View Full Version : Steam power
12-10-2004, 01:44 PM
I am about to design a steam engine for use as a generator. I know there are a few of you out there that really know what you are talking about when it comes to steam. I am new to it, a young guy. It is very interesting to me because you need heat to make it work. Heat can come from anything and future technology make make it very frendly to make heat from hydrogen or some other technology.
Okay here are my questions;
What is a typical presure that they run on? Do most engines use a set "intake dwell time" or is there a reliable way to very this dwell with load?
12-10-2004, 01:57 PM
intake dwell time? Most hobby boilers are around 120 psi or less. They are built usualy with a safety factor of atleast 6.
Most steam engines have variable cut off that is done with the valve gear to conserve steam. Kinda like a gearbox.
12-10-2004, 02:02 PM
I guess cutoff is what I mean when I say dwell. I am a gas engine guy that is why I use that term. I would like to keep the valving simple. If I can't, I will make it electronic control, but I don't want to do that for reliability concerns.
12-10-2004, 02:08 PM
Here, download these programs, you can visualize how its all done, some very simple ones to more complex ones.
Now if your going to run a generator, maybe a steam turbine would be easier for you.
You can adjust the valve timing, and the dimensions, and see how it affects the gear.
12-10-2004, 02:11 PM
That is what I want to use it for. I just don't think I could build a turbine without some very good tools and equipment. I don't even know where to begin to make a turbine blade.
12-10-2004, 02:18 PM
You may want to take a look at a Tesla Turbine. There are some folks who are trying to make them for electrical generation,I have lost the web site, but a quick search should turn it up.
The turbine blades are simply discs, with holes bored in strategic places for exhaust.
Though not widely used this seems to be a technology that could be adapted to small scale use.
12-10-2004, 02:21 PM
I would recomend going to Mike Brown's website on home scale steam power . Many tapes and books in simple terms for common folk.
Hmmm.. Sterling engines come to mind.
12-10-2004, 03:09 PM
Triple expansion steam engines are most economical for steam consumption versus output power.
That was the final word in BOAT engines, the last real development in steam in the last 200 years. THEY are heavy.
There is raw castings, finished engines available. I have a link if you are shopping.
12-10-2004, 03:26 PM
Link to thier page. Never done business with them, nice looking site thou.
I was looking into the design and similar concept using industrial Waste heat to run a steam engine. Not enough or regular enough pressure to run a turbine? you need a piston engine. Turbines require a narrow band of pressure and flow to operate efficiently.
12-10-2004, 04:14 PM
www.tinypower.com (http://www.tinypower.com) has casting kits for a number of engines that will power a home generator.
12-10-2004, 06:23 PM
Steam I like,uses BOTH sides of the piston,no wasted motion,plus they will run nearly forever.
12-10-2004, 06:40 PM
Here is a site that you might want to look at.
12-10-2004, 11:28 PM
CHarlie.. what kind of trickery is this? I went to click on "enter" and steam blowes out.
Since I got a hand for a mouse pointer I donna wanna stick my hand into the steam.
Ha.. ya got a chain to pull? I had to pull the pizza man outa the ditch tonight to retrieve our supper. What a night.
David (neat site)
12-11-2004, 12:17 AM
<font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
Not enough or regular enough pressure to run a turbine? you need a piston engine. Turbines require a narrow band of pressure and flow to operate efficiently.
Turbines were regularly used to extract the energy from the difference in pressure between reciprocating engines exhaust pressure, and the condenser back pressure. That could have been quite low, and still extract significant power if the volume was there.
That kind of turbine requires volume flow, reasonably steady conditions, and yes it is different from the HP turbine. But a low pressure does NOT mean no turbine, in fact a turbine will work on pressure diffrences that a reciprocating engine will not.
Power generation is a perfect application, since rotational speed is set.
12-11-2004, 07:58 AM
A turbine would be good but very hard to make the rotor. I think I will go with a regular piston engine. What materials are used for the cylinder and pistons? Are the pistons flat topped, dished or domed? I think I am going to go with a 2 cylinder horizontally opposed single acting. This makes it simple and rugged.
