Return-Path: Received: from imf24aec.mail.bellsouth.net ([205.152.59.72] verified) by logan.com (CommuniGate Pro SMTP 4.2b6) with ESMTP id 301209 for flyrotary@lancaironline.net; Fri, 09 Jul 2004 22:10:53 -0400 Received: from HpPavilion310n ([65.1.107.56]) by imf24aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040710021024.OGIH1737.imf24aec.mail.bellsouth.net@HpPavilion310n> for ; Fri, 9 Jul 2004 22:10:24 -0400 From: "Bob Perkinson" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] BOV more/less air flow Date: Fri, 9 Jul 2004 21:10:25 -0500 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0078_01C465F9.278B7710" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0078_01C465F9.278B7710 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit So what happens when the BOV opens. The pressure on the intake manifold side starts immediately venting to the atmosphere reducing the pressure inside the manifold – this is of course what the BOV is designed to do. The compressor wheel has been spinning at 90,000 rpm with 1.5 boost pressure ratio. Now the boost pressure ratio may be 1.2 or less in a very short duration of time (milliseconds). This immediately reduces the backpressure on the compressor wheel caused by the manifold pressure being less than it before the venting. . The engine has not yet reacted to this change, as it is still combusting the boost density air it had ingested into the combustion chamber before the BOV opened. Neither has the exhaust gas flow been affected - yet. Ed, In the situation that you describe what would prevent the BOV from alternately opening and closing causing noticeable power surges? IMHO I would also think that the turbine that had the larger compressor would be the one whose shaft would suffer from the sudden attempt to accelerate and the increase in vibration as the speed increases when the back pressure is lost. I would also like to take this opportunity to thank you and all the others on this list for all the information that is freely imparted. Bob Perkinson Hendersonville, TN. RV9A If nothing changes Nothing changes ------=_NextPart_000_0078_01C465F9.278B7710 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

So what happens when the BOV opens. The = pressure on=20 the intake manifold side starts immediately venting to the atmosphere = reducing=20 the pressure inside the manifold =96 this is of course what the BOV is = designed to=20 do. The compressor wheel has been spinning at 90,000 rpm with 1.5 boost = pressure=20 ratio. Now the boost pressure ratio may be 1.2 or less in a very short = duration=20 of time (milliseconds). This immediately reduces the backpressure on the = compressor wheel caused by the manifold pressure being less than it = before the=20 venting. . The engine has not yet reacted to this change, as it is still = combusting the boost density air it had ingested into the combustion = chamber=20 before the BOV opened. Neither has the exhaust gas flow been affected -=20 yet.

 

Ed,

In the situation that you describe = what would=20 prevent the BOV from alternately opening and closing causing noticeable = power=20 surges?

IMHO=20  I would also think that the turbine that had the = larger compressor would be the = one whose shaft would suffer from the = sudden attempt=20 to accelerate and the increase in = vibration as=20 the speed increases when the back pressure is lost.

I=20 would also like to take this opportunity to thank you and all the others = on this=20 list for all the information that is freely imparted.

Bob Perkinson
Hendersonville, TN.
RV9A
If = nothing=20 changes
Nothing changes
 

 
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