Steam jet propulsion

[Steinbrei]

Hi guys,

I was wondering weather anybody out their has already done some steps twoards trying this out in small scale (rc). I'm thinking of the PDX pursuit dynamics steam jet whatever pumping thing.

An imidiate overview of what I'm thinking off can be found here:
www.tfd.chalmers.se/~valeri/Ajax/design.pdf

Try pdx and steamjet and google and you'll get some off more or less qualified information/gibberish on the subject.

Anyway, sounds like a fun thing to play with. Any thermodynamatishians out there that would like to go wild on that field? I less adept at this subject...

Concerning the realiization of such a project: a question to the steamers (I assume there are such modellers out there, even though I haven't done any searches in this direction). How would the hell of boiler look like (for example run on alcohol?)

Go wild guys, lets le what comes of it ;-)

[Capt_Christo]

Gas fired water tube boiler is more efficient for its size, especially in the scales we are talking about as long as the load is reasonably constant. This is because water heats up much quicker in a tube than in a drum and the tube can withstand a much higher higher pressure. Also if a tube fails it is less catastrophic as the steam vents to the fire box and not to the atmosphere as would a fire tube boiler. The flow rate and required pressure would determine the exact boiler specification.

[Steinbrei]

Ok, I'll reread the material and see if I could come up with a flowrate and preasure. Were on the right way. All it would need is a small boiler, and some sort of feeding mechanism. The steam would then go directly to jet, which if made properly should do the job.

[RGinCanada]

The steam jet engine seems to be a very clever design. The obstacles that I see to implementing it in scale is the need for a fairly large reservoir of fresh distilled water, and the size of the boiler.

(I'm sure you already know this, but from what I've read, steam boilers, especially scale ones do not like hard fresh water, and sea water is even worse)

[martin richards]

If you're thinking of something like flash steam, you could try http://www.steamboat.org.uk

[Steinbrei]

What would flash steam be?

Concerning the watersupply: I could test the water I have here, by boiling some in a pot and see what kind and amount of whatever remaines in the pot. A tube shaped boiler that you could open on both ends and scrub through with steal wool could take fresh water I assume. Not talking about salt water here. Where would remains typically cause problems?

[Tony Oliver]

Flash steam is an unbelievably violent form of propulsion - water is pumped into a red/ orange-hot coil of tubing and the resultant steam - lots of it - is passed through a reciprocating engine of some sort or a turbine. The props are impossibly high pitch and some high speed launch system is needed - like a bungee - to get the missile underway. They are used here in the UK at a few meetings each year for speed running only. They are tethered.The noise is indescribable, loud, and music to the ears of engine users.

As good as pulsejets.

[Steinbrei]

Red hot Metal + Water,... Ouch! I can imagine that will do some violent stuff. But combining that with a reciprocating engine sounds like complicated machinery again. What appeals to me is this rather simple looking outlay. The fact that they did all this research at the universitys of course suggests that it is not simple at all. As a matter of a fact rather impossible to really reporduce this effect at our scale. I assume the chance you end up with a pipe making bubbles in the water is about >95%. There are some hints concerning the nozzle shape:
"The pressure gradient across the nozzles accelerates steam to supersonic speeds thus transferring the internal energy to kinetic energy. The low mass, high velocity steam has a certain kinetic energy (hence momentum) which must be imparted to the driven fluid (secondary fluid). "
I'll post some more links. This PDF I posted earlier is to much efficency-trying-to-sell-the-technologie babble. I remember there was a source with more technical aspects. Their patent is something like 27 pages long, and also pretty tiresome to read.

[Steinbrei]

You can also put in "underwater steam jet" in google for some popular magazine type articles giving an overview what its about. The airbubbles seam to be one of the key elements. I remember reading about mass ratios as well. Maybe that was in the patent though.

Here are the best links:
http://www.tfd.chalmers.se/~valeri/Ajax/steam_jet.html

http://www.newscientist.com/news/news.jsp?id=ns99993321

Here are some interesting claims from their patent (United States Patent 6,662,549 Burns December 16, 2003
Propulsion system ):

20. A propulsion system according to claim 1 wherein the aerating gas
comprises air.

21. A propulsion system according to claim 1 wherein the working fluid
comprises water and the aerating gas comprises air, and wherein the
ratio of air to water is not more than about 1:10 by volume.

