Mini steam turbines -- convert a turbocharger?
Mini steam turbines -- convert a turbocharger?
(OP)
I am involved in a project taking place among small communities in rural Peru, mainly in rainforest areas. Population density is low, there is no road infrastructure, and development levels range from third world towns to uncontacted tribes. Power is a major problem. Solar is expensive and not well suited to a rainforest; there's no wind, no hills for hydroelectricity, etc etc etc. Fuel is hard to obtain and expensive. Biofuel infrastructure is not operational.
What I'm wondering is whether we can make low cost steam turbines, perhaps by cannibalising turbochargers (using the exhaust turbine) or superchargers (running them backwards) from vehicle salvage, and get the shaft to do some useful work, for electricity or rotary power in smaller communities. Efficiency is not really an issue; there's no shortage of dead wood we can burn to generate steam. However, the system does have to rugged and field maintainable, preferably with minimal training. If we can get 50W, we can at least get a radio running for each community. With a kilowatt or two, we can really make a difference, maybe with lighting, water purification, even local light industry. As a pipe dream, if we could get a system weighing in the lowish hundreds of kilos (or less) to generate 10kW or more, then this can be used to power boats, which are the only means of transport in the region.
The aim is that with steam, anything can be used as fuel. Even installing basic ethanol distillation in this region is difficult and expensive, and the number of people who could benefit from any fixed installation is small as the population is so spread out.
So, is it feasible, or are we (a) not going to get anything, (b) going to get so little power that it's pointless, or (c) going to kill our turbines in seconds and have systems that won't keep working or chew through parts too fast. Low cost is the main concern; anything technical is going to be expensive here, but raw materials are not too bad and we can easily hire skilled welders and metalworkers (though don't expect much in the way of CNC out here). I'm hoping we could get truckloads of old turbos from broken vehicles to import from the USA.
Any thoughts, or indeed suggestions for totally different systems, much appreciated.
What I'm wondering is whether we can make low cost steam turbines, perhaps by cannibalising turbochargers (using the exhaust turbine) or superchargers (running them backwards) from vehicle salvage, and get the shaft to do some useful work, for electricity or rotary power in smaller communities. Efficiency is not really an issue; there's no shortage of dead wood we can burn to generate steam. However, the system does have to rugged and field maintainable, preferably with minimal training. If we can get 50W, we can at least get a radio running for each community. With a kilowatt or two, we can really make a difference, maybe with lighting, water purification, even local light industry. As a pipe dream, if we could get a system weighing in the lowish hundreds of kilos (or less) to generate 10kW or more, then this can be used to power boats, which are the only means of transport in the region.
The aim is that with steam, anything can be used as fuel. Even installing basic ethanol distillation in this region is difficult and expensive, and the number of people who could benefit from any fixed installation is small as the population is so spread out.
So, is it feasible, or are we (a) not going to get anything, (b) going to get so little power that it's pointless, or (c) going to kill our turbines in seconds and have systems that won't keep working or chew through parts too fast. Low cost is the main concern; anything technical is going to be expensive here, but raw materials are not too bad and we can easily hire skilled welders and metalworkers (though don't expect much in the way of CNC out here). I'm hoping we could get truckloads of old turbos from broken vehicles to import from the USA.
Any thoughts, or indeed suggestions for totally different systems, much appreciated.





RE: Mini steam turbines -- convert a turbocharger?
Mike Halloran
Pembroke Pines, FL, USA
RE: Mini steam turbines -- convert a turbocharger?
rmw
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
I dispute that efficiency is unimportant, mankind has a long history of laziness and expediency.
Given that you always have a river around I'd have thunk a turbine generator in the river would be a better bet.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
Generating and using steam very efficiently involves high pressure and high temperature, and thus relatively high tech. Generating and using steam in a primitive and inefficient mannter involves generating a LOT of steam, so you're looking at a fairly large boiler to power it.
While you might get old turbochargers for cheap, you're not going to find boilers that easy to locate or move.
