X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 14 Mar 2008 11:41:03 -0400 Message-ID: X-Original-Return-Path: Received: from [64.12.143.101] (HELO imo-m13.mail.aol.com) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTP id 2790490 for lml@lancaironline.net; Thu, 13 Mar 2008 16:18:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.143.101; envelope-from=REHBINC@aol.com Received: from REHBINC@aol.com by imo-m13.mx.aol.com (mail_out_v38_r9.3.) id q.c57.2aa59da3 (48576) for ; Thu, 13 Mar 2008 16:17:47 -0400 (EDT) From: REHBINC@aol.com X-Original-Message-ID: X-Original-Date: Thu, 13 Mar 2008 16:17:49 EDT Subject: Re: [LML] Re: Sonic Venturi Orientation on TSIO-550 X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1205439469" X-Mailer: 9.0 Security Edition for Windows sub 5377 X-Spam-Flag: NO -------------------------------1205439469 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Craig, While the more forgiving taper in the downstream section does reduce noise by reducing turbulence, its primary purpose is to maintain metering accuracy. At the most constricted point, the flow will be sonic (choked flow), assuming there is adequate pressure differential. In the divergent section, the flow will become supersonic in part of the divergent section. The taper is more gradual on the down wind side for the same reasons as a wing, to prevent flow separation and turbulence. If flow separation were to occur early in the divergent section of the venturi, the pressure differential across the venturi would be altered and the effective flow constriction could change as well. The accuracy of the system would then approach that of a simple orifice plate. In a past life I used critical flow orifices (fancy name for sonic venturi) to calibrate hydrogen flow monitors. If you install them backwards, they don't work so well. Rob Yes, your sketch is correct. Just for further information, the reason for the diverging cone cross-section being downstream is it helps reduce noise. Craig Berland **************It's Tax Time! Get tips, forms, and advice on AOL Money & Finance. (http://money.aol.com/tax?NCID=aolprf00030000000001) -------------------------------1205439469 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Craig=20 Berland

 



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