X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from exchange.carey.wa.edu.au ([118.82.44.212] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTPS id 4962684 for flyrotary@lancaironline.net; Sat, 30 Apr 2011 10:55:35 -0400 Received-SPF: none receiver=logan.com; client-ip=118.82.44.212; envelope-from=stevei@carey.asn.au Received: from exchange.carey.local ([10.10.0.5]) by exchange.carey.local ([10.10.0.5]) with mapi; Sat, 30 Apr 2011 22:54:51 +0800 From: To: Date: Sat, 30 Apr 2011 22:55:08 +0800 Subject: Re: [FlyRotary] Re: Cooling Inlets Thread-Topic: [FlyRotary] Re: Cooling Inlets Thread-Index: AcwHRo8C6++xcFY4S4G/yVfzuCTp0Q== Message-ID: <183C449C-9621-41BA-961F-F251762B50A1@carey.asn.au> References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_183C449C962141BA961FF251762B50A1careyasnau_" MIME-Version: 1.0 --_000_183C449C962141BA961FF251762B50A1careyasnau_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Thanks Ed You guys are so helpful. Really appreciate listening and learning. Blessings Steve Izett On 30/04/2011, at 10:00 PM, Ed Anderson wrote: I agree, Steve. There is no question each part of the cooling system is c= ritical and the total results is no better than the weakest link. Most studies I have read indicates that after a certain size in inlet area = (from 25-35% of core frontal area) - the outlet size becomes the determinin= g factor and further increases in intake provide no additional benefit and = can hurt by increasing cooling drag. Adding such things as cowl flaps can = reduce the pressure in the outlet region and promote more airflow and cooli= ng but naturally at the cost of more drag. But, then at higher speeds with= plenty of dynamic pressure, you can retract the cowl flaps and reduce the = drag. NACA ducts have been made to work with radiator cores - no question about t= hat. The question is would a different approach have produced a "better" c= ooling system. Again, I think it depends on your intended operating enviro= nment. For a high speed cruise environment, I would think cooling drag might be of= more importance than say perhaps a few pounds of additional weight, on the= other hand if you are flying an already draggy biplane for example, coolin= g drag is probably a very small part of your over all drag, but getting coo= ling with low airspeed might be the system driver. Its all about compromises - space, weight, flow, drag, etc. - oh, yes! - an= d cooling of course {:>) all matched to your constraints and operating env= ironment. Ed From: stevei@carey.asn.au Sent: Friday, April 29, 2011 8:48 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Cooling Inlets Hi Ed and Dwayne I'm working on my inlet and outlet for Renesis powered Glasair SIIRG. It seems whenever we turn our attention to air, it is not about inlets or o= utlets but pressure differentials and the whole system. A great inlet is killed by a lousy outlet, and both made mute by inadequate= diffusion. Perhaps a NACA would work adequately given a system with good diffusion tha= t SUCKED well. Cheers Steve Izett Not flying, so maybe completely deluded. Continues to more than respect Tracy's thoughts and practices. On 30/04/2011, at 7:26 AM, Ed Anderson wrote: Dwayne There is a NACA study on NACA ducts which in essence found that while they = were excellent for feeding an intake (an duct with no internal resistance s= uch as a heat exchanger core) such as an engine intake, that their performa= nce suffered relative to other duct configurations - where you had a radiat= or core installed. The reason appeared to be that the pressure build up be= fore the core hindered the airflow into the duct and caused a lot of the ai= r to flow around the opening. On the good side, they were relatively low dr= ag ducts. Now that being said, several approaches have been found that seems to offse= t the problems. One that comes to mind is the placement of vortex generato= rs which guide more airflow into the ducts and the other one is the placeme= nt of the inlet in a high pressure area. Folks have used them successfully= for cooling - so long as sufficient airflow can be achieved through the du= ct the core doesn't care what kind of opening is used. Ed Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com From: Dwayne Parkinson Sent: Friday, April 29, 2011 5:05 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Cooling Inlets OK, I gotta ask. Does anyone use NACA ducts for cooling inlets? Why or wh= y not? ________________________________ From: Tracy > To: Rotary motors in aircraft > Sent: Fri, April 29, 2011 9:49:00 AM Subject: [FlyRotary] Re: Cooling Inlets Some questions: Prior reading seemed to indicate that the oil cooler did ~1/3 of the coolin= g, implying a 2/1 ratio on air requirements. This setup seems to have a sig= nificantly higher percentage allocated to oil. Is this a byproduct of heat = exchanger differences, or the less efficient heat transfer ability of oil, = or....? 2nd, assuming similar inlet & diffuser efficiencies, could the inlet areas = mentioned be reduced by roughly 1/3 with reasonable expectation of cooling = a 2 rotor Renesis? On the subject of exit area: Does either heat exchanger have an exit duct? = The RV guys with really fast Lyc powered planes all have some variation of = exit ducting to smoothly re-accelerate and redirect exit air parallel to & = at or above the slipstream. Even the stock RV-8 has a rounded lip at the bo= ttom of the firewall (which the really fast guys say is much too small a ra= dius...). And there's always the near-mythical P-51 system... Thanks, Charlie The inlets were originally closer to the 2 - 1 area ratio but many experime= nts (mostly failures) ended up with the current sizes. I just don't have i= t in me to go back and un-do them all. Also wish I had tried these inlets = with my original oil cooler which had about 1/3 more core volume and much t= hicker. Might have been able to do the oil cooling with less CFM airflow.= But, I don't think there is much penalty for having more than enough (bu= t properly faired) inlet area and throttling the airflow with a cowl flap. Yes, I do think both inlets could be scaled down in area for a 2 rotor. Neither of my heat exchangers have exit ducts. Just not enough room to do = this in their current locations. Tracy On Thu, Apr 28, 2011 at 4:23 PM, Charlie England > wrote: On 4/28/2011 8:07 AM, Tracy wrote: Finally got around to finishing my cooling inlets. (pictures attached) Up = until now they were simply round pipes sticking out of the cowl. The pipe= s are still there but they have properly shaped bellmouths on them. The s= hape and contours were derived from a NASA contractor report (NASA_CR3485) = that you can find via Google. Lots of math & formulas in it but I just cop= ied the best performing inlet picture of the contour. Apparently there is= an optimum radius for the inner and outer lip of the inlet. There was no= change to the inlet diameters of 5.25" on water cooler and 4.75" on oil co= oler. The simple pipes performed adequately in level flight at moderate cruise se= ttings even on hot days but oil temps would quickly hit redline at high pow= er level flight and in climb. The significant change with the new inlet shape is that they appear to capt= ure off-axis air flow (like in climb and swirling flow induced by prop at= high power) MUCH better than the simple pipes. First flight test was o= n a 94 deg. F day and I could not get the oil temp above 200 degrees in a m= ax power climb. They may have gone higher if the air temperature remaine= d constant but at 3500 fpm the rapidly decreasing OAT kept the temps well u= nder redline (210 deg F). I have an air pressure instrument reading the pressure in front of the oil = cooler and was amazed at the pressure recovered from the prop wash. At 130= MPH the pressure would almost double when the throttle was advanced to WOT= . That did not happen nearly as much with the simple pipes. These inlets ROCK! Tracy Crook Perfect timing for me; I need to decide whether to take a loss & sell my (R= V-7) James Lyc style cowl & replace it with James' rotary cowl, or just mo= dify the existing cowl. Some questions: Prior reading seemed to indicate that the oil cooler did ~1/3 of the coolin= g, implying a 2/1 ratio on air requirements. This setup seems to have a sig= nificantly higher percentage allocated to oil. Is this a byproduct of heat = exchanger differences, or the less efficient heat transfer ability of oil, = or....? 2nd, assuming similar inlet & diffuser efficiencies, could the inlet areas = mentioned be reduced by roughly 1/3 with reasonable expectation of cooling = a 2 rotor Renesis? On the subject of exit area: Does either heat exchanger have an exit duct? = The RV guys with really fast Lyc powered planes all have some variation of = exit ducting to smoothly re-accelerate and redirect exit air parallel to & = at or above the slipstream. Even the stock RV-8 has a rounded lip at the bo= ttom of the firewall (which the really fast guys say is much too small a ra= dius...). And there's always the near-mythical P-51 system... Thanks, Charlie ________________________________ The contents of this email are confidential and intended only for the named= recipients of this e-mail. If you have received this e-mail in error, you = are hereby notified that any use, reproduction, disclosure or distribution = or the information contained in this e-mail is prohibited. Please notify th= e sender immediately and then delete/destroy the e-mail and any printed cop= ies. All liability for viruses is excluded to the fullest extent of the law= . --_000_183C449C962141BA961FF251762B50A1careyasnau_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Thanks Ed

