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[70.196.200.223]) by mx.google.com with ESMTPS id s1sm3817038anj.1.2012.10.31.09.38.42 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 31 Oct 2012 09:38:44 -0700 (PDT) Subject: Re: [FlyRotary] Re: flow path in conventional radiator References: From: Tracy Content-Type: multipart/alternative; boundary=Apple-Mail-0FA48D74-4267-404F-8DD5-FC4F1A0C9972 X-Mailer: iPad Mail (10A403) In-Reply-To: Message-Id: Date: Wed, 31 Oct 2012 10:38:33 -0600 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-0FA48D74-4267-404F-8DD5-FC4F1A0C9972 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Hi Ken, Will check out Paul's book when I get a chance but Paul & I have had man= y discussions on cooling in the past. I've read much of the same source m= aterial that he uses (K&W for one example) but we frequently disagree on the= interpretation of it. =20 I may have misinterpreted one detail in your original description of the pro= posed system. When you used the term anterior I think I pictured posterior.= The term Front makes it clearer. I assume you are aiming at the idea of= the 'wedge diffuser'. =20 Still, I think your scheme involves more turns and twists in the airflow th= an is necessary or advantageous. You can't find a more natural place to tak= e in high pressure air than the front of the cowl. It has the added advanta= ge of not adding any frontal area to the airframe. Even a 100 MPH airplane b= enefits from drag reduction. I think Getting the air cleanly out of the up= per sides of the cowl might be harder than it sounds. To explain why is a m= uch longer discussion. =20 Again, I realize that compromises must be made so sometimes the theoretical "= best" system isn't practical so you may have to sacrifice a bit of drag. On short grass strips you usually have the advantage of no long taxi or wait= ing for traffic. In this situation, don't wait for the engine to reach nor= mal operating temps. Take off at minimum oil temp (I use 120 F) and you wil= l be far above the trees by the time temps reach max. even on a hot day. Tracy Sent from my iPad On Oct 31, 2012, at 9:03 AM, Kenneth Johnson wrote: > Tracy, > Sorry to get back to you so late, but am now just getting caught up on ema= ils. When I have free time, I am usually out in my garage working on the pl= ane. If you have not read "How to Cool Your Wankel" by Paul Lamar, I would r= ecommend it. It would be worth your time. =20 >=20 > The suggestion to flow air from the bottom up was not made by Paul, but wa= s my thoughts regarding the airplane I am building. The Zenith 801 is the f= our passenger high wing STOL bush-type plane. It's top speed is 110 MPH. I= t's primary purpose is getting in and out of short, grass strips. Where eng= ine cooling is most needed is on short runway take-off with high obstacles s= uch as trees at the runway's end. Stall speed is about 40 MPH. This just m= eans there is very little air flowing through the cooling system on take-off= . The airplane is at a high angle of attack until obstacles are cleared. A= nd again, at this high angle of attack, cooling flow is different and airspe= ed is slow. > Having the cowl opening on the bottom front of the cowl where air flows di= rectly through the radiators and having outlets on the top sides of the cowl= would allow air to flow best when it is most needed to cool the engine. At= flat and level flying, the air would still flow, but the higher speed would= provide more cooling. =20 >=20 > What makes this plane unique is it is not an RV where one is flying at 170= knots and has a mile long runway. =20 >=20 > Please read Paul's book and give me your thoughts. Thanks for your commen= ts. =20 >=20 > Ken Johnson >=20 >=20 >=20 > From: Tracy > To: Rotary motors in aircraft =20 > Sent: Wednesday, October 24, 2012 12:21 PM > Subject: [FlyRotary] Re: flow path in conventional radiator >=20 >=20 >=20 > On Oct 24, 2012, at 10:14 AM, Kenneth Johnson wrot= e: >=20 > > A more efficient design would have intake air entering the bottom anter= ior of the the cowl and to pass through the radiator. As this air is heated= by the radiator it rises and should exit the top sides of the cowl. No one= has done that because of the risk of engine oil on the windshield. >=20 >=20 > I haven't read Paul's book but if this is an example of his suggestions, I= wouldn't have much confidence in it. =20 >=20 > Two basic rules of thumb for A/C cooling systems are: >=20 > 1. Turning high speed air is hard to do and loss prone energy wise. >=20 > 2. The pressure represented by convection of rising hot air is not signif= icant and can safely be ignored for our purposes. =20 >=20 > Tracy > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.= html >=20 >=20 --Apple-Mail-0FA48D74-4267-404F-8DD5-FC4F1A0C9972 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Hi Ken,
    Will c= heck out Paul's book when I get a chance but Paul & I have had many disc= ussions on cooling in the past.    I've read much of the same sour= ce material that he uses (K&W for one example) but we frequently disagre= e on the interpretation of it.  

