X-Virus-Scanned: clean according to Sophos on Logan.com From: "David Leonard" Received: from mail-qa0-f45.google.com ([209.85.216.45] verified) by logan.com (CommuniGate Pro SMTP 6.1c3) with ESMTPS id 7452258 for flyrotary@lancaironline.net; Fri, 30 Jan 2015 14:55:13 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.216.45; envelope-from=wdleonard@gmail.com Received: by mail-qa0-f45.google.com with SMTP id n8so21460213qaq.4 for ; Fri, 30 Jan 2015 11:54:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=+UJOD/6LWNdRwP4clYymCS8mwOBkVLDDbRDgLRbW3/c=; b=Nc4xb2ugsoDbvYrcWChiS300dtH+sMQkniXvbpxBoWRp/TnI52nwSunBMzgk/OIrdw dwJusLR2In1o4cVXfgRbe16pABmn9Wzv/QnEZ3H7WUXkDVe4jbUrxg0+YTjQT2XtnVO4 VHc8jiEyd0fyce0K+SY4WoEBX2FXGFRzSjb+8YH04obYHAphVG/sfCGcIUt2JCPXAhtO tU4uEW8xPfydFkR7wCT5cgslq0bdn5tGxD68hYcFVCDqHSTdd204JB1+Qbt9e/rRMwvb 5fB/QLHnu0+54sFD7s7iTayPXFKeYoNAAvjJozI0vmSmn2G+rq98JN6MbuCDaIBlZwv8 ds7w== MIME-Version: 1.0 X-Received: by 10.224.75.71 with SMTP id x7mr15847903qaj.90.1422647677275; Fri, 30 Jan 2015 11:54:37 -0800 (PST) Received: by 10.140.104.82 with HTTP; Fri, 30 Jan 2015 11:54:37 -0800 (PST) In-Reply-To: References: Date: Fri, 30 Jan 2015 11:54:37 -0800 Message-ID: Subject: Re: [FlyRotary] Re: swirl / expansion tank configuration To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=001a11c304b271d4bc050de3f952 --001a11c304b271d4bc050de3f952 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Steve, That is a great description of the 2 main types of systems. FWIW, my system has evolved through both and I have settled on having the second type, an air volume in the reservoir and no overflow tank. I keep a couple inches of coolant in the bottom of the 1 qt reservoir when cold. That allows enough room for expansion and also allows a visual check of coolant level. I also pre-pressurize that volume with my Mounted Omnipresent Under Tooth Huffer (MOUTH) via a hose to the overflow fitting (just a couple of PSI). That allows me to verify the ability of the system to retain pressure prior to start up. In a system without the air volume, as soon as the engine cools down a little the pressure in the system quickly drops to zero as coolant is sucked back in. So you never know if the loss of pressure is from engine cooling or a newly sprung leak. The alarm also makes passengers nervous. So I have found that I like the "air spring" approach much more. David Leonard Turbo Rotary RV-6, N4VY On Thu, Jan 29, 2015 at 1:19 PM, Steven W. Boese < flyrotary@lancaironline.net> wrote: > =E2=80=8B=E2=80=8BBill, > > > The peak in temperature and pressure at around 25 minutes is due to the > climb. The peaks at about 65 minutes are due to slow flight, the first > with no flaps and the second (highest) peak with full flaps. > > > The lower density of the air at high altitude does have a negative > effect on cooling since it is the mass of air passing through the heat > exchangers per unit time that affects the cooling more so than just the > velocity. This is compensated by the lower amount of power that can be > produced at high altitude with the normally aspirated engine. Also, as y= ou > note, the OAT normally decreases with altitude which also helps. My > experience is that if the cooling system is adequate at low altitude, it > will also be adequate high altitude because of the offsetting factors. > > > With my system, one pint of airspace is not sufficient to prevent > coolant from exiting the overflow. If the airspace is too small, the fir= st > time the system is taken to operating conditions coolant will be > expelled and the entire system will be filled with coolant. Without an > overflow bottle, when the system cools off, air is drawn into the system > through the overflow, establishing an air volume in the expansion tank ju= st > sufficient to accommodate that operating condition. Subsequent operation > at that same or less stressful operating condition would not expel coolan= t > from the overflow. In other words, the air volume in the expansion tank > will reflect the most stressful operating condition encountered. One wou= ld > expect to see evidence of overflow of coolant if it occurred. > > > As far as whether to provide additional air space in the expansion > tank, it depends on how you want the system to operate. If you want the > system to operate at the filler cap pressure whenever the overall coolant > temperature is increasing, fill the expansion tank all the way. Provide = an > overflow bottle with sufficient volume to accommodate the expansion of th= e > coolant and set things up to draw the expelled coolant back into the > expansion tank when the system cools down. With this setup, the pressure > observed when the overall coolant temperature starts to drop will be more= a > function of the vapor pressure of the coolant than a function of the fill= er > cap relief pressure. Pressure changes will be more pronounced with this > type of system. > > > If you want the pressure in the expansion tank to change more gradually > with overall coolant temperature changes, then provide an air volume in t= he > expansion tank greater than the volume change of the coolant due to > heating. An overflow bottle would not be required then. > > > As far as I know, either system works. A possible advantage to the > first setup is that no air is introduced into the system as a result of > thermal cycling. Keeping oxygen out of the system may reduce the chance > for corrosion. My system has an overflow bottle even though the air volu= me > in the expansion tank should be sufficient to accommodate the expansion o= f > the coolant. This provides a record of anomalous coolant expansion and i= s > probably just an indication of my paranoia. I remove the filler cap befo= re > each flight to check the coolant level. As a result, keeping oxygen from > entering the system is not an option. > > > > Steve > ------------------------------ > *From:* Rotary motors in aircraft on behalf > of Bill Bradburry > *Sent:* Thursday, January 29, 2015 1:05 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: swirl / expansion tank configuration > > > Thanks, Steve. > > > > What was going on when the water temp and pressure spiked? Was this > during the climb up to 11.5K? The OAT was pretty low..~40 degrees, does > the thin air have that much of a negative effect on cooling? I am a > flatlander and have never had occasion to get up that high. :>( > > > > I am leaving about a pint or so of air in the top of my expansion tank. > The pressure goes to the cap pressure and is pretty stable there. I wond= er > if I should leave more space? I have never noticed any leakage of coolan= t > out of the overflow, but it goes overboard if it leaks, and I should see > coolant residue I think. > > > > Bill > > > ------------------------------ > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > *Sent:* Thursday, January 29, 2015 11:34 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: swirl / expansion tank configuration > > > > =E2=80=8BBill, > > > > Attached is a plot of coolant temperature, coolant pressure, outside air > temperature, and IAS for a recent flight. The flight consisted of two > touch and go's, a climb from 7200 ft to 11,500 ft MSL, a series of stalls= , > slow flight, steep turns, and a descent to landing. A stock type > thermostat is used and a 14 psi cap is installed on the expansion tank > which has at least a quart of air space when cold. > > > > Steve Boese > > RV6A, 1986 13B NA, RD1A, EC2 > --001a11c304b271d4bc050de3f952 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Steve,

