Where do all of the combustion by-products (tars) go?
The hull speed will likely be significantly less than the velocity of the
water jet. Lots of water movement; not much momentum transfer to the hull.
Not all fuel burned is converted into propulsive energy. Viscous friction
and turbulence eats a good fraction of it. Galley Slaves may be more
efficient.
Dosidicus gigas, the Giant Humboldt squid, propels itself by "jetting'
around. It is the least energy efficient of all sea creatures in terms of
motivation and it's had eons to perfect its propulsion system.
Mark
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Rolf
Uhle
Sent: Thursday, May 26, 2011 9:41 AM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] Fw: Underwater gasification?
But it must have a big volume of pressureproof vessel inside the hull.
And if I calculate it right, the Humphrey pump delivers some 260
net kW. No idea how high it's efficiency is, shure not 100 %!
Neither how efficient a jet propulsion like this could be.
But even 260 kW are not much for a big ship with a huge vessel inside.
ICE's compress the air much more and have a higher energy density.
Sometimes beauty and virtue don't go the same way !
Rolf
Am Donnerstag, 26. Mai 2011 17:13:30 schrieb Henri Naths:
ps
I think the beauty of the a Humphrey-inspired water jet is that it would
have relatively no moving parts so it's weight to power ratio of
efficiency is better than that of other engines overcoming the friction
losses of a conventional water jet engine (as per water ski) H.
----- Original Message -----
From: Henri Naths
To: Discussion of biomass pyrolysis and gasification
Sent: Thursday, May 26, 2011 8:57 AM
Subject: Re: [Gasification] Underwater gasification?
Hi Daniel,and list
< I don't think it would be an efficient means of low speed marine
propulsion though; it would suffer from low propulsive efficiency
because
the jet velocity would be too high.> Have you considered the propulsion
end of a jet ski or a Jet Boat in your analysis . True the efficiency is
slightly lower than a straight prop boat but it is expelling a
relatively
small stream of water at a high velocity. I hear what you are saying
about
the jet engines but as I previously pointed out in a post , water has
700
times the density than that of air so you have to factor that in the
formula. Thanks
Henri
----- Original Message -----
From: Daniel Chisholm
To: Discussion of biomass pyrolysis and gasification
Sent: Sunday, May 22, 2011 5:51 PM
Subject: Re: [Gasification] Underwater gasification?
A Humphrey-inspired water jet is an interesting idea.
FWIW I don't think it would be an efficient means of low speed marine
propulsion though; it would suffer from low propulsive efficiency
because
the jet velocity would be too high. The efficiency of a reaction engine
(which is something that generates thrust by accelerating and expelling
mass - a very broad category that includes not just jet and rocket
engines
but also propellers on aircraft and ships) depends on the speed at which
the mass is expelled. Accelerating a small mass to a large speed, is
not
as efficient as accelerating a larger mass to a lesser speed. If you
look
at aircraft jet engines today (high bypass ratio turbofans) you will
notice that they are much larger in diameter than the jet engines of the
1950s (turbojets) - this is why.
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