Gas turbine

Discussion in 'Propulsion' started by dskira, Dec 14, 2009.

  1. dskira

    dskira Previous Member

    Do you think small gas turbine will have a future on a yacht?
    Since they are extremly light for the power, I thouth it can be a good primer to run a generator. All that can even be on deck, so the maintenance and vents will be easy, and the electrical motor will be down below with direct shaft configuration.
    I don't invent anything, it was done before.
    I saw some turbine chopper second hand for sale. The good thing with turbine is you can use any fuel you can find.
    Just a thought, nothing else
    Cheers
    Daniel
     
  2. Luckless
    Joined: Mar 2009
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    Luckless Senior Member

    One problem I've seen for most gas turbines is they tend to be extremely hungry on start up. (The M1A1 uses a turbine engine, one of the few examples I know of off hand of a mobile turbine not on a plane. It takes 8 gallons of fuel to start it before it produces power.)

    It has been about 10 years since I looked at specs on them, but I remember they also had issues of dropping off in efficiency as you got smaller, and a small low powered turbine is actually more complicated than a large and powerful one. Just how much power do you need?

    Generally you also put your generator inline on the same shaft as your turbine, as that is one design aspect that grants them such high levels of efficiency.

    Also turbines tend to produce very loud and rather high frequency sound waves, which can be very hard to muffle as you will kill your engine performance if you produce a back pressure against the engine.
     
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  3. dskira

    dskira Previous Member

    I apreciate your thourough and professional comment.
    I know nothing about turbine, it was exatly what I expected, a good and honnest opinion.
    Thank you
    Cheers
    Daniel
     
  4. Submarine Tom

    Submarine Tom Previous Member

    Daniel,

    As eluded too above, the transmission required to bring 90 000 RPM down

    to a usable speed cancels out the weight advantage of the turbine.

    An interesting aside, the queen ship of a fleet of three passenger only,

    36 knot ferries ("CLIPPER IV") that run from here to Seattle (80 Nm) has

    recently replaced the screaming turbines with diesels! I was quite

    surprised.

    -Tom
     
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  5. hoytedow
    Joined: Sep 2009
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    hoytedow Fly on the Wall - Miss ddt yet?

    This thread was very informative. Thanks for the knowledge.
     
  6. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    The "modern" diesel has a problem in boat propulsion.

    They are most efficient when very heavily loaded .

    If loaded to run to the Mfg top RPM, when cruising they suck as the prop loading drops so rapidly with rpm.

    A muiti speed tranny would be great for 2 common speeds and with a CPP might be able to pay its high cost , but probably never on a pleasure boat.

    Electric , as in trains , is heavy and not efficient enough to pay the extreme costs of the gear , except in cruise ships with fantastic hotel loads,and AZPODS so they can dock with no tugboat bill.

    What is needed is a variable DIAMETER prop (changing just pitch isn't enough).

    OR an infinitely variable tranny at the same cost as a conventional tranny.

    To the Drawing board!

    FF
     
  7. mark775

    mark775 Guest

    I have postulated this before. Step it down enough that a Synergy Drive can accept the RPM. VOILA! Continuosly variable transmission, generated electricy, heat, a boat light enough to offset the inefficiencies inherant in small turbines. I bought a wrecked hybrid Toyota Hilander at one point to test the system but the electrical was daunting and the wrecked Hilander was too valuable as a rebuild so I sold it. When people get over the current hybrid craze, I will continue with my testing.
    By the way, If anyone thinks that they will bypass the surplus automotive planetary gear infinately variable transmission by buying an "electric wheel", http://technipowersystems.com/commercial-recreational-installations , guess again. These people are not very helpful and they want to make their children's college education from you, alone.
    Helicopter turbines are ideal (ideal because the engines are expensive to rebuild, so they take them out and replace - not good enough for taking passengers in a flying contraption because of the flying hours but good enough for decades of trouble-free service in a boat), by the way - what engine did you find?
    I have looked into micro-turbines and they are wrong for a host of reasons - http://www.microturbine.com/prodsol/products/index.asp but If you are comparing a range-extended piston ICE (30-35% efficient?) to a microturbine, then this comparison makes sense, but it should be pointed out that the Capstones do recapture waste-heat and have efficiencies up to the 40+% range for their larger turbines. With the smaller turbine size and multi-fuel operation, the application would be very compelling. All this assumes the turbine price could be competitive, which is unlikely - hence, the too-many-hour heli turbine but there is less done for you as far as heat re-capture (really making sence in northern latitudes) and the target for efficiency/ matching the right turbine to the right boat is even smaller.
    Argue the efficiencies, if you will, but with the right match of boat and turbine and load the efficiencies are gained by by simply being lighter and a long TBO.
    Salt ingestion means death for these, by-the-way.
     
  8. Submarine Tom

    Submarine Tom Previous Member

    A Bell 206 turbine puts out about 400 hp at 90 000 RPM and is about the

    size of a bread box. It sucks back about 30 gallons an hour if my failing

    memory serves me correctly and makes one hell of a racket.

    -Tom
     
  9. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Lots of misconceptions here....

    1. Turbines do emit noise if not properly installed. The noise is as noted, high frequency so it is relatively easy to address without much weight or backpressure. All you need to do is add dampening material to the ducting and make sure that the soundpath isn't totally straight and it will be very quiet.