12-11-2004, 08:15 AM
I have seen a vane type air motor used as a steam engine,it would be easy to make.
12-11-2004, 09:26 AM
MY last foray? I was looking at a VW diesel engine in a scrapyard. Good heavy block, Downsize the cylinders sequentially then build a cam/valve box. Use a good waterproofing oil or keep the oil heated somehow to stop condensation.
I got plenty to do right now thou. Later. If I live long enough to complete some other things.
Someone sent me a site w/wankel type motor converted to steam. They said it was SLICK.
[This message has been edited by ibewgypsie (edited 12-11-2004).]
12-11-2004, 10:56 AM
Ya that wankel (rotary) engine is neat. That would be a good project. I would worry about sealing the edges of the rotor. Steam might not need as much sealing as gas. The vapour would help seal it. Using steam makes it pretty much a turbine as you don't need compression for a steam engine, thats what the steam is for!
12-11-2004, 11:12 AM
Wankels are not the easiest thing to machine.
12-11-2004, 01:11 PM
Check out keveney.com for some ideas. lots of cool animation.
[This message has been edited by stiven (edited 12-11-2004).]
12-11-2004, 03:20 PM
I think it was a conversion of a factory engine.
12-11-2004, 05:35 PM
It is interesting though David, you could always take an OS wankel engine intended for model airplanes, and run steam thru it. Dont forget the steam oil!
Steam has a compression/expansion cycle, the wankel has more cycles to it. You'd have compression, expansion, compression/exhaust, running steam in a rotary, no?
Hmm, that could have some advantages in a steam locomotive.
12-11-2004, 08:43 PM
David; you will have to put a glove on your hand when you go to that site. http://bbs.homeshopmachinist.net//biggrin.gif
Some people have made steam engines from refrigeration compressors. They make new heads with the valves in the head. The valves are operated through a gear train driven from the crank shaft.
The crank case has to be drained every once in a while to get rid of the condensate that leaks past the pistons.
Another engine was made from, I believe, a chev. gas engine. I am not sure just what was done to the engine to convert it to steam.
Flash; my engine has castiron pistons and castiron cylinders. The piston rings are steel.
Click on the link and check charlies workshop. This may give you some ideas.
12-12-2004, 05:01 PM
How much power do you want to generate? You may be VERY surprised when you learn a bit about steam engine and boiler size. A vertical boiler of about 24-30" dia, as used in many steam launches might be sufficient to generate 3-4 hp. at 746 watts per HP that maybe 2500 watts.
The cheapest gas engine generator sets make 5000 watts or more.
To generate enough power to be usefull will take a near full time fireman to keep the boiler stoked.
Home steam power generation is not very practical.
12-12-2004, 06:43 PM
Get a Fuking Listeroid diesel:
Hoffman in Warner Robins Ga
12-13-2004, 07:40 AM
Nice engine Charlie. I am looking to charge batteries not run washing machines. I am building a house off the grid so in the winter the fire is going all the time so I thought I could use some of the heat to charge the batteries as well as the solar pannels and wind gen. I am thinking the easiest was as well as the most effecient is to make a paddle wheel type turbine. This way the friction is very low and it will turn with low steam presure if I design it right. Also low maintenance just let it turn whenever there is enough steam.
12-13-2004, 06:47 PM
This might be to simple,but how about a tall chimmney and a draft turbo?
Just a section of flue pipe with a scroll added for the paddle fan.
12-13-2004, 06:48 PM
A fully functioning steam power plant for a home appears to me to be quite an undertaking, an quite costly. I think that such a system would be more practical and economical if you could get a number of homes to buy into the system. Building and running the plant would cost only slightly more and take about the same amount of time.
Two other thoughts are to use the waste heat from the plant to heat your house and hot water. Also, try to build some kind of autostoker mechanism to feed the coal. I believe that commercial systems have some kind of conveyor belt system in the fire box fed from a hopper.
Good luck with this! I think building a successful steam plant is a hughly exciting and rewarding project.
