X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao102.cox.net ([68.230.241.44] verified) by logan.com (CommuniGate Pro SMTP 5.3c4) with ESMTP id 4037193 for flyrotary@lancaironline.net; Wed, 23 Dec 2009 20:11:56 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.44; envelope-from=alventures@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao102.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20091224011121.LNJM8308.fed1rmmtao102.cox.net@fed1rmimpo03.cox.net> for ; Wed, 23 Dec 2009 20:11:21 -0500 Received: from BigAl ([72.192.128.205]) by fed1rmimpo03.cox.net with bizsmtp id LpBM1d00W4S1t5C04pBMpn; Wed, 23 Dec 2009 20:11:21 -0500 X-VR-Score: 0.00 X-Authority-Analysis: v=1.1 cv=hxRkenI+XOLoHPjz51PhBd6+pm8nOe1puOOeXS7yE/Y= c=1 sm=1 a=Vegc0WxVmH5BHtpNDyThtA==:17 a=Po_XruMzhGCfnoykBmsA:9 a=MECdd7Fr8W_pJiZrlKw5JjEIIp0A:4 a=yMhMjlubAAAA:8 a=5i9HZP3raa9HOSKq0jgA:9 a=b5FvzMQQdXF0p0NJ1MgA:7 a=C587RV5ubRwelg0l6i_yTaKsCu0A:4 a=Vegc0WxVmH5BHtpNDyThtA==:117 X-CM-Score: 0.00 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Air Flow Question Date: Wed, 23 Dec 2009 17:12:03 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0010_01CA83F3.0BF752D0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6856 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Importance: Normal Thread-Index: AcqD93eWq8CzqDfLSUSFV3ovp+VyUQAO3CMg In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0010_01CA83F3.0BF752D0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable As far as I can tell, thrust recovery in the P-51 is legend. Never found anything in the way of proof that it really occurred. =20 The most detailed, and what I believe to be authentic, analysis of the = P-51 scoop legend is that there is no net thrust - ever. There are certain conditions where it is basically 1 : 1 offsetting drag (top speeds, and = in dives); and yes, the outlet velocity may get slightly higher than inlet, = but the air is less dense so has less momentum per unit volume. For most operations it was in the 1 to .85-.95 range, which is excellent. =20 Anything we can do to accelerate the air back toward the free stream and velocity, and have it exit in the direction of the free stream, helps. = An efficient converging duct with an outlet area in the range of 1.3 to = about 1.6 is good, and the ratio of choice depends on the temperature increase = of the air - which depends on the mass flow rate through the core. (Higher = DT, higher ratio). Analysis that I have seen (and verified) suggests minimum drag and radiator weight is achieved with DT in the range of 50 - 75F, = core thickness 2 1/4 - 3"; and yeah, there are set of assumptions involved, = so YMMV. =20 That's my story; and I'm sticking to it:-). =20 BTW, ED, thanks for the tip on the D; that is very cool. =20 Al G ------=_NextPart_000_0010_01CA83F3.0BF752D0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

As far as I can tell, = thrust recovery in the P-51 is legend. Never found anything in the way of proof = that it really occurred.

The most detailed, and what I = believe to be authentic, analysis of the P-51 scoop legend is that there is no net = thrust – ever. There are certain conditions where it is basically 1 : 1 = offsetting drag (top speeds, and in dives); and yes, the outlet velocity may get = slightly higher than inlet, but the air is less dense so has less momentum per = unit volume. For most operations it was in the 1 to .85-.95 range, which is = excellent.

Anything we can do to accelerate = the air back toward the free stream and velocity, and have it exit in the = direction of the free stream, helps. An efficient converging duct with an = outlet area in the range of 1.3 to about 1.6 is good, and the ratio of choice depends = on the temperature increase of the air – which depends on the mass flow = rate through the core. (Higher D<= font size=3D2 color=3Dblue face=3DVerdana>T, higher ratio). Analysis that I have seen (and verified) = suggests minimum drag and radiator weight is achieved with DT in the range = of 50 – 75F, core thickness 2 1/4 – 3”; and yeah, there are set of assumptions involved, so YMMV.

That’s my story; and = I’m sticking to itJ.

BTW, ED, thanks for the tip on = the D; that is very = cool.

Al G

------=_NextPart_000_0010_01CA83F3.0BF752D0--