X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qw-out-2122.google.com ([74.125.92.27] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4037308 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 22:02:43 -0500 Received-SPF: pass receiver=logan.com; client-ip=74.125.92.27; envelope-from=rwstracy@gmail.com Received: by qw-out-2122.google.com with SMTP id 9so1554752qwb.25 for ; Wed, 23 Dec 2009 19:02:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to :content-type; bh=U3mSuJQV7eUR1Wk7lRGYBj4xnk69WzutfGUH910eUpk=; b=VBST6MOS1DTNbXRMGusABpxpTTUkcpb1vGhHmsYA69EQ/cbKkqL/25mXuna5r0kG5C PaPMFd+AvbGQX6cy0pbjat7Anp/jbvm6d7HxsZjY5eXXMWYqWFWJLH2At+N/oILZGBhm Fy+aUg1xIauGMZsEYm7rM1GVEJN+chWDo9gOI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=K/k9SjXrN2XLJePvAE4ahJ4w23AqZqECzQxRQtIJrNDWV6kuKjDqvJ8sav0wDYNSqW 7khSsMWUD64VhWIRCg4XOduYPuCQYQqa+qlhbzxZ500CWM4eaZ/q8nuPoinXLywCw5gI C8qL99aGdMF7vNAWBLHpSu2zDz/ljwL9xQuYA= MIME-Version: 1.0 Sender: rwstracy@gmail.com Received: by 10.224.50.130 with SMTP id z2mr5636283qaf.206.1261623729281; Wed, 23 Dec 2009 19:02:09 -0800 (PST) In-Reply-To: References: Date: Wed, 23 Dec 2009 22:02:09 -0500 X-Google-Sender-Auth: 22f1e392bb397d12 Message-ID: <1b4b137c0912231902w6d0c5befv3307c8989769d019@mail.gmail.com> Subject: Re: [FlyRotary] Air Flow Question From: Tracy Crook To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=00c09f88d010395dd6047b70aa2f --00c09f88d010395dd6047b70aa2f Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable True, it has yet to be tested on a hot day, nor have I tried any sustained high power climbs. I do get 100+ degree delta Ts on my RV-4 because it was specifically setup to use the absolute minimum air volume to cool (thick rads etc). That is one reason why I had to install cooling plenums on my coils & alternator. It is very hot under the cowl and I fried several D581 coils without the plenum. Haven't gotten good delta T data on the -8 yet= . The prop blast may be helping a lot on the -8. I used the Sam James 'Holey Cowl" with the round inlets set well outboard of the spinner. Not sure what it means, but Harmon Rockets are cooling 260 - 300 HP IO - 540s with inlets smaller than mine. 5" is the dimension after I enlarged the openings. Sam James supplies 3.625 - 4.25" inlet inserts for use with the 200 HP Lycs. I do see significant pressure in the oil cooler diffuser when running the engine up prior to starting the takeoff roll so I assume the ra= d is getting similar benefit. My Catto prop was built with a lot of attention to proper pitch near the hub as well. One other observation from yesterday's tests. When my oil cooling was improved, the water temps went down as well, even though airflow probably went down through the rad when I improved airflow through the oil cooler. There is apparently a lot of internal coupling of the water & oil temperatures inside the engine. Supposed to be warmer tomorrow. Will do some more flight tests. Tracy On Wed, Dec 23, 2009 at 11:20 AM, Al Gietzen wrote: > 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=92s 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=94 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=92s 250 mph. And I=92m guessing= your > climb speed is half that. Similar math suggests you=92d 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 pro= p > give a much higher effective inlet velocity? I=92ve been thinking that t= he > 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 > > > > > > > --00c09f88d010395dd6047b70aa2f Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable True, it has yet to be tested on a hot day, nor have I tried any sustained = high power climbs.=A0 I do get 100+ degree delta Ts on my RV-4 because it w= as specifically setup to use the absolute minimum air volume to cool (thick= rads etc).=A0 That is one reason why I had to install cooling plenums on m= y coils & alternator.=A0 It is very hot under the cowl and I fried seve= ral D581 coils without the plenum. =A0=A0 Haven't gotten good delta T d= ata on the -8 yet.

=A0=A0 The prop blast may be helping a lot on the -8.=A0 I used the Sam= James 'Holey Cowl" with the round inlets set well outboard of the= spinner.=A0 Not sure what it means, but Harmon Rockets are cooling 260 - 3= 00 HP IO - 540s with inlets smaller than mine. =A0 5" is the dimension= after I enlarged the openings.=A0 Sam James supplies 3.625 - 4.25" in= let inserts for use with the 200 HP Lycs.=A0 I do see significant pressure = in the oil cooler diffuser when running the engine up prior to starting the= takeoff roll so I assume the rad is getting similar benefit. =A0 My Catto = prop was built with a lot of attention to proper pitch near the hub as well= .

One other observation from yesterday's tests.=A0 When my oil coolin= g was improved, the water temps went down as well, even though airflow prob= ably went down through the rad when I improved airflow through the oil cool= er.=A0 There is apparently a lot of internal coupling of the water & oi= l temperatures inside the engine.=A0

Supposed to be warmer tomorrow.=A0 Will do some more flight tests.
<= br>Tracy
=A0



On Wed, Dec 23, 2= 009 at 11:20 AM, Al Gietzen <ALVentures@cox.net> wrote:

Tracy wrote:

My 5" round inle= t for the radiator looks ridiculously small compared to yours but so far it is cooling the 20B OK.= =A0

=A0=

Now that s= ort of boggles my mind as it seems to violate the laws of physics. Let=92s just take a modest climb power of, say; 225 hp.=A0 At that power, the energy going into the coolant is about 6000 Btu/min. =A0In order to remove that amount of heat, at a typical air temp increase of 75 degrees; takes about 4000 cfm air flow.=A0 = A 5=94 dia inlet is 0.14 sq feet, meaning an average inlet velocity about 29,= 000 ft/min, or 330 mph.=A0 Even at 100 air temp increase (unlikely on a 90F day= ) it=92s 250 mph.=A0 And I=92m guessing your climb speed is half that.=A0 Similar math suggests you=92d be limited to a steady state (cruise= ) power of about 50%.

=A0=

Of course,= being a pusher driver, I think of inlet air speeds in terms of the speed of the airplane.=A0 So does the fact that the inlet is behind prop give a much higher effective inlet velocity?=A0 I=92ve been thinking that the turbulence in the prop wash woul= d negate a good portion of the extra mean air velocity because of reduced inl= et effectiveness.

=A0=

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

=A0=

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

=A0=

Merry Chri= stmas and Happy New Year to all.

=A0=

Al G

=A0=

=A0=

=A0=


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