12-13-2004, 09:37 PM
If you read up on the history of such things, I visited a museum down in Florida, of an old community that was self sufficient. They have a machine shop there with overhead drive, a power plant, bakery, and other buildings. Really interesting.
Sitting outside the machine shop is an old steam engine that was once used in the generator room. You walk in the generator room, they have a huge fairbanks morse gas or diesel engine that runs the generator.
So for some reason way back when, they decided to go with internal combustion, my bet is that it had much more to do with the boiler than anything else.
12-14-2004, 07:49 AM
Probably the same reason for the switch from steam to diesil locomotives.Them boilers are high maintence.
12-14-2004, 09:43 AM
I've often thought about this using waste heat from a landfill. Rotting stuff in the landfill generates a lot of heat but also produces methane gas that must be burned off. I thought of maybe using the methane gas and outgoing water from the sewage tratment plant.
I still say sterling engine. All it needs is heat and is just about zero maintenance. Since you are charging batteries rpms don't need regulation.
12-14-2004, 10:45 AM
To all and sundry:
My name is Ron Fossum of Portland, Oregon. I've been an active steam hobbysist since 1970 and have owned a number of hobby steamboats. I currently manage my own website at http://www.steamlaunchartemis.net and the Northwest Steam Society's website at http://www.northweststeamsociety.org - among others. I'm up-to-date on most happenings in the development of low pressure (under 200psi) hobby steam.
I'm not going to go into a long diatribe on what is right and wrong with many of the opinions expressed in this thread.
If Flash is sincerely interested in this project, he can contact me at email@example.com and I'll be happy to "fill him in", probably with a phone call if he sends me his phone number.
12-14-2004, 02:16 PM
This company is developing a woodburning steam turbine with cogen capability, doesn't look like they are in production yet, but might be exactly what you are looking to do. From what I recall, they designed a turbine wheel that is very similar to a turbo charger instead of a larger steam turbine since at the lower power ratings the traditional wheel was not very efficient.
You might be able to find a decent size turbo wheel and use that, I worked on a design last year based on that, but didn't get very far yet.
12-14-2004, 06:57 PM
Thanks for the invite Ron. I want to make this thing whatever it is very maintanence free. I have not looked into the sterling engine much, I think I will now. I like the simplicity of a turbine. I don't want to buy anything, just make something. Again this thing is not going to be a power station and not ment to be. We will live with very little power use so just enough is needed to charge batteries. We will have the diesel generator for backup of course. A closed steam system would not be that hard to maintain. I could run the used steam outside into the battery shed to keep it from freezing then run it back into the boiler. How do you feed a boiler or will it draw what it needs much like the radiator resivoir in you car?
12-14-2004, 09:12 PM
Basic law of the world. You can't get something for nothing. So efficiency is the name of the game.
Since you want to generate electricity, remember that Watts = Amps x Volts. 1 HP = 750 Watts/Hour (approx). If you're going to charge 12 Volt batteries, then 1 HP will produce about 55 Amp/Hour if you charge at 13.4 Volts. That's at 100% efficiency. A decent, small steam engine has about 60% efficiency so you'll need a theoretical HP of 1.67 to generate that 750 Watt/Hour. The engine will require about 30 pounds (weight) of steam per hour. It will require about 1,200 BTUs to produce 1 # of steam so you'll need 36,000 BTUs/Hour. 50% efficiency is considered very good for a modern, well designed small boiler. So now you're up to AT LEAST 72,000 BTUs/Hour. About what a small home furnace puts out. That's the facts of life.
Turbines, in small sizes are incredibly inefficient. That's why, although experimentation was done to use them in steam automobile development, they've been abandoned.
The Sterling engine is a neat toy in small sizes. A friend, who is a very competent machinist and researcher took a 1.5 HP steam engine out of his "little" (like 14') boat and replaced it with a Sterling engine. The Sterling engine weighed about the same amount as the steam plant and took up about the same amount of space. The boat was unable to make any "head way" against a current of 1.5 mph.
