X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 30 [X] Return-Path: Received: from imo-m26.mx.aol.com ([64.12.137.7] verified) by logan.com (CommuniGate Pro SMTP 5.1.4) with ESMTP id 1736236 for flyrotary@lancaironline.net; Thu, 04 Jan 2007 17:41:11 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.7; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m26.mx.aol.com (mail_out_v38_r7.6.) id q.ca5.640cd61 (52317) for ; Thu, 4 Jan 2007 17:40:22 -0500 (EST) Received: from FWM-D10 (fwm-d10.webmail.aol.com [205.188.160.202]) by ciaaol-d01.mail.aol.com (v114.2) with ESMTP id MAILCIAAOLD017-cc5d459d825328; Thu, 04 Jan 2007 17:40:19 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Ideal cooling Date: Thu, 04 Jan 2007 17:40:20 -0500 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8C8FE6872C7103A_101C_15B3_FWM-D10.sysops.aol.com" X-Mailer: AOL WebMail 22250 Received: from 65.161.241.3 by FWM-D10.sysops.aol.com (205.188.160.202) with HTTP (WebMailUI); Thu, 04 Jan 2007 17:40:20 -0500 Message-Id: <8C8FE6872C97298-101C-B3A@FWM-D10.sysops.aol.com> X-AOL-IP: 205.188.160.202 X-Spam-Flag: NO ----------MB_8C8FE6872C7103A_101C_15B3_FWM-D10.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" =20 =20 =20 -----Original Message----- From: lors01@msn.com To: flyrotary@lancaironline.net Sent: Thu, 4 Jan 2007 10:49 AM Subject: [FlyRotary] Re: Ideal cooling Monty wrote: Now for the optimum part: =20 The absolute best possible performance would be a system that used just enou= gh air Mdot to heat the cooling air to the same temperature as the water rad= iator exit temp ( water going back to the engine from the radiator). This co= ndition is impossible to achieve in practice. So you try to get as close as=20= you can. How close you get is called the heat exchanger effectiveness. The c= loser the air and water exit temps are, the better the effectiveness. =20 Monty: I=E2=80=99ll respectfully disagree on this part. It may apply if you have u= nlimited dynamic pressure to work with, because it doesn=E2=80=99t consider=20= radiator thickness and air-side pressure drop. We don=E2=80=99t have this c= ase =20 Al=20 =20 Have to vote for Monty's position on this one. His statement (I assume inte= ntionally) did not specifically get into radiator thickness, dynamic pressur= e, etc because he was trying to get down to the basic principal involved. I= n this he is correct (IMO). All these other factors are just that, factors.= They do not change the basic principal. Limited dynamic pressure only mea= ns that the radiator has to be designed to work with what is available. The= goal remains the same. =20 Dynamic pressure data was available from the EM2 data log that I posted but=20= I had to eliminate it and many others for the sake of readability. In this=20= case, dynamic pressure on the left rad inlet was slightly higher than the fu= ll amount available at the current airspeed (I am assuming this is due to th= e benefit of prop blast into the inlet). Note: Dynamic pressure is not a s= tandard feature of the EM2, mine is a custom job. You can use the TAS reado= ut for this function though. You just have to reverse the calculation from=20= pressure to airspeed or get a conversion chart. =20 Really finding the discussion on the EM2 data interesting. As is obvious, i= nterpretation of the data is as important as the data itself. And Rusty was= right, having this capability is a two edged sword, you can spend unlimited= time analyzing data and trying to optimize various things. Identifying th= e "low hanging fruit" is absolutely key if you are to do anything other tha= t tweak on the airplane. When Paul Lamar came here and we did a bunch of in= -flight pressure measurements, a lot of important things came to light but w= e disagreed completely on what they meant and how to address them. (discuss= ion on 'Cooling Study' on my website describes that effort). =20 Paul has done a lot to perpetuate the idea that my cooling system is "margin= al at best". I still can't figure out where he gets this from. You do not=20= fly an aircraft for 12 years and 1600+ hours in Florida, fly it to the deser= t southwest over 10,000+ foot mountains and win air races with a "marginal"=20= cooling system. Much has been made of the 'spray bar' cooling system I used= when racing. Anyone familiar with air racing knows this is common practice= . It is not necessary for normal operation and if you installed a cooling s= ystem that you could race without the spraybar, your top speed and MPG would= suffer significantly. I wish those who have criticized the spraybar setup=20= would enter a race like the Sun 100 and show me how to do it right! =20 Monty is also correct about the need for studying steady state conditions. =20= You need to do that and the transient stuff to get the whole picture. I pos= ted a transient snapshot because it illustrated a few points I was intereste= d in and the fact that a bunch of straight lines on a graph are much less vi= sually interesting. =20 Tracy =20 Tracy, you are totally correct about alternate means of cooling being the no= rm, rather than the unusual when racing. This year at RENO almost every spor= t class racer used some kind of secondary cooling device. (Spray bars, water= /alcohol injection, timing retard devices) Some used several! Your system do= esn't do it like Paul suggests, therefore you must be wrong! Nothing succeed= s like success, and you are the longest flying rotary so I believe you have=20= a good handle on things. I think you can use thicker than auto radiators for= instance. Most cars don't spend most of their life at over 100, so there ar= e differences. Bill Jepson =20 =20 ________________________________________________________________________ Check out the new AOL. Most comprehensive set of free safety and security t= ools, free access to millions of high-quality videos from across the web, fr= ee AOL Mail and more. ----------MB_8C8FE6872C7103A_101C_15B3_FWM-D10.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
 
