Return-Path: <13brv3@bellsouth.net> Received: from imf19aec.mail.bellsouth.net ([205.152.59.67] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 485207 for flyrotary@lancaironline.net; Sun, 24 Oct 2004 20:35:24 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.67; envelope-from=13brv3@bellsouth.net Received: from rd ([65.6.194.9]) by imf19aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20041025003454.GXTO2400.imf19aec.mail.bellsouth.net@rd> for ; Sun, 24 Oct 2004 20:34:54 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: oil cooler duct suggestion Date: Sun, 24 Oct 2004 19:35:14 -0500 Message-ID: <016301c4ba2a$7ec41930$6101a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0164_01C4BA00.95EE1130" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0164_01C4BA00.95EE1130 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable My oil cooler "diffuser" is almost identical to yours except mine tapers = to zero distance from core at back end. Extensive wind tunnel tests = (squirting compressed air nozzle at inlet and feeling where air came out of oil = cooler) showed that most of it was at the back end (no big surprise). Already = been some better permanent solutions suggested here but as a quick fix I put = a piece of ridge vent material (very porous fiber stuff used to vent = roofs) at the back end to equalize the flow through the core. Not a great = solution but did show measurable improvement.=20 =20 I took another look at the scoop today, and there's plenty of room for improvement. I believe I'll smooth out the bottom of the scoop in the = rear to eliminate the wall. I'll also add a steering vane in the middle of = the core. After looking at it today, I can easily imagine that the front quarter or so isn't getting much air due to the way the air has to turn = to get to it. I can even imagine needing a second smaller vane just like = what Al showed in his picture. =20 =20 Only thing I would suggest is to carefully measure the pressure drop = through the scat duct to throttle body. Possibly even worse than the pressure = drop is the heat the air picks up going through that thing (at least that's = my theory). I was flabbergasted at the improvement I got when I eliminated = the scat. Mine was a bit longer than yours so the penalty may not be that = much in your installation. Worth keeping in mind though.=20 =20 I really went overkill with the scat tube this time. Mine is 3" ID, = and it's hard to imagine it having much of a pressure drop. I'm sure = there's some unwanted turbulence though, so eventually, I'll replace this run = with something smooth. I never thought much about the heat issue either. By far, my biggest problem is the inlet located inside the radiator duct. = It's got a big hole, but forces the air to make 90 degree turns to get in, = which just can't be good. I still can't believe I'm really only getting 26" = MAP in climb though, because I'm turning close to 6200 rpm at 120 mph. = Since that's the same as what you were seeing, I find it pretty hard to = imagine that I'm getting as much power as you had, but with 4" less MAP. I sure hope I'm wrong though :-) =20 I've made the decision that I'm not going to do either of the above fiberglass projects until I get my 40 hours flown off. After today's flight, I've only got 2.9 hours to go. I treated the airport to a full showoff climb today. I lifted off, kept the nose level to 100 mph, then pointed it upward at 90 mph. I forgot to look at the VSI though. I = rolled on course as I leveled off a fraction of a minute later at 2000 ft, and = the oil temp was up to about 190. Level at 2000 ft, and 5200 rpm, the oil stabilized at 185, and the water at 144. Just purred like a rotary = kitten :-)=20 =20 Cheers, Rusty (zoom, zoom) =20 =20 =20 ------=_NextPart_000_0164_01C4BA00.95EE1130 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
My oil cooler "diffuser" is almost identical to yours except mine = tapers to=20 zero distance from core at back end.  Extensive wind tunnel tests=20 (squirting compressed air nozzle at inlet and feeling where air came out = of oil cooler) showed that most of it was at the back end (no big=20 surprise).   Already been some better permanent solutions = suggested=20 here but as a quick fix I put a piece of ridge vent material (very = porous=20 fiber stuff used to vent roofs) at the back end to equalize the = flow=20 through the core.  Not a great solution but did show measurable=20 improvement. 
 
I took=20 another look at the scoop today, and there's plenty of room for=20 improvement.  I believe I'll smooth out the bottom of the scoop in = the rear=20 to eliminate the wall.  I'll also add a steering vane in the middle = of the=20 core.  After looking at it today, I can easily imagine that the=20 front quarter or so isn't getting much air due to the way the air = has to=20 turn to get to it.  I can even imagine needing a second = smaller vane=20 just like what Al showed in his picture.  =  
 
Only thing I would suggest is to carefully measure the = pressure drop=20 through the scat duct to throttle body.   Possibly even = worse=20 than the pressure drop is the heat the air picks up going through that = thing (at=20 least that's my theory).  I was flabbergasted at the = improvement I got=20 when I eliminated the scat.  Mine was a bit longer than yours so = the=20 penalty may not be that much in your installation.  Worth keeping = in mind=20 though. 
 
I=20 really went overkill with the scat tube this time.   Mine = is 3"=20 ID, and it's hard to imagine it having much of a pressure = drop.  I'm=20 sure there's some unwanted turbulence though, so eventually, I'll = replace=20 this run with something smooth.  I never thought much about the = heat issue=20 either.  By far, my biggest problem is the inlet located = inside=20 the radiator duct.  It's got a big hole, but forces the air to make = 90=20 degree turns to get in, which just can't be good.  I still = can't=20 believe I'm really only getting 26" MAP in climb though, because=20 I'm turning close to 6200 rpm at 120 mph.  Since=20 that's the same as what you were seeing, I find it pretty hard to = imagine=20 that I'm getting as much power as you had, but with 4" less MAP.  I = sure=20 hope I'm wrong though :-)
 
I've=20 made the decision that I'm not going to do either of the above = fiberglass=20 projects until I get my 40 hours flown off.  After today's flight,=20 I've only got 2.9 hours to go.  I treated the airport to a = full=20 showoff climb today.  I lifted off, kept the nose level to 100 mph, = then=20 pointed it upward at 90 mph.  I forgot to look at the VSI=20 though.  I rolled on course as I leveled off a fraction of a = minute=20 later at 2000 ft, and the oil temp was up to about 190.  Level = at 2000=20 ft, and 5200 rpm, the oil stabilized at 185, and the water at = 144. =20 Just purred like a rotary kitten :-) 
 
Cheers,
Rusty (zoom, = zoom)       
 
 
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