For 50 watts, a pedal-powered generator would work, and be a lot cheaper and more convenient than anything steam-powered you could come up with.
RE: Mini steam turbines -- convert a turbocharger?
I do on the other hand know about steam power plants, especially wood fired power plants and I do know about engine turbochargers, and the two aren't compatible. One is designed for hot low pressure engine exhaust and the other hot higher pressure steam vapor. About the only thing that they have in common is that they spin, and typically not even in the same speed range as noted in an earlier post.
Completely different bearing systems, completely different seal systems, and as JStephen has pointed out, turbo's typically don't have an output shaft.
I keep thinking about if this challenge was mine to solve, how would I go about meeting the need. Turbo's isn't it. But, unfortunately, I don't have anything to offer on that small of a scale as an alternative. I am also familiar with remote sparsely populated villages light years away from anywhere as well. So cannibalizing a small wood fired power plant isn't the answer either, the smallest that I know of would be way too big for a village or even a few nearby villages. And way too technically challenging.
Most of what you want to do is done with small engine generators, but obviously I understand why that isn't feasible. I still own and use a small Honda 2500 kw gen set that was originally used for bringing power to remote third world villages when we needed power for medical instruments.
I wish you luck. I wish I had something to offer. I'll keep thinking....
rmw
RE: Mini steam turbines -- convert a turbocharger?
One other "tried and failed": a similar project to ours tried installing a pilot small scale bioethanol plant a couple of years ago. The village was able to grow a few hectares of sugar cane with no problem, the fermentation and distillation (to azeotrope) worked, and then it all ended up getting drunk. One village with a severe alcoholism problem, plus an epidemic of methanol poisoning, and still no power. Oh, and pilot biodiesel programs in the region (larger scale than we're looking at here, mind) are causing incredible levels of environmental degradation.
RE: Mini steam turbines -- convert a turbocharger?
Steam, by itself, has very little mechanical energy. Only when pressurized steam is released is there sufficient mechanical energy to do the work of turning the generator. High pressure boilers require significant amounts of high strength metals, in addition to the safety aspects of the system.
While river water is obviously a reasonable choice, most locations have insufficient flow rates to generate much electricity, and allowing only natural flow runs the risk of seasonal fluctuations that may be unacceptable for reliable generator. This is why dams are almost invariably associated with hydroelectric power, since the height of dam concentrates the mechanical potential energy into a seasonally consistent source. But, damming a river is a non-trivial exercise, particularly in a region where torrential rains may result in flash flood conditions.
TTFN
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RE: Mini steam turbines -- convert a turbocharger?
http://www.lynxsteamengines.com/converting.cfm
Additionally, if actually do you try that route, you can find loads of places on the net to show how to re-wire a common alternator to turn out 120V 3-phase power, by simply bypasing the voltage regulator and wiring the field coils to a rheostat. Then, it's just a matter of a v-belt and a couple of pulleys.
As for the boiler, this lawnmower system is only appropriate for up to about 40 psi, which is still lethal, but not in the way that a 550 psi, 500 degree boiler is. If you said that you have welders and such, I would think that a re-tasked welding gas bottle (O2 or CO2 - not acetylene) normally used for 3000 psi should be able to handle the task, simply connected with some Swagelock fittings. NOTE: I AM NOT ENDORSING THAT AS A GOOD IDEA. IN FACT, THE TERM "HARE-BRAINED" COMES TO MIND. However, if anyone fancies himself as McGyver, he might try it and then stand inside a bunker.
I think that you should be able to get used lawnmower engines by the boatload for around the same amount you would pay for a used turbo (around 5 bucks).
Be careful.
Engineering is not the science behind building. It is the science behind not building.
RE: Mini steam turbines -- convert a turbocharger?
We ran many years of railroad steam engines on coal and wood (fire-tube boiler, the exhausted steam from the two pistons vents up into the front of the boiler to induce draft from the firebox in the rear through the tubes and out up the stack.
