X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from hub026-NJ-7.exch026.serverdata.net ([206.225.166.170] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6507577 for flyrotary@lancaironline.net; Tue, 08 Oct 2013 21:08:34 -0400 Received-SPF: none receiver=logan.com; client-ip=206.225.166.170; envelope-from=jwhaley@datacast.com Received: from MBX026-E1-NJ-6.exch026.domain.local ([10.240.14.56]) by HUB026-NJ-7.exch026.domain.local ([10.240.14.233]) with mapi id 14.03.0123.003; Tue, 8 Oct 2013 18:07:59 -0700 From: Jeff Whaley To: 'Rotary motors in aircraft' Subject: RE: [FlyRotary] : Multiple coolant pressure Caps Thread-Topic: [FlyRotary] : Multiple coolant pressure Caps Thread-Index: Ac7EirKr1GAgS2lIR0m4u+GP3NK5hQ== Date: Wed, 9 Oct 2013 01:07:57 +0000 Message-ID: <234B758DE9A64449BEB6BB5D1345CA7A3611DF29@mbx026-e1-nj-6.exch026.domain.local> Accept-Language: en-CA, en-US Content-Language: en-CA X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [204.237.115.3] Content-Type: multipart/alternative; boundary="_000_234B758DE9A64449BEB6BB5D1345CA7A3611DF29mbx026e1nj6exch_" MIME-Version: 1.0 --_000_234B758DE9A64449BEB6BB5D1345CA7A3611DF29mbx026e1nj6exch_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Rich: Thanks for the detailed technical response; I'm with you on all the aspects= except for the no-sense multiple caps (maybe a little) as others have expr= essed success with such a setup. For clarity, my expansion tank is actuall= y a swirl pot that is kept 1/3 full of liquid with the rest being air, whic= h is why I call it an expansion tank. From the filler neck of this tank, I= overflow into a non pressurized plastic bottle kept 1/3 full of coolant wh= en cold. As long as this pressure cap is lower than a second cap attached = to the radiator it will continue to control the system pressure as it did b= efore when my radiator had no filler neck or pressure cap - a solid radiat= or with in/out hoses only. I like Bill's system as it closely matches what= I had before - I shall strive to reproduce it - and it will have only 1 pr= essure cap. Jeff From: ARGOLDMAN@aol.com Subject: Re: [FlyRotary] Re: Multiple coollant pressure Caps Date: Tue, 8 Oct 2013 16:58:00 -0400 (EDT) To: flyrotary@lancaironline.net [Message Header] [Undecoded Message] Jeff Interesting conversation about pressure cap(s). Pressure in a coolant syste= m seems to be crated by two phenomena, one being the vapor pressure of the = coolant as the liquid heats up and the other being the expansion of the liq= uid, itself, due to the increased heat. Our rotaries are much more susceptible to thermal damage than are our pisto= n brethren in that at a given temperature (220* of so) we risk damaging som= e of our sealing "O" rings and resultant leakage. It would seem like the he= at transfer from the coolant to the air is of prime importance to keep the = temperatures in the "safe" range. Increased pressure caps, while perhaps co= nstraining the pressure created, also allow the heat carried by the coolant= to be higher before creating a gaseous state (steam). Because of our coolant temperature restraints, the cap pressure relief shou= ld be chosen somewhat carefully. It's purpose is to release pressure and ke= ep the system from blowing up. As the temp, and thus the pressure increases= ,when the cap valve opens, the remainder is sent to the overflow tank (if o= ne is present), or blown overboard. With an overflow tank, in the system, there is no air in the system and as = the water expands the pressure cap will restrain and allow the pressure to = increase until the cap setting is reached at which point it will open somew= hat allowing coolant to overflow into the overflow tank. The amount overflo= wed will be dependant on the volumetric increase when the engine gets to it= s hottest temp. (again this is with a system that has no air in the coolant= loop. The overflow tank is usually (at least in automobiles) made of plast= ic and does not have a pressure cap. As coolant is squirted into it, the ai= r in the tank is vented to atmosphere. Now when the engine cools down and the pressure decreases, the cap (actuall= y 2 valves) allows some of the overflowed coolant to reenter the system so = that there never is (or should be air in the loop) The overflow tank is fil= led from the bottom and thus when the pressure decreases, it will suck (act= ually the coolant is pushed by atmospheric pressure) back into it. That's w= hy you must maintain a certain level of water in the overflow tank even whe= n the engine is cool. There is an alternate system which does not use an overflow tank but uses a= n expansion tank which itself is 1/2 or so filled with air. (the rest with = coolant). This tank feeds, as a header into the pump intake and is at the s= ame pressure as the system. As the water volume increases due to heat, it c= ompresses the air in the expansion tank in proportion to the pressure, thus= no need for the overflow tank. Even though the pressure in this tank is th= e same as general pressure, because the pressure downstream of the pump is = greater, it is a great place to dump the fluid used to heat the aircraft. I= also use a couple of small vents from the high part of the radiator and en= gine to vent any gas (steam) that might form or collect there. With this sy= stem, the pump always sees a head of coolant, in addition to that circulati= ng which might have the effect of decreasing the possibility of cavitation. The pressure cap here serves only to protect the tubing, radiator and "O" r= ings from over pressure. The trick is to control the temp with the radiator. A good place to start f= or the pressure setting is to use what Mazda recommends for their engine. (= they probably know a little more about the pressure and temperature constra= ints than we do. Increasing the pressure cap rating may, although treating = the symptom, be counterproductive.--- Or not 2 pressure caps make no sense. Rich This message, and the documents attached hereto, is intended only for the a= ddressee and may contain privileged or confidential information. Any unauth= orized 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. --_000_234B758DE9A64449BEB6BB5D1345CA7A3611DF29mbx026e1nj6exch_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Rich:

