Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 552886 for flyrotary@lancaironline.net; Wed, 01 Dec 2004 15:49:55 -0500 Received-SPF: none receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-069-132-109-019.carolina.rr.com [69.132.109.19]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id iB1KnLKk010025 for ; Wed, 1 Dec 2004 15:49:22 -0500 (EST) Message-ID: <002301c4d7e7$452f9520$2502a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Reactive vs Absorbtion Mufflers for the Rotary engine Date: Wed, 1 Dec 2004 15:49:36 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0020_01C4D7BD.5C16DED0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0020_01C4D7BD.5C16DED0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Right on the money, Kevin. I did not make it clear in my first message = that I calculated the 1/4 wave length of several harmonics of rpms from = 1500 - 6000. Then I chose the lengths that occurred most frequently in = that matrix for my chamber lengths (distance between discs). This gave me six intervals for the discs spacing ranging from 2.5" to = 11.2". If I had a longer tube I would have picked a couple of longer = intervals as well. According to the theory (If I understand it correctly) what is = happening to deaden the sound is that the exhaust pulse encounters a = disc (what appears to it as a solid disc) and is reflected backwards. = When it encounters other incoming waves it interacts destructively = thereby attenuating both waves. If energy survives to reach the = up-stream end of the chamber it hits that disc and reverses direction = again, etc. This would occur in each of the chambers between discs = repeatedly many times a second. So you have this chaotic mixing of the = waves in the chambers attenuating the sound wave but not seriously = interfering with the exhaust gas movement out the tube (hopefully). The sound waves are reflected from each side of each disc and a bit = from the open end as well - however, if the discs have done their job = the exhaust sound pulses are considerably attenuated by the time they = reach the end of the tube. Ed ----- Original Message -----=20 From: kevin lane=20 To: Rotary motors in aircraft=20 Sent: Wednesday, December 01, 2004 12:43 PM Subject: [FlyRotary] Re: Reactive vs Absorbtion Mufflers for the = Rotary engine Ed -- would it make sense in the placement of the reflecting inserts, = to space them in an increasing series, so that they react to various = frequencies, rather than trying it hit one frequency? are the reflected = sound waves created only from the open end, or from any surface? Kevin Lane Portland, OR e-mail-> n3773@comcast.net web-> http://home.comcast.net/~n3773 (browse w/ internet explorer) ----- Original Message ----- ------=_NextPart_000_0020_01C4D7BD.5C16DED0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Right on the money, Kevin.  I did = not make it=20 clear in my first message that I calculated the 1/4 wave length of = several=20 harmonics of rpms from 1500 - 6000. =20 Then I chose the lengths that occurred most frequently in that matrix = for my=20 chamber lengths (distance between discs).
 
This gave me six  intervals for the discs spacing =  ranging from=20 2.5" to 11.2".  If I had a longer tube I would have picked a couple = of=20 longer intervals as well.
 
According to the theory (If I = understand it=20 correctly) what is  happening to deaden the sound is that the = exhaust pulse=20 encounters a disc (what appears to it as a solid disc) and is reflected=20 backwards. When it encounters other incoming waves it interacts = destructively=20 thereby attenuating both waves.  If energy survives to reach the = up-stream=20 end of the chamber it hits that disc and reverses direction again, = etc. =20  This would occur in each of the chambers between discs repeatedly = many=20 times a second.  So you have this chaotic mixing of the = waves in=20 the chambers attenuating the sound wave but not seriously interfering = with the=20 exhaust gas movement out the tube (hopefully).
 
 The sound waves are = reflected from=20 each side of each disc and a bit from the open end as well - = however,=20 if the discs have done their job the exhaust sound pulses are = considerably=20 attenuated by the time they reach the end of the tube.
 
 
Ed
----- Original Message -----
From:=20 kevin = lane=20
Sent: Wednesday, December 01, = 2004 12:43=20 PM
Subject: [FlyRotary] Re: = Reactive vs=20 Absorbtion Mufflers for the Rotary engine

Ed -- would it make sense = in the=20 placement of the reflecting inserts, to space them in an increasing = series, so=20 that they react to various frequencies, rather than trying it hit one=20 frequency?  are the reflected sound waves created only from the = open end,=20 or from any surface?
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
web-> http://home.comcast.net/~n3773
(browse=20 w/ internet explorer)
----- Original Message -----=20
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