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Rolls Royce Trent Engine Technology

  1. Aug 28, 2007 #1

    Astronuc

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  3. Aug 28, 2007 #2
  4. Aug 28, 2007 #3

    berkeman

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    Thanks, Astro. That was really cool.
     
  5. Aug 28, 2007 #4

    mgb_phys

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    It looks like it means driving the compressor (and fan) electrically, presumably from power taken from the main engine shaft.
    I suppose this must be more efficient/simpler somehow but I don't see it!
     
  6. Aug 28, 2007 #5

    AlephZero

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    Does the word "GENERATOR" on page 34 answer your question?

    The total power output of a large 4-engine a/c at takeoff is about 200 MW. Running an aircraft aircon system isn't a big deal, by comparison.
     
  7. Aug 28, 2007 #6

    AlephZero

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    No, the fan and compressor are still mechanically driven.

    The big saving is getting rid of all the mechanical drives for fuel and oil pumps etc. The basic problem there is that the main shafts of the machine are concentric and buried in the middle of all the working parts so taking a mechanical drive off them to run pumps, gearboxes, electrical generators, etc on the outside of the engine is messy.

    The lubrication system has the same basic design problem - there's no easy way of getting oil to and from the bearings. The REALLY big prize would be to have no oil system at all - in principle, magnetic bearings don't need lubrication, period.
     
  8. Aug 28, 2007 #7

    mgb_phys

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    Ok - I thought it was the next step beyond a three shaft engine was to drive, say the compressor electrically so it's speed can be more quickly and precisely controlled.

    ps. Are the generators/pumps etc driven by a right angle side shaft coming out of the central shaft? I can see how that would be fun to install/maintain.
    Could you make a generator by fitting magnets/coils to the outer edge of the fans and put fixed coils around the outside, turn the whole engine into a large squirrel cage motor?
     
    Last edited: Aug 28, 2007
  9. Aug 28, 2007 #8

    AlephZero

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    You got it. As well as being "fun", accessory failures are a significant cause of engine shutdowns, so zapping them would be very good for reliability.

    EEK!!! The tips of the fan blades have a radial acceleration of something like 9,000g. Putting extra weights on them is probably not a good idea! (Check for yourself - r.omega^2 where r = 50 inches and omega = 3,000 RPM)

    Also, you wouldn't want to increase the overall diameter of the intake. The size is limited by ground clearance, for under-wing engines. The engines make excellent vacuum cleaners for keeping airport runways spotlessly clean already - that functionality doesn't need to be improved.
     
  10. Aug 28, 2007 #9

    mgb_phys

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    That's only about the same as steam turbines in a power plant - and they are much bigger.

    I thought their main use was as buffers for careless luggage cart drivers and to keep the airports free of birds!

    I did see a RR Trent being fitted as a backup power generator, basically the only modification was to bolt it down REALLY securely.
     
  11. Aug 28, 2007 #10

    AlephZero

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    And also much heavier!
     
  12. Aug 28, 2007 #11
    There is no right angle driveshaft to a remote power source shown.

    I could be wrong but what I think I see on page 34 is combustion ignition in the second stage which in turn drives turbines (no compressor ahead of it).

    The generator in the tail cone drives aircraft systems by feeding off the compressor shaft.

    The electric motor driving the big inlet fan gets it's juice from where?
    ..................................................................................

    Page 38 for the blended wing concept seems to have a "gas generator" in the tail section. I'm not sure if I'd call this turbo-fan or turbo-prop, the prop actualy being a ducted fan in this case.

    What do you call a gas turbine driven helicopter?
     
  13. Aug 28, 2007 #12

    AlephZero

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    Correct. The point is to get rid of the angle drive shaft that is in most existing gas turbine designs.

    Yes, you could be wrong - in fact you are wrong.

    I already posted that the fan isn't driven by an electric motor! And I ought to know, I haven't looked at all the slides but I wouldn't be surprised to find that I drew some of them.
     
  14. Aug 29, 2007 #13
    Q1: The electric motor connected to the first large inlet fan is actually an electric generator drawing power from the shaft which is turning via the combustion of gases passing through the compressor blades?

    Q2: What is the "electric" motor providing power to?

    Q3: Generators (not motors) convert mechanical motion into electricity, right?

    Statement-1: I thought motors drove things!
     
  15. Aug 29, 2007 #14

    Astronuc

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    The mechanical energy from the turbine drives the compressor/fan and generator. The fan and the exhaust of the turbine provide thrust for forward motion.

    Lights, avionics, basically anything electrical or electronic on the aircraft.

    Right.

    Motors convert electrical energy into mechanical energy, which is the reverse of a generator.
     
  16. Aug 29, 2007 #15
    Should the first electric motor be labeled a generator then?

    If both motors are acting as generators, why two?
     
  17. Aug 29, 2007 #16

    FredGarvin

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    A three shaft engine. We ran one a few years back. Too bad the project got canceled.

    Aleph, your new swept fan design is pretty incredible compared to ours. I thought ours were getting a bit radical, but that mid span "bump" in there is quite large. Very cool.

    It's "interesting" to see the slide on the tiled wall combustor. :wink:
     
  18. Aug 29, 2007 #17
    From another forum I posted this same topic in.....Carnuts.US

    So that first motor may act as:

    1. Electric transmission (gear reduction unit).

    2. Starter motor

    3. Generator (like regenerative braking the shaft).

    4. RPM regulator

    The second unit in the tail cone is just a parasite, converting rotational motion into current.
     
  19. Aug 29, 2007 #18

    Astronuc

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    I believe the purpose of motor/generator sets in forward section has strictly to do with 'active bearings', but I'll defer to AlephZero and FredGarvin on that.

    The generator in the aft section provides necessary power, I believe, so it's not exactly parasitic - it provides a necessary function.

    For starting, aircraft use external power supplies or on-board auxilliary power systems, i.e. small turbine-generators, usually located in the tail section.
     
  20. Aug 29, 2007 #19

    FredGarvin

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    I could take a guess, but we do not have an engine that incorporates those technologies yet, so I leave that to AlephZero.
     
  21. Aug 29, 2007 #20

    AlephZero

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    Astronuc is right. You can think of an active magnetic bearing as a sort of motor. You use electrical power to keep the rotating shaft centralized inside a ring of magnets. But the "motor" does not provide any power to rotate the shaft.

    There would be other electric motors to drive engine accessories like the fuel and oil pumps. These are driven mechanically in current engine designs. (Even though magnetic bearings greatly reduce the lubrication requirements, I think it will be a little while before anybody builds a completely "oil-free" engine!)

    Also aircraft cabin air would come from an independent electrically powered system, rather than being tapped off from the engine compressors as at present.

    The red block at the right of slide 34 is the generator (driven by the engine fanshaft) to power all these devices.

    There is no way you would even think about driving the engine fan electrically. The idea of replacing a simple steel shaft with a 50MW electrical generator connected to a 50MW motor is ... well, let's say it's not engineering.
     
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