X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.3.1) with ESMTP id 4095868 for flyrotary@lancaironline.net; Mon, 25 Jan 2010 20:30:37 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.0 c=1 a=WbNVUdcZcaUA:10 a=ayC55rCoAAAA:8 a=arxwEM4EAAAA:8 a=QdXCYpuVAAAA:8 a=7g1VtSJxAAAA:8 a=ekHE3smAAAAA:20 a=UretUmmEAAAA:8 a=Ia-xEzejAAAA:8 a=nUuTZ29dAAAA:8 a=-0-9RmDusse63Om2rNYA:9 a=4C6C7Ez-ArH_3lyiOpcA:7 a=tSxxxZjak1mFgPtfIK_S0ZnT5j8A:4 a=5zrLeAV0Z70A:10 a=1vhyWl4Y8LcA:10 a=EzXvWhQp4_cA:10 a=pN_yq26sGF42P6BI:21 a=I4ZRU0RJHG2frYMa:21 a=SSmOFEACAAAA:8 a=OI8opHVKagTa3uHQxggA:9 a=ORaVCFqQ5I59ba5OrysA:7 a=GbD4YrwiL7KzQsyPpdqpzlrF5LkA:4 a=KIxYfMojEOoSpS8Y:21 a=lBCRTf0e6Nfk835j:21 X-Cloudmark-Score: 0 X-Originating-IP: 75.191.186.236 Received: from [75.191.186.236] ([75.191.186.236:2041] helo=computername) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id 76/50-19307-9954E5B4; Tue, 26 Jan 2010 01:30:02 +0000 From: "Ed Anderson" Message-ID: <76.50.19307.9954E5B4@cdptpa-omtalb.mail.rr.com> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Wedge/Oblique Duct Date: Mon, 25 Jan 2010 20:30:05 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002B_01CA9DFD.2E40DD10" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcqeIbkYFSbXnVzxQ4GjnrZDS3r6qgAA2N8Q X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_002B_01CA9DFD.2E40DD10 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit What Al, said George with a heavy dose of what Ernest Said. As Al said, you really need to start knowing approx how much heat you will need to remove under the worst conditions. If you don't know that then all else is probably worst than guess work. For my book, take off is the worst of all cooling conditions. You are producing maximum heat and have minimal air mass flow for cooling. Yes, you can add things like core water sprayers that can temporarily help for a limited amount of time. But, in my opinion, the best approach is to first determine you cooling requirements as in how many BTU/min you need to get rid of under the worst conditions unaided through your cores. The most efficient way is to transfer the heat directly from coolant/oil to the air. However, space and other considerations may force you to consider oil/coolant heat exchangers for example - but, you get the greatest heat transfer efficiency going from liquid medium straight to the air medium in one step - any intermediate steps in heat transfer are going to cost you some efficiency. But, like I said - at times there may be reasons to do otherwise. Yes, you will have to make some assumptions, like what will be the delta T across the core - I think 80-100F seems to be achievable across a coolant core and perhaps 40-60F across your oil cooler. But, until you determine the size of core you that will meet your requirement, its premature to start getting concern about the inlet size. Now if for some reason (design of the aircraft perhaps), you are really constrained to inlet size, then you may need to work it from maximum inlet size to the core size you need. From what I have read it appears that an inlet area ranging from 25 - 40 % of your core surface area is in the ball park. At least you can start there, then calculated your mass flow needed to get rid of the requirement amount of heat through your core. Then determine which size inlet will give you 10% of your cruise airspeed or 30% of your climb airspeed after being slowed down by the diffuser. But, all of this is just back of the envelope calculations to get you in the ball park. As Ernest pointed out, some folks will heat the nail on the head the first time - but, most of us have to work at it a bit. Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen Sent: Monday, January 25, 2010 7:52 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Wedge/Oblique Duct George; I haven't been following this thread, and stepping in here may reflect that; but I don't really understand your question. The size of the inlet opening is determined by the amount of heat you need to reject, best taken as corresponding to something close to the climb power. That; with the density and specific heat of air, gives you the cfm required. When you know that, and the approximate climb speed of your application, you can calculate the required inlet opening. Having done all those calcs, I (or ED, I'm sure) could scale those numbers for you fairly readily to your power level and speed. Other things follow from there; including the face area of the rad. Optimally, you'd like to have a way of adjusting inlet and exit areas for absolute minimum drag; but that's very complicated. If you can do one of those, adjust the exit area. If both are fixed and you want least drag, you can size the inlet for something closer to cruise speed, and add the complexity of the spray-bar idea for added cooling during high power regimes. It's good to have some sort of control over the amount of cooling to maintain engine temps within some reasonable range. If the cooling system is sized for climb on a hot day, a thermostat is a way to maintain temps for other regimes. There is the rare possibility of a thermostat sticking closed, but that is something that hopefully would be noted before takeoff. Not that I advocate this approach, but I have a setup that doesn't require any pilot intervention and serves quite well. I have 2 coolant radiators, one which can handle the cooling for normal cruise (both coolant and some of the oil heat), and one (connected in parallel) that can handle maybe 30-40% more (in the wing root with presumably a fairly low drag inlet/outlet. The second has an in-line thermostat, so only comes into service during high-power operation, or very hot days. I have an oil/air cooler that handles normal cruise power, and small oil/water exchanger (in parallel) that keeps the oil temps at a safe level for high power by transferring heat to the coolant. Yeah; the plumbing is a little more complicated, but I like the way it works. (Sorry, it seems what starts out to be a simple answer always turn into more complicated discussions). Al G -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich Sent: Monday, January 25, 2010 2:31 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Wedge/Oblique Duct Ed, I have been thinking about this, if I use A1V1=A2V2 to solve for the inlet opening size, how do I know if the speed of air through the duct is correct i.e. 10% for cruise and 30% for climb. Also If I use the Cessna 171 speed of approx 100 K for cruise = 10 K through core, 70 knot climb and approx 20 K through core. Do I then use the climb speed to calculate inlet air openings and attach an adjustable louver exit OR I suppose I could do as Tracy does and calculate for cruise and attach a spray bar. I'm still a little confused on the best approach. George ( down under) BTW it's Australia Day today - arrival of the first fleet. George, For the bell shaped duct, what I have read in K & W it appears they say the inlet area should be between 0.25 - 0.40 of the core area. The more slowing of the air velocity that needs to be done by the diffuser before the core that is needed appears to call for lower area ratio values of Ai/Ab (area inlet/area core). In the example plotted of an streamline duct in K&W the chart shows the area ratio was 0.40. Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich Sent: Wednesday, January 20, 2010 6:16 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Wedge/Oblique Duct Ed, If Ai is .33 Ab and .44 Ab for the wedge ducts, what's it for the bell shaped duct - is there any similar drawing? George ( down under) ----- Original Message ----- From: Ed Anderson To: Rotary motors in aircraft Sent: Wednesday, January 20, 2010 3:39 AM Subject: [FlyRotary] Wedge/Oblique Duct George, here are two figures from K&W - one could be described as a "Wedge" figure 12-6 and the other one a "streamline" wedge figure 12-12. Always dangerous for me to try to interpret what K&W are really saying, but from what I get from these two figures, it would appear that the "streamline" wedge permits you to use a smaller inlet (Ai = 0.30 Ab) for the same performance (same losses) that you get with a larger opening Ai = 0.44 Ab for the pure Wedge. But, that is just my take on it. The slight bump (where the 64 deg angle is annotated) of the Streamline wedge may be to increase the boundary layer velocity to delay separation of the boundary layer in that far corner where duct meets core. Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com _____ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_002B_01CA9DFD.2E40DD10 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