The above information is not "hogwash". If you want to put together your own generating set, great. Many people have done it sucessfully. There's a lot of info on the internet about it. And you can do it yourself for very little capital outlay. Just don't expect to "light up the sky".
If you're still interested, drop me an email at firstname.lastname@example.org and I'd be happy to point you to the info you're after.
12-15-2004, 02:41 AM
These guys have an interesting site. http://www.nyethermodynamics.com/nt6/nt6.htm#videos
12-15-2004, 09:56 PM
You wrote "And you can do it yourself for very little capital outlay." How much do you consider very little?
When I took just a cursory look at building a home steam power gen set to produce about 3kW the cost was quite significant, about $10,000. This included a tripple expansion engine (efficiency is everything) that I would build from a kit, a pre-fabbed boiler, a generator, batteries, sync-inverter, and shed. That didn't include the tinkering I was going to do to try to build an auto-stoker to feed the coal.
If you know of a source that can provide these parts significantly cheaper, please let us know.
12-16-2004, 12:27 AM
The much admired efficiency of the compound and triple expansion engines is very real in "commercial" sizes, primarily marine. Many harbor tugs and other, similar vessels were fitted with compound engines, not primarily for efficiency, but rather because of the 90deg. self-starting crank angle. In the size range you are talking the savings would amount to probably less than 5% due to the small size of the engine. Additionally there are a great many more parts to lubricate and maintain.
For generating electricity a high speed (relatively speaking for steam) engine is best. Something that will turn up to at least 600 rpm (1000 rpm is better). And requires little or no attention (lubrication, etc.)
Reliable Steam Engine Co. http://www.reliablesteam.com sells drawings and castings for a very nice 2 cylinder, single acting engine which is ideal for this type of thing. Strath Steam Engine http://users.olis.net.au/strathsteam/ got sidetracked into building complete generating units (boiler, engine, gen, etc.) for stations in the outback of Australia and have much experience in this area. They only sell completed engines but I can personally testify to their quality having installed a couple in hobby steamboats. Tiny Power http://www.tinypower.com/ is now under new ownership, but on their marine engines page is the "M", a single acting unit which- with the 14" flywheel - is recommended for generating electricity. They sell castings only.
All the above is to get us to prices. I assumed that most people frequenting this BB would be doing their own machine work. Castings for the Reliable or Tiny Power engines noted above are about $ 1,000. I also figured that most of you could do much of the boiler work short of the actual welding (you really should have a certified welder do that part). Reliable sells plans for a Roberts type boiler that would do nicely (and any competent machinist could fabricate ready for welding). Beckmann Boatshop http://www.steamboating.net/ sells a wide variety of completed boilers, code and otherwise and Mosquito Enterprises http://www.mostquitoenterprises.com sells high quality, ASME code boilers. Prices range from $ 4,500 to $ 6,500 for the built units. If you know a good welder, you could build one for under $ 1,500. I have no idea what the generator, inverter, etc. would cost.
I suppose one could build some sort of automatic stoking device for coal, but that does not remove the necessity of a person who pokes his head in the engine/boiler room at least every 1/2hour or so to make sure there's water in the boiler, etc. Large installations can get by with fully automated equipment, but as one shrinks the size of the plant what were minor discrepancies in a large installation become major.
12-16-2004, 05:54 PM
The price seems pretty steep. More importantly, the need to tend to the plant twice and hour seems onerous.
Instead, maybe the way to go is to use a regular gas engine, but run it on producer gas. I've seen several books on this advertised at lindsaybks.com If a supply of hardwood is available, the this could be an option. The resulting charcoal could then be burned to head the house and water.
12-18-2004, 10:53 PM
Yup. During WWII a lot of "gasoline" engines on buses, taxis, etc were converted to "producer gas". I've seen photos of buses and taxis in British Commonwealth countries (the African and Caribbean area) that had a unit bolted on the back that "looked" like a boiler - it was actually a "heater" to create the gas. All sorts of stuff was used from walnut shells to coconut husks. They worked.