22. A propulsion system according to claim 21 wherein the ratio of air
to water is about 1:300.

[UncleMatt]

Hi,
I have been researching the PDX steam jet for some time now (years). I found your forum and thought it might be a good idea to join forces to produce a small scale SWATH boat that I want to power with this steam jet. The thing is, I want to use lithium batteries to power the steam generator, and I have an idea for an electrode steam boiler that could be made fairly simply for this application, and could be scaled up to full size if we get good results with a RC model.

I know this thread is old. but if the OP is still around, please contact me if you want to hear more.

thanks,

Matt

[Steinbrei]

Hi Matt,

it might sound arrogant but I only use SI-units. I'm surprised you would suggest generating the steam from batteries. I suggest doing a short calculation to estimate the possibilities. I'm making this up as I go along, so let me know if I fall of the trak at some point.

Starting temperature: 20 °C
Thermal capacity of water: ~4,2 J/(°C*g).
Energy to evaporate: 2260 J/g

Lets heat one gram of water:
80°C till we boil, that is 336J + 2260 J to evaporate.

That will be something like 2,6 kJ.

Lets say you exhaust a 2000mAh battery with 13V in 20 min (as long as you want to ride arround. That would be 78 J/sec. Every ~29 sec you could use one gram of steam for your propulsion.

How big would the boat be you could drive with that?

[Steinbrei]

Hi Matt,

one more: Sorry that I immediatly homed in on the battery powered steam generator in that way.

After giving the story some more thought I would like to ask you what according to you are crucial questions you would want to look into during the process of creating such a piece of cake. Where would you expect the real challenge? What would you have to know to be able to relize the project?

Greetings,

Rolf

[LtDoc]

"How big would the boat be you could drive with that?"... Not very big at all. Now, if you could miniturize water...
- 'Doc

[UncleMatt]

First of all, I need more information on how much volume of steam is used by the jet, and how much force in generated by that volume. This will tell me how much steam pressure I need to maintain that level of flow through the jet orifice. Once I determine this, I will be able to determine what amount of energy per second the lithium batteries would have to maintain. Problem is, the PDX company is not pursuing this marine drive at the moment, and it may be difficult to get info from them about it. I will attempt to contact them and see what happens there.

just for the sake of argument:

1 once of water = 28.349 grams

To raise the water temperature to boiling point, we will need:

Heat = Mass x (Final temp -Starting temp)
Heat = 28.349 x (100 - 10)
Heat = 2551.41 calories

Vaporization energy of water = Mass x calories required
Steam = 28.349 x 540
Steam = 15308.46 calories

Total energy needed to steam 1 oz of water is:

Total = delta Heat to 100 + vaporization energy
Total = 2551.41 + 15308.46
Total = 17859.87 calories

Since 1 KWh = 860424.76302468 calories, then:

Total = 17859.87 / 860424.76302468
Total = 20.757 Watt hours

lets assume for fun that in a full size jet one ounce of water per second was turned to steam, so we would need 20.757 Watt hours per second

1 lithum battery from thunder-sky - 200A at 3 to 4.2 volts = 600 Wh's.

600 / 20.757 = 28.9 seconds before battery is depleted. So if you had 60 of these battteries you would get about 28 minutes of continuous use.

While this does not sound encouraging, new kinds of lithium batteries are close to production (altairnano.com) that would increase the range signifigantly and be rechargable enough to last 20 years. I also don't know for sure how much steam will be needed to power this jet, full size or scale model, so all of this is just a calculated guess. If a proper battery can be come up with, you could use land wind or solar power to charge the batteries, or any green or renewable energy source.
Barring the use of batteries, if a fuel cell, a generator, or perhaps a micro-turbine could be used to power the full size version, it might work.

I am looking at 2 ways to generate steam right now - magnetrons and an electrode style boiler. Both would use electricity only, and would be very efficient. The feeder water would be used to cool the magnetrons, and pre-heat the water, so that would help the microwave version come close to as efficient as the electrode version.

If anyone knows or can find the specs on the amount of steam used by this jet, please let me know. Even if I knew the area of the steam nozzle they used on their test unit, that would help a lot.

thanks

[Shaun Hendricks]

My guess, for the sake of discussion:

Ultrasonics. Low power consumption, high volume return. The engine seems to work off 'volume' of expansion, like a ram-jet. A half dozen or so piezo transducers could probably power a small boat. Certainly no speed demon, but you could probably design an efficient thrust system for it. These transducers are routinely found in humidifers.

