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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Never mind about what i previously said, I thought this was supposed to be a unmanned sub of some-sort. (which I will be doing at Lake Shasta as part of my business.) Uzzor2k has some on his sight as i said.
20 meters of water, with a petrol engine under my seat is to far for me to go, with out some serious $500k and personal investment of time to make sure were not getting killed or hurt. Though this is a cool idea, and here at 4HV, you'll get better answers, I think, than at other forums with radicals.
I was thinking this was a "bue-fin 21" like idea.
Carbon Rod, it looks like WeeWow is a toy maker? is that all they do?
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Sulaiman wrote ...
ultimately you have the same requirement as 'spaceships' ... energy storage density. I think liquid O2 and H2 are current 'best'.
No, the energy storage density of liquid hydrogen is fairly awful. Rockets use it because the exhaust velocity is very high, but that's not going to be useful in a submarine.
If you want high energy density LOX/Kero is much better. Actually, I think High Test Peroxide/Kero may be better still because HTP has a higher density, but I might be wrong, I know it has a better ISP density, but that's not quite the same thing.
In the context of a submarine, LOX/Kero might burn a bit hot. It might be possible to recirculate the exhaust gases around, cooling them with sea water and to remove some but not all of the carbon dioxide, dumping water overboard, and then inject more LOX and send it back around again, but it's quite complicated.
A simpler alternative is to use liquid air, but that has much lower energy density.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
Planning on have batterys for five min run at max, the motors will be induction 10kw with three, and two power settings. A Vfd drive controls one from zero to hunderd, the three from zero to hunderd percent. About the batterys, ive seen lead acid with 20C, which should give about 500mA at 12volt,2Ah, Im abit lost on what setup would work, I would like 30kw of drain for say five mins, with a 10kw genny, and have roughtly 5kw of general thrust.
Supercapactors,Sla,Lipoly,Nimh For the genny, a lister desiol engine, a custom themopile setup, a car air engine, batterys by th err m selves(no genny on board).
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
BigBad wrote ...
Sulaiman wrote ...
ultimately you have the same requirement as 'spaceships' ... energy storage density. I think liquid O2 and H2 are current 'best'.
No, the energy storage density of liquid hydrogen is fairly awful. Rockets use it because the exhaust velocity is very high, but that's not going to be useful in a submarine.
If you want high energy density LOX/Kero is much better. Actually, I think High Test Peroxide/Kero may be better still because HTP has a higher density, but I might be wrong, I know it has a better ISP density, but that's not quite the same thing.
In the context of a submarine, LOX/Kero might burn a bit hot. It might be possible to recirculate the exhaust gases around, cooling them with sea water and to remove some but not all of the carbon dioxide, dumping water overboard, and then inject more LOX and send it back around again, but it's quite complicated.
A simpler alternative is to use liquid air, but that has much lower energy density.
Liquid air is abrely a viable option. The nitrogen boils off first (which is useless for combustion) then the liquid oxygen that's left boils off and feeds nearly pure oxygen into the engine which also isn't good... A stack of car or truck batteries still looks to me like a good idea.
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
Got two battery choices, the lead acid has more storage for price, but the NiMh with the same price proable can discharge more juice at once.
For 15mins run time at 20kw, what one do you lot thing would be better, andtake up less room with wireing.
Would it be a good idea to use the metal structure as the negtive earth connection for the batterys, aswell as ground for the mains ac source, would it be better for the people inside aswell is releabile for the electronics?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Even if the lead acid has more rated capacity for the price, that will be at the C/10 or C/20 rate. For a 15 min run time, that's a 4C rate. Lead acid gets much less efficient as the rate goes up. If you want to compare two battery chemistries for cost, compare them at the rate you will be using.
Cycle life. Lead doesn't like deep discharge, more than 50% shortens its life dramatically. So you would want to install 2x rated capacity with lead acid for a similar lifetime. NimH OTOH will discharge to full depth.
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Running a petrol generator underwater with compressed air tanks
