X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 04 May 2006 18:58:16 -0400 Message-ID: X-Original-Return-Path: Received: from imo-d23.mx.aol.com ([205.188.139.137] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1092338 for lml@lancaironline.net; Thu, 04 May 2006 18:31:08 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.137; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d23.mx.aol.com (mail_out_v38_r7.5.) id q.416.b34828 (3699) for ; Thu, 4 May 2006 18:30:19 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <416.b34828.318bda7b@aol.com> X-Original-Date: Thu, 4 May 2006 18:30:19 EDT Subject: Re: [LML] oil cooler NACA inlet & prop size X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1146781819" X-Mailer: 9.0 Security Edition for Windows sub 5300 X-Spam-Flag: NO -------------------------------1146781819 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 5/4/2006 9:50:10 A.M. Central Standard Time, elippse@sbcglobal.net writes: If you don't know the characteristics of the NACA curved-divergent inlet for its proper design, I would advise you to instead use a stagnation/pitot inlet, that is, one which projects out from the cowling pointing forward and with a streamlined aft body. See Hoerner's "Fluid Dynamic Drag" for some inlet shapes and their drag coefficients. You might also want to look at the NACA parallel-wall submerged duct which has a square outlet that is much easier to interface to a round duct. It also has better pressure-recovery characteristics than the curved-divergent inlet at duct velocities greater than half of the free-stream velocity. Look at your oil-cooler's spec sheet from the manufacturer, pick the cooling flow from the middle of the graph of heat-rejection vs flow, size the inlet for that flow at cruise, then add 25% to the area. Say the center of your spec sheet graph shows 300 cfm/ 5cfs, and your cruise speed is 230 mph. Then your inlet area is 5 * 144 / (230 * 22/15) = 2.13 square inches. Increase that by 25% to get 2.67 sq. in. 1 5/8 " square, 2 5/16" X 1 3/16" rectangle or 1 7/8" diameter round, all with nice, rounded lips. Then provide a diverging duct from that inlet to the oil cooler to slow the flow and increase the pressure, and then a converging duct from the cooler to the cowl outlet, pointed toward the rear, with an outlet area of about 3-3.5 sq in to get the flow back up to freestream velocity. Paul, My friend with a Lancair 360 and he uses a race car inlet for oil cooler air on the side of his cowling - it is shaped like an angled rearward offset funnel (yes, just a funnel). He also has to shut off the air during winter since the cooling flow is too much. He does not need sophisticated exit plenums - just submerged shark gill exits since his cooler is mounted on the cowl itself. There are so many way to skin the cat - just ask mine...... Scott Krueger AKA Grayhawk Lancair N92EX IO320 CS Prop Slow Build 1989, Flown 1996 Aurora, IL (KARR) Eschew Obfuscation! -------------------------------1146781819 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 5/4/2006 9:50:10 A.M. Central Standard Time,=20 elippse@sbcglobal.net writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>If you don't know the characteristics of the NACA curved-dive= rgent=20 inlet for its proper design, I would advise you to instead use a=20 stagnation/pitot inlet, that is, one which projects out from the cowling=20 pointing forward and with a streamlined aft body. See Hoerner's "Flui= d=20 Dynamic Drag" for some inlet shapes and their drag coefficients. You=20 might also want to look at the NACA parallel-wall submerged duct which has= a=20 square outlet that is much easier to interface to a round duct. It also ha= s=20 better pressure-recovery characteristics than the curved-divergent=20 inlet at duct velocities greater than half of the free-stream=20 velocity. Look at your oil-cooler's spec sheet from the manufacturer,= =20 pick the cooling flow from the middle of the graph of heat-rejection vs=20 flow, size the inlet for that flow at cruise, then add 25% to the are= a.=20 Say  the center of your spec sheet graph shows 300 cfm/ 5cfs, and you= r=20 cruise speed is 230 mph. Then your inlet area is 5 * 144 / (230 * 22/= 15)=20 =3D 2.13 square inches. Increase that by 25% to get 2.67 sq. in. 1 5/= 8 "=20 square, 2 5/16" X 1 3/16" rectangle or 1 7/8" diameter round, all wit= h=20 nice, rounded lips.  Then provide a diverging duct from that inl= et=20 to the oil cooler to slow the flow and increase the pressure, and then a=20 converging duct from the cooler to the cowl outlet, pointed toward the rea= r,=20 with an outlet area of about 3-3.5 sq in to get the flow back up to freest= ream=20 velocity.
Paul,
 
My friend with a Lancair 360 and he uses a race car inlet for oil coole= r=20 air on the side of his cowling - it is shaped like an angled rearward offset= =20 funnel (yes, just a funnel).  He also has to shut off the air during wi= nter=20 since the cooling flow is too much.  He does not need sophisticated exi= t=20 plenums - just submerged shark gill exits since his cooler is mounted on the= =20 cowl itself.  There are so many way to skin the cat - just ask mine....= ..=20
 
Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 CS Prop
Slow Build 1989, Flown 1996=20
Aurora, IL (KARR)

Eschew=20 Obfuscation!
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