Sealed CO2 Turbine Drive

Discussion in 'Hybrid' started by DaS Energy, Jul 14, 2012.

  1. DaS Energy
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    DaS Energy Junior Member

    Hello People,

    Same time back DaS Energy posted on a liquid piston supply of force to a turbine. The piston has now been replaced and is is turbine only. It too is OPEN TECHNOLOGY.

    It actualy apes the workings of a fridge, and takes in American NASA use of CO2 as new Refrigerant R774(CO2)

    Carbon Dioxide the weirdest gas ever. Begins as a block of Dry-Ice. Heat increase changes to gas, then to liquid, then to gas, then to Dry-Ice. It’s the only gas that behaves like liquid.
    CO2 gas at temperature above 31.2* will not convert to liquid no matter what compression is applied.
    The energies of CO2 are thousands time greater than Steam.
    Energy as a force is measured in bar, one bar being the equivalent of 14.2 PSI or one atmosphere.
    One litre of Water, Steam or Gas per second at 9 bar pressure passing through a turbine generator produces 720 watts. Any increase in bar pressure or volume per second increases the wattage output.
    Working from a base line of 0* Celsius Steam is beginning to form at 100*C whilst CO2 has already reached 7,000 bar.
    The attached diagram operates in two different mode, the first below 31.2*C using the cooling loop of a fridge to cool the hot gas before going to the compressor which squeezes the gas into liquid before feeding it back in heating point.
    The other uses a boiler and exploits the fact CO2 at temperature above 31.2*C formats into Dry-Ice. At 100*C it’s 50/50. 50% Dry-Ice coats boiler ceiling and wall and the other 50% remains high pressure hot gas.
    This design does away with the fridge cooling loop and instead exploits the Dry-Ice field constant in the boiler. CO2 though gas but behaving like liquid is force drained from the bottom of the Boiler then piped back through the Dry-Ice field which cools the CO2 gas back to liquid. Hot gas exiting the Boiler forces the cold liquid at the same pressure of the gas exiting the boiler. The cold liquid at force then drives a Hydro turbine which empties into a screw pump Boiler feed. The technology is fully sealed and 100% recycling.

    Peter

    http://i1225.photobucket.com/albums/ee397/DaSEnergy/DAS.png
     
  2. Yellowjacket
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    Yellowjacket Senior Member

    There are a few systems that use supercritical CO2 as a working fluid also. While it is possible to use CO2 as a working fluid what you will really find out is that the higher energy capacity of the fluid simply makes the turbomachinery smaller. Smaller turbomachinery is less expensive, but it runs at really high rotational speeds (think like 100,000 rpm) and as a result tip clearance issues result in machines that are less efficienct than a larger machine. These machines run at very high pressure, working pressures are over 3,000 psi.

    The U.S. Navy is currently looking at bottoming cycles to extract energy from the waste heat created by the gas turbines aboard ships. Supercritical CO2, at first glance looks like a good candidate, since it results in smaller tubomachinery and good thermodynamic performance. Problem is, if you have a leak or a line ruptures, or you have battle damage, you can flood a compartment with CO2. That doesn't sound too bad, you won't have a fire, but in the closed confines of a ship, a compartment that floods with CO2 kills everybody inside in about 30 seconds. The concentration of CO2 that is lethal is only 14%.

    There are any number of working fluids that can be used for closed cycle engines, but the most common is steam because it is relatively safe and easy to maintain, non lethal if it escapes. The downside of steam is that it's a nasty working fluid that causes corrosion, scale buildup and lots of maintenance headaches.

    There is one other working fluid that actually makes a lot of sense for marine bottoming cycle systems, and that is air... Safe, relatively low pressure, low maintenance, and pretty decent heat recovery capability. Look for that in the future...

    You heard it here first..
     
  3. DaS Energy
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    DaS Energy Junior Member

    Hello Yellowjacket,


    Thank you for a most interesting reply. Much appreciated.


    I fully agree if a line ruptures the CO2 escape would be deadly, however high pressure CO2 escape into a area of larger volume immeadiatly turns to Dry-Ice, (a CO2 fire extinguisher demonstrates in part, however thats CO2 at low pressure). giving some time to escape before the Dry-Ice flashes off to gas. Superheated Steam pipe rupture on the other hand is one huge explosion.

