Underwater Steam Jet

[MantaRay]

This thread is intended to carry on from this one but with more of a focus of the mechanics of the underwater steam jet (intro articles 1 and 2). Pursuit Dynamics have been developing an underwater jet engine for marine craft. They have also produced a similar machine for fire extinguishing.

The engine is simple, therefore energy efficient (no moving parts and 99.9% thermal energy of the steam is used for work). Not only does it claim to be very efficient (more efficient than propeller engines) but the fact that it runs off steam means it can be run on most other fuels other than diesel. This benefits the cost, carbon emissions and flexibility. Other benefits such as low maintenance and doing less harm to marine environment are a few amongst others. I have not found any significant cons to the engine so far.

A basic overview of the engine is found here with more detail here and the patent here.

The general principle is based on the water hammer effect. The steam is jet sprayed with high pressure into a open rear chamber where it mixes with water and air bubbles. When the steam comes in contact with the water it condenses back into water and in doing so creates a vacuum. This vacuum causes water to rush in to fill this void. This is an implosive reaction in contrast to most engines that are explosive. The reaction is directed rearward so that the jet stream creates thrust.

You can do an experiment of the hammer effect yourself (1, 2).

Few extra videos (1, 2)

I intend on building a prototype of this engine for experimental use. As soon as I get some results I will post photos/videos.

[MantaRay]

* New post as I cannot update the previous one.

Basic diagram:



Another basic diagram (same engine but different use - processing pump)

[RAMSET]

Oh how I love the hammer...

Seems quite simple [the beauty of steam !:"]

thx for sharing

☤ Physiká For Future Tesla's ☤ : Understanding Water Hammer & Cavitation (Compilation) - YouTube


Chet

[MantaRay]

I will be building a prototype today as the 6mm microbore copper pipe has arrived for the mini flash boiler. It will not be ready for testing until tomorrow though.

There are some simple toy mechanisms that use steam in a somewhat similar way to the water jet, namely the Pop-Pop boats. They simply work by heating water in a small copper coil until it turns to steam. When the steam reaches a particular temperature (above 100c) it also reaches a particular expansive pressure which causes the steam to expel from the copper pipe to behind the boat, therefore propels the toy boat forward. This expelled steam causes low pressure within the coil so at the inlet water is sucked into the coil for heating and the cycle repeats. Here is a clearer explanation of the cycle.

Unlike the steam jet I am investigating currently, the Pop-Pop boats are propelled by the expansion of steam, not the implosion. However, the boat could be modified so that it works in both ways (in theory). The current Pop-Pop boat configuration consists of the inlet and outlet being places in the same direction (fig.1). By moving the inlet to the front of the boat (fig.2) this may cause water to be sucked/pulled in from the front and expelled/pushed out the back. This configuration fits well with Newton's third law.

pop.jpg

If anyone has any experience in Pop-Pop boats or have experimented with similar ideas it could be interesting to explore it further.

[tachyon]

When there is a low pressure gradient on the front of the boat by the implosion , the higher pressure on the rear of the boat pushes the boat forward but this is not traditional jet propulsion where there is conservation of momentum acting between the expelled mass and the mass of the vehicle, the pop pop boat you say acts like jet propulsion or like the hose of your garden.

[MantaRay]

My experiments has been delayed due to a lack of a welder. No way can any glue, cement or anything non-metallic be able to deal with the temperature and pressure of the heat coming from the steam. I am in the process of building a HHO torch to help me in this project and others.

Meanwhile, good old Grant demonstrates a steam vacuum here.

[MantaRay]

Meanwhile I have been thinking about how the steam implosion could work within a piston configuration. Simply have a steam inlet that fills the piston chamber, then a cooled-water spray inlet that condenses the steam and an exhaust out let for the moisture.

It turns out there is in fact such an engine that was invented in 1712 and used as a water pump. It was invented by Thomas Newcomen in which you can see a small working model here.

This engine maybe far more powerful than a conventional steam engine due to the fact that all the heat energy from the steam is used up in the implosion - no waisted energy. The implosion also seems to have a much stronger force than the pressure used by steam in conventional engines.

I originally imagined a double acting process where in each stroke is caused by an implosive reaction. While one piston is imploding, the other piston is inleting steam which the pressure can help in the push/pull relationship (unless the pressure of the steam inlet does not have an effect but actually is sucked into the chamber due to the implosive force of the other piston.)

steamimplosionengine.jpg

A lack of tools to build a prototype of these ideas is very frustrating.

[tachyon]

you need to have a pressure differential in order for this to work it's the pressure outside of the chamber doing work NOT the implosion if you were to do this inside a vacuum space nothing would happen.

where are you going to put the piston rod? you need to create an air tight space to achieve a vacuum otherwise nothing will happen..or are you going to use a magnetic piston and use some coils to extract energy?

