Return-Path: Received: from mail.viclink.com ([66.129.220.6] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2779090 for flyrotary@lancaironline.net; Mon, 01 Dec 2003 09:18:24 -0500 Received: from mail.viclink.com (p191.AS1.viclink.com [66.129.192.191]) by mail.viclink.com (8.11.7/8.11.7) with ESMTP id hB1EIJs58223 for ; Mon, 1 Dec 2003 06:18:19 -0800 (PST) Message-ID: <3FCB4C72.7090600@mail.viclink.com> Date: Mon, 01 Dec 2003 06:13:06 -0800 From: Perry Mick User-Agent: Mozilla/5.0 (Windows; U; Win95; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: radiator size References: Content-Type: multipart/alternative; boundary="------------030801020602020906080006" X-RAVMilter-Version: 8.4.3(snapshot 20030217) (mail.viclink.com) --------------030801020602020906080006 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Ed Anderson wrote: >----- Original Message ----- >From: "Joseph M Berki" >To: "Rotary motors in aircraft" >Sent: Monday, December 01, 2003 6:26 AM >Subject: [FlyRotary] Re: radiator size > > > =20 > >>I am glad someone brought up cooling vs expected horsepower. George wa= s >>running three rads at one time and found that he had to pumb the rear >>heater (in the car) connection into the system. His cooling problems w= ent >>away. Another successful rotary was Greg Riechters Cozy III. He elect= ed >>to go with jet power so we have not heard a lot about performance. Joh= n >>Slade probably has numbers. I believe Gregg was running over 488 cubic= >>inches of cooling volume. Right now I am leaning toward two of the lar= ge >>GM evaporator cores fed by a scoop under the belly that starts at 46 >> =20 >> >inches > =20 > >>from the rad face and expands from the inlet opening to the rad face. = I >>thought K&W curve at the rad face would help. The oil cooler will be i= n >>the strake closeout fed by another small scoop and will exhaust to the >>augmenter or overboard. I wanted to use a single scoop to feed everyth= ing >>but i think it generates more air flow problems. >> >>Joe Berki >>Limo EZ >> >> =20 >> >Joe, There's no question in my mind that your cooling system design need= s to >start with the expected HP(and therefore waste heat) AND flight Regime = (and >therefore airspeed) you expect to operate in. For an aircraft that spe= nds >most of its time at cruise (and don't most?) with an NA 13B engine, a ra= nge >of from approx 80 - 100HP (7.5 -11GPH) is probably a good figure to plan= on. >That would mean you need to get rid of from 3800 - 5500 total BTU/Min at= >cruise airspeed. > > Now, you would undoubtedly (hopefully) produce more power for takeoff a= nd >climb. So now you are faced with the challenges of a different cooling >regime. High power (and lots of waste heat) and low airspeed (minimal >cooling airflow available). If you design for this regime (successfully= ) >then you will certainly have taken care of your cruise regime. On the o= ther >hand, you may well be incurring more cooling drag penality at cruise (wh= ere >you will spend most of your flying time) than necessary. > > Again, I think you need to consider your aircraft and operating situati= on. >If you spend most of your time at high speed cruise (such as most carnar= d >types are likely to do) then perhaps optimizing for cruise is the way to= go. >If a "bush" plane climbing in and out of valleys at high power settings,= >then perhaps the high power, low airspeed is the design point to shoot f= or. >Perhaps cowl flaps or fans could bridge the gap. > >Anyhow, I think we understand that like most other decisions on an aircr= aft, >cooling is another compromise. > > Be realistic! For an 13B NA engine, probably the person getting the mo= st >out of an engine is Tracy Crook producing a bit over 180HP. For most of= us, >its probably closer to 160HP and a few range in the 120-150HP range for = max >power such as take off. Cruise is probably no more than 75% of that and= >probably closer to 50%. > > >Ed Anderson >RV-6A N494BW Rotary Powered >Matthews, NC >eanderson@carolina.rr.com > > =20 > Good points Ed, but from practical experience I think you really need to = plan for continuous climb for as much as 10 to 20 minutes. When I had my = previous oil cooler, on a hot day, I could only climb full power to about= 2000' AGL before having to throttle back and climb at a lower rate. That= was just not practical, I would much prefer to climb full power for the = 10 to 20 minutes it takes to get to 10,000' +. So I would recommend plann= ing your cooling requirements for extended climb, and devise some variabl= e mechanism such as cowl flaps for drag reduction in cruise. The exits of= both my oil cooler and rad now dump directly to the airstream (both orig= inally did not), and I have found this to be the most effective exit. It = also takes much less volume in your cowl to implement. Of course you cann= ot implement any kind of variable cowl flap with no exit ducting. But wit= h a pusher there is precious little room available between the engine and= the prop to implement such devices/ducting. --=20 Perry Mick http://www.ductedfan.com --------------030801020602020906080006 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Ed Anderson wrote:
----- Original Message -----
From: "Joseph M Berki" <Joseph.M.Berki@grc.nasa.gov>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, December 01, 2003 6:26 AM
Subject: [FlyRotary] Re: radiator size


