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  #1  
Old 07-27-2010, 02:37 PM
rainy rainy is offline
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Convert a gas engine to steam?

Could you take a modern car and modify it to run on steam?

Would it be possible to just pipe steam, from say a boiler in the bed of a pickup truck, into the cylinders and expect the steam to do the job the gas and spark does?

Or are the fundamentals of the two designs so different you could never get it work?
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  #2  
Old 07-27-2010, 02:48 PM
Bryan Ekers Bryan Ekers is offline
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Conversion gas-to-steam is often done as a hobby project. Google turns up multiple examples, but it ain't for the faint of heart or shallow of pocket. I have serious doubts you could get steam pressure comparable to that of a standard ICE explosion of vapourized fuel, let alone feed it to the engine through a network of pipes. The pipes themselves would have to be as thick as the cylinder walls.
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Old 07-27-2010, 02:50 PM
Hypno-Toad Hypno-Toad is online now
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I think that the cylinders on a gas engine are just too small. The steam needs significantly more room to expand. My memory is that steam has a lower energy density and therefore you need more of it to perform the same work as a lesser amount of exploding gasoline.

But I could be wrong.
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  #4  
Old 07-27-2010, 03:16 PM
Bryan Ekers Bryan Ekers is offline
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Assuming I read these cites correctly:

"As a rule, most engines should have 140 to 160 lbs. Of cranking compression with no more than 10% difference between any of the cylinders."

150.3 PSI of gauge pressure corresponds to a steam temperature of 365.99 degrees Fahrenheit (pdf file)

So if you wanted to use steam to drive an ICE engine's pistons, you'd have to superheat it, with all the risk and hassle that entails. It's possible, I suppose, but I'd rather replace the whole engine.
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  #5  
Old 07-27-2010, 03:24 PM
engineer_comp_geek engineer_comp_geek is online now
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You'd do better to convert the engine to run on something like wood gas.

Steam engines are generally external combustion engines where gasoline engines are internal combustion engines. Converting one to the other isn't trivial.

A car engine goes suck squeeze bang whoosh. The camshaft opens the valve to let in gas, which is pulled in by the cylinder going down (suck) then the valves close and the cylinder compresses (squeeze). Then, with the valves still closed, the spark plug ignites the gas (bang) which forces the cylinder down. The exhaust valve then opens up and as the cylinder moves back up and pushes out the exhaust gases (whoosh) and then the cycle starts all over again.

If you tried to force steam into the engine you can force the pistons down during the suck phase and the steam will be expelled during the whoosh phase, but in between you've got the piston compressing the steam which doesn't do anything useful. It's going to be horribly inefficient, and as Bryan Ekers pointed out, your steam lines will need to be pretty hefty. You could modify the camshafts to eliminate the extra piston throw in the middle but if you are completely ripping apart the engine to fit the steam lines and a new camshaft and all of that it's probably easier and cheaper to just replace the pickup's engine with a true steam engine at that point.

A regular gasoline engine also probably won't survive long with steam being forced through it. Even if you change the oil like mad to get rid of the water that condenses into it, the rest of the engine parts aren't designed to be exposed to that much moisture.
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Old 07-27-2010, 03:36 PM
engineer_comp_geek engineer_comp_geek is online now
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I probably should have explained wood gas instead of just mentioning it so briefly.

This was done a lot in Germany during WWII when gasoline got really scarce. You basically burn wood in a reactor in the back of ye ol pickup truck. Combustible products essentially boil off from the wood and are sucked into the engine where they are used for combustion.

A simple old pickup truck engine will run just fine on wood gas. A modern fancy shmancy computer controlled engine probably wouldn't do so well.

