Mailing List flyrotary@lancaironline.net Message #623
From: Tracy Crook <lors01@msn.com>
Sender: Marvin Kaye <marv@lancaironline.net>
Subject: Re: [FlyRotary] Re: Coolant loss : One more theory.
Date: Sun, 01 Dec 2002 15:53:22 -0500
To: <flyrotary>
 
My latest thought on the surprising amount of overflow is based on the time when it occurs. 
The overflow (from the 1 qt. bottle) would occur during prolonged periods of full throttle operation and was a relatively fixed amount (2 - 3 oz).  I now hypothesize that local boiling (nucleate boiling) in the combustion chamber (CC) area of the cooling jacket is increasing the volume in the system.  Local boiling creates steam bubbles which are immediately swept away from the wall and are almost immediately condensed to liquid again because the bulk coolant temperature is well below the boiling point. 
 
The temperature of the CC wall is still above boiling point so another bubble of steam starts forming after the first is swept away.  The "life span" of these  steam bubbles is very short but at any given moment, there are thousands of them being "born". 
 
This activity stops immediately after power is reduced to the point where heat is carried away fast enough to eliminate nucleate boiling.  Volume then drops in the cooling system to normal conditions.
 
I suspect this rarely happens in a car because the engine is never at WOT for more than a few seconds.  Even race cars back off in the corners which give the CC walls a chance to cool off a bit.
 
Just another theory,

Another factor that affects the coolant volume is the expansion of the metal in the engine.  The coolant is essentially contained in an annular region around the rotors.  The inside of that annulus gets pretty hot.  Could be that the coolant capacity in the engine is decreased. 
 
I have no idea how big a factor this is, but it seems that that overall coolant "expansion" is more in a rotary.  I'd estimate that the amount of coolant that gets pushed into the catch bottle on the V-8 in my van is a pint or less.
 
Al

.Tracy and others, what is the theory behind so much liquid in the external
expansion tank? Thermal expansion of the initial coolant volume doesn't
account for such a large overflow. So is vapor building up inside? If it is
there is no longer a liquid filled system. I don't get it.
Peter


>>  Homepage:  http://www.flyrotary.com/

Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster