X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Received: from ms-smtp-03.southeast.rr.com ([24.25.9.102] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1875305 for flyrotary@lancaironline.net; Wed, 28 Feb 2007 22:15:06 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-03.southeast.rr.com (8.13.6/8.13.6) with SMTP id l213EI3r028482 for ; Wed, 28 Feb 2007 22:14:19 -0500 (EST) Message-ID: <000701c75baf$b40ec620$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Diffuser Design Rules Date: Wed, 28 Feb 2007 22:14:18 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0004_01C75B85.CA620D30" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0004_01C75B85.CA620D30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hey, Dave You have sat through just too many presentations - your skepticism = shows through (I sat through 26 years of briefings in the Air Force and = another 15 as a contractor - give me enough graph paper and the right = scale and I can prove anything you want{:>).=20 Actually, I could have thrown a few more slides in adding more = information supporting my deductive reasoning - but no one/no where has = published any data on a "pinched" duct {:>) - and more words would be = just that - more words. It was not intended to be a research paper - = just a informal presentation to folks with a common interest. =20 But, to answer your question - No data at all. and therefore I get to = "write the rules". I can only take the credit (or blame) for the = pinched duct concept all of the rest of the information is available in = documents or on the web. However, I DID NOT invent the words about = boundary layer separation and ducts and their effect on cooling. =20 It appear to follow ( from what I think I understand about boundary = layers in a duct) and my installation constraints. Higher energy = boundary layers penetrate further into the pressure recovery zone = (expansion area) than lower energy boundary layers. Ergo - if I = increase the energy of that boundary layer, it will penetrate further = and separate later. If that is not correct then my basic assumption is = flawed. Again,certainly not claming superior or performance even close = to par with the streamline duct. I was faced with truncating a streamline duct which with only 3-6" to = play with would have left the inlet opening around 75% the area of my = core - not appealing from a drag standpoint. With the pinched duct, I = can keep the size of the opening even smaller than the streamline duct = calls for, with the pinched area I can speed up the air velocity thereby = adding more energy to the boundary layer, which hopefully causes it to = penetrate further into the pressure recovery zone before separating and = all ends well - it cools. =20 Again, I am not trying to sell anything to anybody - those are the = conclusions I came to and applied - others are welcome to do their own = research and come up with something better. I spent weeks going over = chapter 12 of K&W and working through each equation (well, there was = perhaps 1 or 2 I had to take Mr. Kuchman's word for {:>).). That does = not mean my understanding is not flawed - but, its the best I can do.=20 I admit this is an exercise in what I hope is deductive logic - not = data verified experiment. I hope you do not expect me to rationally = defend it with data - when I don't have any data and no interest in = taking the time and effort to instrument {:>).=20 So everyone is certainly free to draw their own conclusions. I may be = wrong, but until somebody points out exactly where my deductive = reasoning is flawed, I'm going to keep on flying with those pinched = ducts.{:>) Ed ----- Original Message -----=20 From: David Leonard=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 28, 2007 9:19 PM Subject: [FlyRotary] Re: Diffuser Design Rules Hi Ed, Pretty slides. They SEEM authoritative but who gets to write the = "rules"? :-) In other words, where is the rest of the data. I = completely agree that a streamline duct is better than the conventional = duct, and that separation needs to be avoided. But do you have any data = comparing a restricted neck style to a regular streamline duct?=20 Dave Leonard =20 Once again, the only "creative" bit of thinking on my part was the = pinched duct in order to cope with the limitations of having a very = small area for a duct. All the rest of the credit belongs to K&W and = Horner as well as few others.=20 Ed --=20 David Leonard Turbo Rotary RV-6 N4VY My websites at: http://members.aol.com/_ht_a/rotaryroster/index.html=20 http://members.aol.com/_ht_a/vp4skydoc/index.html http://leonardiniraq.blogspot.com ------=_NextPart_000_0004_01C75B85.CA620D30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hey, Dave
 
You have sat through  just too many=20 presentations - your skepticism shows through (I sat  through 26 = years of=20 briefings in the Air Force and another 15 as a contractor - give me = enough graph=20 paper and the right scale and I can prove anything you=20 want{:>). 
 
