> Suggestion - invert what you have so the liquid is on the bottom
with
> the coolant line at the bottom of the vessel. Place the spring
on the
> air side with a shutoff valve at the base of the coolant for pre-
filling
> the unit with liquid during maintenance. The package would be at
the low
> point in the system to maintain fluid in the system. At the high
point
> in the system have a small accumulator / air bleed valve with sight
> glass - at preflight you look for trapped air in the sight glass
and
> crack the valve to let out the small amount of air. This should
not be
> regular as the constant pressure accumulator will expand and
contract
> with the 10% change in volume the system will experience every
fight.
> Ideas ?
> -dave
Dave,
I had some thoughts along those lines, i.e. coolant at the bottom, air
raises to the surface - could have a one way valve in the sealing
section
which separates the coolant from the spring/air side (top). Or
something
like a pool filter air release valve( as you say).
Question, if you have a spring do you still need air pressure?
George ( down under)
----------------------------------------------------------------------
-------------------
When I designed, tested and used this orignally, air worked out to be
the best and easiest option.
It does not rust, is easy to setup the pressures. With Springs you
have
got to find one thats suitable or have it made.
Then you have to make additonal bits to make sure you can set the
correct pressure on the coolant at operating temperature, allow for
spring travel to ensure it does not bind etc, I think you get the
idea.
Under air pressure the piston is in balance between the air and
coolant.
Cannister positioning, It is easier to let out air if the coolant
is at
the top. If a leak does occur you will now be able to see see it refer
below about plastics although if a leak does occur it will very minor
seals simply do not collapse suddenly in this design it is relatively
low temperature enviroment. I used air because it is very easy to
setup
your pressures once the engine is running at operating temperature.
I saw somebody ask about topping up or setting air pressure well a
bicycle pump works it's simple, small & light or you could one of
those 12v
operated mini compressors but it is not nessecary.
I have a done a bit a research on plastics, it is quite feasable to
make
the main tube/pipe out of specific type/s of plastics,
which are see-through. I am waiting for some extra information about
diameters available and a couple of other things.
More about the floating piston system, This design is essentially a
coolant recovery tank or very similar to an accumulator it allows the
coolant in stay IN the cooling system rather than exiting the cooling
system which is what most do atmospheric coolant recovery tanks do.
The draw back to allowing coolant to exit is that it evaporates that's
why people have to top up the "coolant reserve / coolant recovery"
tanks if you stop the evaporation of the coolant then you should not
need to top it up, unless you have a leak. Having a leak in an
aircraft
is bad. Also air in the cooling system will also eventually cause
things
like corrosion and other air related problems. The other draw back
to an atmospheric coolant type tank is that when doing various types
manoeuvres some coolant will almost certainly exit the tank.
You can use a floating piston design this way for those that do not
like
a pre-presurized system.
A cold engine will have a either zero near zero pressure in it, so
concerns about "O" rings seals being under pressure should not be a
concern at all.
An atmospheric coolant recovery system needs extra coolant to allow
for
evaporation. Not so for this design. Since the coolant does not
need to
leave the cooling system, unlike an atmospheric coolant recovery tank,
there will be no evaporation. A leak in the cooling system will be
more
easily to be detected because the floating piston will not be where it
should be. Once the coolant has lost any air that maybe in the coolant
itself it will not be reintroduced into the cooling system by air from
outside. Unless you have a leak.
There is more than one way to setup a floating piston system, for most
it will be when cold the cooling system will have either
a minimal pressure or zero.
During warm up the pressure will increase smoothly as the engine warms
up until nomal operating temp/pressure has occured.
If the cooling system goes beyond its normal rated temp it will allow
for extra expansion with the approiate increase in pressure.
As everybody is aware an increase in pressure also fights the tendancy
for cooling systems to boil. So while a blowoff valve
is needed should the worst happen, there should be time for a pilot to
do something before engine failure occurs due to overheating.
If a cooling system of 10 litres expands and increases its volumes
by an
additonal 1 litre (10% which it doesn't) of coolant at full temp then
a canister of 100 mm (4"approx) Inside Diameter x 320mm (13"approx)
long
will well and truly exceed the requirements
of the cooling system for expansion, in fact the cooling system when
cold will have either no pressure
or a minimal pressure in it, you will actually have to add some
coolant
or air to the system to ensure that you
reached an applicable operating pressure.
Therefore if the coolant in a cooling system actually expands by I
beleive somebody mentioned 7% at some stage
then for 10 litres, it represents a 700ml increase by volume so the
above length would actually be
somewhat shorter. (no need to make it longer than really needed) to
make
this design shorter simply cut the tube shorter.
For bigger engines with upto 25 litres of coolant, you could either
simply add another one of the same dimensions in parrallel,
or you could make it longer, just depends on room.
I saw the spring thing it is not required, unless you like adding
additional components
So for basically any engine unless you want to pre-pressurise it you
will always wind up with zero or near zero pressure in the cooling
system.
when it is cold. Rotary or otherwise.
Regards David Gaze
Technical Director
Corporate Systems Pty Ltd.
David, coolant capacity for my installation is between 7 and 8
quarts. Eight quarts = 7.5 liters. I am interested in buying one,
once you have completed testing. Jerry
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