X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2463704 for flyrotary@lancaironline.net; Fri, 09 Nov 2007 13:47:00 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Received: from edward2 ([24.74.103.61]) by cdptpa-omta04.mail.rr.com with SMTP id <20071109184623.WEIQ5837.cdptpa-omta04.mail.rr.com@edward2> for ; Fri, 9 Nov 2007 18:46:23 +0000 Message-ID: <001701c82300$9336bf70$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Total,duct, Ambient or Velocity???? Date: Fri, 9 Nov 2007 13:44:35 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01C822D6.AA205310" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0014_01C822D6.AA205310 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Good to hear, Monty, I'll save my money for snazzy video games {:>) Ed ----- Original Message -----=20 From: M Roberts=20 To: Rotary motors in aircraft=20 Sent: Friday, November 09, 2007 11:27 AM Subject: [FlyRotary] Re: Total,duct, Ambient or Velocity???? But, semantics aside, yes, I agree, lower exit pressure is what you = are after and that does not always equate to larger exit duct area. In = fact, if the air heated by the core flows through a nozzle it might even = produce thrust and lower exit pressure using a smaller exit. But, in = general, I still believe that in most of our cases, we are short of the = level of duct design that would reliably permit that. What we need is = someone to invest in one of those $$$$ Computer Fluid Flow software = programs and see what they would reveal.=20 Ed Ed, I have to disagree with the big $$$ CFD idea. Until I see proper exit = ducts and every effort made to do things right inlet wise....CFD is a = waste of time. I have yet to see an installation at the level of = refinement where CFD would start to make sense. You can get to 90% of = optimum by following a few simple guidelines and some fairly simple = math.=20 1.) do a heat balance at the cruise condition to figure out how much = air you need to ingest. 2.) Size your inlet appropriately. 3.) Provide a real exit duct. 4.) Use a cowl flap. 5.) Do some testing with oil and tufts to make improvements. A properly done CFD will only get you another 5% beyond these simple = steps that are within reach of mere mortals. In fact if the guy/gal = doing the CFD work is not intimately familiar with the situation and = what sort of assumptions to make/conditions to assign it is very likely = that the results will be less successful that the empirical method. In other words CFD=3Ddecimal dust. Monty ------=_NextPart_000_0014_01C822D6.AA205310 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Good to hear, Monty, I'll save my money for = snazzy video=20 games {:>)
 
Ed
----- Original Message -----
From:=20 M=20 Roberts
Sent: Friday, November 09, 2007 = 11:27=20 AM
Subject: [FlyRotary] Re: = Total,duct,=20 Ambient or Velocity????

But, semantics aside, = yes, I agree,=20 lower exit pressure is what you are after and that does not always = equate to=20 larger exit duct area.  In fact, if the air heated by the core = flows=20 through a nozzle it might even produce thrust and lower exit=20 pressure using a smaller exit.  But, in general, I still = believe=20 that in most of our cases, we are short of the level of duct design = that would=20 reliably permit that.  What we need is someone to invest in one = of those=20 $$$$ Computer Fluid Flow software programs and see what they would=20 reveal.=20
 
Ed
 
 
Ed,
 
I have to disagree with the = big $$$ CFD=20 idea. Until I see proper exit ducts and every effort made to do things = right=20 inlet wise....CFD is a waste of time. I have yet to see an = installation at the=20 level of refinement where CFD would start to make sense. You can get = to 90% of=20 optimum by following a few simple guidelines and some fairly simple = math.=20
 
1.) do a heat balance at the = cruise=20 condition to figure out how much air you need to ingest.
 
2.) Size your inlet=20 appropriately.
 
3.) Provide a real exit = duct.
 
4.) Use a cowl = flap.
 
5.) Do some testing with oil = and tufts to=20 make improvements.
 
A properly done CFD will only = get you=20 another 5% beyond these simple steps that are within reach of mere = mortals. In=20 fact if the guy/gal doing the CFD work is not intimately familiar with = the=20 situation and what sort of assumptions to make/conditions to assign it = is very=20 likely that the results will be less successful that the empirical=20 method.
 
In other words CFD=3Ddecimal=20 dust.
 
 
Monty
------=_NextPart_000_0014_01C822D6.AA205310--