 
 
-----Original Message-----
From: lors01@msn.com
To: flyrotary@lancaironline.net
Sent: Thu, 4 Jan 2007 10:49 AM
Subject: [FlyRotary] Re: Ideal cooling

Monty wrote:
Now for the optimum= part:
 
The absolute best p= ossible performance would be a system that used just enough air Mdot to heat the cooling air = ;to the same temperature as the water radiator exit temp ( water going=20= back to the engine from the radiator). This condition is impossible to achie= ve in practice. So you try to get as close as you can. How close you get is=20= called the heat exchanger effectiveness. The closer the air and water e= xit temps are, the better the e= ffectiveness.
 
Monty:
I=E2=80=99ll respectfully disagree on this part. =20= It may apply if you have unlimited dynamic pressure to work with, because it= doesn=E2=80=99t consider radiator t= hickness and air-side pressure drop.  We don=E2=80=99t have this case
 = ;
Al
 = ;
Have to vote for Monty's position on this one.&nbs= p; His statement (I assume intentionally) did not specifically get into radi= ator thickness, dynamic pressure, etc because he was trying to get down to the basic principal involved.  I= n this he is correct (IMO).  Al= l these other factors are just that, factors.  They do not change the b= asic principal.  Limited dynamic pressure only means that the radiator=20= has to be designed to work with what is available.  The goal remains th= e same.
 = ;
Dynamic pressure da= ta was available from the EM2 data l= og that I posted but I had to eliminate it and many others for the sake of r= eadability.  In this case, dynamic pressure on the left rad inlet was slightly higher than the fu= ll amount available at the curr= ent airspeed (I am assuming this is due to the benefit of prop blast into th= e inlet).  Note:  Dynamic pressure is not a standard fea= ture of the EM2, mine is a custom jo= b.  You can use the TAS readout= for this function though.  You just have to reverse the calculation fr= om pressure to airspeed or get a conversion chart.
 = ;
Really finding the=20= discussion on the EM2 data interesti= ng.  As is obvious, interpretation of the data is as important as the d= ata itself.  And Rusty was right, having this capability is a two edged= sword, you can spend unlimited time analyzing data and trying to optimize v= arious things.  Identifying  the "low hanging fruit"  is abso= lutely key if you are to do anything other that tweak on the airplane. = When Paul Lamar came here and we did a bunch of in-flight pressure measurem= ents, a lot of important things came to light but we disagreed completely on= what they meant and how to address them.  (discussion on 'Cooling Stud= y' on my website describes that effo= rt).
 = ;
Paul has done a lot= to perpetuate the idea that my cooling system is "marginal at best". =20= I still can't figure out where he ge= ts this from.  You do not fly an aircraft for 12 years and 1600+ hours=20= in Florida, fly it to the desert southwest over 10,000+ foot mountains=20= and win air races with a "marginal" cooling system.  Much has been made= of the 'spray bar' cooling system I used when racing.  Anyone familiar= with air racing knows this is common practice.  It is not necessary fo= r normal operation and if you installed a cooling system that you could race= without the spraybar, your top spee= d and MPG would suffer significantly= .  I wish those who have criticized the spraybar setup would enter a race like the Sun 100 and sh= ow me how to do it right!
 = ;
Monty is also corre= ct about the need for studying steady state conditions.  You need to do= that and the transient stuff to get the whole picture.  I posted a tra= nsient snapshot because it illustrated a few points I was interested in and=20= the fact that a bunch of straight lines on a graph are much less visually in= teresting.
 = ;
Tracy=
 = ;
Tracy, you are totally correct about alternate means=20= of cooling being the norm, rather than the unusual when racing. This year at= RENO almost every sport class racer used some kind of secondary coolin= g device. (Spray bars, water/alcohol inject= ion, timing retard devices) Some used several! Your system doesn't do it lik= e Paul suggests, therefore you must be wrong! Nothing succeeds like success,= and you are the longest flying rotary so I believe you have a good handle o= n things. I think you can use thicker than auto radiators for instance. Most= cars don't spend most of their life at over 100, so there are differences.<= /SPAN>
Bill Jepson
 
 
Check=20= out the new AOL. Most comprehensive set of free safety and security=20= tools, free access to millions of high-quality videos from across the web, f= ree AOL Mail and more.
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