[PSUBS-MAILIST] Propane sub

[CWall@swri.edu]

(*chuckle*)   You guys are funny...;-)

1) I don't know where the comment about having to use pure oxygen comes
from...that's a strange one.

2) A "backfire" into a ballast tank filled with propane does....nothing.  
Propane needs air to burn, and as long as the air is purged- an operator
controlled situation- it might as well be filled with argon.   (Of course,
you'd have to be pretty damned stupid to not include a checkvalve and flame
arrestor in the plumbing. Filling and isolating a separate header fuel tank
would obviously be a good backup to prevent failure propagation.)

3) "Have" to burn the ballast tank propane in the engine before submerging? 
Please.  It's an option.  Venting will still be possible; you just don't have
to *waste* the propane if you don't want to.

4) Turbo compounding is not turbo charging.   It is energy recovery by spinning
 an exhaust turbine attached to an energy recovery device, in this case a PM
alternator.  I can't think of a good reason to turbocharge a submarine engine
(or at least, not one that is highly derated in the first place). I'm surprized
 you thought I'd suggest that, and frankly, it's a bit insulting, though you
might not think so. While full mechanical turbo compounding can lower fuel
specifics, the goal here is to use a long-life, readily available engine.  Why
drive it off it's sweet spot?  All you'd do is decrease the reliability.

5) Pneumatic compounding with a reciprocating motor would be done from the
propane tanks, not the ballast tank, and you are right- if I were trying to put
 the output directly into the carb it would be too much...so don't. Send it to
the ballast tanks- but be aware that I'm not trying to feed an engine
developing 5hp; that engine would be derated in cruise mode down to about 1/2hp
 unless I was trying to buck a current and needed to speed up. That means that
getting as little as 1/4 hp pneumatic or even less is still significant at low
cruise.  And in fact, the ideal situation would be to use the propane to
extract heat from the Honda to boost the pressure before the pneumatic stage. 
It's a win-win situation. The propane pneumatic recip can be very small-
perhaps even an external device with it's own prop. Since it can turn very
slowly and with full torque, the argument could be made that with a large prop
one could do away with the Honda altogether.  Obviously this would not get you
maximum range, but there would be something to be said for it if range didn't
matter.  And the pnemo drive could be used for other things besides propulsion.


6) As for worries that propane would be trapped in a confined space and
ignited....well, *duh*.


  C'mon, guys.   I work with this stuff day in and day out: hydrogen, propane,
DME, etc- and it just doesn't hold the terrors for me that it apparently does
for you. I respect it, but I also know that good engineering can tame it.

I'd hate to think this list is top-heavy with "nannies", but I suppose I'll
find out.  So far I'm hearing expressions of fear, but I haven't heard a single
 objection based on things I didn't already know.  I was hoping I would!  I
don't claim to be omniscient, but I take the lack of *substantial* objection to
 be an encouragement.

Hand-wringing I don't need- tell me something I don't know!

Craig Wall