X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4037214 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 21:12:45 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.0 c=1 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=nUuTZ29dAAAA:8 a=pH489v5Hg5h2hQnYfJkA:9 a=tyK6vNu88UiLsAuhamMA:7 a=Z7oSHnMTu3OjVTbUahm82v-G9xAA:4 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=SSmOFEACAAAA:8 a=yMhMjlubAAAA:8 a=n9o30857QTnh366qRzIA:9 a=BeFP5z2Sak3XbWMFnpYA:7 a=HLUctjxVnat8rJtUSDK0NmvW2hEA:4 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:4391] helo=computername) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 51/62-01567-AFDC23B4; Thu, 24 Dec 2009 02:12:10 +0000 From: "Ed Anderson" Message-ID: <51.62.01567.AFDC23B4@cdptpa-omtalb.mail.rr.com> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Air Flow Question Date: Wed, 23 Dec 2009 21:12:19 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0013_01CA8414.9CDEA610" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcqENh6aIN5x0yWRTH6GMvU7owIhaQABxL1Q X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0013_01CA8414.9CDEA610 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Welcome, Al Yes, Swapping Dt for Dt or DeltaT just looks sexier {:>). I agree with your assessment of Meredith effect, certainly useful and helpful when done properly to offset cooling drag, but have never seen any evidence/proof that there was a net thrust (probably for the primary reason you mentioned). Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen Sent: Wednesday, December 23, 2009 8:12 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Air Flow Question As far as I can tell, thrust recovery in the P-51 is legend. Never found anything in the way of proof that it really occurred. The most detailed, and what I believe to be authentic, analysis of the P-51 scoop legend is that there is no net thrust - ever. There are certain conditions where it is basically 1 : 1 offsetting drag (top speeds, and in dives); and yes, the outlet velocity may get slightly higher than inlet, but the air is less dense so has less momentum per unit volume. For most operations it was in the 1 to .85-.95 range, which is excellent. Anything we can do to accelerate the air back toward the free stream and velocity, and have it exit in the direction of the free stream, helps. An efficient converging duct with an outlet area in the range of 1.3 to about 1.6 is good, and the ratio of choice depends on the temperature increase of the air - which depends on the mass flow rate through the core. (Higher DT, higher ratio). Analysis that I have seen (and verified) suggests minimum drag and radiator weight is achieved with DT in the range of 50 - 75F, core thickness 2 1/4 - 3"; and yeah, there are set of assumptions involved, so YMMV. That's my story; and I'm sticking to it:-). BTW, ED, thanks for the tip on the D; that is very cool. Al G __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0013_01CA8414.9CDEA610 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Welcome, = Al

 

Yes, Swapping = Dt for Dt or DeltaT = just looks sexier {:>).

 

 I agree with your assessment = of Meredith effect, certainly useful and helpful when done properly to offset = cooling drag, but have never seen any evidence/proof that there was a net thrust = (probably for the primary reason you mentioned). 

 

  

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Wednesday, December = 23, 2009 8:12 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Air Flow Question

 

As far as I can tell, = thrust recovery in the P-51 is legend. Never found anything in the way of proof = that it really occurred.

 

=

The most detailed, and what I = believe to be authentic, analysis of the P-51 scoop legend is that there is no net = thrust – ever.  There are certain conditions where it is basically 1 = : 1 offsetting drag (top speeds, and in dives); and yes, the outlet velocity = may get slightly higher than inlet, but the air is less dense so has less = momentum per unit volume.  For most operations it was in the 1 to .85-.95 = range, which is excellent.

 

Anything we can do to accelerate = the air back toward the free stream and velocity, and have it exit in the = direction of the free stream, helps.  An efficient converging duct with an = outlet area in the range of 1.3 to about 1.6 is good, and the ratio of choice = depends on the temperature increase of the air – which depends on the mass = flow rate through the core. (Higher D<= font size=3D2 color=3Dblue face=3DVerdana>T, higher ratio). Analysis that I have seen (and verified) = suggests minimum drag and radiator weight is achieved with DT in the range = of 50 – 75F, core thickness 2 1/4 – 3”; and yeah, there are = set of assumptions involved, so YMMV.

 

That’s my story; and = I’m sticking to itJ.

 

BTW, ED, thanks for the tip on = the D; that is very = cool.

 

Al G



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

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