Here's a picture of a VW Beetle that was converted to run off of wood gas.
http://ww2.whidbey.net/jameslux/bugwood.gif
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  #7  
Old 07-27-2010, 03:45 PM
Bryan Ekers Bryan Ekers is offline
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Quote:
Originally Posted by engineer_comp_geek View Post
Here's a picture of a VW Beetle that was converted to run off of wood gas.
http://ww2.whidbey.net/jameslux/bugwood.gif
Good thing that's not a powder post beetle, or it'd consume wood even faster.
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  #8  
Old 07-27-2010, 04:11 PM
GHO57 GHO57 is offline
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Quote:
Originally Posted by engineer_comp_geek View Post
If you tried to force steam into the engine you can force the pistons down during the suck phase and the steam will be expelled during the whoosh phase, but in between you've got the piston compressing the steam which doesn't do anything useful. It's going to be horribly inefficient, and as Bryan Ekers pointed out, your steam lines will need to be pretty hefty. You could modify the camshafts to eliminate the extra piston throw in the middle but if you are completely ripping apart the engine to fit the steam lines and a new camshaft and all of that it's probably easier and cheaper to just replace the pickup's engine with a true steam engine at that point.
Actually... now that you brought it up... Compressing steam does seem counterproductive... and running multiple cylinders in sequence is excessive, but I got to thinking. If the valve system can be reconfigured...
Something like;
1) Exhaust valve open during up-stroke to evacuate the cylinder.
2) Exhaust valve closed, intake valve open to allow steam to enter cylinder.
Turn it into a 2 stroke basically. Perhaps by simply ripping the whole valve assembly out and bolting some high-speed solenoid valves instead (possibly hack the ECU to run them)?

And since superheated steam is... how should I put it... slightly unsafe? How about accepting lower pressure and less power. Meaning lower RPM... reducing the need for lubrication and getting rid of some of the oil based problems.

Yes, it would self-destruct soonish but would it work?
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  #9  
Old 07-27-2010, 11:22 PM
Kevbo Kevbo is offline
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A decade or more back, "Live Steam" magazine published a long series of articles on the Barret (sp? working from memory here) steam car. This was VW beetle/kit car based conversion. Only two cylinders of the VW's 4 were retained, the other side of the crankcase was blocked off. New cylinders and heads were made, and the pistons had steel caps added to the crowns to take the heat and erosive effects of high pressure steam entering the cylinders. IIRC this was a single acting uniflow design, and retained the VW electric starter, since it was not self starting.

Water is the biggest hurdle to overcome for any steam vehicle (it is the primary factor that killed steam locomotives). The car mentioned above used a condenser and centrifugal oil separator. Similar to what was used on steam ships. Locomotives did not do this because they needed the power of very high pressure steam, and the cylinder oil breaks down at those temperatures, and can't be separated from the feed water. If oil gets in the boiler, it fouls the surface, causing hot spots and rapid boiler failure. For this reason, condensing steam engines are limited to ~100psi steam which makes for rather low power density....the engine will be pretty large and heavy for the power produced. You can overcome this with higher pressure, but then you have to make frequent water stops.
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  #10  
Old 07-27-2010, 11:33 PM
Snnipe 70E Snnipe 70E is offline
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As to pressure. The mean effective pressure if IC engines when I was going to school was around 180 psi. this was with babbit bearings. I would imanage that they are in the area of 300 psi today.

So a boiler in the range of 300 psi would work.

Piping would have to be schdule 80.

The steam could be superheated a few degrees to help with power.

Piston size would not be a problem. I have seen generators with smaller pistons that a medium size V8.

Problems and changes that would be incountered.

The cam shaft would have to be replaced.

A new and larger intake and exhaust maifold would be required.

If it is going to be run condensing a condenser would have to be added along with pumps.

burners and fuel controls added.

If the steam is superheated to high then a problem with lubrication would develop.

Valve stems are not designed for high pressure gasses and would leak.

This engine would have single acting cylinders and steam would leak past the piston rings into the crank case, adding mositure to the crank case.

If the engine is run non condensing then a large reserve supply of treated water would have to be carried on the truck.

The boiler would have to be large. And a high pressure boiler (over 15 psi) needs to be operated by an experienced operator.