Microwave (magnetron) energy is very high for power requirements, you'd have a very high drain, but if you could master it, you could get some nicely hot steam, good luck on getting your batteries to support it though!

How about attempting electric arc induction of 'steam'? A pulse stream of steam should be possible at very low power costs. Boost up to about 100,000 volts AC and tune in the right frequency... who knows? Any budding Tesla's willing to try?

Water has some very wierd properties that can be taken advantage of. MagnetoHydroDynamic (MHD) propulsion is the ultimate water-jet to take advantage of water-strangeness, but so far there have only been some very inefficient prototypes of it. Maybe it could work on a smaller scale rather than a larger one? :D

Things to think about! LOL!

[65535]

The main downside to using the MHD system is the incredibly high voltage requirements not to mention a very strong magnetic field. My friend talked about making one for a graduation requirement at a private school. It sounds elaborate. Maybe your looking the wrong way. Try using a generator. High rpm scale motor spinning a large brushless generator wired to a high voltage controller. I may try and produce one. WOuldn't want to stick your hand in the water. ZAPP

[Steinbrei]

Say we stick with the PDX steam jet as propulsion.

A major concern you seem to have is how we produce the steam. So let's set that aside for a moment.

What other questions do you identify? (Before contacting PDX).

[65535]

A compressed gas with burner would be a good system. Or a small scale nuclear reactor. :eek: :eek:

[spiffy_spaceguy]

Water has some very wierd properties that can be taken advantage of. MagnetoHydroDynamic (MHD) propulsion is the ultimate water-jet to take advantage of water-strangeness, but so far there have only been some very inefficient prototypes of it. Maybe it could work on a smaller scale rather than a larger one? :D

Things to think about! LOL!

The issue with MHD is that water electrolyses at potentials of about 1.5 volts. In order to get an acceptable water stream, you need a lot more potential than that, and that means you're making gas bubbles. That's noisy, has less propulsive efficiency (since there is less mass being driven backwards) amd produces copious amounts of hydrogen gas (don't light a match!)

It might work OK with a ridiculously powerful magnetic field (IE stack 30 of the biggest neodymium magnets you can find), but I wouldn't expect anything like The Hunt For Red October.

http://www.rmcybernetics.com/projects/DIY_Devices/homemade_magnetohydrodynamic_thruster_mhdt.htm

That said, it would be SERIOUSLY COOL.

[UncleMatt]

Actually, the inventors, claim that the resulting vacume force created by the phase transition from steam to water in the jet( a reduction of around 1,600 times the volume) is what pulls more water into the front of the jet, and causes thrust to the rear. They also claim that air introduced into the water stream at the front of the jet has a big, positive effect on propulsion.

I am not sure if the energy requirements of this system are large or not yet, need mroe info and data, but they did have a Royal engineering society in Britain determine that at the least it had the efficiency of a two stroke marine motor. With further refinement, maybe more?

[65535]

Matt SPiffy is talking about the system we where sidetracking about you system looks to work quite well. Ours not so much.

[Shaun Hendricks]

LOL... I only brought up MHD as an aside, there's still a lot of work to be done there...

However, the first three things I brought up might be workable as a straight electric system. I didn't bring up the microwave system first, but it is sound if you have a huge power source. I would be more inclined to think Ultrasonics and arc-pulse are reasonably reachable in a model setup. How effective they'd be is another question.

[UncleMatt]

sorry guys, I shoulda quoted which post I was responding too, because it was a couple back from where it ended up in the thread. I am always open to cool propulsion stuff, I am just trying to figure this one out for now. :-D

I am jammed today, but will spend some of my free time tonight thinking of a specific list of questions to pose to PDX. Please feel free to make usefull suggestion to add to that list about the steam jet.

[Steinbrei]

I guess that the geometry of the jet should be of importance. You're not very likely to recieve very detailed instructions on that one. Can we extract some useful hints from the patent on that one?

[spiffy_spaceguy]

Wouldn't something with a conic outlet cone be the best? That would allow steam jet to expand and speeds the jet up.

And then you could put another ring around that to bring cooler, slower water into that stream to increase thrust (ie bollard-pull power). They used to do that on pulsejets and ramjets.

Like this: (Please ignore the spastic-ness of the drawing.;). Thank you for your understanding.)

