Return-Path: Received: from smtpauth01.mail.atl.earthlink.net ([209.86.89.61] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 854549 for flyrotary@lancaironline.net; Mon, 04 Apr 2005 14:56:16 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.86.89.61; envelope-from=jerryhey@earthlink.net Received: from [63.189.97.100] (helo=earthlink.net) by smtpauth01.mail.atl.earthlink.net with asmtp (Exim 4.34) id 1DIWjS-0005cQ-2G for flyrotary@lancaironline.net; Mon, 04 Apr 2005 14:55:31 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=simple; s=test1; d=earthlink.net; h=Date:Subject:Content-Type:Mime-Version:From:To:Content-Transfer-Encoding:In-Reply-To:Message-Id:X-Mailer; b=prHPBxHWq4V7jUxJGGHgydvvuBgif0ncjjMDvkI0Ka/8svAm0JN7o2MOtO/Hlskb; Date: Mon, 4 Apr 2005 13:56:55 -0500 Subject: Re: [FlyRotary] Re: Cooling -Learned a lot Content-Type: text/plain; charset=US-ASCII; format=flowed Mime-Version: 1.0 (Apple Message framework v552) From: Jerry Hey To: "Rotary motors in aircraft" Content-Transfer-Encoding: 7bit In-Reply-To: Message-Id: <50692EF7-A53B-11D9-932C-0003931B0C7A@earthlink.net> X-Mailer: Apple Mail (2.552) X-ELNK-Trace: 8104856d7830ec6b1aa676d7e74259b7b3291a7d08dfec79387c1c649d5b1b2df947547b5fda0471350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 63.189.97.100 Ed, I was unable to read my messages for a couple of days and so I got to read the entire discussion generated by your insightful analysis. Thanks for taking the time and making the issues so clear. NASCAR is a good example of theory becoming a bug on the windshield of practical reality since they often cover most of the perfectly designed duct openings with tape. Jerry On Sunday, April 3, 2005, at 06:04 PM, Ed Klepeis wrote: > Dear Ed > How about a rad 16x18x2.25 with a mazda oil cooler along side > mounted in a sq tube frame hung under the eng mount in rubber mounts, > could you go for such a set up. let me know. > > regards > Ed K > techwelding@comcast.net > ----- Original Message ----- From: "Ed Anderson" > > To: "Rotary motors in aircraft" > Sent: Sunday, April 03, 2005 9:14 AM > Subject: [FlyRotary] Cooling -Learned a lot > > >> Too right, Jerry >> >> My first 40 hours or so were in the marginal cooling zone. {:>). As >> other >> things in this hobby, there are so many variables that interact, that >> what >> may appear simply at first, is almost always a bit more complex. I >> say(Cooling Axiom 1) if you have enough cooling surface area and air >> mass >> flow then it WILL cool. However, you may incur a high penalty in >> cooling >> drag - which may not be as important for draggy airframes (such as >> biplanes) >> as it is to sleeker airframes. Also a system that adequately cools >> an >> engine producing 150 HP may not cool an engine producing 180 HP. >> Picking >> your cooling design point is important. Optimizing for cruise and >> your will >> be less than optimum for take and climb. Optimize for climb and you >> will >> probably have more cooling drag than required at cruise. Compromise, >> compromise - cowl flaps are sometimes used to try to have the best of >> both >> worlds. >> >> Some folks advocate a thinner, larger surface area core -which is >> great for >> slow moving automobiles stuck in traffic with low dynamic pressure >> potential, but I think is not the optimum for most aircraft. Once >> you trip >> the airflow and turn it turbulent you have incurred most of the drag >> penalty. Larger surface area cores disrupt a larger airstream and >> incur >> more drag. Yes, thicker cores produce a bit more drag than the SAME >> frontal >> area thinner cores. But, with a thicker core you can use a core with >> smaller frontal area. >> >> The NASCAR radiator's average 3" thick and on the long tracks where >> speeds >> are higher some even go up to 7" thick. My contention is their >> operating >> environment is more akin to ours than regular automobiles moving at >> slower >> speeds. You know that the NASCAR folks will spend $$ for just a tiny >> advantage - so clearly they don't use thick cores because it is a >> disadvantage. But, some folks will continue to point to the large thin >> radiators designed for environments with much lower dynamic pressure >> as >> being the way to go. Will it cool? sure it will (Cooling axiom 1 >> above). >> Is it the lowest drag option for an aircraft of the RV/TailWind type, >> I am >> convinced it is not. >> >> The diffuser makes a considerable amount of difference and can made >> the >> difference between a system that cools adequately and one which does >> not. >> The biggest culprit that lessens cooling effectiveness is turbulent >> eddies >> that form inside the duct due to flow detachment from the walls. >> These >> eddies in effect act to block effective airflow through part of the >> core. >> So keeping the airflow attached to the sides of the diffusers is >> crucial for >> good cooling from two standpoints. A good diffuser will reduce airflow >> velocity through the core which will reduces cooling drag. Pressure >> across >> the core is increased which further enhances cooling. >> >> I have gone from a total of 48 sq inches opening (total) for my two >> GM cores >> and that provided marginal cooling - down to 28 sq inches (total) with >> adequate cooling with an engine now producing more HP. Experimenting >> with >> the diffuser shape made the difference. >> >> The K&W book (Chapter 12) really provided the insight to how and which >> diffuser shapes provided the better dynamic recovery. The Streamline >> duct >> was shown to be able to provide up to 82% recovery of the dynamic >> pressure. >> Some folks reading the chapter misinterpreted the chart to show only >> 42% >> recovery where there chart was actually only showing the pressure >> recovery >> contribution due to the duct walls and did not include the >> contribution due >> to the core. On the same chart, an equation (which apparently gets >> ignored) >> clearly shows that the TOTAL pressure recovery is 82%. >> >> I have taken the Streamline duct as a starting point, but since I do >> not >> have the space to provide the 12-14" for a proper Streamline duct, I >> did >> some "creative" things to try to insure that there was no separation >> even >> though my walls diverge more rapidly than the Streamline duct. Won't >> claim >> mine are as good as a Streamline, but they clearly are much better >> than the >> previous design which basically just captured the air and forced it >> through >> the cores. >> >> FWIW >> >> Ed Anderson >> RV-6A N494BW 275 Rotary Hours (Plugs Up) >> Matthews, NC >> eanderson@carolina.rr.com >> >> >> ----- Original Message ----- >> From: "Jerry Hey" >> To: "Rotary motors in aircraft" >> Sent: Sunday, April 03, 2005 9:27 AM >> Subject: [FlyRotary] Re: phase I flight restrictions was:N19VX flys >> >> >>> It was not long ago that "cooling" was the major issue. Now it seems >>> that we have learned enough to make several different configurations >>> work. I can't lay my finger on what it is we have learned but my >>> recommendation is to use smaller radiators and EWPs. Jerry >>> >>> >>> >> >> >> >> >>>> Homepage: http://www.flyrotary.com/ >>>> Archive: http://lancaironline.net/lists/flyrotary/List.html > > >>> Homepage: http://www.flyrotary.com/ >>> Archive: http://lancaironline.net/lists/flyrotary/List.html >