Two (cheap loose pistons will work OK, and you get better efficiency with better machineing when you want to pay higher prices) pistons driving a slow speed dc generator at 12 volts. Picture an old steam engine with generator on the "axle"
1) Battery power bank gets charged for use when steam plant is down, solar cells as alternate power. Use an inverter to get the ac needed, run as much dc appliances as you can to avoid transfer inefficiencies. 12volt power gives you compatibility with lots of car and aftermarket radios and service gear.
2) Later, when your steam gets to more than 100 - 150 psi (the old standard of 150 lb flanges and fittings still holds true! -
3) Steam engines used multiple driven wheels from two pistons getting routinely more than 100 mph in the later years. 60 mph was done many times before and during the Civil War. You will get enough power to run as many small generators as you want to burn fuel.
4) Or go the other way_ Run 4, 6, or 8 pistons like they did in ships at the turn of the century. USS Texas (1910 technology) used multiple-expanding pistons to improve efficiency.
RE: Mini steam turbines -- convert a turbocharger?
Capstone's gas turbine generators drive a PM synchronous generator directly and uses an inverter to convert to 50/60 Hz.
http://ww
Benta.
RE: Mini steam turbines -- convert a turbocharger?
If it's for small power demands, re-think solar cells and a battery. No moving parts, no high pressures or temperatures. If it's for lighting, LED lighting cuts power demand to a minimum compared to traditional types of lighting.
If it's for larger power demands the first option is to try to cut power demand so that you can re-think it as a small power demand.
If that's not possible then you need to re-think the thermal efficiency equation and in this day and age, re-think emissions, too. The old locomotive piston engine steam plants were only around 6% efficient and, from the modern perspective, emissions of all types were beyond extreme.
A central power plant of even a moderate size will allow things to be done (regarding both efficiency and emissions) that are not possible via simple backyard fixes.
Air conditioning and refrigeration are possible using thermal absorption cycles so that there is no electricity demand for the compressor; circulating pumps and fans associated with these systems can be low power demand devices. Google "ammonia absorption cycle".
RE: Mini steam turbines -- convert a turbocharger?
I was investigating small steam turbines quite a few years ago. It looked like an interesting hobby project.
You have steam at some temperature and pressure. You will pass it through some number of stages until it reaches room pressure. Your steam turbine must be designed around these pressure drops. Your turbocharger is single stage, right? Even steam piston engines use multiple stages, hence the triple expansion engines you read about on old steamships.
You have two efficiency problems. Your turbocharger almost certainly is not adapted to your pressure conditions. Small turbines have proportionally more blade clearance than large turbines.
RE: Mini steam turbines -- convert a turbocharger?
If you have cooling water available, you condense the steam so outlet pressure is less than atmospheric; also lets you re-use the water, which is fairly essential on an oceangoing ship.
RE: Mini steam turbines -- convert a turbocharger?
smells like a stirling engine to me
RE: Mini steam turbines -- convert a turbocharger?
You say you have plenty of dead wood available.
B.E.
RE: Mini steam turbines -- convert a turbocharger?
Fundamentally, what you're saying is the best available fuel/energy source you have is wood. For some of your applications you need to generate electricity, however for water pumping at least, and potentially boat propulsion, there is no need for the intermediate electricity step.
Long before anyone had heard of the turbinia steam engines were being used for both stationary power needs (including water pumps) and for vehicles - including the boats you mentioned.
Given the technology infrastructure in your region I suggest you at least consider more primitive steam engine designs than turbines. A quick internet search should turn up something - for instance this steam powered generator.
Alternatively, if it's easier to ship in small existing IC engines and just adapt them to wood fuel then Berkshire's wood gas proposal has serious merit.
http://www.green-trust.org/woodgas.htm
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Mini steam turbines -- convert a turbocharger?
I still have problems imagining a system designed to run on a gasoline/oil mixture wont have issues running on steam but maybe it's a start. Perhaps it doesn't matter if the engine life runs out a bit quick if you can replace it.
There are plenty of steam enthusiasts that home build scale steam engines. Maybe you can find enough information to piece together a design for a gen set using moderate technology.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Mini steam turbines -- convert a turbocharger?
