Return-Path: Received: from fed1rmmtao07.cox.net ([68.230.241.32] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 854304 for flyrotary@lancaironline.net; Mon, 04 Apr 2005 12:23:39 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.32; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao07.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050404162250.PZEP13104.fed1rmmtao07.cox.net@BigAl> for ; Mon, 4 Apr 2005 12:22:50 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Cooling Inlet Areas/Bernie's RV9 Date: Mon, 4 Apr 2005 09:22:59 -0700 Message-ID: <000001c53932$915f0a00$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C538F7.E5027BF0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C538F7.E5027BF0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Doug; =20 I agree with your 'rule-of-thumb' numbers. My analysis came up with = coolant inlet area in sq. in. of 1/3 the HP (.33) for climb out on a 90F day. = It assumes a 120kt climb speed for my Velocity. I used 45% of that = additional for the oil cooler. Assumes scoop efficiencies of 85% or better. =20 Al =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Shearbond@aol.com Sent: Monday, April 04, 2005 6:49 AM To: Rotary motors in aircraft Subject: [FlyRotary] Cooling Inlet Areas/Bernie's RV9 =20 From my work on Compact Heat Exchangers especially as related to my = friend's 13B powered RV-3, Bernie has plenty of heat exchanger "frontal area" and "volume". =20 =20 That said, there are two further considerations in the "gotta have" = category to be able to confidently taxi out and T/O WOT for as long as one wants = in Military Air (+40 deg F over std.) conditions. =20 First....if cooling air can't get out, it can't get in. That is: = adequate air exit area is absolute. The exit area must be sufficient for both coolant and oil cooling exit air. For 200 HP that is about 2.1(oil + coolant + now heated air) x .30 x HP or 2.1 x .30 x 200 =3D 126 sq. in. = total for 200 HP. =20 =20 Yes, that is larger than an air cooled engine would require but = investigate the temperature differentials between a 350 deg F air cooled cylinder = and a 200 deg F hot coolant and one will quickly realize that there must be = more lbs. of air flow for a coolant cooled engine. =20 Second, even if cooling can get out, if it can't get in, it can't be = there to cool the heat exchangers. Rule of thumb: 0.3 sq. in. of cowling = inlet air opening per HP. 200 HP x .3 =3D 60 sq. in. Note: This assumes a reasonably shaped inlet cowl which has been discussed online often. = IMHO: Berni's plane inlet shape and inlet cowl is fine, but I question his = inlet opening area. =20 Note: the exhaust area requirement is greater than the inlet = combination of oil and coolant due to the now considerable hotter air temperature. = Rule of thumb: Coolant air inlet opening for 200 HP coolant cooled engine ~60 = sq. in., oil inlet opening ~30 sq. in. equals a total opening of 90 sq. in. = A good place to start with exhaust opening is 1.4 times the inlets or 126 = sq. in. Close the exit area down with cowl flaps to as little as 80% of the inlet combination at cruise conditions! =20 Don't mean to start another stream of threads on an old subject, but we sweated over this one for 3 months and 3 systems and one might save a = lot of time by comparing ones system to these simple "works great" rules of = thumb which are the result of LOTS of technical and experimental work. =20 Doug Dempsey N6415Q and RV7 in process Colorado, USA ------=_NextPart_000_0001_01C538F7.E5027BF0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Doug;

 

I agree with your = ‘rule-of-thumb’ numbers.  My analysis came up with coolant inlet area in sq. in. of = 1/3 the HP (.33) for climb out on a 90F day.  It assumes a 120kt climb = speed for my Velocity.  I used 45% of that additional for the oil = cooler.  Assumes scoop efficiencies of 85% or better.

 

Al

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Shearbond@aol.com
Sent: Monday, April 04, = 2005 6:49 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] = Cooling Inlet Areas/Bernie's RV9

 

From my work on Compact Heat Exchangers especially as related to my friend's 13B powered RV-3, Bernie has plenty of heat exchanger "frontal = area" and "volume". 

 

That said, there are two further considerations in the "gotta have" = category to be able to confidently taxi out and T/O WOT for as long as one wants = in Military Air (+40 deg F over std.) conditions.

 

First....if cooling air can't get out, it can't get in.  That is: adequate air = exit area is absolute.  The exit area must be sufficient for both = coolant and oil cooling exit air.  For 200 HP that is about 2.1(oil + coolant + now heated air) x .30 x HP or 2.1 x .30 x 200 =3D 126 = sq. in. total for 200 HP. 

 

Yes, that is larger than an air cooled engine would require but investigate = the temperature differentials between a 350 deg F air cooled cylinder and a = 200 deg F hot coolant and one will quickly realize that there must be more lbs. = of air flow for a coolant cooled engine.

 

Second, even if cooling can get out, if it can't get in, it can't be there = to cool the heat exchangers.  Rule of thumb: 0.3 sq. in. of cowling inlet = air opening per HP.  200 HP x .3 =3D 60 sq. in.  Note: This = assumes a reasonably shaped inlet cowl which has been discussed online = often.  IMHO: Berni's plane inlet shape and inlet cowl is fine, but I = question his inlet opening area.

 

Note:  the exhaust area requirement is greater than the inlet combination = of oil and coolant due to the now considerable hotter air temperature.  = Rule of thumb:  Coolant air inlet opening for 200 HP coolant cooled engine = ~60 sq. in., oil inlet opening ~30 sq. in. equals a total opening of 90 sq. = in.  A good place to start with exhaust opening is 1.4 times the inlets or 126 = sq. in.  Close the exit area down with cowl flaps to as little as 80% = of the inlet combination at cruise conditions!

 

Don't mean to start another stream of threads on an old subject, but we = sweated over this one for 3 months and 3 systems and one might save a lot of time by comparing ones system to these simple "works great" rules of = thumb which are the result of LOTS of technical and experimental = work.

 

Doug Dempsey

N6415Q and RV7 in process

Colorado, USA

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