X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from ms-smtp-04.southeast.rr.com ([24.25.9.103] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1181933 for flyrotary@lancaironline.net; Sat, 17 Jun 2006 18:11:49 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-111-186.carolina.res.rr.com [24.74.111.186]) by ms-smtp-04.southeast.rr.com (8.13.6/8.13.6) with SMTP id k5HMB2ev005842 for ; Sat, 17 Jun 2006 18:11:04 -0400 (EDT) Message-ID: <000b01c6925b$0e923560$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Exit area smaller than intake was External Diffusion Date: Sat, 17 Jun 2006 18:12:00 -0400 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2869 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 X-Virus-Scanned: Symantec AntiVirus Scan Engine Ok, thanks, Thomas. I understood correctly 135% OF the exit - just conveyed my understanding improperly. Yes, if you have them already scanned I would like a copy. I hope there are a few photos as I am interested whether or not they may be using exhaust augmentation (whether they realize it or not). Ed ----- Original Message ----- From: "Thomas y Reina Jakits" To: "Rotary motors in aircraft" Sent: Saturday, June 17, 2006 4:30 PM Subject: [FlyRotary] Re: Exit area smaller than intake was External Diffusion > Ed, > there is a mistake as the intake is not 135%bigger than, but 135% of the > exit. > It still makes it 1.35 times bigger than the exit. > > I posted this last in April 2005, the latest response to the subject was > on > 14th of december by Monty Roberts. > It always starts with a question to verify the intake bigger than exit > claim,but "no mistake" that's what it is! > > Please search the archive or let me know if you want me to repost the > post! > It was about Brian Schmidtbauers Mustang II being the fastest around! > Also menetioned is Dave Anders' RV-4, details in the CAFE report. > I have the essential pages of the Kitplanes article scanned, let me know > if > you want them emailed.... > > It just shows that rules of thumb are not always the best solution. Most > likely just the most economic one to build..... > > Thomas > > PS: Search "Kitplanes" and go for the 14th Dec.,2005 posts!! > > > ----- Original Message ----- > From: "Ed Anderson" > To: "Rotary motors in aircraft" > Sent: Saturday, June 17, 2006 6:35 AM > Subject: [FlyRotary] Exit area smaller than intake was External Diffusion > > >> That's very interesting, Thomas. I too recall seeing in several places >> reference to >> exit area being some multiple of the inlet with the ratios varying from >> 1.2 -1.7. >> There certainly could be some kind of phenomena I have not hear of or >> read about, but seems strange you would ever have your intake area more > than >> the exit area. But assuming no error then it would appear to me that >> external diffusion is taking place. >> >> What that indicates to me is that the exit area (what ever size >> it was) provides adequate airflow for cooling flow through the engine >> compartment.(assumption is the engine did not get cooked). Enough air > mass >> HAD to leave the cowling sufficient to carry away the necessary BTUs of >> heat. That said, then if the inlets were 135% larger than the exit area, >> then air HAD to be spilling around the inlet or area of external > diffusion. >> The air molecules in this part of the airflow (external to the cowl) then >> contributed NOTHING to carrying away heat from the engine, but do add to >> drag - that left only >> the air that past through the core (or over the cooling fins of the > cylinder >> head) to provide for cooling. Since this air has now been heated and > expands >> to a larger volume, you traditionally need a larger exit area to > accommodate >> this large volume of heated air. That air must leave the engine >> compartment via the exit. So I just am unable to come up with a scenario >> where having an inlet larger than the exit area would be beneficial. >> >> Having said that, it did just trigger a thought about why this might be >> tried and >> how it might be made to work. >> . >> We do know that for air exiting the cowl to provide minimum drag it > ideally >> should be accelerated back to the airstream velocity before intermixing. > We >> can theoretically do this by taking the larger volume of heat air and >> designing an exit area >> which would accelerate the air molecules increasing the velocity of the >> exiting air and reducing drag. However, to accelerate the cowl air > velocity >> to anything really meaningful, >> would require added energy. This leads me to believe that perhaps an >> exhaust augmentation system could be used to provide increased velocity >> to >> the exiting air using the energy in >> the exhaust flow. If the exiting airflow velocity is increased over than >> normally associated with exiting air, then more air of course could flow >> through a smaller opening, this would perhaps permit one to have a >> smaller >> exit area than intake area and still >> get good cooling and low cooling drag. >> >> So with an exhaust augmentation system "helping" the air in the cowl to > exit >> quicker and at a higher velocity, I can see where a smaller exit area > might >> indeed be workable. >> But, without an exhaust augmentation system, I just don't see how a > smaller >> exit area would be beneficial. >> >> Any mention of exhaust augmentation?? >> >> Well that my $0.02 worth on the topic >> >> Ed >> >> Ed Anderson >> Rv-6A N494BW Rotary Powered >> Matthews, NC >> eanderson@carolina.rr.com> Hi Steve, >> > >> >> >> >> >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ >