X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4036982 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 16:44:23 -0500 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id A3ECD173B41 for ; Thu, 24 Dec 2009 05:43:48 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id F1EAEBEC00C for ; Thu, 24 Dec 2009 05:43:47 +0800 (WST) Message-ID: From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Air Flow Question Date: Thu, 24 Dec 2009 07:43:47 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01CA846C.D3A4FCA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 091223-0, 12/23/2009), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_001F_01CA846C.D3A4FCA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Well Al, it's got me beat to. George ( down under) Tracy wrote: My 5" round inlet for the radiator looks ridiculously small compared = to yours but so far it is cooling the 20B OK. =20 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.=20 Great that you have your 20B in the air and working well. Merry Christmas and Happy New Year to all. Al G ------=_NextPart_000_001F_01CA846C.D3A4FCA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Well Al, it's got me beat = to.

George ( down under)

Tracy=20 wrote:

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

Now that = sort of=20 boggles my mind as it seems to violate the laws of physics. Let=92s = just take a=20 modest climb power of, say; 225 hp. At that power, the energy = going into=20 the coolant is about 6000 Btu/min. In order to remove that = amount of=20 heat, at a typical air temp increase of 75 degrees; takes about 4000 = cfm air=20 flow. A 5=94 dia inlet is 0.14 sq feet, meaning an average inlet = velocity=20 about 29,000 ft/min, or 330 mph. Even at 100 air temp increase = (unlikely=20 on a 90F day) it=92s 250 mph. And I=92m guessing your climb = speed is half=20 that. Similar math suggests you=92d be limited to a steady state = (cruise)=20 power of about 50%.

Of = course, being a=20 pusher driver, I think of inlet air speeds in terms of the speed of = the=20 airplane. So does the fact that the inlet is behind prop give a = much=20 higher effective inlet velocity? I=92ve been thinking that the = turbulence=20 in the prop wash would negate a good portion of the extra mean air = velocity=20 because of reduced inlet effectiveness.

It will = be=20 interesting to know how it works out on a hot day.

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

Merry = Christmas and=20 Happy New Year to all.

Al=20 G

------=_NextPart_000_001F_01CA846C.D3A4FCA0--