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View Diary: How Airliners Work - Propulsion (191 comments)

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  •  The exhaust end fan, the turbine (1+ / 0-)
    Recommended by:
    fisheye

    is being pushed by the hot air leaving the engine. It provides the power that makes the rest of the fans spin.

    "The problems of incompetent, corrupt, corporatist government are incompetence, corruption and corporatism, not government." Jerome a Paris

    by Orinoco on Tue Apr 02, 2013 at 10:54:05 AM PDT

    [ Parent ]

    •  Funny I always assumed different stages of (1+ / 0-)
      Recommended by:
      RiveroftheWest

      fans and turbines spun at different speeds. But it's all on a solid state shaft? It's actually much simpler than I imagined. I suppose that accounts for it's durability which I could never quite reconcile with a geared system.

      I think there's a multi-stage engine that super-compressed air on that old SR-71. Or like a turbo fan into a hyper turbo fan with maybe even successive ignition stages.  

      And then I read (surfing off this diary) that Pratt & Whitney just developed a gear box for the fan at the front of their turbofan engine and it saves a ton of fuel. Because the fan operates better at lower speed than the turbines and compressor.

      I suppose that's the same effective limitations confronted with a turboprop

      Anyway. Another great diary. I love them all Major.

      •  Different RPMs for Different Stages (1+ / 0-)
        Recommended by:
        fisheye

        The first axial flow turbines had a single compressor attached to a shaft connected to the turbine section.  More modern jet turbines/turbofan have two separate compressor and turbine sections.  The low-pressure compressor section is hard physically attached to the low-pressure turbine section while the high-pressure compressor attaches to the high-pressure turbine via a separate shaft.  The one shaft is hollow to allow the other to run through it.   That enable the high-pressure section to run at a higher RPM than the low-pressure sections.  Some engine designers have even built three-section designs to squeeze out more efficiency from this approach.

        "Love the Truth, defend the Truth, speak the Truth, and hear the Truth" - Jan Hus, d.1415 CE

        by PrahaPartizan on Wed Apr 03, 2013 at 01:58:44 PM PDT

        [ Parent ]

      •  ... (0+ / 0-)

        That fact means that jets/turbines are very inefficient off their design speeds. IIRC, 90% N1 is typically 50% thrust or so.

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