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An actuator disk accelerating a fluid flow from right to left. In fluid dynamics, momentum theory or disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by W.J.M. Rankine (1865), [1] Alfred George Greenhill (1888) and Robert Edmund Froude (1889).
Campbell Diagram of a steam turbine. Analysis shows that there are well-damped critical speed at lower speed range. Analysis shows that there are well-damped critical speed at lower speed range. Another critical speed at mode 4 is observed at 7810 rpm (130 Hz) in dangerous vicinity of nominal shaft speed, but it has 30% damping - enough to ...
Rotordynamics (or rotor dynamics) is a specialized branch of applied mechanics concerned with the behavior and diagnosis of rotating structures. It is commonly used to analyze the behavior of structures ranging from jet engines and steam turbines to auto engines and computer disk storage.
When a helicopter is being maneuvered, its disk loading changes. The higher the loading, the more power needed to maintain rotor speed. [3] A low disk loading is a direct indicator of high lift thrust efficiency. [4] Increasing the weight of a helicopter increases disk loading. For a given weight, a helicopter with shorter rotors will have ...
Coning is a phenomenon which affects helicopter rotor discs. The tips of the helicopter rotor blades move faster through the air than the parts of the blades near the hub, so they generate more lift, which pushes the tips of the blades upwards, resulting in a slight cone shape to the rotor disc. This is balanced by centrifugal force.
A model of a blisk used in a gas turbine Instead of making bare compressor disks and attaching the blades later, blisks are single elements combining the two. This eliminates the need to attach the blades to the disk (via screws, bolts, etc.), thus decreasing the number of components in the compressor, while at the same time decreasing drag and ...
The transverse flow effect is where the front of the rotor disc is moving into undisturbed air, whereas the rear of the rotor disc is moving into downward-moving air. The front of the rotor disc therefore has a higher angle of attack, and generates more lift, causing flapback. As airspeed increases, the pilot must counter flapback by applying ...
However, when the helicopter starts moving into undisturbed air, a portion of the disc is in clean, unaccelerated air, while the remaining portion of the rotor disc is still working on descending air. The part of the disc working on clean air therefore sees a higher angle of attack than the portion of the disc which is working on descending air ...