What Al, said George with a heavy = dose of what Ernest Said.

 

As Al said, you really need to = start knowing approx how much heat you will need to remove under the worst conditions. If you don’t know that then all else is probably worst = than guess work.

 

 For my book, take off is the = worst of all cooling conditions.  You are producing maximum heat and have minimal air mass flow for cooling.  Yes, you can add things like = core water sprayers that can temporarily help for a limited amount of time.  = But, in my opinion, the best approach is to first determine you cooling = requirements as in how many BTU/min you need to get rid of under the worst conditions = unaided through your cores. 

 

 

The most efficient way is to = transfer the heat directly from coolant/oil to the air.  However, space and = other considerations may force you to consider oil/coolant heat exchangers for example – but, you get the greatest heat transfer efficiency going = from liquid medium straight to the air medium in one step – any = intermediate steps in heat transfer are going to cost you some efficiency.  But, = like I said - at times there may be reasons to do = otherwise.

 

Yes, you will have to make some assumptions, like what will be the delta T across the core – I = think 80-100F seems to be achievable across a coolant core and perhaps 40-60F = across your oil cooler.   But, until you determine the size of core = you that will meet your requirement, its premature to start getting concern about = the inlet size.

 

Now if for some reason (design of = the aircraft perhaps), you are really constrained to inlet size, then you = may need to work it from maximum inlet size to the core size you need.  =

 

From what I have read it appears = that an inlet area ranging from 25 – 40 % of your core surface area is in = the ball park.  At least you can start there, then calculated your mass = flow needed to get rid of the requirement amount of heat through your = core.  Then determine which size inlet will give you 10% of your cruise = airspeed or 30% of your climb airspeed after being slowed down by the = diffuser.  But, all of this is just back of the envelope calculations to get you in the = ball park.  As Ernest pointed out, some folks will heat the nail on the = head the first time – but, most of us have to work at it a = bit.

