X-CGP-ClamAV-Result: CLEAN X-VirusScanner: Niversoft's CGPClamav Helper v1.23.0 (ClamAV engine v0.103.0) X-Junk-Score: 0 [] X-KAS-Score: 0 [] From: "Marc Wiese cardmarc@charter.net" Received: from [47.43.20.30] (HELO impout006.msg.chrl.nc.charter.net) by logan.com (CommuniGate Pro SMTP 6.3.5) with ESMTPS id 153805 for flyrotary@lancaironline.net; Tue, 20 Jul 2021 13:11:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=47.43.20.30; envelope-from=cardmarc@charter.net Received: from smtpclient.apple ([174.202.203.34]) by cmsmtp with ESMTPA id 5tH6mGBvnaWeU5tH6mAqhr; Tue, 20 Jul 2021 17:11:21 +0000 Authentication-Results: charter.net; auth=pass (PLAIN) smtp.auth=cardmarc@charter.net X-Authority-Analysis: v=2.4 cv=bJ7TnNyZ c=1 sm=1 tr=0 ts=60f703ba a=wuZb5LKXEFYg6oTVAQWxDQ==:117 a=wuZb5LKXEFYg6oTVAQWxDQ==:17 a=o1OHuDzbAAAA:8 a=Ia-xEzejAAAA:8 a=ayC55rCoAAAA:8 a=pGLkceISAAAA:8 a=_6GpL_ENAAAA:8 a=Tzmlwhqbuxhh7eSfI5YA:9 a=7Zwj6sZBwVKJAoWSPKxL6X1jA+E=:19 a=QEXdDO2ut3YA:10 a=4PR2P7QzAAAA:8 a=Ra7HEjbMLNVbfQJuFFsA:9 a=IMYp1ddMJxEragqR:21 a=_W_S_7VecoQA:10 a=5YQ6H4ZxyGn-KoBYtt8s:22 a=Urk15JJjZg1Xo0ryW_k8:22 a=B_RyunTPg8udlmYm5Cu2:22 a=4dqwQCo7Po2mVW515mGf:22 Content-Type: multipart/alternative; boundary=Apple-Mail-2A5EE54C-1E5F-4218-B320-3E82DB02F1C1 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) Subject: Re: [FlyRotary] Re: Cooling Inlets-shape Date: Tue, 20 Jul 2021 12:11:19 -0500 Message-Id: <72EBA6A0-5054-41CB-B0B8-9240CA7D6301@charter.net> References: In-Reply-To: To: Rotary motors in aircraft X-Mailer: iPhone Mail (18F72) X-CMAE-Envelope: MS4xfIppEbsSIjiYq5WRrz+JaNE/kzHIedVdPiUS+wBziurFBkypJ8qTs6nAoQo4LzQwk9m/R1ccsERus4gT4QYccrAdgAPKKtwiqfiwAPKH6Dvvt/mUucAV ztLUxO8Hvl5eTAKx/DpBBN7oX6+sJpecJEoid9KGlEyPZIT4kZch5DivhtBBG5XWgpBCw4LZp+dF14ApdmhlnXv0NW1gEp05mGw= --Apple-Mail-2A5EE54C-1E5F-4218-B320-3E82DB02F1C1 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Can someone post pictures of Tracy=E2=80=99s inlets or point me to where the= y are in the archives? M Sent from my iPhone > On Jul 20, 2021, at 10:58 AM, Finn Lassen finn.lassen@verizon.net wrote: >=20 > =EF=BB=BF > Thanks Ed. >=20 > Not been making much progress on the RV-4 over the last month. I guess th= e heat and humidity is getting to me ... >=20 > Finn=20 >> On 7/13/2021 11:57 AM, eanderson@carolina.rr.com wrote: >> Hi Finn, >>=20 >> Its been a long time since I dove this deep into cooling ducts/lip contou= rs etc. But, here goes. >>=20 >> The duct (lip + diffuser) is suppose to convert air velocity to air press= ure with minimum loss/drag and turbulence. However, like almost everything e= lse involving flight - there is no single best answer - only an optimization= or approximation to the best (that you are going to get with the compromise= s you have to make). So in our case one set of compromises might be between= cooling effectivness and cooling drag. As you know the larger your radiato= r the more heat you are going to get rid of, but, the larger your core the m= ore cooling drag you are going to encounter. =20 >>=20 >> Now at low speeds you might get away with sticking the radiator out in th= e airstream without any ducting and get adequate cooling, but it will have h= igher drag - now at biplane/slow airspeed the drag might be acceptable, but a= t 200 mph quite unacceptable. Again, it depends on what you are trying to a= chieve. >>=20 >> Its been quite a while, but Ill give it a shot on trying to explain the c= harts. I presume that External refers to air factors prior to the lip and I= nternal refers to air factors after the lip of the diffuser (or internal to t= he duct). you mention wanting a 100-20 mph slow down. That is a data point= , but as I recall that is the overall slow down which would include the slow= down across the lip of the duct and the across the radiator combined. Also= for a faster aircraft where Vo is quite high, perhaps Vi/Vo =3D 0.40 makes= for less drag but gives you all the cooling needed as opposed to selecting= cooling as a Vi/Vo =3D 0.20. >>=20 >> Also the Positive CPs are all below the horizontal line for Internal flow= . With lower Vi/Vos resulting in higher positive CPs. That makes sense bec= ause if we have Vi/Vo =3D 1.0 then that would imply the least conversion of v= elocity to internal pressure, and we get a negative ratio Cp =3D -0.6. Con= versly if Vi/Vo =3D 0 then that would imply all the velocity energy is cover= ted to pressure Vi/Vo =3D 0 then Cp =3D max or approx positive 1.0 which ten= ds to jive with the graphs. >>=20 >> The Cp external magnitude tends to increase as A (lip Curvature) becomes m= ore pronounced (with A=3D40 being the most pronounced and A=3D10 the less pr= onounced lip curvature). External pressure would be considered a drag compo= nent in my opinon, so you want the least of that possible consisten with oth= er objectives (such as cooling). =20 >>=20 >> So I think A=3D20 was chosen as the best compromise of lesser drag and ad= equate cooling. Also, other lip curvatures might have had "Separation" or o= ther problems at different angles of attach (from 12 to -12 degrees). For e= xample perhaps if A=3D40 was choose, separation may have occured at angles b= elow 12 Degs and for that reason alone been unacceptable. =20 >>=20 >> Best this old brain can do perhaps someone of the younger generation can j= ump in and clarify. >>=20 >> Ed >>=20 >>=20 >> =20 >> ------ Original Message ------ >> From: "Finn Lassen finn.lassen@verizon.net" = >> To: "Rotary motors in aircraft" >> Sent: 7/11/2021 11:12:23 AM >> Subject: [FlyRotary] Re: Cooling Inlets >>=20 >>> So Ed, you're bored? >>>=20 >>> Want to take a stab at helping me understand the below graphs and how th= ey lead to the selection of the optimum outside/inside lip radius ratio? >>>=20 >>> I understand that Cp is pressure coefficient, pressure relative to other= pressures in the vicinity. >>>=20 >>> Not clear to me if we're looking for positive or negative Cp inside the d= iffuser, I assume positive? (Converting airspeed into pressure) >>> I also assume we're looking for a profile with maximum Cp over a wide AO= A range. >>> Why did they pick A-20 and Vi/Vo =3D 0.4 for figure 36d? >>> Aren't we shooting for a Vi/Vo of 0.2 or better? (slowing 100 mph down t= o 20 mph)=20 >>>=20 >>> Finn >>>=20 >>>> On 6/30/2021 11:18 PM, Finn Lassen finn.lassen@verizon.net wrote: >>>> Thanks. I guess I kept missing it because I don't understand what I'm l= ooking at. >>>> Can anyone help me understand the following and show me the optimum ins= ide/outside radius ratio (which I assume is one of the A-10 to A-40 contours= ): >>>>=20 >>=20 >>>> >>>>=20 >>>> Finn >>>>=20 >>>>> On 6/30/2021 9:45 PM, Charlie England ceengland7@gmail.com wrote: >>>>> Seems likely; I don't recall seeing a CR3485 referenced anywhere, eith= er. >>>>>=20 >>>>> On 6/30/2021 4:42 PM, Finn Lassen finn.lassen@verizon.net wrote: >>>>>> I tried in vain to find NASA_CR3485 (well, I found a NASA contractors= report on animal studies). >>>>>>=20 >>>>>> I wonder of he meant 3405? >>>>>> >>>>>>=20 >>>>>>=20 >>>>>> Anyone found a better match? >>>>>>=20 >>>>>> Finn >>>>>>=20 >>>>>>> On 4/28/2011 9:07 AM, Tracy wrote: >>>>>>> Finally got around to finishing my cooling inlets. (pictures attache= d)=C3=AF=C2=BF=C2=BD Up until now they were simply round pipes sticking out o= f the cowl.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD The pipes are still there bu= t they have properly shaped bellmouths on them.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF= =C2=BD The shape and contours were derived from a NASA contractor report (NA= SA_CR3485) that you can find via Google.=C3=AF=C2=BF=C2=BD Lots of math & fo= rmulas in it but I just copied the best performing inlet picture of the cont= our.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD Apparently there is an optimum radi= us for the inner and outer lip of the inlet.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2= =BD There was no change to the inlet diameters of 5.25" on water cooler and 4= .75" on oil cooler. >>>>>>>=20 >>>>>>> The simple pipes performed adequately in level flight at moderate cr= uise settings even on hot days but oil temps would quickly hit redline at hi= gh power level flight and in climb.=C3=AF=C2=BF=C2=BD=20 >>>>>>>=20 >>>>>>> The significant change with the new inlet shape is that they appear t= o capture off-axis air flow=C3=AF=C2=BF=C2=BD (like in climb and swirling fl= ow=C3=AF=C2=BF=C2=BD induced by prop at high power)=C3=AF=C2=BF=C2=BD MUCH b= etter than the simple pipes. =C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD First flig= ht test was on a 94 deg. F day and I could not get the oil temp above 200 de= grees in a max power climb. =C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD They may ha= ve gone higher if the air temperature remained constant but at 3500 fpm the r= apidly decreasing OAT kept the temps well under redline (210 deg F). >>>>>>>=20 >>>>>>> I have an air pressure instrument reading the pressure in front of t= he oil cooler and was amazed at the pressure recovered from the prop wash.=C3= =AF=C2=BF=C2=BD At 130 MPH the pressure would almost double when the throttl= e was advanced to WOT. =C3=AF=C2=BF=C2=BD That did not happen nearly as much= with the simple pipes.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD=20 >>>>>>>=20 >>>>>>> These inlets ROCK! >>>>>>>=20 >>>>>>> Tracy Crook >>>>>>>=20 >>>>>>=20 >>>>>>=20 >>>>>> Virus-free. www.avast.com >>>>>=20 >>>>=20 >>>=20 >=20 --Apple-Mail-2A5EE54C-1E5F-4218-B320-3E82DB02F1C1 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable Can someone post pictures of Tracy=E2=80=99= s inlets or point me to where they are in the archives?
M