[65535]

A ventrui with a cylinder manifold with a space for water to enter between if the simply way to go. The one online is very well designed it use's' a flow thourhg design opposed to a venturi design.

[UncleMatt]

I guess that the geometry of the jet should be of importance. You're not very likely to recieve very detailed instructions on that one. Can we extract some useful hints from the patent on that one?

I have been attempting to do exactly that. I will get back to you.

[UncleMatt]

Wouldn't something with a conic outlet cone be the best? That would allow steam jet to expand and speeds the jet up.

And then you could put another ring around that to bring cooler, slower water into that stream to increase thrust (ie bollard-pull power). They used to do that on pulsejets and ramjets.

Like this: (Please ignore the spastic-ness of the drawing.;). Thank you for your understanding.)

The last prototype I saw them test on Beyond Tomorrow on the science channel had an opening all around the jet cylinder just behind the mixture chamber. A conical collar faced faced opening forward and diverted water into the thrust stream from outside the jet, I guess because they found it could increase thrust and efficency.

Here are the initial questions I came up with for PDX when they are contacted:

Steam related question:

1. What is the normal operating steam pressure of the jet?
2. What volume of steam flows through the jet at full open steam valve?
3. What effect does superheating the steam have on the force generated by the jet, if any?
4. What volume of steam per liter of water flows through the jet at full open steam valve?
5. What force per unit of steam is generated by the jet at various steam pressures?

Jet related questions:

1. What is the best form for the jet to take out of those in the patent?
2. What is necessary to take into account when you scale up the jet? Further, can the jet be best scaled up or down in power through jet size in diameter or steam pressure increases?
3. What is the area of the steam nozzle opening? Can this nozzle opening area be related in a linear way with the size of some other part of the jet, like the main tube diameter?
4. Would the jet be controlled by varying the steam nozzle orifice, or through varying steam pressure?
5. What is the smallest scale at which the steam jet would still operate?
6. What is the highest efficiency the jet has achieved to date?

Development questions:

1. Are there any current plans to bring a steam jet marine drive to market through third party
licensing and manufacture?
2. What would PDX be willing to do to help individuals with a desire to refine the jet through
experiments of scale models on various marine platforms and hull designs.
3. Would PDX be willing to supply any prototypes for testing, or provide plans and schematics
so that test prototypes could be produced independently?

[Steinbrei]

Possible rephrase Steam 4: How do mass flows or volume flows of steam and water compare? (Air to water flows are quoated in patent to be <1/10, typicaly 1/300)


In any case we will get thrust if we blow out steam twoards the back. The interesting question here is: What did they do to increase this thrust (Geometry of channels, steam nozzle, chambers for mixing,....) and how much did they increase the thrust by doing this.

I mean we can build a steam thrust boat. But how much more can we possibly expect to get out of the system if we happen to stumble over a geometry that produces these effects their talking about?

[UncleMatt]

roger all that,
I have illustrations from the patent that I could measure, but they would have been pretty careless to put an illustration in a patent that gave away anything proprietary. I think we will have to hope they will share some info with us, but I think that is unlikely. The only other options I see are to build and test, or simulate in software and test.

I know that they made their last prototype out of clear plastic to reveal internal functions, so it is possible we could do some modeling in plastic that would still function. Not that that is cheap or easy or anything... :-)

[green-boat]

[QUOTE=spiffy_spaceguy]Wouldn't something with a conic outlet cone be the best? That would allow steam jet to expand and speeds the jet up.

And then you could put another ring around that to bring cooler, slower water into that stream to increase thrust (ie bollard-pull power).[QUOTE]


Looks very similar to an injector/ ejector used on full scale steam locomotives.

[65535]

I don't think you would get in much trouble copying the patent closely providing it was't mass produced. The hole point of this propulsion is to take advantage of the property of steam to rapidly decrease when cooled to under 100 C. I would say make the unit like a sub and use a venturi system Ill draw some planes on paper and post them here tomorrow.

[UncleMatt]

I don't think you would get in much trouble copying the patent closely providing it was't mass produced. The hole point of this propulsion is to take advantage of the property of steam to rapidly decrease when cooled to under 100 C. I would say make the unit like a sub and use a venturi system Ill draw some planes on paper and post them here tomorrow.

