X-Virus-Scanned: clean according to Sophos on Logan.com From: "Bill Bradburry" Received: from vms173023pub.verizon.net ([206.46.173.23] verified) by logan.com (CommuniGate Pro SMTP 6.1.2) with ESMTPS id 7693803 for flyrotary@lancaironline.net; Fri, 15 May 2015 12:40:48 -0400 Received-SPF: pass receiver=logan.com; client-ip=206.46.173.23; envelope-from=bbradburry@verizon.net Received: from Desktop ([71.164.185.6]) by vms173023.mailsrvcs.net (Oracle Communications Messaging Server 7.0.5.32.0 64bit (built Jul 16 2014)) with ESMTPA id <0NOE004GGGYX4AV0@vms173023.mailsrvcs.net> for flyrotary@lancaironline.net; Fri, 15 May 2015 11:40:10 -0500 (CDT) X-CMAE-Score: 0 X-CMAE-Analysis: v=2.1 cv=B/MOC1ok c=1 sm=1 tr=0 a=20weQFHSdBTlwctzPCQ/Gw==:117 a=kUPQlYmSbg0A:10 a=o1OHuDzbAAAA:8 a=oR5dmqMzAAAA:8 a=-9mUelKeXuEA:10 a=h1PgugrvaO0A:10 a=r77TgQKjGQsHNAKrUKIA:9 a=9iDbn-4jx3cA:10 a=cKsnjEOsciEA:10 a=gZbpxnkM3yUA:10 a=Ia-xEzejAAAA:8 a=ild7t_Y58BLCcPM-chUA:9 a=CjuIK1q_8ugA:10 a=SSmOFEACAAAA:8 a=yMhMjlubAAAA:8 a=UEMX6ytAtXn9j-zUqCoA:9 a=Q8grtGj4Phy7zl3I:21 a=gKO2Hq4RSVkA:10 a=UiCQ7L4-1S4A:10 a=hTZeC7Yk6K0A:10 a=frz4AuCg-hUA:10 To: "'Rotary motors in aircraft'" References: In-reply-to: Subject: RE: [FlyRotary] Return to Flight - 2 Date: Fri, 15 May 2015 11:40:11 -0500 Message-id: MIME-version: 1.0 Content-type: multipart/alternative; boundary="----=_NextPart_000_0009_01D08F03.E71A9FE0" X-Mailer: Microsoft Office Outlook 11 Thread-index: AdCPIqE0hF9IOW4uSZCxgyN479V9jgACeDsA X-MIMEOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 This is a multi-part message in MIME format. ------=_NextPart_000_0009_01D08F03.E71A9FE0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Jeff, It is difficult to build a cooling system that will keep the water temp on a hot day during a full power takeoff below 212 that doesn't produce way too much drag and excess cooling at cruise. I think I remember Tracy saying that short excursions to 230-240 will not hurt the engine. What happens after you reduce the power and go around the pattern? Does the temp start to immediately drop? Take a couple of trips around the pattern at cruise and see where the temp stabilizes before you start to tear your cooling system down. Bill _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] Sent: Friday, May 15, 2015 10:19 AM To: Rotary motors in aircraft Subject: [FlyRotary] Return to Flight - 2 Well, the second flight occurred last night with same results as before; one short low-level circuit due to insufficient cooling . looks like Al Wick made the correct prediction. There are 3 things I can try with the current configuration: 1) Increase inlet area 2) Increase outlet area (adjustable cowl flap) 3) Re-profile the pinched diffuser. I will do all 3 and see what happens. If all of the above show remarkable improvement then repositioning the radiator is the only alternative. Jeff From: Bobby J. Hughes [mailto:flyrotary@lancaironline.net] Sent: Wednesday, May 06, 2015 12:36 PM Subject: RE: [FlyRotary] Re: Return to Flight Al, "Sorry to say, the pressure you see has no significant effect on cooling efficiency (heat transfer). The next time you fly, since you've removed most of that air, you will still see 210F. Just like before". If the air was trapped at the top of the heat exchanger I would expect improved temperatures. Could be wrong. Bobby Hughes From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] Sent: Wednesday, May 06, 2015 11:15 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Return to Flight Hi Jeff. I've done lot's of experimenting with cooling sys. Tough to explain all this, but I'll give it a try: Pretty clear you saw 6 psi only because you took off with 3+ cups of air in the system. If you'd taken off with 2 cups of air, then pressure would have been 9 psi. 1 cup, 14 psi. No air in system, then you would have seen rated cap pressure (16 psi in your case). Sorry to say, the pressure you see has no significant effect on cooling efficiency (heat transfer). The next time you fly, since you've removed most of that air, you will still see 210F. Just like before. There's one huge exception to that statement, that's if you have air in sys that can't move to a high point out of the flow. In that case air in sys has huge negative effect. Causes local boiling when it passes hot areas and inflates cooling temp. You don't have to fly to prove these concepts. Ground running at idle is all that's needed. Let's assume all air is removed. Then letting engine warm up to 180 F will result in rapid pressure rise to 16 psi (rated cap pressure). Fluid will exit system. With 2 cups of air in sys, that same 180F will yield slow rise in pressure to only 9 psi. No fluid will leave sys. A good cooling design pretends air is stuck in block, so you add a path for that air to rise out of the block coolant flow. This is called a dynamic bleed. Air is automatically removed from engine coolant flow. Super low risk way to fly as you no longer care if air is in system. It's can't affect cooling. It's a bit higher risk to fly without dynamic air bleed, you just make darn sure you purge all air from block sys prior to flight. Applying vacuum to rad cap is great way to remove air. One of the ironies about cooling design is that air that resides above engine flow is a safety asset. For example, your cap is highest point in sys and you have 2 cups of air under cap. Big safety advantage simply because your pressure gage is then a great predictor of how well your sys is doing. A leak will be detected long before overheating. A bunch of other assets to this design. Conversely, air in engine flow has overwhelming negative affect. Temps soar and risks boil over. Clear as mud eh? Fwiw -al wick This message, and the documents attached hereto, is intended only for the addressee and may contain privileged or confidential information. Any unauthorized disclosure is strictly prohibited. If you have received this message in error, please notify us immediately so that we may correct our internal records. Please then delete the original message. Thank you. ------=_NextPart_000_0009_01D08F03.E71A9FE0 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Jeff,