    Peter
     
  4. Yellowjacket
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    Yellowjacket Senior Member

    While it is at high pressure, the CO2 in an engine is also at high temperature. The coolest part of an engine would have the working fluid over 200F, and the peak temperature of the working fluid will be over 1,000 F if it is taking waste heat from the exhaust of a turbine, or higher if it is a fired application. Depending on where your leak is in the engine it can very easily remain a gas, and at 3000 psi, it can empty in a very short period of time. Even if some of it turns into a solid, enough will become a gas that you will have a lethal amount of CO2 in your compartment in seconds.

    In the turbine industry we commonly use Cardox systems to supress fire in test cells. At concentrations greater than 17 percent, such as those encountered during carbon dioxide fire suppressant use, loss of controlled and purposeful activity, unconsciousness, convulsions, coma, and death occur within 1 minute of initial inhalation of carbon dioxide. In order to work in areas that are protected by Cardox systems, you have to take a training class so that you understand the system. You very quickly learn that if the warning horn goes off, you get the H out of there as fast as you can or you die.

    Just my personal opinion, but high pressure CO2 systems aren't something that I would want in my ship.
     
  5. DaS Energy
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    DaS Energy Junior Member

    Hello Yellowjacket,

    I can appreciate your concerns to safety, petrol and diesel engines both go boom and kill if a leak happens, and a compartment filled entirely or near so with CO2 will also kill. CO2 leakage death may be overcome by ensuring the engine compartment has larger air volume than the amount of CO2 stored in the turbine, that way a shortness of breath may occur but death is elimated. Entirely unlike being scalded to death when a Steam line bursts.

    If I may draw your atttention to couple of further points. The engine design pictured coolest part is cooler than +31.2C not 200F and the peak temperature is 100*C not 1,000F

    The system is designed to do away with combustion engine or other heat engine, but may draw heat from such other engine. CO2 fluid return to the Boiler must not be greater than 31.2*C or it will not be fluid no matter how much compression is applied. CO2 when heated to 100*C has a gas drive force of 7,000 bar. CO2 at 100*C has 40 times the pressure of Steam at temperature of +550*C. I have not been able to find chart or graph of CO2 of 1,000 F. A Diesel engine having a compression of 300 PSI and combustion force at best 5 times higher or 1,500 PSI is a drive force of 105 bar. CO2 at 100*C has 66 times the power of Diesel combustion from such compression comprssion ratio. I am informed the US Navy is now experimenting with Supercritical CO2.

    I do applogise for replying in C and F but every time I go net for conversion everything I have written dissapears and I have to begin all over again.
     
  6. Yellowjacket
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    Yellowjacket Senior Member

    Any engine that has only a 70*C thermal difference isn't going to be efficient at all. Simply put, you aren't going to get any meaningful work out of it. A perfect engine Carnot efficiency would be 18% and typical turbines are closer to 30% of that, so you are looking at getting back 6% of the heat as power. Add generator or gearbox efficiencies on that and it sure isn't much. Hardly worth the effort. It might be "free" energy if you are getting it from waste heat, but it's probably easier to try to improve the existing engine by a small amount than it is to add all that hardware and maintain it for such a small energy return.

    I was talking about a realistic engine where you can get something closer to 25% of the waste heat back to power. This entails a lot bigger temperature differential, in order to efficiently get some work out of it. Turbine exhaust gases are typically about 1,000 F and you have a heat sink (the ocean) at about 100 F (worst case, I know most of the time it will be better, but systems are rated on worst case). That gives you a decent temperature to work with and recover some energy from. Most waste heat recovery systems don't bother with trying to use the water from cooling reciprocating engines since the heat is of so low a temperature that it is really worthless.

    This is one of the advantages of a gas turbine compared to a diesel. A typical diesel turns about 1/3 of the energy into shaft work, rejects about 1/3 of the energy thru the cooling system, and the last third goes out the exhaust. A gas turbine has a few points lower overall efficiency, but all of the heat rejected goes out the exhaust, so there is actually twice as much energy available to be converted into work in a bottoming cycle.

