Hypothetical crazy turbine steam boat

Discussion in 'Boat Design' started by parkland, Mar 12, 2015.

  1. parkland
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    parkland Senior Member

    OK This is less serious, and more for farts and giggles.
    I'm not trying to build this, lol.

    I recently came across these 'inventions':
    Turbocharger jet engines people made:
    https://www.youtube.com/watch?v=zyZRQ1btI6A
    https://www.youtube.com/watch?v=IND3eAI3YZk

    So what if we used that heat to make steam, and drive this bad boy?
    Steam engine:
    https://www.youtube.com/watch?v=ZSzPjDBQnLo

    I know what your thinking, "what a waste of fuel", "It will melt the turbocharger in 10 minutes of run time", things like that.

    So, what if.....

    What if the steam coil was partially inside the burning chamber? This would reduce combustion chamber temperatures enough to add more and more fuel. There could be a boiler coil in the smoke stack, but that would be to bring cooler water up to high temp, then it would get brought up to even higher temperatures inside the coils in the combustion chamber. This would keep the turbocharger 'jet engine' running at much safer temperatures than in the videos on go karts etc. As a 2 stage boiler system, the secondary stage of coil in the smoke stack would be the cooler exhaust met with the cooler water/steam, then in the combustion chamber, the highest exhaust temperatures would bring it up to as hot as you want. Just add as much fuel as you want, as long as the temperatures stay safe. I think doing that, the combustion chamber might run at insane temperatures, but by the time the exhaust reaches the turbine blades, it should be far cooler, and very safe for continued use.

    Why? Why even consider this, it would burn ungodly amounts of fuel?

    Well, waste oil is basically free all the way up to about 20 cents per liter, lots of guys getting it delivered for even less. Not only is it cheap, but it has crazy BTU's in it. The insane high combustion temperatures of the turbocharger engine would turrn a fuel pipe coile red-white hot, and the oil getting pumped in would burn off like natural gas.
    Not sure what type of metal tubing would be needed, or the cost.
    For the boiler tube or fuel vaporization tube.
    It should be able to burn almost any liquid fuel available.

    But, wouldn't it be cool to drive a steamboat with a jet boiler? :D

    I'm sure it would be plenty ineffecient, but if the fuel is that cheap, would it really cost any more than a good ol diesel engine to run?
    It would be quieter than diesel boat.
    Unlike normal boilers, it could be run to full power only seconds after getting the turbines to light off and spool up.

    I think it would be cool :)
    Not cool enough that I'd go make one right now, but if I won a 50 million dollar lottery, I'd build it tomorrow haha.
     
  2. fredrosse
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    fredrosse USACE Steam

    Just a different type of burner.

    These small jet engines, generally made from a turbocharger, have an operating speed so high that it is not practical to get any power off of them. They only are good for jet airplanes, and they have exhaust with plenty of oxygen left over, so an afterburner is possible.

    As shown on the videos you posted, they put out very much heat, but actually no more heat than you can get from any number of oil burners that don't need a turbo screaming at 100,000 + RPM to work. Motor driven oil burners, or vaporizing oil burners, to name two, will do the same job with far less noise and fuss.
     
  3. parkland
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    parkland Senior Member


    An afterburner, OR, put steam coils right in the end of the combustion chamber, before the exhaust drives the turbine. The more heat you can suck out of the exhaust, the more fuel you can run and still keep the temperatures safe.

    Granted, yes, you could replace the turbocharger engine with an air pump of some type, all it essentially does it move air. But, the cool thing is that the turbocharger jet engine is variable speed depending on fueling. Also the velocity achieved I think would be a very expensive burner.

    I know it's not a perfect idea, but I think it's cool.
     
  4. Rurudyne
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    Rurudyne Senior Member

    As I understand your idea you are basically suggesting using this as the burner element for what amounts to a compact water tube boiler, delivering a lot of heat in a small volume.

    First let me suggest the sort of boiler used by White steam cars, the gut of which are shown here: http://www.kitfoster.com/images/2006-8-2_WhiteBoilerWeb-Large.jpg

    Here's Jay "He of a Many Excellent Toys" Leno talking about one of his White's cars: http://youtu.be/Lf8miprLH60

    ... and about his 1925 Doble, which has a similar tube arrangement: http://youtu.be/ACO-HXvrRz8

    Additionally, have you considered a pulse jet like arrangement based on fluidic valves rather than a turbocharger jet? Your boiler throttle could then come from having the ability to fire one or more smaller jets.
     
  5. fredrosse
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    fredrosse USACE Steam

    The concept of having steam generator coils preceeding the gas turbine expander has been done many times, I think since WW2. Makes for a very compact boiler because the combustion space runs pressurized at about 5 to 10 atmospheres pressure, so the products of combustion are 5x to 10x more dense than in conventional boilers. The technical difficulties of this arrangement however make it impractical for general use. There have been some built over the years for marine propulsion, the latest article I could find:

    (1963), THE SUPERCHARGED STEAM GENERATOR. Naval Engineers Journal, 75: 443–448. doi: 10.1111/j.1559-3584.1963.tb04885

    Of course the examples you saw on youtube generate the large combustion heat output downstream of the gas turbine expander (at essentially atmospheric pressure), so the potential advantages of a boiler with the combustion gasses pressurized would not be available. These devices have no advantage over conventional burners without the use of a gas turbine.
     
