X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036715 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 12:36:42 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; 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=GttrITpTa4rR4gxzbUEA:9 a=62oxd1SaIB2_L4F9C9wA:7 a=a22X1-e_UJk7jm1zhsy_DR-5kYsA:4 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=jHUA8AjvNyWtmuzP:21 a=ASMa0fpbUuyVuE5S:21 a=SSmOFEACAAAA:8 a=YiwKswYKS_HLNN3cbDsA:9 a=rRt09fnwNlLXta1juWcA:7 a=P5zhqDyNNEVCldPkXUt9QHZQRhMA:4 a=EXrSfqM1o_Ldo6KE:21 a=dPnFjoDhXG_WSm1N:21 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:1767] helo=computername) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 79/A7-01470-605523B4; Wed, 23 Dec 2009 17:36:07 +0000 From: "Ed Anderson" Message-ID: <79.A7.01470.605523B4@cdptpa-omtalb.mail.rr.com> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Air Flow Question Date: Wed, 23 Dec 2009 12:36:15 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002D_01CA83CC.84C43A60" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcqD696u40xC+nAAT4+P1ABm57g7nAACaDXw X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_002D_01CA83CC.84C43A60 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Al, looking at photos of Tracy's inlets, I would hazard a guess that the inlet may be more than 5" in diameter. If Tracy misspoke and meant 5" radius then that would give 10" diameter or approx 78 sq inch = 0.547 sq ft which then taking 4000 CFM /0.547 = 7322 ft/min = 83 MPH somewhat more realistic But, then Tracy may mean 5" diameter in which case I am going to fly down, pour him full of beer and badger the secret out of him {:>) 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 11:21 AM To: Rotary motors in aircraft Subject: [FlyRotary] Air Flow Question Tracy wrote: My 5" round inlet for the radiator looks ridiculously small compared to yours but so far it is cooling the 20B OK. Now that sort of boggles my mind as it seems to violate the laws of physics. Let's just take a modest climb power of, say; 225 hp. At that power, the energy going into the coolant is about 6000 Btu/min. In order to remove that amount of heat, at a typical air temp increase of 75 degrees; takes about 4000 cfm air flow. A 5" dia inlet is 0.14 sq feet, meaning an average inlet velocity about 29,000 ft/min, or 330 mph. Even at 100 air temp increase (unlikely on a 90F day) it's 250 mph. And I'm guessing your climb speed is half that. Similar math suggests you'd be limited to a steady state (cruise) power of about 50%. Of course, being a pusher driver, I think of inlet air speeds in terms of the speed of the airplane. So does the fact that the inlet is behind prop give a much higher effective inlet velocity? I've been thinking that the turbulence in the prop wash would negate a good portion of the extra mean air velocity because of reduced inlet effectiveness. It will be interesting to know how it works out on a hot day. Great that you have your 20B in the air and working well. Merry Christmas and Happy New Year to all. 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_002D_01CA83CC.84C43A60 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Al, looking at photos of Tracy’s inlets, I would hazard = a guess that the inlet may be  more than 5” in diameter.  If = Tracy misspoke = and meant 5” radius = then that would give 10” diameter or approx 78 sq inch = =3D 0.547 sq ft which then taking

 

4000 CFM /0.547 =3D 7322 ft/min =3D = 83 MPH somewhat more realistic

 

But, then Tracy may mean 5” diameter in = which case I am going to fly down, pour him full of beer and badger the secret = out of him {:>)

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Wednesday, December = 23, 2009 11:21 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Air = Flow Question

 

Tracy wrote:

My 5" round inlet for the radiator looks ridiculously small compared to yours but so far it is cooling the 20B = OK. 

 

Now that sort of boggles my mind = as it seems to violate the laws of physics. Let’s just take a modest = climb power of, say; 225 hp.  At that power, the energy going into the = coolant is about 6000 Btu/min.  In order to remove that amount of heat, at = a typical air temp increase of 75 degrees; takes about 4000 cfm air = flow.  A 5” dia inlet is 0.14 sq feet, meaning an average inlet velocity = about 29,000 ft/min, or 330 mph.  Even at 100 air temp increase (unlikely = on a 90F day) it’s 250 mph.  And I’m guessing your climb = speed is half that.  Similar math suggests you’d be limited to a = steady state (cruise) power of about 50%.

 

Of course, being a pusher driver, = I think of inlet air speeds in terms of the speed of the airplane.  = So does the fact that the inlet is behind prop give a much higher effective = inlet velocity?  I’ve been thinking that the turbulence in the prop = wash would negate a good portion of the extra mean air velocity because of = reduced inlet effectiveness.

 

It will be interesting to know = how it works out on a hot day.

 

Great that you have your 20B in = the air and working well.

 

Merry Christmas and Happy New = Year to all.

 

Al G

 

 

 



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The message was checked by ESET NOD32 Antivirus.

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