X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTP id 4962637 for flyrotary@lancaironline.net; Sat, 30 Apr 2011 10:02:02 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=r4yJ8ACLDmU9N8MfnU6qGSvboKzSN9UnPAeXToqJDNE= c=1 sm=0 a=RKxS59jiEN8A:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=pGLkceISAAAA:8 a=Ia-xEzejAAAA:8 a=pedpZTtsAAAA:8 a=vGGU_15EGXLTXUxZsJkA:9 a=ssuSUQ6WFzydifHmVzYA:7 a=wPNLvfGTeEIA:10 a=MSl-tDqOz04A:10 a=EzXvWhQp4_cA:10 a=eJojReuL3h0A:10 a=tq3nTttx1z_N23ga:21 a=LETV8OXfXiBi69co:21 a=CjxXgO3LAAAA:8 a=WLPpi0MU3Z8Mreov2goA:9 a=3lu_BEiAwq-Se_qArloA:7 a=rC2wZJ5BpNYA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:62977] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 5D/9C-09483-6361CBD4; Sat, 30 Apr 2011 14:01:26 +0000 Message-ID: <182FFD65938B48219D3761166ABD2261@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Cooling Inlets Date: Sat, 30 Apr 2011 10:00:48 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0053_01CC071D.7AD61C00" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0053_01CC071D.7AD61C00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I agree, Steve. There is no question each part of the cooling system = is critical and the total results is no better than the weakest link. =20 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 = determining 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 cooling 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 that. The question is would a different approach have produced a = "better" cooling system. Again, I think it depends on your intended = operating environment. =20 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, cooling drag is probably a very small part of your over all = drag, but getting cooling with low airspeed might be the system driver. Its all about compromises - space, weight, flow, drag, etc. - oh, yes! - = and cooling of course {:>) all matched to your constraints and = operating environment. Ed From: stevei@carey.asn.au=20 Sent: Friday, April 29, 2011 8:48 PM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Cooling Inlets Hi Ed and Dwayne=20 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 outlets 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 = that SUCKED well. Cheers Steve Izett Not flying, so maybe completely deluded.=20 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 such as a heat exchanger core) such as an engine intake, that = their performance suffered relative to other duct configurations - where = you had a radiator core installed. The reason appeared to be that the = pressure build up before the core hindered the airflow into the duct and = caused a lot of the air to flow around the opening. On the good side, = they were relatively low drag ducts.=20 Now that being said, several approaches have been found that seems to = offset the problems. One that comes to mind is the placement of vortex = generators which guide more airflow into the ducts and the other one is = the placement 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 duct 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 why not? =20 -------------------------------------------------------------------------= ----- 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 = cooling, implying a 2/1 ratio on air requirements. This setup seems to = have a significantly 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 bottom of the firewall (which the really fast guys = say is much too small a radius...). 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 = experiments (mostly failures) ended up with the current sizes. I just = don't have it 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 thicker. 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 (but 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 =20 On Thu, Apr 28, 2011 at 4:23 PM, Charlie England = wrote: On 4/28/2011 8:07 AM, Tracy wrote:=20 Finally got around to finishing my cooling inlets. (pictures = attached) Up until now they were simply round pipes sticking out of the = cowl. The pipes are still there but they have properly shaped = bellmouths on them. The shape 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 copied 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 cooler. The simple pipes performed adequately in level flight at moderate = cruise settings even on hot days but oil temps would quickly hit redline = at high power level flight and in climb. =20 The significant change with the new inlet shape is that they = appear to capture 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 on a 94 deg. F day and I could not get the oil = temp above 200 degrees in a max power climb. They may have gone = higher if the air temperature remained constant but at 3500 fpm the = rapidly decreasing OAT kept the temps well under 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. =20 These inlets ROCK! Tracy Crook Perfect timing for me; I need to decide whether to take a loss & = sell my (RV-7) James Lyc style cowl & replace it with James' rotary = cowl, or just modify the existing cowl. Some questions: Prior reading seemed to indicate that the oil cooler did ~1/3 of the = cooling, implying a 2/1 ratio on air requirements. This setup seems to = have a significantly 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 bottom of the firewall (which the really fast guys = say is much too small a radius...). 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 the sender immediately and then delete/destroy the e-mail = and any printed copies. All liability for viruses is excluded to the = fullest extent of the law. ------=_NextPart_000_0053_01CC071D.7AD61C00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I agree, Steve.  There is no question each = part of=20 the cooling system  is critical and the total results is no = better=20 than the weakest link. 
 
Most studies I have read indicates that after a = certain=20 size in inlet area (from 25-35% of core frontal area) - the outlet size = becomes=20 the determining factor and further increases in intake provide no = additional=20 benefit and can hurt by increasing cooling drag.  Adding such = things as=20 cowl flaps can reduce the pressure in the outlet region and promote more = airflow=20 and cooling but naturally at the cost of more drag.  But, then at = higher=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 = different=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 = think cooling=20 drag might be of more importance than say perhaps a few pounds of = additional=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
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: Cooling Inlets

Hi Ed and Dwayne=20

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=20 outlets but pressure differentials and the whole system.
A great inlet is killed by a lousy outlet, and both made mute by = inadequate=20 diffusion.
Perhaps a NACA would work adequately given a system with good = diffusion=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 = intake=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 = opening.=20 On the good side, they were relatively low drag = ducts. 
 
Now that being said, = several=20 approaches have been found that seems to offset the problems.  = One that=20 comes to mind is the placement of vortex generators which guide more = airflow=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 long=20 as sufficient airflow can be achieved through the duct the core = doesn't care=20 what kind of opening is used.
 
Ed
 
Edward L. = Anderson
Anderson=20 Electronic Enterprises LLC
305 Reefton Road
Weddington, NC = 28104
http://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 = ducts for=20 cooling inlets?  Why or why not?  

From: Tracy <rwstracy@gmail.com>
To: Rotary motors in aircraft = <flyrotary@lancaironline.net>
Sent: Fri, April 29, 2011 9:49:00 = 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 the=20 less efficient heat transfer ability of oil, or....?

2nd, = assuming=20 similar inlet & diffuser efficiencies, could the inlet areas = mentioned 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 have=20 an exit duct? The RV guys with really fast Lyc powered planes all have = some=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 = system...

Thanks,
Charlie

The inlets were originally = closer=20 to the 2 - 1 area ratio but many experiments (mostly failures) ended = up with=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 = faired)=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@bellsouth.net>= ; wrote:
On 4/28/2011 8:07 AM, Tracy = wrote:=20
Finally got around to finishing my cooling inlets. = (pictures=20 attached)  Up until now they were simply round pipes sticking = out of=20 the cowl.   The pipes are still there but they have = properly=20 shaped bellmouths on them.   The shape and contours were = derived=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.  =20 There was no change to the inlet diameters of 5.25" on water = cooler and=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 = would=20 quickly hit redline at high power level flight and in = climb.  

The significant = change=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 = flight=20 test was on a 94 deg. F day and I could not get the oil temp above = 200=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. =20 At 130 MPH the pressure would almost double when the throttle was = advanced=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.

Some=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 = seems=20 to have a significantly higher percentage allocated to oil. Is this = a=20 byproduct of heat exchanger differences, or the less efficient heat = transfer=20 ability of oil, or....?

2nd, assuming similar inlet & = diffuser=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 = subject=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 = above=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





The contents of this email are = confidential=20 and intended only for the named recipients of this e-mail. If you have = received=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 = the=20 e-mail and any printed copies. All liability for viruses is excluded to = the=20 fullest extent of the law.
 ------=_NextPart_000_0053_01CC071D.7AD61C00--