  6. parkland
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    parkland Senior Member

    Well I don't know about that, while a turbocharger based jet engine is certainly no engineered turbine, the combustion chamber pressure can be 30 PSI or more on some of them.
    They could always be compounded too, or use a VVT turbo, to increase pressure.
    The afterburner concept is useless for a steam tube boiler, however it shows that a lot of fresh air is available in the combustion to burn much hotter.

    I was thinking the exhuast turbine would vent out the smoke stack, where the pre-heat coils would be. Bring the water from warm water, to steam, then the coils inside the combustion chamber would bring the low temp steam up to high temp steam.

    The way it would work, is that it would run much more fuel in the combustion chamber, and the steam coils would reduce temperatures to a safe level for the exhaust turbine. Without the steam coils in the chamber, I'm sure the amount of fuel would cause several thousand degree temperatures, and overspeed the turbo if the fins didn't melt off the turbine first.

    "Heat exchanging" the exhaust gasses before the turbine would allow much greater amounds of fuel to be burned, because you wouldn't be passing all that heat to the exhaust turbine. Lots of it would go into the steam coils.

    Anyone have a clue as to how many liters/ hour / hp a steam setup would run?
    Fuel oil - ~137,000 btu/hour /us gal
    1 boiler HP = ~33,500 btu / hour

    http://www.internationalsteam.co.uk/trains/newsteam/modern50.htm

    Since the turbocharger jet engine's purpose in a role like this is to generate heat, and not to perform effeciently, some design changes could be done to capture a lot of heat back into the system.

    So in the combustion chamber, would be the part of the steam tubes that are heated the most, and from there to the steam engine.
    The exhaust temperature would need to be around 1000* or less by the time it leaves through the turbine into the exhaust stack. Water flow / steam rate would need to be adjusted to the fuel rate to make this happen.
    After the exhaust leaves the turbine at around 1000*, it would travel into the stack. In the stack, there would be a large stack of boiler coils, where the water gets pumped into. After the exhaust leaves these coils, maybe it would be about 500*.
    On top of those coils, in the 500* exhaust, there could be an air-air exchanger, where the air compressed by the compressor wheel travels through, to pre-heat the combustion air to about 400*.
    After that air exchanger, the exhaust gasses could now be around 200*, and yet another air-air exchanger, would provide hot intake air for the turbocharger jet engine. Complete opposite of what you'd want in a car or truck, but remember this is in the name of creating heat, not effecient shaft power.

    Turbochargers can easily swallow hot air, they do it constantly in compound setups. The coil in the combustion chamber can keep EGT's at safe levels. So, there is no reason the turbocharger jet engine should fail prematurely.

    By capturing a lot of the exhaust heat back into the heat production, shouldn't that make a pretty effecient boiler system?
    As for the waste steam out of the actual steam engine, could not a condenser be used, to bring the effeciency level up quite a bit? Just build a steam exhaust tank, with a few coils running through it, say 3 coils, each with a fresh water pump and thermostat, and just have the pumps automatically turn on as pressure rises in the tank, to condense the steam into water, but really hot water so it takes less engery to reheat.
     
  7. Rurudyne
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    Rurudyne Senior Member

    Parkland, you will need to have the cool water encounter the coolest exhaust first and then use the combustion chamber as superheat. If you go hot-to-cold first you may have issues with the hot end of your steam giving up heat to the cooler exhaust of else you'll need to be very conservative in exhaust end coils to avoid this.
     
  8. parkland
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    parkland Senior Member


    Thats what I meant, although maybe didn't say clearly.


    The water/ steam coil would get pumped to the stack on top, and pick up heat as it gets closer to the turbo-combustion chamber, then become super heated in the combustion chamber, then go to the steam motor.

    That, and since there is likely lots of hot air left after heating the coils in the stack, also pre-heat the air for the combustion.
    Every bit of waste heat re-captured should mean more efficient boiler.
     

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  9. fredrosse
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    fredrosse USACE Steam

    Parkland, I think you are very nearly describing what typically happens in a “Supercharged” Boiler, where a gas turbine is used to pressurize the boiler casing. These units have been built ranging from about 80 years ago. The pressurized boiler casing keeps the combustion gasses at high pressure = high density = enhanced heat transfer character. This can allow development of a more compact steam boiler.

