In a message dated 12/19/2009 2:34:25 P.M. Pacific Standard Time,
ojaivalleybeefarm@dslextreme.com writes:
Hi All,
I'm looking into schemes to handle the intake and
exhaust
Hi Brian. Not expert advice but just a couple thoughts.
I think I remember hearing about a double valve system on the
application. There was a poppet valve to prevent "splash" from getting sucked
into the intake side, and it makes sense to have a similar set-up on the
exhaust.
There was a hard "gate" valve for actual diving to lock out the pipes
much like any other hull penetration.
These valves were coupled with a "drain" bypass to dump any water that
gets in there before starting up the motor. Maybe like a water trap on a
compressed air system in a shop.
Depending on how deep you go, the intake and exhaust "pipes" need to be
sufficiently thick to withstand the pressure.
The water cooling system also has a set of valves to "lock-out" the
system when submerging.
If the fuel system is diesel then you need a means of evacuating water
from the lines, as the environment will be conducive to condensation with the
heating and cooling cycles experienced between surface ops and submerged ops.
Big temperature changes there.
A diesel motor vibrates and the vibration would need to be isolated
from the hard piped thru-hulls.
On the exhaust side, the temperature changes from a "long run time" to
"shut off and submerging" will make the exhaust pipe exposed to salt water
corrode fairly quickly. The exposed parts will need to be designed for
replacement when they get corroded. Even if it's stainless, the many cycles
from hot to cold will reduce the anti-corrosion properties of the metal.
Bolt-up stuff so it can be replaced without using a torch and welder.
The valves on the exhaust side will need to have seats and seals that can
take the many heat cycles.
It's fairly complicated but should be do-able.
On my little boat, I'm going with an outboard motor that will be mounted
and un-mounted so no extra thru-hulls are needed. The steering is controlled
by the same actuator that controls the submerged steering rudders. Throttle
will be another simple actuator or maybe just a quick disconnect cable running
through a small ( 3/8 inch ) thru-hull with a ball valve.
The outboard is small enough to fit through the hatch, and the fuel tank
( gasoline ) will be small too.
A 20 horse Mercury outboard looks to just fit, and is light enough
to pick up easily.
Typically the outboard will not be carried inside the sub but I want it
to fit just in case. I expect to always have a surface boat with me, unless
it's just playing around in a lake for the day. The outboard would be
un-mounted from the sub and placed in the surface boat when diving.
I've often thought about how to add a diesel powered "module" to my sub
that would be more or less self contained in it's own pressure vessel but
connected by a couple of electrical thru-hulls for engine controls and
system monitoring. In the current design it would be basically a pressure
vessel split in half with mating flanges, hard valves on
intake/exhaust/cooling water, and the prop would be on a magnetic
coupler.
Of course, being the dreamer that I am, the concept quickly evolved into
a pressure cabin, fuel tanks, gen set, extra battery banks, bunks, galley, and
head stretching the thing to 24 feet long !
I think I showed you the concept sketch once when you visited.
Anyway, good luck with the diesel and keep us informed as the design
progresses. It sounds very interesting.
Frank D.