I watched the animation, and I see where the misunderstanding is. My "nozzle" is SMALLER than the pipe leading to it. Think of it as putting your finger over the end of the hose.
-----Original Message-----
From: Joseph Perkel <joeperkel@hotmail.com>
To: personal_submersibles@psubs.org
Sent: Sat, 08 Apr 2006 20:50:29 +0000
Subject: Re: [PSUBS-MAILIST] motor thought
"Nozzles increase fluid velocity, but decrease pressure"
Bernoulli's Principle, here's a link to an animation...I really have nothing to do at work today!!
Joe
From: "Sean T. Stevenson" <cast55@telus.net>
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] motor thought
Date: Sat, 08 Apr 2006 14:12:34 -0400
>Nitpick: Nozzles increase fluid velocity, but decrease pressure
>(i.e. from pump pressure to ambient). Conversely, diffusers
>increase pressure at the expense of velocity.
>
>-Sean
>
>
>RiskEverything21@aol.com wrote:
>
>>In response to Bill Atkins:
>> Water doesn't compress. The pump simply sucks water in and
>>increases it's velocity. The nozel then decreases the apeture which
>>creates pressure as the large volume of water increases speed to
>>get out of the smaller opening.
>> Since water doesn't compress, the pump can suck and blow just as
>>efficiently at 1,000ft as 10ft. Certain other fluids have been
>>created that do not compress, but also lubricate and protect. These
>>hydraulic fluids would be the best thing to seal an electric motor
>>at depth. As long as the seal can keep the fluid in at sea-level,
>>it should be capable of doing the same when submerged. Then a seal
>>much like a dripless packing tube found on inboard-powered boats
>>may be an adequate seal.
>> I would still rather have two pumps on board, in case one failed,
>>and to give added manueverabilty. Also I'd want to be able to aim
>>the nozels.
>> My question, however, is this- would a jet stream be as efficient
>>as a propeller AT SLOW SPEEDS? The benefit of a propeller is that
>>it can be tuned to the work it is doing. Angle, pitch, diameter- a
>>psub like ours will have a lot of resistance and won'!
t be ver
y
>>fast.
>> That being said, consider this: A hydraulic pump mounted inside
>>the hull, driven by an electric motor. This pump works on a
>>closed-system, and recirculates hydraulic fluid which drives
>>propellers. Again, I'd choose two pumps (one for each side, which
>>provision to drive both props off just one pump), for added safety
>>and manueverabiltiy. You don't have to pressure-compensate
>>anything, and no moving parts are exiting the main hull, just a few
>>pipes with cut-off valves.
>
>
>
>
>
>
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