    The way these "supercharged" boilers have been typically arranged is as follows:
    1. Gas Turbine Compressor Section - takes in air, with a pressure ratio typically around 7:1, pumping air up to around 100 PSIA. (The actual pressure ratios for gas turbines is variable, modern machines are approaching pressure ratios of around 15:1, whereas gas turbines made from typical turbochargers have a much lower operating pressure ratio, in the vicinity of 2:1)
    2. Combustion Chamber - where fuel is added, and gas temperature rises considerably. (In typical gas turbines the firing temperature must be kept low, on the order of 1500F so the downstream component (the expander turbine) will survive. This is done by providing very much excess air to supress the combustion temperature. However, in a supercharged boiler, the temperature is made very high, around 3000F - 3500F with very little excess air.
    3. Pressurized Boiler Casing - Boiling and Superheat Generating Tubes - Hot High Pressure Combustion Gasses pass through banks of boiler tubes and generate output steam. (Usually arranged with a couple of rows of steam generating tubes {boiling heat transfer}, then thru rows of superheating tubes, then thru the bulk of the boiling section tubes. The superheating tubes are usually placed after enough temperature reduction of the hot gasses has occurred to assure no burnout of these tubes.)
    4. Gas Turbine Expander - Expands the gas down to nearly atmospheric pressure, and produces enough power to drive the compressor. (The temperature reduction of the previous section has brought down the gas temperature low enough to protect this component from burnout, but still hot enough to allow getting power output to drive the compressor, and often some excess power to run auxiliaries or generate electricity)
    5. Atmospheric Boiler Casing - Generating Tubes & Economizer Section – Captures heat available downstream of the expander. ( The outlet from the expander still has considerable temperature, near 1000F. This hot gas flow is used to generate more steam and to heat the feedwater up to the boiling point before actual boiling begins.
    6. Exhaust Stack – Products of combustion released to atmosphere, usually a few hundred degrees F.
     
  10. parkland
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    parkland Senior Member


    More or less, that is exactly what I was thinking.
    Even without the ultra high combustion pressure, I think it would still work well. The pressure plus velocity would make a difference over an ambient pressure boiler.
    Pressure could be increased by compounding a few turbochargers, but I don't know if that would accomplish much if space wasn't an issue.

    So whats the verdict then? I can't seem to find any information on these supercharged boilers. Were they a good idea?
    Did they perform better than conventional?
    Is this crazy idea too crazy? lol.
     
  11. Rurudyne
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    Rurudyne Senior Member

    Fred, what you just described sounds in effect something like the Doble, more over the top, but a lot like it. In particular, if anyone is thinking about steam with a burner anywhere near that hot, Leno mentions a special liner for your fire box that let's that actually work.
     
  12. parkland
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    parkland Senior Member

    The combustion chamber design with the turbocharger jet engine, is a fire tube, so the air flows from the outside in.
    If that tube is extended in length, with the fuel and steam coils inside, by the time the exhaust gasses leave, they should be safe enough for steel.
    The only expensive or exotic metals would be for the flame tube, and the oil vaporization coil. The steam coil should stay a lot cooler.

    The steam pipe at the foremost to the heat part, could have an EGT probe inside the pipe, and if it got too hot, it could release steam into the chamber, cooling everything off. That would only be if other systems failed.

    Maybe boiler tube could even be made from copper?
     
  13. fredrosse
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    fredrosse USACE Steam

    “So whats the verdict then? I can't seem to find any information on these supercharged boilers. Were they a good idea?”

    Conceptually they are interesting, but for many practical reasons, it is just easier to make a boiler that has a casing containing the combustion gasses at close to atmospheric pressure. In utility sized boilers, furnaces are run with the boiler furnace usually at minus one half an inch water column (in WC). Utility “pressurized” furnaces were popular some decades ago, but these boiler casings would run at about 20 in WC, essentially at atmospheric pressure. These types were largely converted to operate at minus 1/ 2 inch WC, because the leakage of hot noxious gasses from the boiler casings became problematic. For comparison, a supercharged boiler casing, running at just 30 psi would be equivalent to around 800 in WC.

    For a perspective on these pressures, the vacuum you need to draw Cola up a soda straw, only 1/ 2 inch, is not much at all. 20 to 40 in WC is what a typical domestic vacuum cleaner can produce. Ordinary atmospheric pressure, 14.7 psia, is equivalent to about 400 inches water column absolute.


    “what you just described sounds in effect something like the Doble, more over the top, but a lot like it.”

    Not really, the Doble boilers always ran with furnace pressures of a few inches water column (in WC), so they are essentially atmospheric pressure boiler casings. Doble boilers are a good example of the high performance one can get without resorting to a supercharged furnace design.
     
  14. fredrosse
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    fredrosse USACE Steam

    "Maybe boiler tube could even be made from copper?"

    For heat exchange conditions found in boilers, the high thermal conductivity of copper provides only very slight advantages compared to steel. However the steel material can endure temperatures far in excess to what copper can take. This is why all industrial and commercial and utility boilers never use copper, no real advantage.
     

  15. Rurudyne
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    Rurudyne Senior Member

    Fred, I was referring to the use of a draft booster, a turbocharger like affair, that enables the Doble to run at the temperatures it does. One would normally associate kit like that with pressurization in an ICE.
     
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