Return-Path: <eanderson@carolina.rr.com> Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2881619 for flyrotary@lancaironline.net; Mon, 08 Dec 2003 09:10:55 -0500 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hB8EAod3029926 for <flyrotary@lancaironline.net>; Mon, 8 Dec 2003 09:10:53 -0500 (EST) Message-ID: <000e01c3bd94$a2ef3120$1702a8c0@WorkGroup> From: "Ed Anderson" <eanderson@carolina.rr.com> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net> References: <list-2881247@logan.com> Subject: Re: [FlyRotary] Re: K&M and Thick Radiators Date: Mon, 8 Dec 2003 09:07:37 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000B_01C3BD6A.B9BD9BA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000B_01C3BD6A.B9BD9BA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 > <... How do the Mass Air requirements change with altitude ...> > They don't, except as the heat rejection requirements change. > You get the same mass airflow at 180 kias at sea level or 15 k ft. Of = course > your TRUE airspeed at 15k is a lot higher and that's what pumps more = of the > thinner air through the system. Also, to the extent that fuel flow is = less at > 15 k ft, so you have less heat rejection requirements and therefore = less mass > flow requirements. >=20 > <... if the fuel burn was 8.5gph and altitude was 25K ...> > .... you'd be making about 300 kts TAS and would no doubt have the = same mass > airflow as at SL 8.5 gph. >=20 > Mass airflow is a function of indicated airspeed which is dynamic = pressure which > is how many molecules are going past a point in a unit of time. >=20 > Just a theory ... Jim S. >=20 One common formula for air mass flow is as follows: W =3D p*V*A Where W is air mass flow either in Slugs/Unit time or pounds mass (lbm) = or kilograms/unit time, etc. p is the density of the air mass, V the = velocity of the air stream and A the area of the duct (or what ever) you = have the air flowing through. A formula for Dynamic pressure on the other hand is=20 Pd =3D 1/2pV^2 which results in units of pressure (lbf - pound force per square foot, = square inch, square CM or other such area units. So Dynamic pressure = and air mass flow are two separate things. However, density and = velocity of the air are a factor in both.=20 You can have high dynamic pressure and low mass flow or vise versa. = Velocity (V^2) is the dominate factor in dynamic pressure whereas volume = (V*A) is the dominate factor in dynamic pressure. =20 FWIW Ed Anderson ------=_NextPart_000_000B_01C3BD6A.B9BD9BA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-Type content=3D"text/html; = charset=3Diso-8859-1"> <META content=3D"MSHTML 6.00.2800.1264" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2> <BR></FONT></DIV> <DIV><FONT face=3DArial size=3D2>> <... How do the Mass Air = requirements=20 change with altitude ...><BR>> They don't, except as the heat = rejection=20 requirements change.<BR>> You get the same mass airflow at 180 kias = at sea=20 level or 15 k ft. Of course<BR>> your TRUE airspeed at 15k is a lot = higher=20 and that's what pumps more of the<BR>> thinner air through the = system. =20 Also, to the extent that fuel flow is less at<BR>> 15 k ft, so you = have less=20 heat rejection requirements and therefore less mass<BR>> flow=20 requirements.<BR>> <BR>> <... if the fuel burn was 8.5gph and = altitude=20 was 25K ...><BR>> .... you'd be making about 300 kts TAS and would = no=20 doubt have the same mass<BR>> airflow as at SL 8.5 gph.<BR>> = <BR>> Mass=20 airflow is a function of indicated airspeed which is dynamic pressure=20 which<BR>> is how many molecules are going past a point in a unit of=20 time.<BR>> <BR>> Just a theory ... Jim S.<BR>> = <BR></FONT></DIV> <DIV><FONT face=3DArial size=3D2>One common formula for air mass flow is = as=20 follows:</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D4><STRONG>W =3D = <EM>p</EM>*V*A</STRONG></FONT></DIV> <DIV><STRONG><FONT face=3DArial size=3D4></FONT></STRONG> </DIV> <DIV><FONT face=3DArial size=3D2>Where W is air mass flow either in = Slugs/Unit time=20 or pounds mass (lbm) or kilograms/unit time, etc. p is the density = of the=20 air mass, V the velocity of the air stream and A the area of the duct = (or what=20 ever) you have the air flowing through.</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>A formula for Dynamic pressure on the = other hand is=20 </FONT></DIV> <DIV><FONT face=3DArial></FONT> </DIV> <DIV><FONT face=3DArial size=3D4><STRONG>Pd =3D = 1/2pV^2</STRONG></FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial><FONT size=3D2><FONT> which results in = units of=20 pressure (lbf - pound force per square foot, square inch, square CM or = other=20 such area units. So Dynamic pressure and air mass flow are two = separate=20 things. However, density and velocity of the air are a factor in=20 both.</FONT> </FONT></FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>You can have high dynamic pressure and = low mass=20 flow or vise versa. Velocity (V^2) is the dominate factor in = dynamic=20 pressure whereas volume (V*A) is the dominate factor in dynamic = pressure. =20 </FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>FWIW</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>Ed Anderson</FONT></DIV></BODY></HTML> ------=_NextPart_000_000B_01C3BD6A.B9BD9BA0--