I think you are missing something here Jon. When you are in a car

or a boat and your engine boils over it is not life threatening. You pull
over to the side of the road

     or row home.  Not so in an airplane. Perhaps having the boiling

temp (not necessarily the operating temp) up around 300 degrees is a safety
issue. Perhaps we can find something better than 90%, 95% or pure ethylene
glycol. I think it is a worthwhile goal.

No argument whatsoever. What I would try to address is "what might cause

the coolant to boil?" First of all, with a properly designed and operational
cooling system, it WILL NOT boil under any conditions that one will
encounter. What failure modes will cause it to boil?  (I hope others will
add to this brainstorming list...)

1. Water pump stops turning -- belt failure.

2. Water pump stops turning -- seizure or other pump mechanical failure

3. Thermostat sticks closed

4. Airflow to radiator impeded

5. Collapse of hose

6. Blockage of fluid flow with debris

7. Loss of sufficient coolant allowing pump to ventilate (NOT cavitate!)

8. Loss of system pressure (in conjunction with high power / high

altitude) due to failure of pressure cap

9. Loss of system pressure due to loss of coolant.

Will any of these be addressed by a different coolant media? Perhaps

numbers 3, 4, and

8. I think 3 could be addressed as you have proposed -- design the system

to leave the damn thing out (although I think they are pretty reliable
devices, especially if they are changed on a reasonable PM schedule). I
would guess that number 4 is pretty unlikely to occur.

Jon

That reminds me of what Jim Mederer said when we were talking about apex

seal fracture

when the turbo engines detonated. Jim said; "Well then just don't let it

detonate!" :)

A fuel pump could fail, a filter could plug or an injector could fail

causing a too lean

mixture.

Those cooling system failure modes you mentioned above are rare in our

aircraft fortunately. Most people are competent enough to handle all those
details in a very reliable manner. Those issues are straight forward and
easy to deal with. True those failure modes can lead to emergencies in the
air just like a failed fuel system.

What is common is improperly designed radiator installations and air

ducting. This leads to marginal cooling systems that tend to boil over when
ambient air temperatures hit 90 F and above.  A ten or twenty degree F
increase in the boiling temperature can be very helpful because of the rapid
rise in heat transfer with the increase in delta T.

Properly designed is the key. It is not easy to design a cooling system in

an airplane. People make mistakes and there is a lot we still don't know. We
are slowly evolving towards a properly designed cooling system but at this
rate it will take another ten years. It took the aircraft industry 50 years
starting in 1903 and cooling system design was still evolving up until the
liquid cooled aircraft engine was replaced by the turbojet. Since then other
than what we and the other alternative engine guys are doing the design
evolution has stagnated.

You would think I was asking for the moon here. I would not be a bit

surprised if many people are running their car engines with a 80% EG mixture
as we speak. These engines are not automatically catastrophically failing
because of it. All I want to do is go to a 90 or 95% mixture.

Paul Lamar

So do I understand that right? You want to raise the cooling temp
"possibilities" as high as possible, for emergency cases, but run it
generally at lower, more common temps?
What about limp-home modes for a rotary/aircraft instalation, like the
Cadillac/Northstar, which uses fuel to cool the cylinders, by not firing
them in a certain sequence. When this was new, I read in a German car
magazine, that 2 reporters actually tested this feature, right down "Death
Valley" - they would actually drain the coolant and just drive off. All they
noticed, was a warning light and lower power than with coolant. Is there a
simple way (from a programming point of view) to incorporate something like
this in e.g. Tracy's engine controllers and would it actually have any
benefit for the rotary?
I am thinking of potential problems with the unburned mixture in the (very)
hot rotary exhaust - might get a real "afterburner" there! But it might work
with just cutting out every other injection cycle....

Thomas J.

Yes. The rotary does not run well on one rotor. Firing every other
time
might work.

Paul Lamar
 
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