Thanks for the detailed technical response; I'm with you on all the aspe= cts except for the no-sense multiple caps (maybe a little) as others have e= xpressed success with such a setup.  For clarity, my expansion tank is= actually a swirl pot that is kept 1/3 full of liquid with the rest being air, which is why I call it an expansio= n tank.  From the filler neck of this tank, I overflow into a non pres= surized plastic bottle kept 1/3 full of coolant when cold.  As long as= this pressure cap is lower than a second cap attached to the radiator it will continue to control the system pressu= re as it did before when my radiator had no filler neck or pressure cap -&n= bsp; a solid radiator with in/out hoses only.  I like Bill's system&nb= sp;as it closely matches what I had before - I shall strive to reproduce it - and it will have only 1 pressure cap.

Jeff 

 

From: ARGOLDMAN@aol.com
Subject: Re: [FlyRotary] Re: Multiple coollant pressure = Caps
Date: Tue, 8 Oct 2013 16:58:00 -0400 (EDT)
To: flyrotary@lancaironline.net
3D"Message

3D"Undecoded
Jeff
Interesting conversation about pressure cap(s). Pressure in a coolant = system seems to be crated by two phenomena, one being the vapor pressure of= the coolant as the liquid heats up and the other being the expansion of th= e liquid, itself, due to the increased heat.
Our rotaries are much more susceptible to thermal damage than are our = piston brethren in that at a given temperature (220* of so) we risk damagin= g some of our sealing "O" rings and resultant leakage. It would s= eem like the heat transfer from the coolant to the air is of prime importance to keep the temperatures in the "sa= fe" range. Increased pressure caps, while perhaps constraining the pre= ssure created, also allow the heat carried by the coolant to be higher befo= re creating a gaseous state (steam).
Because of our coolant temperature restraints, the cap pressure relief= should be chosen somewhat carefully. It's purpose is to release pressure a= nd keep the system from blowing up. As the temp, and thus the pressure incr= eases,when the cap valve opens, the remainder is sent to the overflow tank (if one is present), or blown o= verboard.
With an overflow tank, in the system, there is no air in the system an= d as the water expands the pressure cap will restrain and allow the pressur= e to increase until the cap setting is reached at which point it will open = somewhat allowing coolant to overflow into the overflow tank. The amount overflowed will be dependant on the vol= umetric increase when the engine gets to its hottest temp. (again this is w= ith a system that has no air in the coolant loop. The overflow tank is usua= lly (at least in automobiles) made of plastic and does not have a pressure cap. As coolant is squirted into i= t, the air in the tank is vented to atmosphere.
Now when the engine cools down and the pressure decreases, the cap (ac= tually 2 valves) allows some of the overflowed coolant to reenter the syste= m so that there never is (or should be air in the loop) The overflow tank i= s filled from the bottom and thus when the pressure decreases, it will suck (actually the coolant is pushed = by atmospheric pressure) back into it. That's why you must maintain a certa= in level of water in the overflow tank even when the engine is cool.
There is an alternate system which does not use an overflow tank but u= ses an expansion tank which itself is 1/2 or so filled with air. (the rest = with coolant). This tank feeds, as a header into the pump intake and is at = the same pressure as the system. As the water volume increases due to heat, it compresses the air in the ex= pansion tank in proportion to the pressure, thus no need for the overflow t= ank. Even though the pressure in this tank is the same as general pressure,= because the pressure downstream of the pump is greater, it is a great place to dump the fluid used to heat= the aircraft. I also use a couple of small vents from the high part of the= radiator and engine to vent any gas (steam) that might form or collect the= re. With this system, the pump always sees a head of coolant, in addition to that circulating which might have t= he effect of decreasing the possibility of cavitation.
The pressure cap here serves only to protect the tubing, radiator and = "O" rings from over pressure.
The trick is to control the temp with the radiator. A good place to st= art for the pressure setting is to use what Mazda recommends for their engi= ne. (they probably know a little more about the pressure and temperature co= nstraints than we do. Increasing the pressure cap rating may, although treating the symptom, be counterprod= uctive.--- Or not
2 pressure caps make no sense.
Rich

This message, and the documents attached hereto, is intended only for the a= ddressee and may contain privileged or confidential information. Any unauth= orized 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 origin= al message. Thank you. --_000_234B758DE9A64449BEB6BB5D1345CA7A3611DF29mbx026e1nj6exch_--