    Bottom line is that a turbine with a bottoming cycle can approach 50% thermal efficiency, and yes, I know some will chime in that there are low speed diesels that can do that, but the power density of those is so poor that they can only be considered for cargo ships where they can afford the weight and don't need as much power. For a large fast ship, like a destroyer a gas turbine with some type of heat recovery is actually a very attractive system.
     
  7. blisspacket
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    blisspacket Junior Member

    That's an important discussion, gents. Thanks for your erudition.
     
  8. Submarine Tom

    Submarine Tom Previous Member

    YJ!

    Thought provoking comments, thank you.

    CO2 is dangerous yes, and effective in fire supression on ships but not without it's deadly sideffects for sure, like loss of life for anyone trapped in the engine room after lockdown, required for effective use. Toughest discission a captain will ever make, pull the CO2 with crew remaining in the sealed off area in order to save the remaining crew and ship.

    But I digress...
     
  9. DaS Energy
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    DaS Energy Junior Member

    Hello Yellowjacket,

    "Any engine that has only a 70*C thermal difference isn't going to be efficient at all"
    Best case scenerio. A Diesel engine having compression of 300 PSI, then injected with Diesel fuel, burn temperatures 1200*C, expansion of five to one, provides 1500 PSI or 106 bar piston force. CO2 at 30*C has force 426 PSI or 30 bar, temperature increased to 100*C has force 99400 PSI or 7,000 bar. As Diesel engine will run underwater, it may be fully immersed including the exhaust, however air intake need remain clear.
    Untill the liquid heat sink reaches the same temperature of Diesel engine 100% heat transfer occur. Co2 at pressure of 7,000 bar provides its own cooling by way of osmosis within the boiler unit. Heat transfer passes to the formed in boiler Dry-Ice causing it to flash off into CO2 gas. The CO2 gas if not transfered to turbine forms into Dry-Ice within the boiler. CO2 I understand is unique in turning into Dry-Ice at temperature above 35*C.

    Peter
     
  10. DaS Energy
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    DaS Energy Junior Member

    Hello Submarine Tom,

    I agee a hard call for any person to make. Sealing somebody to their death. CO2 however in place of Steam save people from being broiled alive when a Steam pipe bursts. CO2 escaping confinement flash cools. More a danger from things freezing than being cut in half by super heated Steam.

    Peter
     
  11. Yellowjacket
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    Yellowjacket Senior Member

    Peter,

    You need to look at the thermal efficiency, not the pressures created. While you can indeed create a lot of pressure with the phase change process, you aren't going to gain useful work without a temperature differential. That's basic thermodynamics. Look at your thermal efficiency and go from there.
     
  12. DaS Energy
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    DaS Energy Junior Member

    Hello Yellowjacket

    "a temperature differential" 30*C to 100*C then back from 100*C to 30*C is a temperature differential of 70*C.

    Peter
     
  13. Submarine Tom

    Submarine Tom Previous Member

    That is correct Peter.

    What is your point?
     
  14. DaS Energy
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    DaS Energy Junior Member

    Hello Submarine Tom,

    I beleive it was reply to "you aren't going to gain useful work without a temperature differential"

    Peter
     

  15. Yellowjacket
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    Yellowjacket Senior Member

    Peter,

    Yes, we all can agree that you have a 70C temperature differential. But the problem is you can't do much useful work with that much temperature change. In a perfect world you would get 18% (Carnot efficiency) of the heat you put in. But you have a real cycle with real component efficiencies and that's the rub. A large scale Rankine cycle power plant gets an efficiency of about 42%. That's about 66% of its Carnot efficiency. In something smaller (like what you power a ship or a yacht) you are looking at getting 50% of the Carnot efficiency. So you are likely to get about half of 18%, or something like 10% of the heat that you put into the cycle into useful work.

    If you think that getting 10% of the energy that you put into a system out as useful work, then go for it. But you have to look at the cost of the system, and then figure out how much you save in terms of fuel burned by improving the efficiency of a system by 10%. More than likely you just can't make a case for a system with that poor an efficiency.
     
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