I may have mi= sinterpreted one detail in your original description of the proposed system.=  When you used the term anterior I think I pictured posterior.   T= he term Front makes it clearer.   I assume you are aiming at the idea o= f the 'wedge diffuser'.   

 Still, I= think your scheme involves more turns and twists in the airflow than is nec= essary or advantageous.  You can't find a more natural place to take in= high pressure air than the front of the cowl.  It has the added advant= age of not adding any frontal area to the airframe.  Even a 100 MPH air= plane benefits from drag reduction.   I think Getting the air cleanly o= ut of the upper sides of the cowl might be harder than it sounds.   To e= xplain why is a much longer discussion.  

Agai= n, I realize that compromises must be made so sometimes the theoretical "bes= t" system isn't practical so you may have to sacrifice a bit of drag.
<= div>
On short grass strips you usually have the advantage of n= o long taxi or waiting for traffic.   In this situation, don't wait for= the engine to reach normal operating temps.  Take off at minimum oil t= emp (I use 120 F) and you will be far above the trees by the time temps reac= h max. even on a hot day.

Tracy

Sent from my= iPad

On Oct 31, 2012, at 9:03 AM, Kenneth Johnson <kjohnsondds@yahoo.com> wrote:
Tracy,
Sorry to get back to you so late,= but am now just getting caught up on emails.  When I have free time, I= am usually out in my garage working on the plane.  If you have not rea= d "How to Cool Your Wankel" by Paul Lamar, I would recommend it.  It wo= uld be worth your time.  

= The suggestion to flow air from the bottom up was not made by Paul, but was my t= houghts regarding the airplane I am building.  The Zenith 801 is the fo= ur passenger high wing STOL bush-type plane.  It's top speed is 110 MPH= .  It's primary purpose is getting in and out of short, grass strips.&n= bsp; Where engine cooling is most needed is on short runway take-off with hi= gh obstacles such as trees at the runway's end.  Stall speed is about 4= 0 MPH.  This just means there is very little air flowing through the co= oling system on take-off.   The airplane is at a high angle of att= ack until obstacles are cleared.  And again, at this high angle of atta= ck, cooling flow is different and airspeed is slow.
Havi= ng the cowl opening on the bottom front of the cowl where air flows directly through the radiators and having outlets on the to= p sides of the cowl would allow air to flow best when it is most needed to c= ool the engine.  At flat and level flying, the air would still flow, bu= t the higher speed would provide more cooling.  
What makes this plane unique is it is not an RV= where one is flying at 170 knots and has a mile long runway.  &nb= sp;

Please read= Paul's book and give me your thoughts.  Thanks for your comments. = ;

Ken Johnson
<= /div>



From: Tracy <rwstracy@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wednesday, October 24, 2012 12:21 P= M
Subject: [FlyRotary] R= e: flow path in conventional radiator



On Oct 24, 2012, at 10:14 AM, Kenneth Johnson <kjohnsondds@= yahoo.com> wrote:

> A more efficient design would  hav= e intake air entering the bottom anterior of the the cowl and to pass throug= h the radiator.  As this air is heated by the radiator it rises and sh= ould exit the top sides of the cowl.  No one has done that because of t= he risk of engine oil on the windshield.


I haven't read Paul's bo= ok but if this is an example of his suggestions, I wouldn't have much confid= ence in it. 

Two basic rules of thumb for A/C cooling systems a= re:

1. Turning high speed air is hard to do and loss prone energy wis= e.

2.  The pressure represented by convection of rising hot air= is not significant  and can safely be ignored for our purposes.  =

Tracy
--
Homepage:  http://www.flyrotary.com/
Arch= ive and UnSub:  http://mail.lancaironline.net:81/lists/flyrotary/List.html<= /a>


= --Apple-Mail-0FA48D74-4267-404F-8DD5-FC4F1A0C9972--