A damper for damping vibrations of a structure comprises: a first damping unit, comprising a first damping body having a first mass (m.sub.1), a first spring element having a first spring constant (k.sub.1) and a first damping element having a first damping constant (c.sub.1), wherein said first damping body is configured to be attached to said structure via said first spring element and said first damping element; and a second damping unit, comprising a second damping body having a second mass (m.sub.2), a second spring element having a second spring constant (k.sub.2) and a second damping element having a second damping constant (c.sub.2), wherein said second damping body is configured to be attached to said first damping body via said second spring element and said second damping element.

Methods for installing a wind turbine blade on a wind turbine hub include hoisting the wind turbine blade towards the wind turbine hub; bringing the wind turbine blade and the wind turbine hub into contact through an adaptable resilient body such that the adaptable resilient body is compressed between the wind turbine blade and the wind turbine hub; reducing a dimension of the adaptable resilient body such that the wind turbine blade approaches the wind turbine hub; and mounting the wind turbine blade to the wind turbine hub. Also, assemblies for assisting in mounting the wind turbine blade to the wind turbine hub and adapted wind turbine hubs are provided.

A method of controlling pitch of individual blades in a wind turbine is described, together with a suitable controller. Wind speed is determined as a function of azimuthal angle. Wind speed is then predicted for individual blades over a prediction horizon using this determination of wind speed as a function of azimuthal angle. The predicted wind speed for each individual blade is used in a performance function, which is optimized to control individual blade pitches.

An acoustic damper for a rotary machine includes at least one wall, at least one inlet, at least one outlet, at least one separating wall, and at least one neck. The wall extends from the back side of a combustor front panel and defines a damping chamber. The inlet is defined within the wall and is oriented to channel a flow of air into the damping chamber. The outlet is defined within the back side of the front panel. The separating wall is oriented to separate the damping chamber into a first volume and a second volume. The first volume of the damping chamber is configured to damp an acoustic pressure oscillation at a first frequency. The second volume of the damping chamber is configured to damp the acoustic pressure oscillation at a second frequency. The neck extends through the separating wall and is axially offset from the outlet.

A compressor includes: a case, a compression unit that is provided inside the case and that includes a cylinder and a piston configured to reciprocate inside the cylinder to compress refrigerant, a driving unit that includes a stator disposed inside the case and a plurality of permanent magnets configured to reciprocate with respect to the stator and that is configured to provide a driving force to the compression unit, and a resonator that is configured to reduce noises generated while the compression unit is operated, that is disposed between the compression unit and an inner surface of the case facing the compression unit in an axial direction, and that is spaced apart from the compression unit.

A method of assembling a tower section of a wind turbine tower is provided. The method includes arranging the tower section of the wind turbine tower in a horizontal orientation; transporting a damper unit to a position inside the tower section while the tower section is arranged in the horizontal orientation; and mounting the damper unit to the tower section, wherein the damper unit is configured to damp motions of the wind turbine tower. Further, a horizontal transport system is provided that is supported at least at one position by the tower section and that includes a movable part configured to support a damper unit and to transport the damper unit in a horizontal direction from a position adjacent to an end of the tower section to a position at or adjacent to a mounting position of the damper unit inside the tower section.

A blade damping device for damping vibrations during standstill of a wind turbine blade, wherein the blade damping device is adapted to be detachably attached to the pressure side and/or the suction side of the airfoil region of the wind turbine blade, the blade damping device comprising a base plate adapted to conform to the exterior shape of the wind turbine blade when the blade damping device is attached to the wind turbine blade, and a spoiler protruding from the base plate to a spoiler height along a height direction and having a spoiler length along a length direction, the height direction being adapted to extend outwardly from the wind turbine blade, wherein the spoiler height is adapted to be at least 20% of a chord line located at two thirds of the blade length along the longitudinal axis from the root end of the wind turbine blade.

It is provided a wind turbine having a modified eigenfrequency, the wind turbine having a tower including a first tower flange arranged at an upper end portion of a top part of the tower; and, an eigenfrequency modifier including a plurality of weights suspended from the first tower flange by a plurality of rigid supports. It is further provided a method of modifying an eigenfrequency of a wind turbine, the method including modifying the eigenfrequency of the wind turbine by suspending a plurality of weights from a first tower flange arranged at an upper end portion of a top part of a tower of the wind turbine using a plurality of rigid supports.

Method for vibration damping of and vibration damper assembly for semi-submerged or submerged structure, based on separating hydrodynamic added mass from the semi-submerged or submerged structure by means of a vibration damper assembly exhibiting spring and/or damper properties and use the hydrodynamic added mass as a reaction mass in the vibration damper assembly.

The invention provides a method for stabilising a wind turbine blade (106), the method comprising, attaching (S2) an air blowing arrangement (201) to the blade, detecting (S4) an oscillation of the blade, and operating (S5) the attached air blowing arrangement to provide a thrust to counteract the oscillation.