Actually, I could have thrown a few more slides = in adding=20 more  information supporting my deductive reasoning - but no one/no = where=20 has published any data on a "pinched" duct {:>) - and more words = would be=20 just that - more words.  It was not intended to be a research paper = - just=20 a informal presentation to folks with a common interest.  =
 
But, to answer your question -  No data at = all. and=20 therefore I get to "write the rules".   I=20 can only take the credit (or blame) for the pinched duct concept all of = the rest=20 of the information is available in documents or on the = web. However,=20  I DID NOT invent the words about boundary layer separation and = ducts and=20 their effect on cooling. 
 
It appear to follow ( from what I think I = understand=20 about boundary layers in a duct) and my installation constraints. =20  Higher energy boundary layers penetrate further into the pressure = recovery=20 zone (expansion area) than lower energy boundary layers.  Ergo - if = I=20 increase the energy of that boundary layer, it will penetrate further = and=20 separate later.  If that is not correct then my basic assumption is = flawed.=20 Again,certainly  not claming superior or performance even close to = par with=20 the streamline duct.
 
I was   faced with truncating a = streamline duct=20 which with only 3-6" to play with would have left the inlet opening = around 75%=20 the area of my core - not appealing from a drag standpoint.  With = the=20 pinched duct, I can keep the size of the opening even smaller than the=20 streamline duct calls for, with the pinched area I can speed up the air = velocity=20 thereby adding more energy to the boundary layer, which = hopefully causes=20  it to penetrate further into the pressure recovery zone before = separating=20 and all ends well - it cools. 
 
Again, I am not trying to sell anything to = anybody - those=20 are the conclusions I came to and applied - others are welcome to do = their own=20 research and come up with something better.  I spent weeks going = over=20 chapter 12 of K&W and working through each equation (well, there was = perhaps=20 1 or 2 I had to take Mr. Kuchman's word for {:>).).  That does = not mean=20 my understanding is not flawed - but, its the best I can = do. 
 
 I admit this is an exercise in what I hope = is=20 deductive logic - not data verified experiment.  I hope you =  do=20 not  expect me to rationally defend it with data - when I don't = have any=20 data and no interest in taking the time and effort to instrument = {:>).=20
 
So everyone is certainly free to draw their own=20 conclusions.  I may be wrong, but until somebody points out exactly = where=20 my deductive reasoning is flawed, I'm going to keep on flying with those = pinched=20 ducts.{:>)
 
Ed
 
 
----- Original Message -----
From:=20 David=20 Leonard
Sent: Wednesday, February 28, = 2007 9:19=20 PM
Subject: [FlyRotary] Re: = Diffuser Design=20 Rules

Hi Ed,
 
Pretty slides.  They SEEM authoritative but who gets to = write=20 the "rules"?  :-)  In other words, where is the rest of the=20 data.  I completely agree that a streamline duct is better than = the=20 conventional duct, and that separation needs to be avoided.  = But do=20 you have any data comparing a restricted neck style to a regular = streamline=20 duct?
 
Dave Leonard
 

 
 
 
Once again, the only "creative" bit of = thinking on=20 my part was the pinched duct in order to cope with the = limitations of=20 having a very small area for a duct.  All the rest of the = credit=20 belongs to K&W and Horner as well as few others.
 
 
Ed

--
David=20 Leonard

Turbo Rotary RV-6 N4VY
My websites at:
http://memb= ers.aol.com/_ht_a/rotaryroster/index.html=20
http://members= .aol.com/_ht_a/vp4skydoc/index.html
http://leonardiniraq.blogspot.= com=20 ------=_NextPart_000_0004_01C75B85.CA620D30--