  
I am glad someone brought up cooling vs expected horsepower.  George was
running three rads at one time and found that he had to pumb the rear
heater (in the car) connection into the system.  His cooling problems went
away.  Another successful rotary was Greg Riechters Cozy III.  He elected
to go with jet power so we have not heard a lot about performance.  John
Slade probably has numbers.  I believe Gregg was running over 488 cubic
inches of cooling volume.  Right now I am leaning toward two of the large
GM evaporator cores fed by a scoop under the belly that starts at 46
    
inches
  
from the rad face and expands from the inlet opening to the rad face.  I
thought K&W curve at the rad face would help.  The oil cooler will be in
the strake closeout fed by another small scoop and will exhaust to the
augmenter or overboard.  I wanted to use a single scoop to feed everything
but i think it generates more air flow problems.

Joe Berki
Limo EZ

    
Joe, There's no question in my mind that your cooling system design needs to
start with the expected HP(and therefore waste heat)  AND flight Regime (and
therefore airspeed)  you expect to operate in.  For an aircraft that spends
most of its time at cruise (and don't most?) with an NA 13B engine, a range
of from approx 80 - 100HP (7.5 -11GPH) is probably a good figure to plan on.
That would mean you need to get rid of from 3800 - 5500 total BTU/Min at
cruise airspeed.

 Now, you would undoubtedly (hopefully) produce more power for takeoff and
climb.  So now you are faced with the challenges of a different cooling
regime.  High power (and lots of waste heat) and low airspeed (minimal
cooling airflow available).  If you design for this regime (successfully)
then you will certainly have taken care of your cruise regime.  On the other
hand, you may well be incurring more cooling drag penality at cruise (where
you will spend most of your flying time) than necessary.

 Again, I think you need to consider your aircraft and operating situation.
If you spend most of your time at high speed cruise (such as most carnard
types are likely to do) then perhaps optimizing for cruise is the way to go.
If a "bush" plane climbing in and out of valleys at high power settings,
then perhaps the high power, low airspeed is the design point to shoot for.
Perhaps cowl flaps or fans could bridge the gap.

Anyhow, I think we understand that like most other decisions on an aircraft,
cooling is another compromise.

 Be realistic!  For an 13B NA engine, probably the person getting the most
out of an engine is Tracy Crook producing a bit over 180HP.  For most of us,
its probably closer to 160HP and a few range in the 120-150HP range for max
power such as take off.  Cruise is probably no more than 75% of that and
probably closer to 50%.


Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

  
Good points Ed, but from practical experience I think you really need to plan for continuous climb for as much as 10 to 20 minutes. When I had my previous oil cooler, on a hot day, I could only climb full power to about 2000' AGL before having to throttle back and climb at a lower rate. That was just not practical, I would much prefer to climb full power for the 10 to 20 minutes it takes to get to 10,000' +. So I would recommend planning your cooling requirements for extended climb, and devise some variable mechanism such as cowl flaps for drag reduction in cruise. The exits of both my oil cooler and rad now dump directly to the airstream (both originally did not), and I have found this to be the most effective exit. It also takes much less volume in your cowl to implement. Of course you cannot implement any kind of variable cowl flap with no exit ducting. But with a pusher there is precious little room available between the eng
ine and the prop to implement such devices/ducting.

-- 
Perry Mick
http://www.ductedfan.com

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