That is a great description of t= he 2 main types of systems.=C2=A0 FWIW, my system has evolved through both = and I have settled on having the second type, an air volume in the reservoi= r and no overflow tank.=C2=A0 I keep a couple inches of coolant in the bott= om of the 1 qt reservoir when cold. That allows enough room for expansion a= nd also allows a visual check of coolant level.=C2=A0 I also pre-pressurize= that volume with my Mounted Omnipresent Under Tooth Huffer (MOUTH) via a h= ose to the overflow fitting (just a couple of PSI).=C2=A0 That allows me to= verify the ability of the system to retain pressure prior to start up.

In a system without the air volume, as soon as the en= gine cools down a little the pressure in the system quickly drops to zero a= s coolant is sucked back in.=C2=A0 So you never know if the loss of pressur= e is from engine cooling or a newly sprung leak.=C2=A0 The alarm also makes= passengers nervous.=C2=A0 So I have found that I like the "air spring= " approach much more. =C2=A0

David Leonard
Turbo Rotary RV-6, N4VY

<= div class=3D"gmail_quote">On Thu, Jan 29, 2015 at 1:19 PM, Steven W. Boese = <flyrotary@lancaironline.net> wrote:

=E2=80=8B=E2=80=8BBill,


The peak in temperature and pressure at around 25 minutes is due to the = climb.=C2=A0 The peaks at about 65 minutes are due to slow flight, the firs= t with no flaps and the second (highest) peak with full flaps.


The lower density of the air at high altitude does have a negative effec= t on cooling since it is the mass of air passing through the heat exchanger= s per unit time that affects the cooling more so than just the velocity.=C2= =A0 This is compensated by the lower amount of power that can be produced at high altitude with the normally as= pirated engine.=C2=A0 Also, as you note, the OAT=C2=A0normally decreases wi= th altitude which also helps.=C2=A0 My experience is that=C2=A0if the=C2=A0= cooling system is adequate at low altitude, it will also be adequate high altitude because of the offsetting factors.