If the fix bed is what's required for a village or remote mine or farm or business, buy the standard kit with no wheels. If the truck/tractor car/bus is what's needed instead of a farm and business implement, don't run the PTO.
Simple, standardized run-of-the blacksmith shop repairable parts. Power from 2-6 Hp up the 30 to 50 to 150 Hp.
RE: Mini steam turbines -- convert a turbocharger?
Something to watch out for on the hobby-type steam engines is that most of them probably are actually run very few hours. So you never really know how well the lubricating systems are set up and all. It may be a great little engine, but can you run it 20,000 hours without an overhaul? Or does it take a machinist building a new engine every 200 hours? (If I recall, one of the downfalls of the steam locomotives was they spent about 30% of their time in the shops being overhauled and all.)
As an alternate to lawnmower engines, you can buy new air compressors (just the compressor part, minus the electric motor and tank), that would be equally adaptable. In either case, you're liable to have lubrication problems when putting it into steam service.
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
Reliability is the big concern, I guess. If I get little power from a big heavy engine, then I can live with that; but if it's going to need a mechanic to come out and fix it every few weeks, we might as well just send him with a few jerrycans of gas and run regular engines. And some of these villages take a week to get to, so maintenance is the real bugbear.
Thanks again for all the thoughful and innovative suggestions!
RE: Mini steam turbines -- convert a turbocharger?
It's not just maintenance but also potentially safety concerns.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Mini steam turbines -- convert a turbocharger?
The original steam engines on ships were inefficient for their size, and their boilers blew up regularly. Eventually, they learned that wood was not a good material for boilers. Then they learned that iron and steel boilers had to be manufactured skillfully, then they learned how to analyze and manufacture them.
An efficient steam engine runs at high temperatures and pressures, requiring reliable analysis and fabrication techniques. This is an issue for safety as well as efficiency, and might be a good case against steam.
RE: Mini steam turbines -- convert a turbocharger?
http://www.youtube.com/watch?v=2LOcyjZthsg
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
I suggested a stirling because you are on a low budget,without mechanic support, without fuel infrastructure.
OK, I put my mc Gyver hat on and give it a try:
1.go to a scrapyard and get 2 motor blocks of a mass produced (popular) car (4 in line design)
block A will have 3 cylinders acting as the hot cylinders 1 cylinder will be converted to act as a compressor.
block B will have 3 cylinders acting as the cold cylinders 1
cylinder will be converted to act as a compressor.
2.the cylinders used to charge the engine with air should be located on the opposite site of the cooling water inlet.
To convert the 4 stroke cycle to a compressor cycle, you have two options:modify the camshaft so the cams are mirrored or modify the drive train from 2:1 to 1:1.
Next you need to provide 3 way ball valves, which give the following operating modes to your 2 cylinder compressor:
2.1.charging motor with air (starting and toppig up): both inlets of the cylinders are connected to open air, the outlets are connected to the motor circuit.
2.2.charging wood combustor with air (running): the outlets are connected to the wood combustor.
3.design a motor frame to support the two motor blocks and to interconnect the two crankshafts via the open gear, which was used to engage the starter motor.(one starter motor can be removed).The opposite cylinders of the two blocks should have a 90 deg crank angle difference
4.hot cylinders:the cooling inlet of the block is connected to the exhaust of the combustor, the cooling outlet serves as the exhaust of the motor.The valves on the ports not facing the other block should remain closed (remove their cams on the camshaft.the other 3 valves (of the ports facing the other block) are removed and the hole were the valve stems used to be are plugged.
5.cold cylinders:the cooling circuit is left in place (pump remains, thermostat valve is replaced by a dummy (so cylinders are cooled as much as possible).Same story on the valves,facing ports removed, other three remain closed.
