Return-Path: Received: from [216.52.245.18] (HELO ispwestemail2.mdeinc.com) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 149800 for flyrotary@lancaironline.net; Sat, 12 Jun 2004 09:25:45 -0400 Received: from 7n7z201 (unverified [67.136.145.246]) by ispwestemail2.mdeinc.com (Vircom SMTPRS 3.1.302.0) with SMTP id for ; Sat, 12 Jun 2004 06:25:09 -0700 Message-ID: <002901c45080$a9021b20$f6918843@7n7z201> From: "William" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] New Truncated Streamline Ducts Date: Sat, 12 Jun 2004 08:24:57 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0026_01C45056.BF15E830" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 This is a multi-part message in MIME format. ------=_NextPart_000_0026_01C45056.BF15E830 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Nice work ED, looking forward to the tests. Bill Schertz KIS Cruiser # 4045 ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Saturday, June 12, 2004 7:39 AM Subject: [FlyRotary] New Truncated Streamline Ducts Here are a few photos of my new radiator ducts modeled along the = Streamline Duct profile. The Right radiator duct inlet has been reduced = from 24 sq inch to 14 sq inch and the left one from 24 to 10 sq inches. = Both use a "truncated" version of the Streamline Duct profile described = in K&W Section 12. =20 K&W shows that the full (untruncated) version can provide a pressure = recovery of up to 84% of the dynamic pressure potential. The Duct wall = shape contribute approx 48% of this recovery with the core resistance = contributing the remaining 40%. The truncated version looks like it = will still provide approx 64% pressure recovery. Not as good as the full = Streamline duct, but, just one of the space compromises sometimes = (often?) required when putting anything in an aircraft. In my first experiment using a truncated Streamline duct profile, I = was able to reduce my overall inlet area for my two radiators from 48 sq = inch to 33 sq inches with the left duct inlet being reduced to 9 sq = inches. This was an apporx 30% reduction in inlet area and the results = was my coolant temp increased 5 F. The right duct was still the old = -very UNstreamline duct. So I believe that now having both ducts with a truncated version of = the streamline duct and its clearly better recovery (than my old box = ducts), I can reduce the overall inlet area even more - down to say 50% = or 24 sq inch total for the both. =20 Smaller duct opens have a plus and minus side. The greater expansion = ratio of entrance area to core area should raise the pressure drop = across the core and slow the air flow through the core reducing drag. = This should cause the heat transfer coefficient to increase resulting = in more heat rejected to the airflow - the downside is there will be = less airflow (less drag as a result, but less mass flow for cooling). = So long as the increased heat transfer to the air compensates for the = reduced mass flow it should work OK. This means I should see higher air = temps out of the cores than before. Now if the expansion is too much = for the duct's internal pressure to preclude flow separation from the = walls, then the cooling effect can be severely restricted, so trying to = find where those limits might be. The flared entrances are not part of the streamline duct. They are = simply to smooth the airflow from the cowl duct opening to the actual = duct inlet. This could in effect result in more air moving into the = inlet than my previous ducts which had an approx 1/2 -3/4" blunt lip = around the entrance. Also, it may provide more inlet velocity (Bernoulli = effect) which in turn may provide more energy conversion to pressure = increase inside the duct - just speculation. But, at a minimum, the = smoothed transition should produce less drag than the previous blunt = duct entrance. On the other hand, the flares could act like an external = diffuser and slow the air before the entrance. Just too many factors to = analytically account for them and their interactions. I have kept the old ducts and will put them back on when I get some = instrumentation hooked up so we can do a side by side comparison. Best Regards Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0026_01C45056.BF15E830 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Nice work ED,
looking forward to the = tests.
Bill Schertz
KIS Cruiser # 4045
----- Original Message -----
From:=20 Ed=20 Anderson
Sent: Saturday, June 12, 2004 = 7:39=20 AM
Subject: [FlyRotary] New = Truncated=20 Streamline Ducts

Here are a few photos of my new = radiator ducts=20 modeled along the Streamline Duct profile.  The Right radiator = duct inlet=20 has been reduced from 24 sq inch to 14 sq inch and the left one from = 24 to 10=20 sq inches.  Both use a "truncated" version of the Streamline Duct = profile=20 described in K&W Section 12. 
 
K&W shows that the full = (untruncated) version=20 can provide a pressure recovery of up to  84% of the dynamic = pressure=20 potential.  The Duct wall shape contribute approx 48% of = this=20 recovery with the core resistance contributing the remaining = 40%.  The=20 truncated version looks like it will still provide approx 64% pressure = recovery. Not as good as the full Streamline duct, but, just  one = of the=20 space compromises sometimes (often?) required when putting anything in = an=20 aircraft.
 
In my first experiment using a = truncated=20 Streamline duct profile, I was able to reduce my overall inlet area = for my two=20 radiators from 48 sq inch to 33 sq inches with the left duct inlet = being=20 reduced to 9 sq inches.  This was an apporx 30% reduction in = inlet area=20 and the results was my coolant temp increased 5 F.  The right = duct was=20 still the old -very UNstreamline duct.
 
So I believe that now having both = ducts with a=20 truncated version of the streamline duct and its clearly better = recovery=20 (than my old box ducts),  I can reduce the overall inlet area = even more -=20 down to say 50% or 24 sq inch total for the both. 
 
Smaller duct opens have a plus and = minus=20 side.  The greater expansion ratio of entrance area to core area = should=20 raise the pressure drop across the core and slow the air flow through = the core=20 reducing drag.  This should cause the heat transfer=20 coefficient to  increase resulting in more heat rejected to = the=20 airflow - the downside is there will be less airflow (less drag as a = result,=20 but less mass flow for cooling).  So long as the increased heat = transfer=20 to the air compensates for the reduced mass flow it should work = OK.  This=20 means I should see higher air temps out of the cores than = before.  Now if=20 the expansion is too much for the duct's internal pressure to preclude = flow=20 separation from the walls, then the cooling effect can be severely = restricted,=20 so trying to find where those limits might be.
 
The flared entrances are not part of = the=20 streamline duct.  They are simply to smooth the airflow from the = cowl=20 duct opening to the actual duct inlet.  This could in effect = result in=20 more air moving into the inlet than my previous ducts which had an = approx 1/2=20 -3/4" blunt lip around the entrance. Also, it may provide more inlet = velocity=20 (Bernoulli effect) which in turn may provide more energy conversion to = pressure increase inside the duct - just speculation.  But, at a = minimum,=20 the smoothed transition should produce less drag than = the previous=20 blunt duct entrance.  On the other hand, the flares could = act like=20 an external diffuser and slow the air before the entrance.  Just = too many=20 factors to analytically account for them and their = interactions.
 
I have kept the old ducts and = will put them=20 back on when I get some instrumentation hooked up so we can do a side = by side=20 comparison.
 
Best Regards
 
Ed
 
 
Ed Anderson
RV-6A N494BW Rotary=20 Powered
Matthews, NC

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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