 

Ed

 

 

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Monday, January 25, = 2010 7:52 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Wedge/Oblique Duct

 

George;

 

I haven’t been following = this thread, and stepping in here may reflect that; but I don’t really understand your question.  The size of the inlet opening is = determined by the amount of heat you need to reject, best taken as corresponding to = something close to the climb power.  That; with the density and specific heat = of air, gives you the cfm required.  When you know that, and the = approximate climb speed of your application, you can calculate the required inlet = opening.

 

Having done all those calcs, I = (or ED, I’m sure) could scale those numbers for you fairly readily to your = power level and speed.

 

Other things follow from there; including the face area of the rad. Optimally, you’d like to have = a way of adjusting inlet and exit areas for absolute minimum drag; but = that’s very complicated.  If you can do one of those, adjust the exit = area. If both are fixed and you want least drag, you can size the inlet for = something closer to cruise speed, and add the complexity of the spray-bar idea for = added cooling during high power regimes. 

 

It’s good to have some sort = of control over the amount of cooling to maintain engine temps within some reasonable range.  If the cooling system is sized for climb on a = hot day, a thermostat is a way to maintain temps for other regimes. There is the = rare possibility of a thermostat sticking closed, but that is something that hopefully would be noted before takeoff.

 

Not that I advocate this = approach, but I have a setup that doesn’t require any pilot intervention and = serves quite well.  I have 2 coolant radiators, one which can handle the cooling = for normal cruise (both coolant and some of the oil heat), and one = (connected in parallel) that can handle maybe 30-40% more (in the wing root with = presumably a fairly low drag inlet/outlet. The second has an in-line thermostat, so = only comes into service during high-power operation, or very hot days.  = I have an oil/air cooler that handles normal cruise power, and small oil/water exchanger (in parallel) that keeps the oil temps at a safe level for = high power by transferring heat to the coolant. Yeah; the plumbing is a little more complicated, but I like the way it works.

 

(Sorry, it seems what starts out = to be a simple answer always turn into more complicated = discussions).

 

Al G

 

 

 

-----Original = Message-----
From: Rotary motors in aircraft = [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich
Sent: Monday, January 25, = 2010 2:31 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Wedge/Oblique Duct

 

 Ed,=

I have been thinking about = this, if I use A1V1=3DA2V2 to solve for the inlet opening size, how do I know if = the speed of air through the duct is correct i.e. 10% for cruise and 30% for = climb.

 

Also If I use the Cessna = 171 speed of approx 100 K for cruise =3D 10 K through core, 70 knot climb and = approx 20 K through core. Do I then use the climb speed to calculate inlet air = openings and attach an adjustable louver exit OR I suppose I could do as = Tracy does and = calculate for cruise and attach a spray bar.

 

I'm still a little confused = on the best approach.

George ( down = under)

BTW it's Australia Day = today - arrival of the first fleet.

 

=

George, For the = bell shaped duct, what I have read in K & W it appears they  say the = inlet area should be between 0.25 – 0.40 of the core area.  The = more slowing of the air velocity that needs to be done by the diffuser before = the core that is needed appears to call for lower area ratio values of Ai/Ab = (area inlet/area core).  In the example plotted of an streamline duct in = K&W the chart shows the area ratio was 0.40.

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich
Sent: Wednesday, January = 20, 2010 6:16 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Wedge/Oblique Duct

 

Ed,=

If Ai is .33 Ab and .44 Ab = for the wedge ducts, what's it for the bell shaped duct - is there any =  similar drawing?

George ( down = under)

----- Original Message = -----

From: Ed Anderson

Sent: Wednesday, January 20, 2010 3:39 AM

Subject: [FlyRotary] Wedge/Oblique Duct

 

 

George, here are two = figures from K&W – one could be described as a “Wedge” figure = 12-6 and the other one a “streamline” wedge figure = 12-12.

 

Always  dangerous for = me to try to interpret what K&W are really saying, but from what I get from = these two figures, it would appear that the “streamline” wedge permits = you to use a smaller inlet (Ai =3D 0.30 Ab) for the same performance (same = losses) that you get with a larger opening Ai =3D 0.44 Ab for the pure Wedge.  = But, that is just my take on it.

 

The slight bump (where the = 64 deg angle is annotated) of the Streamline wedge may be to increase the = boundary layer velocity to delay separation of the boundary layer  in that = far corner where duct meets core. 

 

Ed<= /p>

Ed = Anderson

Rv-6A N494BW Rotary = Powered

Matthews, = NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html<= o:p>

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.r= otaryaviation.com/Rotorhead%20Truth.htm

 



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

------=_NextPart_000_002B_01CA9DFD.2E40DD10--