    2. Turbines do run at high speed, but not as high as some of you are thinking. The gas generator of the Bell 206 runs at 52,000 rpm, the output power turbine section runs at 33,000 rpm, which is geared down within the engine to 6,000 rpm.

    3. The idea that the weight of the gearbox negates the weight advantages of the turbine is just silly. The Allison Model 250 in the Bell 206 weighs 158 pounds and that includes the gearbox to drop it down to the the 6,000 rpm output shaft speed, and the engine is rated at 420 hp. Show me ANY reciprocating engine of a similar power and output shaft speed that weighs 158 pounds and runs for thousands of hours and I will eat it.

    4. A properly designed free turbine does not need a multi speed transmission or electric drive to operate in a typical high speed marine application. The power turbine acts like a torque converter and provides higher torque at low speeds. A turbine can turn a high pitch prop and still pull the boat out of the hole and run at high speeds, something that diesels have a lot of trouble doing.

    5. Salt air isn't a big problem, most marine engines use a fresh water wash procedure to clean out the salt, and turbines can ingest a lot more water than a diesel without damage. This is more of an installation issue than an inherent problem.

    6. Smaller turbines generally have higher specific fuel consumption than larger ones. That is changing. Expect in the not too distant future to see turbines in the 500 to 700 hp class that have fuel consumption within 10-15% of a diesel at high power.

    7. Turbines burn more fuel at low power as compared to diesels, so it is more a function of how the boat is to be used that determines the suitiblity of a turbine for a given application. The higher fuel burn is partially offset by the substantially lower weight of the engine and transmission. That is, if you remove thousands of pounds of diesel engine, the boat is lighter, and at typical planing speeds will require less power to cruise, so even though the fuel consumption per horsepower is higher, the ligher weight reduces the power demand so that at some speed the turbine actually becomes more efficient that the diesel. If you look at 700 hp diesels, they weigh almost 3,000 pounds, compared to a turbine that will weigh around 250 pounds. That is a lot of weight savings. If you are moving a 50 foot hull at or over 35 kts the turbine is actually more fuel efficient.

    As noted, the reliability and life of turbines far exceeds that of reciprocating engines, so in applications where they are used a lot there is a big payoff.

    For conventional monohulls, depending on the fuel consumption, turbines start to make a lot of sense once you get above the 15-20m length and if you want to consistently cruise at or above 30 knots. Below that point the higher fuel consumption of the turbine makes it more difficult to justify, but there are applications where they make sense if you want to go faster (say consistently cruise at 40kts) or need to carry more payload. The larger and faster you go the more a turbine makes sense. Beyond 1500 hp (per engine) and over 30 knots cruise in a planing hull and you should be thinking turbines.
     
  10. Submarine Tom

    Submarine Tom Previous Member

    Yellowjacket,

    I guess that's why we see so many of them around.

    Here, there are about... hmm, lets see... gee... zero.

    So that's a surprise. I wonder why?

    -Tom
     
  11. mark775

    mark775 Guest

    I am not going to pick the entire post apart because after he stated that there were "Lots of misconceptions here" he proceded to concur - only nobody said anything about a high speed marine application, and yes, brain-trust, salt air is a problem. That's why there is an installation issue.
    You know, if I ever come across that way ("Lot of misconceptions around here", "I actually know something about the subject at hand unlike anybody that has commented on this thread.") would somebody give me a nudge? - because I just don't want to be an *******.
     
  12. Submarine Tom

    Submarine Tom Previous Member

    Well said 775, LOL
     
  13. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    Excuse me Mark, but how many years have you been involved in the design development and servicing of gas turbine engines?

    I've been doing it for over 35 years in both aircraft and marine applications. I have been a lead turbine engine design engineer and program manager for a major turbine engine company and am currently program lead for an effort under contract to the Navy doing development work on an advanced turbine application. Before you even suggest for a moment that you have any knowledge in this area you should have the experience and the credentials to back it up. Otherwise you are, like many others on this forum, considerably outside of your experience base and are only advertising you lack of knowledge.

    The original poster was trying to understand if turbines had a future in yachts. My point is that only in high speed applications do turbines make sense. If you are going to putt up and down the ICW at 5 knots go buy a diesel. If you want high speed get a turbine.

    As to the issue of salt air, salt absolutely can build up on compressors, but it is also easily washed off. Most marine turbines have water washing ports installed so that a water wash solution can be introduced to the flowpath and the salt removed. It isn't a big issue, it is a maintenance item. And it can be greatly reduced with proper detail attention to the design of the installation so as to segregrate spray and keep it out of the engine inlet. Recent advances in barrier filters also allow the spray to be collected and much of the salt dried out in the filter element, significantly reducing the amout of salt entering the engine. The remaining salt that enters the engine is washed out in periodic maintenance. It is also dependent on the design of the engine, some engines are much more effected by salt air, other are not.
     
  14. Submarine Tom

    Submarine Tom Previous Member

    Yellowjacket,

    Would you comment on why Clipper Transportation would have recently

    removed the turbines from their 36 knot passenger ferries that run 80 Nm

    four to six times a day and replaced them with diesels?

    Also, why don't I see any turbine boats around here. There are hundreds of

    internal combustion engined boats.

    -Tom
     

  15. mark775

    mark775 Guest

    It was obvious by your first post that you had been around turbines, Mr Anonomous "Lead engine design engineer", "for a major turbine engine company" , and equally obvious that you can be an *******. Now offer something constructive.
     
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