6.regenerators:basically a cavity with a gas volume equal to the volume of one cylinder, stuffed with SS demister mesh.The three regenerators connect the opposing cylinder ports of hot and cold motorblock.Hot motorblock and regenerators need some insulation on the outside.Provide a tiny little pipe between the regenerators, so static pressure of the three cylinder pairs remain the same
7.interlink the two oil sumps and use the converted radiator on the cold block to cool the oil
8.wood combustor:an empty gas bottle (a tall one)is converted to use as combustor (before cutting remove the valve and fill with water)
bottom section:provide a port to remove ashes and to get the woodcharge going, this port is also used to make a starting fire. provide a connection to the compressor.(you might need a compressed air storage tank to facilitate starting (provide a flow to heat up the hot block)
mid section: this section is separated from the bottom section with grating.while stuffing the combustor with woodchips/sawdust, a pipe is placed in the centerline of the combustor.Once the woodchips/sawdust is compressed, the pipe is retracted, leaving an air channel.
top section:provide a port to load the combustor and to put and retract the centerpipe.Provide a line to the cooling water inlet of the hot motor block,provide a blow off valve on this line to discharge excess of heat.
if you need more power,build more machines to the same specification.Remember diversifying a design only increases the profit of the supplier.
I believe the proposed design is called an alfa type stirling
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
ahum... I did some calculation and you might want the scrap the proposed design for following reason (I guess you're right with regards to the stirling cycle):
a dreadfull power output, reason being:
stirling engine uses a temperature swing
ICE,gas turbine, steam turbine uses a temperature and pressure swing
so back to the drawing board:
1.find a 4 stroke engine
2.convert to a two stroke design,half the cylinders work as compressor, half as expander(camshaft modifacion)
compressors should be on the up stroke, while expanders are on the down stroke
choke the inlet flow to the expanders, by seriously reducing their inlet valve lift (cam shaft design,trial and error)
4. pay enough attention on the sealing of the ports on the combustor, so it can be pressurised (pressure swing depends on valve choke inlet expanders)
5.use a filter mesh on the outlet of the combustor
6.oil and water circuit remains intact.
good luck!
RE: Mini steam turbines -- convert a turbocharger?
if you're able to provide excellent sealing on the combustor,the maximum obtainable pressure swing is limited by a single stage compressor design (about 8 bar) and the spring load on the inlet valves of the expanders (probably<8bar)
RE: Mini steam turbines -- convert a turbocharger?
RE: Mini steam turbines -- convert a turbocharger?
Find a junkyard engine that runs, and run it on wood gas you will have half the conversion work to do.
You can also run a Honda generator set on wood gas with very little additional plumbing.
http://www
B.E.
RE: Mini steam turbines -- convert a turbocharger?
convert a turbocompressor to use as a steam turbine:
-requires a turbocompressor,a furnace with boiler, super heater, feed pump, level control,safety valves,flow regulating valve, PTO involving coupling and gearbox
convert a 2 stroke engine to use as a steam expansion machine:
-not feasable because 2 stroke engine uses normally oil in the fuel to lubricate the crankshaft, before entering the cylinder (2stroke without valves),using as a steam expander, wet steam will destroy crankshaft bearings.
convert 2 4 stroke engines to stirling:
-to much motor mass for usefull power output
use a gasifier with modified 4stroke engine(ignition timing, carburation):
combustor:
H+O2>H2O
C+O2>CO2
CH4+5O2>CO2+4H2O
gasifier:
H2O+2C(charcoal)>H+2CO
CO2+C>2CO
CH4+O>CO+H4
+well proven design (thanks berkshire for excellent info)
-providing combustion gas with a constant quality
-handling CO (poisonous)
-fuel preparation=chipping+dehumidification
use a combuster and a modified 4 stroke (camshaft)
combustor:
H+O2>H2O
C+O2>CO2
CH4+5O2>CO2+4H2O
expander (motor):
pressurised H2O(steam)+CO2(hot) expands to atmosphere
+combustor is easier to construct than gasifier
+fuel preparation=chipping
-continuous operation requires 2 combustors
-re engineering a camshaft
-design not proven (innovation gots us away from living in caves though)
RE: Mini steam turbines -- convert a turbocharger?
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