Xem 1-9 trên 9 kết quả Rotor systems
  • Maintenance costs, as defined by normal plant accounting procedures, are normally a major portion of the total operating costs in most plants. Traditional maintenance costs (i.e., labor and material) in the United States have escalated at a tremendous rate over the past 10 years. In 1981, domestic plants spent more than $600 billion to maintain their critical plant systems. By 1991, the costs had increase to more than $800 billion, and they were projected to top $1.2 trillion by the year 2000.

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  • Vibration absorption has been a very attractive way of removing oscillations from structures under steady harmonic excitations. There are many common engineering applications yielding such undesired oscillations. Helicopter rotor vibration, unbalanced rotating power shafts, bridges under constant speed traffic can be counted as examples.

    pdf42p goixanh 27-09-2010 27 5   Download

  • Helicopter aerodynamics is the branch of physics dealing with the forces and pressures exerted by air in motion. The atmosphere, the mass of air, which completely envelops the earth, is composed of varying and nonvarying constituents. The nonvarying constituents include oxygen (21%) and nitrogen (78%). The varying constituents include CO2, argon, hydrogen, helium, neon, krypton, and water vapor, which will vary from negligible amounts to approximately 4% by volume (100% relative humidity). Air is a fluid and is affected by changes in temperature, pressure, and humidity....

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  • Gyroscopic precession is a key factor involved in the concept of operation for the north-seeking gyrocompass, as will be discussed later. Friction in the support bearings, external influences, and small imbalances inherent in the construction of the rotor cause even the best mechanical gyros to drift with time. Typical systems employed in inertial navigation packages by the commercial airline industry may drift about 0.1 during a 6-hour flight [Martin, 1986]. 2.1.

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  • This volume, based on the proceedings of the Sixth International Symposium on Unsteady Aerodynamics, Aeroacoustics and Aeroelasticity of Turbomachines and Propellers aims at promoting an international exchange of current research in unsteady flow phenomena in turbomachines and propellers.

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  • Contents: Gold East Paper, Dagang – A non-plus-ultra papermaking line, “Stonebridge” – the world’s biggest single-line deinking system in China, Energy efficient HM Rotor – Power saving solution for virgin bale repulping applications, Voith Paper – A perfect partner at any time International Customer Symposium “Graphic Grades”: May 9 to 11, 2006, A vision becomes reality – Online calendering of LWC offset/rotogravure printing grades with high DIP content at LEIPA, Schwedt, Voith keeps customers “...

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  • Synchronous machines come in a variety of different constructions and designs. The differences occur in the physical outlay of the rotor and in the way in which excitation flux is provided (if it is provided at all) in the machine. Regardless of the type however, all the synchronous machines have the same construction of the stator. Stator is of cylindrical crosssection, manufactured from laminated sheets of steel, and it carries a three-phase winding that is supplied with (in the motor case) or that produces (in the generator case) a system of threephase voltages....

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  • A synchronous machine is an ac rotating machine whose speed under steady state condition is proportional to the frequency of the current in its armature. The magnetic field created by the armature currents rotates at the same speed as that created by the field current on the rotor, which is rotating at the synchronous speed, and a steady torque results. Synchronous machines are commonly used as generators especially for large power systems, such as turbine generators and hydroelectric generators in the grid power supply. ...

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  • Finally, electromagnetic bearings involve complex design problems to ensure that the heavy spindle, with its high inertia, does not fall and damage the magnetic bearing when power is shut off or momentarily discontinued. Therefore, a noninterrupted power supply is required to operate the magnetic bearing, even at no load or at shutdown conditions of the system. In order to secure safe operation in case of accidental power failure or support of the rotor during shutdown of the machine, an auxiliary bearing is required. Rolling-element bearings with large clearance are commonly used.

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