Sent from my iPhone

On Jul 20, 2021, at 10:58 AM, Finn Lassen finn.lassen@verizon.net <= flyrotary@lancaironline.net> wrote:

=EF=BB=BF =20 =20 =20
Thanks Ed.

 Not been making much progress on the RV-4 over the last month. I= guess the heat and humidity is getting to me ...

Finn
On 7/13/2021 11:57 AM, eanderson@carolina.rr.com wrote:
=20 =20
Hi Finn,

Its been a long time since I dove this deep into cooling ducts/lip contours etc.  But, here goes.

The duct (lip + diffuser) is suppose to convert air velocity to air pressure with minimum loss/drag and turbulence.  However, like almost everything else involving flight - there is no single best answer - only an optimization or approximation to the best (that you are going to get with the compromises you have to make).  So in our case one set of= compromises might be between cooling effectivness and cooling drag.  As you know the larger your radiator the more heat you= are going to get rid of, but, the larger your core the more cooling drag you are going to encounter.  

Now at low speeds you might get away with sticking the radiator out in the airstream without any ducting and get adequate cooling, but it will have higher drag - now at biplane/slow airspeed the drag might be acceptable, but at 200 mph quite unacceptable.  Again, it depends on what you are trying to achieve.

 Its been quite a while, but Ill give it a shot on trying to explain the charts.  I presume that External refers to air= factors prior to the lip and Internal refers to air factors after the lip of the diffuser (or internal to the duct).  you= mention wanting a 100-20 mph slow down.  That is a data point= , but as I recall that is the overall slow down which would include the slow down across the lip of the duct and the across the radiator combined.  Also for a faster aircraft where Vo is quite high, perhaps Vi/Vo =3D  0.40 makes for les= s drag but  gives you all the cooling needed as opposed to selecting cooling as a Vi/Vo =3D 0.20.