With my system, one pint of airspace is not sufficient to prevent coolan= t from exiting the overflow.=C2=A0 If the airspace is too small, the first = time the system is taken to operating conditions coolant will be expelled= =C2=A0and the entire system=C2=A0will be=C2=A0filled with coolant.=C2=A0 Without an overflow bottle, when the system cools off, air = is drawn into the system through the overflow, establishing an air volume i= n the expansion tank just sufficient to accommodate that operating conditio= n.=C2=A0 Subsequent operation at that same or less stressful operating condition would not expel coolant from the ove= rflow.=C2=A0 In other words, the=C2=A0air volume in the expansion tank will= reflect the most stressful operating condition encountered.=C2=A0 One woul= d expect to see evidence of overflow of coolant if it occurred.


=C2=A0As far as whether to provide additional air space in the expansion= tank, it depends on how you want the system to operate.=C2=A0 If you want = the system to operate at the filler cap pressure whenever the overall coola= nt temperature is increasing, fill the expansion tank all the way.=C2=A0 Provide an overflow bottle with sufficient volume = to accommodate the expansion of the coolant and set things=C2=A0up to draw = the expelled coolant back into the expansion tank when the system cools dow= n.=C2=A0 With this setup, the pressure observed when the overall coolant temperature starts to drop will be more a functio= n of the vapor pressure of the coolant than a function of the filler cap re= lief pressure.=C2=A0 Pressure changes will be more pronounced with this typ= e of system.


If you want the pressure in the expansion tank to change more gradually = with overall coolant temperature changes, then provide an air volume in the= expansion tank greater than the volume change of the coolant due to heatin= g.=C2=A0 An overflow bottle would not be required then.


As far as I know, either system works.=C2=A0 A possible advantage to the= first setup is that no air is introduced into the system as a result of th= ermal cycling.=C2=A0=C2=A0Keeping oxygen out of the system=C2=A0may reduce = the chance for corrosion.=C2=A0 My system has an overflow bottle even though the air volume in the expansion tank should be sufficie= nt to accommodate the expansion of the coolant.=C2=A0 This provides a recor= d of anomalous coolant expansion and is probably just an indication of my p= aranoia.=C2=A0 I remove the filler cap before each flight=C2=A0to check the coolant level.=C2=A0 As a result,=C2=A0keepi= ng oxygen from entering the system is not an option.=C2=A0

=C2=A0=C2=A0=C2=A0

Steve=C2=A0

From: Rotary motors in aircraft <flyrotary@lancaironlin= e.net> on behalf of Bill Bradburry <flyrotary@lancaironline.net>
Sent: Thursday, January 29, 2015 1:05 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: swirl / expansion tank configuration=
=C2=A0

Thanks, Steve.

=C2=A0

What was going on when the wate= r temp and pressure spiked?=C2=A0 Was this during the climb up to 11.5K?=C2= =A0 The OAT was pretty low..~40 degrees, does the thin air have that much of a negative effect on cooling?=C2=A0 I = am a flatlander and have never had occasion to get up that high.=C2=A0 :>= ;(

=C2=A0

I am leaving about a pint or so= of air in the top of my expansion tank.=C2=A0 The pressure goes to the cap= pressure and is pretty stable there.=C2=A0 I wonder if I should leave more space?=C2=A0 I have never not= iced any leakage of coolant out of the overflow, but it goes overboard if i= t leaks, and I should see coolant residue I think.

=C2=A0

Bill

=C2=A0

From: Rotary motor= s in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Thursday, January 29, = 2015 11:34 AM
To: Rotary motors in aircraf= t
Subject: [FlyRotary] Re: swi= rl / expansion tank configuration

=C2=A0

=E2=80=8BBill,

=C2= =A0

Attac= hed is a plot of coolant temperature, coolant pressure,=C2=A0outside air te= mperature, and IAS for a recent flight.=C2=A0 The flight consisted of two touch and go's, a climb from 7200 ft to 11= ,500 ft MSL, a series of stalls, slow flight, steep turns, and a descent to= landing.=C2=A0 A stock type thermostat is=C2=A0used and a 14 psi cap is in= stalled on the expansion tank which has at least a quart of air space when cold.

=C2= =A0

= Steve Boese

= RV6A, 1986 13B NA, RD1A, EC2


--001a11c304b271d4bc050de3f952--