I look forward to seeing your plans.

the concept as I understand it - the steam provides intitial momentum to the water with its velocity exiting from the nozzle. Air bubbles that are introduced into the water stream at the front of the jet then mix with steam, expand initially from the heat, but then cool and condense VERY rapidly in the venturi area. This condensation produces shock waves that then pull more water from the front of the jet, and adds energy to the water/steam mixture being expelled from the back of the jet. More cool water is drawn in through a collar and an opening around the jet, and adds further efficiency to the process.

I am not so worried about violating the patent as I am in trying to get practical measurements from patent drawings that can be used to create a functioning model. That is what I think will be difficult, if it works at all.

[Steinbrei]

I can assure you that as long as you are not commercially taking advantage of what is described in the patent you are not going to have any problems.

The main question will be: how crucial is the exact shape concering the proper generation and use of these shockwaves. Getting the changing diameters in the right sequence (expanding, contracting... along the unit) is something we might be able to figure out from the patent.

[65535]

I just remembered how bad I at am drawing. Maybe I can find a free cad program and make a 3 d model using a venturi system.

[UncleMatt]

I can assure you that as long as you are not commercially taking advantage of what is described in the patent you are not going to have any problems.

The main question will be: how crucial is the exact shape concering the proper generation and use of these shockwaves. Getting the changing diameters in the right sequence (expanding, contracting... along the unit) is something we might be able to figure out from the patent.

I am going to make a call to PDX's US office and see if I can get their cooperation. It won't hurt to try and get some help from them, especially since they would benefit greatly if their product was able to enter the marine drive sector. I will let you know how that goes, though I will probably wait until after July 4.

[LtDoc]

Steam has been around for awhile (hows that for an understatement?). It's use has been explored by almost every ship builder/designed, and in most cases has been found wanting. I would think primarily because generating it, compared to other forms of propulsion, is just too costly and inefficient. It's a fair way of transfering power, though. If the point is to learn about steam then by all means experiment! If it's to produce a really 'neat' model boat, then do that too. But if it's to produce some really efficient model boat, quit while you're ahead.
- 'Doc

[UncleMatt]

I can assure you that as long as you are not commercially taking advantage of what is described in the patent you are not going to have any problems.

The main question will be: how crucial is the exact shape concering the proper generation and use of these shockwaves. Getting the changing diameters in the right sequence (expanding, contracting... along the unit) is something we might be able to figure out from the patent.

I was taking a look at the jet cross section in the patent, and I think it would be fairly easy to make a 2 piece jet unit, with the inner piece being threaded to the outer so that you could vary the steam orifice size by screwing the inner part of the jet to the rear, reducing the steam orifice gap in the process. With experimentation of various combinations of steam pressure and steam nozzle gap, you might be able to maximize efficiency and thrust. You might also use this as a way to throttle the jet, or fine tune maneuvering thrust.

One of the journal article is read on the concept claimed the steam is supersonic as it leaves the nozzle and enters the water. Anyone know flow chart/formula to verify that one? Steam velocity, orifice size, steam pressure, steam heat, would be variables? Also, at what relationship does the level of submergence of the jet under water (ambient pressure) effect the steam velocity exiting the nozzle?

I think you are right about the critical nature of the dimensions of the jet. Is there any modeling software we could play with that anyone knows of?

[UncleMatt]

Steam has been around for awhile (hows that for an understatement?). It's use has been explored by almost every ship builder/designed, and in most cases has been found wanting. I would think primarily because generating it, compared to other forms of propulsion, is just too costly and inefficient. It's a fair way of transfering power, though. If the point is to learn about steam then by all means experiment! If it's to produce a really 'neat' model boat, then do that too. But if it's to produce some really efficient model boat, quit while you're ahead.
- 'Doc

The difference with this system is that is does not use pistons or turbines to capture the energy of steam to do work. No moving parts, but the question of total efficiency is still unknown. Time will tell if this concept has anything new to offer the marine world.

