manifold air temp would also stabilize the rpm at
which DIE occurs.
Thanks Jim, I stand corrected.
Ed
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