These are some of the problems there would be more. the danger thing caused Howard Hugues to walk away from steam cars.
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  #11  
Old 07-27-2010, 11:47 PM
Snnipe 70E Snnipe 70E is offline
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Quote:
Originally Posted by Kevbo View Post


Water is the biggest hurdle to overcome for any steam vehicle (it is the primary factor that killed steam locomotives). The car mentioned above used a condenser and centrifugal oil separator. Similar to what was used on steam ships. Locomotives did not do this because they needed the power of very high pressure steam, and the cylinder oil breaks down at those temperatures, and can't be separated from the feed water. If oil gets in the boiler, it fouls the surface, causing hot spots and rapid boiler failure. For this reason, condensing steam engines are limited to ~100psi steam which makes for rather low power density....the engine will be pretty large and heavy for the power produced. You can overcome this with higher pressure, but then you have to make frequent water stops.
Water was not the only major factor. Steam required more maintenance almost daily. Recip steam engines normally do not have cyllinder lubrication, unless high superheated steam is used. Normal steam pressure for marine recips was in the 200 to 300 psi. Efficiency was a big killer of steam both in locomotives and ships.
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  #12  
Old 07-28-2010, 02:04 AM
Kevbo Kevbo is offline
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Having some trouble finding online sources that specifically mention operating pressure, but here are some:

http://www.norwayheritage.com/articl...id=87&zoneid=5

Quote:
On the S/S Servia buit in 1881... Steam was supplied at 90 lb. per sq. in. pressure. The total number of furnaces was thirty-nine, constructed with Fox's corrugated flues. On trial the engines indicated 10,300 horse-power, and the vessel attained a speed of 17.8 knots.
That site also gives a P/V diagram for a triple expansion engine of unknown vintage, with the pressure/temperature axis unlabeled as to units, and with the name of the site, it may be European units , but the peak pressure is shown to be 150. (150 goats?)*

From:
http://www.apl.com/history/timeline/stat5.htm
It looks like the typical working pressure at the end of the recip. steamship era was 220psi. The higher pressure vessels (~265psi) appear to be steam turbines.

I'm not having much luck finding cites for steam oil being used on large recip. steamships, but yours is the first time I have ever heard it suggested that they ran without lubrication.

Here is an article about lubrication of Stanley steam car engines:
http://www.stanleymotorcarriage.com/...atorDesign.htm
Quote:
The pistons and slide valves are lubricated as the engine runs by steam cylinder oil injected in the engine’s steam supply. The oil is carried along with the supply steam and lubricates the surfaces of the slide valves as well as the piston and cylinder walls.
Same site, different page mentions boiler problems caused by steam steam cylinder oil:
http://www.stanleymotorcarriage.com/Parts/Boiler.htm
Quote:
t was found that the steam cylinder oil would dissolve into the water as the steam was condensed. This water-oil mixture would be discharged into the water supply tank only to end up in the boiler. As the water was heated in the boiler the oil tended to collect on the lower flue sheet and cause hot spots (the oil would burn onto the bottom flue sheet and act as in insulator). This created uneven heating and allowed the flue tubes to start leaking
Here is a current source for steam cylinder oil, including suggested applications up to quite large and high pressure engines:
http://www.steamenginelube.com/cylinderoil.htm

Apparently modern oils can allow condensing operation at high temperature and pressure without boiler issues.

* Mr Walters, one of my high school teachers: "Any number that does not indicate units will be assumed to be in goats, and goats will never be the right answer."
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  #13  
Old 07-28-2010, 02:20 AM
Kevbo Kevbo is offline
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An example of a modernish steam ship running condensing at 400 psi:

[pdf] http://files.asme.org/ASMEORG/Commun...marks/5496.pdf

and Lo! on page 7 we find
Quote:
24. Injectors for steam cylinder oil. Two for each
high-pressure cylinder.
So the old issue of saphonated steam cylinder oil breaking down and making it's way to the boiler has been licked. And I had it a bit wrong about the working pressures, but I am very sure that any reciprocating steam engine needs steam cylinder oil if it is to last.
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  #14  
Old 07-28-2010, 05:47 AM
Icerigger Icerigger is offline
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It worked for John Saxon and Gene Roddenberry in Planet Earth.

http://www.youtube.com/watch?v=SmmTq...eature=related
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