I did attempt to take exhaust gas temperature into consideration, Bill.  I
assumed the average temp along the tube was 1500F (hotter at the port end
and cooler at the open end of the tube).  The stainless steel tubing is
turning color its entire length and you can see the locations of the discs
on the tube as it apparently gets a bit hotter at those points.  I then
calculated the speed of sound based on that average temp and used that for
my calculations.  Clearly only an approximation of what is probably
happening to temps along the tube, but at least an attempt to accommodate
that factor.

Ed

----- Original Message -----
From: "Bill Dube" <bdube@al.noaa.gov>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, December 01, 2004 3:54 PM
Subject: [FlyRotary] Re: New Muffler Design


> Don't know if you concerned yourself about this as you designed your
> muffler, but the speed of sound is strongly influenced by the temperature.
> The speed of sound in gasses is proportional to the square root of the
> absolute temperature. (There is only a tiny change due to pressure, by the
> way.)
>
> At room temperature (20 C), the speed of sound in dry air is 344 m/s. At
> 500 C, the speed of sound in air is 553 m/s. The exhaust gas temperature
> would probably be something like 500 C as it entered the muffler, perhaps
> hotter.
>
> The resonance length will scale with the square root of temperature.
>
>
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