X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from zproxy.gmail.com ([64.233.162.196] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 989491 for flyrotary@lancaironline.net; Wed, 08 Jun 2005 22:46:46 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.233.162.196; envelope-from=wdleonard@gmail.com Received: by zproxy.gmail.com with SMTP id 34so430471nzf for ; Wed, 08 Jun 2005 19:46:00 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:in-reply-to:mime-version:content-type:references; b=ZAe1Aw4rBYgBZVSoXkM8FWRlFxYXaJeaY7SWWB9GmWfXoBCyccShMrP+rC09vd/7rYn+ieRMFx7NLR0/VTcYAmq7hQ7r3KhbbIwSno0Js79+WOo9VmaTopd2zshNnJBMX8Ir8S6RSCnlWLWWvDWcB+y+6TwCdSVP9TwvmdBNT+g= Received: by 10.36.74.17 with SMTP id w17mr86897nza; Wed, 08 Jun 2005 19:46:00 -0700 (PDT) Received: by 10.36.9.4 with HTTP; Wed, 8 Jun 2005 19:45:58 -0700 (PDT) Message-ID: <1c23473f050608194535b46d4a@mail.gmail.com> Date: Wed, 8 Jun 2005 19:45:58 -0700 From: David Leonard Reply-To: David Leonard To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: coolant leak In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_5201_28068504.1118285158842" References: ------=_Part_5201_28068504.1118285158842 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On 6/8/05, al p wick wrote:=20 >=20 > I've got sensors up the wazoo....some on my plane too. I record this info= =20 > every few milliseconds. Calibrated sensors. So here is what I see. > If I want my cooling system to operate at 24 psi, all I have to do is=20 > fill my swirl pot to the top with coolant. If I don't want it to see that= =20 > high pressure, I just leave around a cup of air at the top of swirl pot.= =20 > With my cup of air, it never exceeds 7 psi. Why? Air is compressible,=20 > coolant is not. > When you first fire up engine, pressure is 0, relative to atmosphere. It= =20 > takes around 8 minutes for pressure to slowly climb to 1 psi. The fluid= =20 > level starts to rise too. All pressure increase is due to expansion of=20 > coolant due to heat. Coolant is not compressible, and can greatly increas= e=20 > force against the contained cooling system.=20 > After you shut off your engine, the 7 psi gradually drops over the next= =20 > few minutes. It only takes around 12 minutes for the system to develop a= =20 > vacuum relative to atmosphere. At that point the little valve in the=20 > radiator cap opens and allows fluid or air to flow into system. (Check ou= t=20 > your rad cap, can you find both valves?) > Logically, from that point on, you can't have a pressurized system. Ther= e=20 > is no added energy supplied to the system. With one exception: If you hav= e=20 > compression leak into cooling system. But even that should have limited= =20 > duration.=20 > Also, if you had a cooling sys that was normally under pressure, then non= e=20 > of the vehicles would be able to replenish their coolant. They rely on th= e=20 > atmospheric pressure to exceed the coolant pressure 12 minutes after=20 > shutdown. That's what forces that liquid in our "overflow" bottle to ente= r=20 > radiator.=20 > I'd double check my gage calibration if seeing pressure on startup. > When I did ground testing with compression leak, this pattern would=20 > change. 1 second after full throttle, the pressure would jump to 24 psi,= =20 > fluid level max out, temperature still cold. This would last for only 5= =20 > seconds. This entrained air then had profound effect on the entire coolin= g=20 > sys. I think that was the most interesting part. >=20 > -al wick > Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 > N9032U 200+ hours on engine/airframe from Portland, Oregon > Prop construct, Subaru install, Risk assessment, Glass panel design info: > http://www.maddyhome.com/canardpages/pages/alwick/index.html > On Wed, 8 Jun 2005 18:05:23 -0700 "Al Gietzen" =20 > writes: >=20 > Some of the coolant is going to vaporize. This pressurises the system.= =20 > Some of that vapor will never go back into solution so there should be=20 > pressure in the system even when cold.=20 >=20 > Dave; this may be the weak link in your logic chain. Why would some of= =20 > the vapor not re-condense? I hope there is some other reason for the=20 > pressure. I'd hate for you to have to tear open the engine. >=20 > Al Gietzen >=20 > Ah ha, I see the error in my thinking, but it is not what you think. No= t=20 all the vapor will go back into liquid because vapor pressure of water is= =20 about 1/4 atmosphere (depending on temp of course), same with EG. Once=20 evaporated they will not go back into liquid form unless the partial=20 pressure of water is higher than that, which can never happen in a closed= =20 system. Although the volume can be quite small. My error in thinking is because most are using closed systems with a=20 standard cap. No air volume, so there is no need for vapor pressure volume.= =20 As soon as the coolant begins to cool it will have negative pressure and=20 start sucking in coolant. My system starts with about a quart of air in the pressurized expansion=20 can. This way I have an "air spring" on my coolant and even during cooler= =20 periods of flight the pressure in the system will never drop below ambient= =20 pressure. This volume of air must now hold 1/4 atmosphere of coolant vapor= =20 pressure in addition the the air that was in there to start, so the pressur= e=20 never falls even after cooling. If I were getting combustion pressure in my cooling system I think I would= =20 be boiling off my coolant PDQ. But I find that it only drops very slowly,= =20 about like in my car. But now I understand how Ed discovered his problem. --=20 Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/vp4skydoc/index.html ------=_Part_5201_28068504.1118285158842 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline

On 6/8/05, a= l p wick <alwick@juno.com>= wrote:
I've got sensors up the wazoo....some on my plane too. I record this i= nfo every few milliseconds. Calibrated sensors. So here is what I see.
 
If I want my cooling system to operate at 24 psi, all I have to do is = fill my swirl pot to the top with coolant. If I don't want it to see t= hat high pressure, I just leave around a cup of air at the top of swirl pot= . With my cup of air, it never exceeds 7 psi. Why? Air is compressible, coo= lant is not.
When you first fire up engine, pressure is 0, relative to atmosphere. = It takes around 8 minutes for pressure to slowly climb to 1 psi. The fluid = level starts to rise too. All pressure increase is due to expansion of cool= ant due to heat. Coolant is not compressible, and can greatly increase forc= e against the contained cooling system.=20
 
After you shut off your engine, the 7 psi gradually drops over th= e next few minutes. It only takes around 12 minutes for the system to devel= op a vacuum relative to atmosphere. At that point the little valve in the r= adiator cap opens and allows fluid or air to flow into system. (Check out y= our rad cap, can you find both valves?)
 Logically, from that point on, you can't have a pressurized= system. There is no added energy supplied to the system. With one exceptio= n: If you have compression leak into cooling system. But even that should h= ave limited duration.=20
Also, if you had a cooling sys that was normally under pressure, then = none of the vehicles would be able to replenish their coolant. They re= ly on the atmospheric pressure to exceed the coolant pressure 12 minutes af= ter shutdown. That's what forces that liquid in our "overflow&quo= t; bottle to enter radiator. 
 
I'd double check my  gage calibration if seeing pressure on start= up.
 
When I did ground testing with compression leak, this pattern would ch= ange. 1 second after full throttle, the pressure would jump to 24 psi, flui= d level max out, temperature still cold. This would last for only 5 seconds= . This entrained air then had profound effect on the entire cooling sys. I = think that was the most interesting part.

-al wick
Artificial intelligence in cockpit, Cozy IV powered by= stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Or= egon
Prop construct, Subaru install, Risk assessment, Glass panel design= info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
 = ;
 
 
On Wed, 8 Jun 2005 18:05:23 -0700 "Al Gietzen" <ALVentures@cox.net> writes:

<= span style=3D"FONT-SIZE: 12pt"> 

<= span style=3D"FONT-SIZE: 12pt">Some of the coolant is going to vaporize.&nb= sp; This pressurises the system.  Some of that vapor will never go bac= k into solution so there should be pressure in the system even when cold.&n= bsp;=20

 

Dave; this may be the weak link= in your logic chain.  Why would some of the vapor not re-condense?&nb= sp; I hope there is some other reason for the pressure.  I'd hate for = you to have to tear open the engine.

 

Al Gietzen

 

<= /div>
 
Ah ha, I see the error in my thinking, but it is not what you think.&n= bsp;Not all the vapor will go back into liquid because vapor pressure of wa= ter is about 1/4 atmosphere (depending on temp of course), same with EG.&nb= sp; Once evaporated they will not go back into liquid form unless the parti= al pressure of water is higher than that, which can never happen in a close= d system.  Although the volume can be quite small.
 
My error in thinking is because most are using closed systems with a s= tandard cap.  No air volume, so there is no need for vapor pressure vo= lume.  As soon as the coolant begins to cool it will have negative pre= ssure and start sucking in coolant.
 
My system starts with about a quart of air in the pressurized expansio= n can.  This way I have an "air spring" on my coolant and ev= en during cooler periods of flight the pressure in the system will never dr= op below ambient pressure.  This volume of air must now hold 1/4 atmos= phere of coolant vapor pressure in addition the the air that was in there t= o start, so the pressure never falls even after cooling.
 
If I were getting combustion pressure in my cooling system I think I w= ould be boiling off my coolant PDQ.  But I find that it only drops ver= y slowly, about like in my car.
 
But now I understand how Ed discovered his problem.

--
Dave= Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index= .html
http://memb= ers.aol.com/vp4skydoc/index.html
------=_Part_5201_28068504.1118285158842--