It is difficult to build a cooling = system that will keep the water temp on a hot day during a full power takeoff below = 212 that doesn’t produce way too much drag and excess cooling at cruise.  I think I remember Tracy saying that short excursions to 230-240 will not hurt the engine.  = What happens after you reduce the power and go around the pattern?  Does the = temp start to immediately drop?  Take a couple of trips around the pattern at = cruise and see where the temp stabilizes before you start to tear your cooling = system down.

 

Bill

 

 

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Friday, May 15, = 2015 10:19 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] = Return to Flight - 2

 

Well, the = second flight occurred last night with same results as before; one short = low-level circuit due to insufficient cooling … looks like Al Wick made the = correct prediction.

There are 3 = things I can try with the current configuration: 1) Increase inlet area 2) = Increase outlet area (adjustable cowl flap) 3) Re-profile the pinched = diffuser.  I will do all 3 and see what happens.

If all of = the above show remarkable improvement then repositioning the radiator is the only alternative.

Jeff

 <= /o:p>

From: Bobby = J. Hughes [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, May 06, = 2015 12:36 PM
Subject: RE: [FlyRotary] = Re: Return to Flight

 

Al,

 <= /o:p>

“Sorry = to say, the pressure you see has no significant effect on cooling efficiency = (heat transfer). The next time you fly, since you’ve removed most of = that air, you will still see 210F. Just like = before”.

 

If the air = was trapped at the top of the heat exchanger I would expect improved temperatures. = Could be wrong.

 

Bobby = Hughes

 <= /o:p>

 <= /o:p>

 <= /o:p>

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironlin= e.net]
Sent: Wednesday, May 06, = 2015 11:15 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Return to Flight

 

Hi Jeff. = I’ve done lot’s of experimenting with cooling sys. Tough to explain all = this, but I’ll give it a try:

Pretty clear = you saw 6 psi only because you took off with 3+ cups of air in the system. If = you’d taken off with 2 cups of air, then pressure would have been 9 psi. 1 = cup, 14 psi. No air in system, then you would have seen rated cap pressure (16 = psi in your case).

 

Sorry to say, = the pressure you see has no significant effect on cooling efficiency (heat transfer). The next time you fly, since you’ve removed most of = that air, you will still see 210F. Just like before. There’s one huge = exception to that statement, that’s if you have air in sys that can’t = move to a high point out = of the flow. In that case air in sys has huge negative effect. Causes local = boiling when it passes hot areas and inflates cooling temp. =

 

You = don’t have to fly to prove these concepts. Ground running at idle is all = that’s needed. Let’s assume all air is removed. Then letting engine warm = up to 180 F will result in rapid pressure rise to 16 psi (rated cap pressure). = Fluid will exit system. With 2 cups of air in sys, that same 180F will yield = slow rise in pressure to only 9 psi. No fluid will leave sys. =

 

A good = cooling design pretends air is stuck in block, so you add a path for that air to rise = out of the block coolant flow. This is called a dynamic bleed. Air is = automatically removed from engine coolant flow. Super low risk way to fly as you no = longer care if air is in system. It’s can’t affect cooling. =

 

It’s a = bit higher risk to fly without dynamic air bleed, you just make darn sure = you purge all air from block sys prior to flight. Applying vacuum to rad cap is = great way to remove air.

 

One of the = ironies about cooling design is that air that resides above engine flow is a = safety asset. For example, your cap is highest point in sys and you have 2 cups = of air under cap. Big safety advantage simply because your pressure gage is = then a great predictor of how well your sys is doing. A leak will be detected long = before overheating. A bunch of other assets to this design. =

 

Conversely, = air in engine flow has overwhelming negative affect. Temps soar and risks boil = over.

 

Clear as mud = eh?

 

Fwiw

 

-al = wick

 

This message, and the documents attached hereto, is intended = only for the addressee and may contain privileged or confidential information. = Any unauthorized disclosure is strictly prohibited. If you have received = this message in error, please notify us immediately so that we may correct = our internal records. Please then delete the original message. Thank you. =

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