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Date: Thu, 12 May 2005 00:32:11 -0600
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: "BillDube@killacycle.com" <billdube@killacycle.com>
Subject: Re: [FlyRotary] Re: More about Mufflers
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At 05:19 PM 5/11/2005, you wrote:
>Hey, Bill!
>
>Great find.  Boy talk about a thorough investigation.  Will take a bit to 
>digest even a part of it, but it looks hopeful that their may be something 
>I can use to quite this louder engine.

         They don't specifically address absorption style mufflers, but 
they indirectly do so when they evaluate "concentric" style resonators and 
vary the size and number of the connecting orifices. Looking at the charts, 
an absorption muffler looks like it might be a good option because of the 
broad band attenuation. The biggest hurdle would be to build one that is 
lightweight, small, robust, and can take the high exhaust temps. I think 
that a couple of layers Inconel screen might work for the inside "tube" of 
an absorption muffler.

         The section on varying the connection tube length on a single 
chamber resonator looks quite useful for designing the cross-over between 
rotors. I think the tube leading to an adjacent rotor will behave as a 
single chamber resonator with a small chamber volume. By cleverly selecting 
the length of the header tube before the Y, one might be able to reduce the 
exhaust noise at cruise significantly with no reduction in performance and 
no significant increase in weight.

         Bill Dube'