[LtDoc]

No moving parts, true. But also less 'capture' of the force of the steam flow. If the steam's production wasn't a big factor, as in weight, energy expenditure, etc, then it might stand a chance of having enough mass to provide the needed movement. Not exactly the best try at explaining what I mean but a steam 'jet' isn't much practical. Jets work well if there's enough 'stuff' thrown out the nozzel. Just ain't enough 'stuff' with steam. Good luck. Think I'll wait on my lottery ticket to win...
- 'Doc

[UncleMatt]

No moving parts, true. But also less 'capture' of the force of the steam flow. If the steam's production wasn't a big factor, as in weight, energy expenditure, etc, then it might stand a chance of having enough mass to provide the needed movement. Not exactly the best try at explaining what I mean but a steam 'jet' isn't much practical. Jets work well if there's enough 'stuff' thrown out the nozzel. Just ain't enough 'stuff' with steam. Good luck. Think I'll wait on my lottery ticket to win...
- 'Doc

Do you have any numbers or references to support your perspective? I welcome anyone who can disprove the effectiveness of this steam jet concept, since no one wants to waste time on a dead end. I would ask, though, that until we have a definite answer one way or the other that can be shown with experimental data or good theoretical numbers that we maintain an open mind. If the steam were just being vented to the rear in an open tube, you would probably be right, but that is not the case with this design. This is a new concept, so it will not be similar to previous applications of steam, and needs further study before we decide it isn't worth pursuing.

[LtDoc]

What's 'new' about this is the use of steam instead of combustion products, gases. It would be a steam 'jet'.
Do I have 'numbers' for any of this? No. It's been something like 40 years since my last physics class, I don't have the textbook, and am too lazy to prove it.
The efficiency of the expelled steam would be pretty high. But, the efficiency of the whole system would be very low. Lawrence Welk would'a loved it, ought'a be a pretty good bubble maker!
- 'Doc

[UncleMatt]

What's 'new' about this is the use of steam instead of combustion products, gases. It would be a steam 'jet'.
Do I have 'numbers' for any of this? No. It's been something like 40 years since my last physics class, I don't have the textbook, and am too lazy to prove it.
The efficiency of the expelled steam would be pretty high. But, the efficiency of the whole system would be very low. Lawrence Welk would'a loved it, ought'a be a pretty good bubble maker!
- 'Doc

This concept has already been commercialized as a pump for industrial and food liquids. It works VERY WELL in practice, plain and simple, and there are many units already in use. There have also been several technology shows on TV spotlighting this technology, and many articles have been written about its success. So I am a little confused as to what you are basing your opinion on, especially since you admit you can't show any numbers to lend weight to your opinion. For further info, please visit http://www.pursuitdynamics.com/.

[UncleMatt]

At the PDX site I posted above there is a video of this jet/pump operating in a plexiglas tube with a red reference liquid. Please go take a look at it and see what your impressions are. From the exterior dimensions of the unit, it doesn't appear that much complexity is involved in the structure other than the critical interior dimensions.

I am going to try to set up a small test rig at a relatively small scale. I once saw this jet being tested in a big tank with a plexiglass wall, so I may replicate that in a smaller way. I might even use a big fish tank. My first thought is to put a torque gauge on a shaft across the top of the tankand then attach the jet mounting shaft to it at a distance of 1 foot. Crude for sure, but simple. Any constructive input or thoughts about designing the test rig would be appreciated, especially when it comes to the sensors for thrust.

Next I am going to visit a friend of mine who has a lathe and have him turn out a 2 piece version of the jet style version in the patent. Then I will drill a couple of holes to place the air and steam passages and attach a mounting shaft to the side. I will be able to adjust the steam nozzle orifice area, but not the diameter of the exhaust tube. Again, any constructive thoughts would be appreciated.

[LtDoc]

UncleMatt,
I did take a look at the 'PDX' site and was particularly impressed with the video of the steam generator used for firefighting (been there done that stuff!). The 'problem' still stands, how do you transport the required equipment to generate the steam? For models or full scale ships, I seriously doubt if the resulting steam flow would be anywhere close to what's needed to just move the required equipment. Could I be wrong? Of course I could! But I doubt it.

Completely beside the point as far as this thread is concerned, but steam is what puts out almost all fires. It's generated by the fire it's self (very efficient), the FD only has to supply the water. Getting the water to where it's turned to steam is the hard part. Admitedly, steam is a lot lighter than water, but posses other problems which are much more serious than weight. Sorry, couldn't resist.

- 'Doc

[UncleMatt]

Here area a couple of links to more info:

article with a photo of the tank test I referred to earlier:

www.rina.org.uk/rfiles/warship/ws_steam_oct02.pdf

Another article, which among other things shows the rear collar concept in a drawing:

www.tfd.chalmers.se/~valeri/Ajax/design.pdf

[UncleMatt]

In the second article there are several interesting graphs and text, especially on page 4 where steam flow vs. thrust is shown as well as steam temp vs. velocity. Please check it out.