You guys are so helpful. Really appreciate listening and learning.=

Blessings

Steve Izett
On 30/04/2011, at 10:00 PM, Ed Anderson wrote:

I agree, Steve.  There is no question each p= art of=20 the cooling system  is critical and the total results is no bette= r=20 than the weakest link. 
 
Most studies I have read indicates that after a c= ertain=20 size in inlet area (from 25-35% of core frontal area) - the outlet size bec= omes=20 the determining factor and further increases in intake provide no additiona= l=20 benefit and can hurt by increasing cooling drag.  Adding such things a= s=20 cowl flaps can reduce the pressure in the outlet region and promote more ai= rflow=20 and cooling but naturally at the cost of more drag.  But, then at high= er=20 speeds with plenty of dynamic pressure, you can retract the cowl flaps and= =20 reduce the drag.
 
NACA ducts have been made to work with radiator=20 cores - no question about that.  The question is would a differen= t=20 approach have produced a "better" cooling system.  Again, I think it=20 depends on your intended operating environment. 
 
For a high speed cruise environment, I would thin= k cooling=20 drag might be of more importance than say perhaps a few pounds of additiona= l=20 weight, on the other hand if you are flying an already draggy biplane for=20 example, cooling drag is probably a very small part of your over all drag, = but=20 getting cooling with low airspeed might be the system driver.
 
Its all about compromises - space, weight, flow, = drag,=20 etc. - oh, yes! - and cooling of course {:>)  all matched to your=20 constraints and operating environment.
 
Ed
 

Sent: Friday, April 29, 2011 8:48 PM
Subject: [FlyRotary] Re: Cooling Inlets

Hi Ed and Dwayne=20

I'm working on my inlet and outlet for Renesis powered Glasair SIIRG.<= /div>
It seems whenever we turn our attention to air, it is not about inlets= or=20 outlets but pressure differentials and the whole system.
A great inlet is killed by a lousy outlet, and both made mute by inade= quate=20 diffusion.
Perhaps a NACA would work adequately given a system with good diffusio= n=20 that SUCKED well.

Cheers
Steve Izett
Not flying, so maybe completely deluded. 
Continues to more than respect Tracy's thoughts and practices.

On 30/04/2011, at 7:26 AM, Ed Anderson wrote:

Dwayne
 
There is a NACA study on = NACA ducts=20 which in essence found that while they were excellent for feeding an inta= ke=20 (an duct with no internal resistance such as a heat exchanger core) such = as an=20 engine intake, that their performance suffered relative to other duct=20 configurations - where you had a radiator core installed.  The= =20 reason appeared to be that the pressure build up before the core hindered= the=20 airflow into the duct and caused a lot of the air to flow around the open= ing.=20 On the good side, they were relatively low drag ducts. 
 
Now that being said, seve= ral=20 approaches have been found that seems to offset the problems.  One t= hat=20 comes to mind is the placement of vortex generators which guide more airf= low=20 into the ducts and the other one is the placement of the inlet in a high= =20 pressure area.  Folks have used them successfully for cooling - so l= ong=20 as sufficient airflow can be achieved through the duct the core doesn't c= are=20 what kind of opening is used.
 
Ed
 
Edward L. Anderson
And= erson=20 Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104http://www.andersonee.com
http://www.eicommander.com

Sent: Friday, April 29, 2011 5:05 PM
Subject: [FlyRotary] Re: Cooling=20 Inlets

OK, I gotta ask.  Does anyone use NACA du= cts for=20 cooling inlets?  Why or why not?  

From: Tracy <rwstracy@gmail.com>
To:<= /span> Rotary motors = in aircraft <fl= yrotary@lancaironline.net>
S= ent: Fri, Apri= l 29, 2011 9:49:00=20 AM
Subject: [FlyRotary] Re: Cooling=20 Inlets

Some questions:
Prior reading seemed to indicate = that=20 the oil cooler did ~1/3 of the cooling, implying a 2/1 ratio on air=20 requirements. This setup seems to have a significantly higher percentage= =20 allocated to oil. Is this a byproduct of heat exchanger differences, or t= he=20 less efficient heat transfer ability of oil, or....?

2nd, assuming= =20 similar inlet & diffuser efficiencies, could the inlet areas mentione= d be=20 reduced by roughly 1/3 with reasonable expectation of cooling a 2 rotor=20 Renesis?

On the subject of exit area: Does either heat exchanger h= ave=20 an exit duct? The RV guys with really fast Lyc powered planes all have so= me=20 variation of exit ducting to smoothly re-accelerate and redirect exit air= =20 parallel to & at or above the slipstream. Even the stock RV-8 has a=20 rounded lip at the bottom of the firewall (which the really fast guys say= is=20 much too small a radius...). And there's always the near-mythical P-51=20 system...