Also the Positive CPs are all below the horizontal line for Internal flow.  With lower Vi/Vos resulting in higher positiv= e CPs.  That makes sense because if we have Vi/Vo =3D 1.0 then that would imply the least conversion of velocity to internal pressure, and we get a negative ratio Cp =3D  -0.6.  Con= versly if Vi/Vo =3D 0 then that would imply all the velocity energy is coverted to pressure Vi/Vo =3D 0 then Cp =3D max or approx positive 1.0 which tends to jive with the graphs.

The Cp external magnitude tends to increase as A (lip Curvature) becomes more pronounced (with A=3D40 being the most pronounced and A=3D10 the less pronounced lip curvature).  External pressure would be considered a drag component in my opinon, so you want the least of that possible consisten with other objectives (such as cooling).  

So I think A=3D20 was chosen as the best compromise of lesser drag and adequate cooling. Also, other  lip curvatures might have had "Separation" or other problems at different angles of attach (from 12 to -12 degrees).  For example perhaps if A=3D= 40 was choose, separation may have occured at angles below 12 Degs and for that reason alone been unacceptable.  

Best this old brain can do perhaps someone of the younger generation can jump in and clarify.

Ed


 
------ Original Message ------
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net&g= t;
Sent: 7/11/2021 11:12:23 AM
Subject: [FlyRotary] Re: Cooling Inlets

So Ed, you're bored?

Want to take a stab at helping me understand the below graphs and how they lead to the selection of the optimum outside/inside lip radius ratio?

I understand that Cp is pressure coefficient, pressure relative to other pressures in the vicinity.

Not clear to me if we're looking for positive or negative Cp inside the diffuser, I assume positive? (Converting airspeed into pressure)
I also assume we're looking for a profile with maximum Cp over a wide AOA range.
Why did they pick A-20 and Vi/Vo =3D 0.4 for figure 36d?
Aren't we shooting for a Vi/Vo of 0.2 or better? (slowing 100 mph down to 20 mph)

Finn

On 6/30/2021 11:18 PM, Finn Lassen fi= nn.lassen@verizon.net wrote:
Thanks. I guess I kept missing it because I don't understand what I'm looking at.
Can anyone help me understand the following and show me the optimum inside/outside radius ratio (which I assume is one of the A-10 to A-40 contours):

3D""
<kbdejbnihmgdehea.png>= ;

Finn

On 6/30/2021 9:45 PM, Charlie England = ceengland7@gmail.com wrote:
Seems likely; I don't recall seeing a CR3485 referenced anywhere, either.

On 6/30/2021 4:42 PM, Finn Lassen finn.lassen@verizon.net wrote:
I tried in vain to find NASA_CR3485 (well, I found a NASA contractors report on animal studies).

I wonder of he meant 3405?
<bnmfmdnlndmefidc.png>


Anyone found a better match?

Finn

On 4/28/2011 9:07 AM, Tracy wrote:
Finally got around to finishing my cooling inlets. (pictures attached)=C3=AF=C2=BF=C2=BD Up until now t= hey were simply round pipes sticking out of the cowl.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD The pipes a= re still there but they have properly shaped bellmouths on them.=C3=AF=C2=BF= =C2=BD=C3=AF=C2=BF=C2=BD The shape and contours were derived from a NASA contractor report (NASA_CR3485) that you can find via Google.=C3=AF=C2=BF=C2=BD Lots of math &= ; formulas in it but I just copied the best performing inlet picture of the contour.=C3=AF=C2=BF=C2=BD=C3=AF= =C2=BF=C2=BD Apparently there is an optimum radius for the inner and outer lip of the inlet.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF= =C2=BD 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.=C3=AF=C2=BF=C2= =BD

The significant change with the new inlet shape is that they appear to capture off-axis air flow=C3=AF=C2=BF=C2=BD (like in climb and swirling f= low=C3=AF=C2=BF=C2=BD induced by prop at high power)=C3=AF=C2=BF=C2=BD MUC= H better than the simple pipes. =C3=AF=C2=BF=C2=BD=C3=AF=C2=BF= =C2=BD 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. =C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD They may have g= one 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.=C3=AF=C2=BF=C2=BD At 130 MPH the pressure woul= d almost double when the throttle was advanced to WOT. =C3=AF=C2=BF=C2=BD That did not happen nearly as muc= h with the simple pipes.=C3=AF=C2=BF=C2=BD=C3=AF=C2=BF=C2=BD
These inlets ROCK!

Tracy Crook



3D"" Virus-free. www.avast.com




=20
= --Apple-Mail-2A5EE54C-1E5F-4218-B320-3E82DB02F1C1--