[UncleMatt]

I discovered last night that the jet operates between 2.5 to 7 bars of pressure. FYI

[Steinbrei]

www.tfd.chalmers.se/ ~valeri/Ajax/steam_jet.html

This animation is similar to what you have in the one of your articles.

In the PDF you posted there is a cross section through the jet. I assume that was one of the first designs, I get the impression mixing the air further up front is beneficial. I have some other pictures I downloaded somewhere in the internet. I don't know about a copyright being on them, so I'll not post them for the moment. They give some impression of aspects to think about when building a prototype. I'd suggest to discuss some ideas before you get you lathe running.

A question to all STEAMERs out there. What preassures do your machines usually run with? And how much water do you typically use in a time span? (Just tu get a feeling).

[Steinbrei]

http://www.andersondahlen.com/pdxdiagramwin.htm
See here a recent unit (mixing/pumping?) as it is for sale now.

[UncleMatt]

hey Steinbrei,
If the operating pressure is indeed 7 bars at the top end, that is only a little over 100 psi. I think we can easily find a tank that can hold twice that pressure. I honestly think we could turn out something that would work, even if it was not optimised for efficiency and power. I am still working on how to create a couple of prototypes in the easiest/cheapest way possible. Do you know of a plastic product that I could pour into molds that would be strong enough to withstand that kind of pressure and heat once cured? Let me know.

[65535]

Maybe a high temp epoxy? Pour it into a wax mold melt off the wax that may work. You need at least 400F I would say at least. Steam can get super heated depending on your system. Flash steam could be super duper hot while boiler steam if hardly above the boilding point. Maybe using a pump to pump water into a flash steam chamber.

[UncleMatt]

I just realized in the steam calcs I did earlier in the thread, I failed to take into account that once the bolier reaches full operating temperature, whatever form it takes, the energy needed to turn the water into steam will be reduced.

So hypothetically, lets say we have a cylindrical pressure vessel, hereafter called the boiler. Inside the boiler lets say two strips of steel are suspended a few inches apart from each other in the center of the cylinder. AC electricity supplied to the strips would heat the water in between them, and the strips would never reach temps higher than the water, so little or no scale would form on them. Salts added to the boiler would increase the temps produced and remain when the water flashes to steam. This system is as efficient a boiler as can be achieved currently, unless you can post sources that prove me wrong of course. :-) Anyway, if you surround this boiler setup with expansive foam to a depth of several inches, little energy will be lost and radiated away from the system, the starting temp of the water will be much higher than 10 degrees centigrade, and therefore the amount of electricity needed to continue producing steam should be reduced dramatically. If the walls of the boiler are relatively thick and can store a considerable amount of energy within its mass, this effect should be increased and also smooth out temp variations.

I will do the numbers and post them in a while.

[UncleMatt]

Ooops. I was wrong. The reduced energy to continue steam production once full operating temp is achieved wasn't that much after all, assuming the water temp started at 40 degrees centigrade instead of 10.

[Steinbrei]

In my earlier calculation I found that the energy for evaporating the water is about 7 times as much as to heating the liquid water till it is boiling.
I think our main focus at the moment should not be producing the steam. You can do that on your stove in the kitchen for a test rig if necessary.
For the jet, I would suggest lathe/mill/drill what ever made aluminium parts. I'm thinking of a waterjet with a diameter arround 3mm.
Producing steam is difficult and costly. We're considering a solution in model dimensions so in my eyes it would make sense to use a unit in approximatley that size.

[UncleMatt]

In my earlier calculation I found that the energy for evaporating the water is about 7 times as much as to heating the liquid water till it is boiling.
I think our main focus at the moment should not be producing the steam. You can do that on your stove in the kitchen for a test rig if necessary.
For the jet, I would suggest lathe/mill/drill what ever made aluminium parts. I'm thinking of a waterjet with a diameter arround 3mm.
Producing steam is difficult and costly. We're considering a solution in model dimensions so in my eyes it would make sense to use a unit in approximatley that size.
Sounds good. I will talk to my machine work friend and see if I can get him to turn a couple of things out for me in aluminum.

[Steinbrei]

Hi Matt,

whats up? You seem to have hit the wall. What about your questions to PDX? Concering making a steam jet (the very parts), how bout looking at the pictures of sections of the jet we can find on the net and the patent?