Thanks,
Charlie

The inlets were originally clo= ser=20 to the 2 - 1 area ratio but many experiments (mostly failures) ended up w= ith=20 the current sizes.  I just don't have it in me to go back and un-do = them=20 all.  Also wish I had tried these inlets with my original oil cooler= =20 which had about 1/3 more core volume and much thicker.   Might = have=20 been able to do the oil cooling with less CFM airflow.   But, I don'= t=20 think there is much penalty for having more than enough (but properly fai= red)=20 inlet area and throttling the airflow with a cowl flap.

Yes, I do = think=20 both inlets could be scaled down in area for a 2 rotor.

Neither of= my=20 heat exchangers have exit ducts.  Just not enough room to do this in= =20 their current locations.

Tracy
  


On Thu, Apr 28, 2011 at = 4:23 PM,=20 Charlie England <ceengland@bell= south.net> = wrote:
On 4/28/2011 8:07 AM, Tracy wro= te:=20
Finally got around to finishing my cooling inlets. (pictures= =20 attached)  Up until now they were simply round pipes sticking ou= t of=20 the cowl.   The pipes are still there but they have properl= y=20 shaped bellmouths on them.   The shape and contours were de= rived=20 from a NASA contractor report (NASA_CR3485) that you can find via=20 Google.  Lots of math & formulas in it but I just copied the= best=20 performing inlet picture of the contour.   Apparently there= is=20 an optimum radius for the inner and outer lip of the inlet. &nbs= p;=20 There was no change to the inlet diameters of 5.25" on water cooler a= nd=20 4.75" on oil cooler.

The simple pipes performed adequately in = level=20 flight at moderate cruise settings even on hot days but oil temps wou= ld=20 quickly hit redline at high power level flight and in climb.  

The significant cha= nge=20 with the new inlet shape is that they appear to capture off-axis air= =20 flow  (like in climb and swirling flow  induced by prop at = high=20 power)  MUCH better than the simple pipes.    First fl= ight=20 test was on a 94 deg. F day and I could not get the oil temp above 20= 0=20 degrees in a max power climb.    They may have gone higher = if=20 the air temperature remained constant but at 3500 fpm the rapidly=20 decreasing OAT kept the temps well under redline (210 deg F).

= I=20 have an air pressure instrument reading the pressure in front of the = oil=20 cooler and was amazed at the pressure recovered from the prop wash.&n= bsp;=20 At 130 MPH the pressure would almost double when the throttle was adv= anced=20 to WOT.   That did not happen nearly as much with the simple=20 pipes.   =

These inlets=20 ROCK!

Tracy=20 Crook

Perfect timing for me; I need to = decide whether to=20 take a loss & sell my (RV-7)  James Lyc style cowl & replace= =20 it with James' rotary cowl, or just modify the existing cowl.

So= me=20 questions:
Prior reading seemed to indicate that the oil cooler did = ~1/3=20 of the cooling, implying a 2/1 ratio on air requirements. This setup se= ems=20 to have a significantly higher percentage allocated to oil. Is this a=20 byproduct of heat exchanger differences, or the less efficient heat tra= nsfer=20 ability of oil, or....?

2nd, assuming similar inlet & diffus= er=20 efficiencies, could the inlet areas mentioned be reduced by roughly 1/3= with=20 reasonable expectation of cooling a 2 rotor Renesis?

On the subj= ect=20 of exit area: Does either heat exchanger have an exit duct? The RV guys= with=20 really fast Lyc powered planes all have some variation of exit ducting = to=20 smoothly re-accelerate and redirect exit air parallel to & at or ab= ove=20 the slipstream. Even the stock RV-8 has a rounded lip at the bottom of = the=20 firewall (which the really fast guys say is much too small a radius...)= . And=20 there's always the near-mythical P-51=20 system...

Thanks,

Charlie


<= /div>



The contents of this email a= re confidential=20 and intended only for the named recipients of this e-mail. If you have rece= ived=20 this e-mail in error, you are hereby notified that any use, reproduction,=20 disclosure or distribution or the information contained in this e-mail is=20 prohibited. Please notify the sender immediately and then delete/destroy th= e=20 e-mail and any printed copies. All liability for viruses is excluded to the= =20 fullest extent of the law.

= --_000_183C449C962141BA961FF251762B50A1careyasnau_--