[MantaRay]

you need to have a pressure differential in order for this to work it's the pressure outside of the chamber doing work NOT the implosion if you were to do this inside a vacuum space nothing would happen.

where are you going to put the piston rod? you need to create an air tight space to achieve a vacuum otherwise nothing will happen..or are you going to use a magnetic piston and use some coils to extract energy?

tachton, there is a huge pressure difference between the collapsing steam on one side of the piston and the expanding steam on the other side. In usual double acting steam engines the exhaust steam is being pushed out the cylinder by the fresh working steam - so some of the work is waisted in exhausting the used steam. In the configuration I presented the new fresh steam is actually being sucked into the cylinder by the opposing collapsing steam on the other side. The unit is coherent and working together rather than against itself like in most other engines. For example, in an internal reciprocating engine, some of the work is used to compress the fuel/air mixture (and to ignite it for 2 stroke) in order to gain work. Again, with the gas turbine, some of the energy from the driving turbine is directed to the compressor turbine in order to work.

The cylinder needs to be air-tight for sure but the electrical induction unit will be outside of the cylinder in connection with the rod.

For now I am still experimenting with steam and soon I will have the tools to test the jet.

[Allcanadian]

@MantaRay
This has been tried before and there are a few reasons why it was not successful. When steam at 100 degrees C condenses to water at 100 degrees C it gives up 2257 KJ/Kg of energy. This is called Latent heat where there is a change of state but no change in temperature. So when we add a cold water spray to condense the steam this cold water absorbs the 2257 KJ/Kg of energy and ends up at a slightly higher temperature.

We could say we have turned hot steam and cold water into warm water and diffused the energy which we cannot recover. This is the hidden loss most people overlook and the reason the condensing steam engine is no longer used. Another problem is the fact that the cylinder walls which are cool from the last cycle condense the incoming steam as it enters the cylinder before it can do work. Then we lose again when the cold water spray absorbs heat given to the cylinder wall by the steam which has now condensed.

There may be ways to work around these issues but these are the main problems with this technology.

AC

[MantaRay]

@MantaRay
This has been tried before and there are a few reasons why it was not successful. When steam at 100 degrees C condenses to water at 100 degrees C it gives up 2257 KJ/Kg of energy. This is called Latent heat where there is a change of state but no change in temperature. So when we add a cold water spray to condense the steam this cold water absorbs the 2257 KJ/Kg of energy and ends up at a slightly higher temperature.

We could say we have turned hot steam and cold water into warm water and diffused the energy which we cannot recover. This is the hidden loss most people overlook and the reason the condensing steam engine is no longer used. Another problem is the fact that the cylinder walls which are cool from the last cycle condense the incoming steam as it enters the cylinder before it can do work. Then we lose again when the cold water spray absorbs heat given to the cylinder wall by the steam which has now condensed.

This issue did come to mind when I first thought of it but when I saw this video and read about the Newcomen engine I discarded the concern. However generally I agree with the theory you have described, and my priority still remains with the steam induced jet therein the theory is been put into practise (although I have not seen a working video of the underwater jet).

I am curious as to your thoughts on the jet.

My concerns of the workings of the steam induced jet is:
1. if there is not enough steam pressure entering the jet would the water be sucked up and through the steam inlet then into the boiler?
2. how does the jet create a shockwave?

[Ruphus]

I have built a pop pop boat using the simpler coil method. There isn't an inlet and and outlet. Both ends are both in and out. I didn't understand why they moved until I read that the water that is sucked back into the coil to equalize pressure actually helps with forward movement because of it's forward momentum against the coil.

Be careful with high pressure steam!!!

[philmZ]

jet engine tested?

Hi MantaRay,
Just discovered your thread when looking for a steam marine engine. Great explanations and links, thanks!
It's 5 months late but, did you experiment the engine? Is it working fine?
I wonder if it need an initial cold water flow?

[MantaRay]

Hi MantaRay,
Just discovered your thread when looking for a steam marine engine. Great explanations and links, thanks!
It's 5 months late but, did you experiment the engine? Is it working fine?
I wonder if it need an initial cold water flow?

Hi Phil. No I have not tested it to the extent I wanted due to lack of materials and tools and over time I lost some interest in the project. However, I did do some tests with the limited supplies I had.

I constructed an experimental jet using two aluminium tubes - a smaller inner tube and a larger outer tube where the outer tube tapers off at the end where the steam and water mix. It was a poor setup but it was good enough for an initial test.

Firstly I just blew into the inlet that was attached to the jet (the small acrylic hose) and observed how powerful my breath was in propelling the jet through the water. The jet moved very slowly but surely. I then attached the inlet and tried my best to attach it to an outlet of a pot of boiling water that produced some steam. After some time tweaking I finally got the steam to feed into the jet and when the steam/water mixture occurred it thrusted through the water instantaneously. My previous test with my breath just did not compare. The thrust produced by the collapsing steam felt like a shock.

I did not make any quantifiable measurements but I can tell you it works and if done properly I expect it will be very powerful. It does seem as though all the energy is literally being sucked out of the steam.

I would encourage others to give this a go. It is very fascinating to see how powerful steam is when all it's energy is being utilized for work.

[philmZ]

Thanks for your quick reply!
Hmm, interesting, do you have other photos of your setup? I think of building one too if I can
did you keep the pressure generated by the steam or was it open?
did you keep the temperature from boiling pot to jet (insulated pipe) or was it a regular pipe?