Pulsed Outboard Motor?

[Axt]

Moving water is FAR more effective then moving air right, therefore I propose that if one was to put the exhaust underwater it would create a seriously powerful outboard motor.

By pushing against water there will be far more pressure in the chamber, so you would need strong valves (slow), but this is helped by using exhaust valves preventing backflow ... therefore the vacuum can only be filled by the intake air. A blast reflector helps shoot back some exhaust for a sustained pulse.

Think its workable? or is this just another idea thats been posted before........ :(

[marksteamnz]

Sorry jets don't push against air or water etc. The propelling force is due to hurling as much stuff away as fast as possible (Rockets work better in a vaccum). As an example jet boats squirt the water from the jet unit out above the water line. The New Zealand built Hamilton jet unit only worked once this was done and of course three people claim to have been the one who sugested the obvious on the vital day.

[Mike Everman]

Maybe not a jet cycle, but a water piston reciprocating cycle?

Faaascinating.

[mk]

Hello!

Nice idea, Axt!


But I think pulsejets aren't creating enough underpressure for sucking water into the engine, at least if the engine is mounted above sea/ water level. Then only the end of the tailpipe should be put slightly under water.
During the exhaust periode the water is pushed away, after first acting as a kind of "compression stage". This effect is adjustable via "diving" depth of the tailpipe end. Then air can be sucked back into the engine, but into the tailpipe as well (, when water has been pushed away), so no ignition would be necessary, at least in my way of thinking. Please correct me if I'm wrong.

[sparks]

I am sure i read somwhere about what i remember as a valveless p-jet using the pulses to pressurise a watercolumn driving the boat.
Maybe not all correct discription, but something like that.
What was interesting about it was that it was invented many years ago.
I think it was called "something"-"something"-waterpump.
Not much to go on, but theres a good chanse it was in the big valveless document on this site i saw it mentioned.

[Al Belli]

When I worked at Bowles Engineering during the mid 60's, a gentleman I worked with was trying to build a pistonless outboard motor based on the pulsejet principle. Ray Bowles was encouraging Him to try it.
While assisting him in doing some testing, He told Me about a giant waterpump somewhere in Europe that worked on the sane principle.
The pump consisted of a long underwater tunnel with a combustion chamber underground, on land, that operated with a frequency of about 30 seconds per cycle.

Has anyone heard of this, or was this guy a " space cadet " !!!!!

Al Belli

[sparks]

The only thing i can think of is a theory about the pyramids in egypt being gigantic waterpumps (reminded of some liquid-piston-stirlings i have seen).
But egypt is in north africa, so Scottys probably beamed him up by now.

[Mark]

I remember that one pulsejet patent, Bruno has it and I remember one other kind of pulse engine that used collapsing bubbles to draw the water along, I mentioned it in some previous post, it was out of an article in Popular Science or Popular Mechanics.
Mark

[Mark]

In the science article I read in the past, I wanted to clarify somewhat how it worked. It was a water pumper pulsejet, the inventor injected steam into a duct so as to produce zillions of tiny steam bubbles which collapsed/cooled and created a vacuum of sorts.
In some vague way this reminds me of the little putt putt boats that vaporize water into steam in a tiny copper tubing, and then a backflow of water races in the tube and then re-vaporizes into steam. To me this is kind of the same effect, but also a variation on a theme with lots of surface area for the steam bubbles to cool and collapse quickly.
Mark

[Bruno Ogorelec]

Axt,

You need to push water backwards, while your engine would essentially push gas backwards. The gas would only pass through water instead of through air.

What you need to do is encase the lower (horizontal) part of your L-tube in a larger diameter water tube open in front and in the back. You don't need check valves at the back! You want the horizontal tube to be filled with water at all times.

That way, gas will push against the water and use it as the propulsion medium. A kind of two-medium ejector.

Here's an illustration from an old patent application for this.

I have also included a diagram of a putt-putt boat engine made the man who made the toy putt-putt boats popular in the US a long time ago. It is not a pulsejet, but it's interesting, nevertheless. He actually built a man-sized boat that worked well. As you can see, that one requires a check valve where the water enters and another where it exits.

The only problem -- people say -- was that it was not particularly better that the other ways of propelling your boat along. That's the case of many ideas of this kind. They work, but they are not sensationally better than what we already have.

[Mike Everman]

Sure is simpler than an IC engine. Was it too loud or unreliable?

[Viv]

Was it too loud ?

Only for the fish:-)

Viv

[yipster]

You want the horizontal tube to be filled with water at all times.

saw the pic off the pulse piston before, interesting but i still wonder if a submerged water pulse/jet wouldnt work directly on steam. perhaps efficiently hydrolising the hot exhoust steam making its H2 and O fuel. exess steam heat (thousends celsius) may pulse in vented water for a greater displacement volume. any thoughts on something like that?

[Bruno Ogorelec]

efficiently hydrolising the hot exhoust steam cycle in its H2 and O fuel.

Nothing efficient about it. Breaking water apart into hydrogen and oxygen by heat requires more energy than you get from burning hydrogen as fuel. It would not a power producer, but consumer.

[yipster]

Bruno thanks for the quik reply, you beat me in editting my text :) yes it would be a power consumer, i was not refering to a overunity device. only know hydrolising steam is more efficient than cold water and thought specially for a boat H and O may be powerfull fuel. direct steam jet/pulse propulsion dont stand against piston, turbine unless going plasmodail? http://ippex.pppl.gov/