Showing papers on "Ground resonance published in 2012"

Computational Techniques of Rotor Dynamics with the Finite Element Method

Abstract: Part I: Theoretical Foundation of Rotor Dynamics Introduction to Rotational Physics Fixed Coordinate System Rotating Coordinate System Forces in the Rotating System Transformation between Coordinate Systems Kinetic Energy Due to Translational Displacement Kinetic Energy Due to Rotational Displacement Equation of Motion in Rotating Coordinate System Equation of Motion in the Fixed Coordinate System Coupled Solution Formulations Matrix Formulation of Lagrange's Equations Coupling Nodal Translations to the Stationary Part Simultaneous Coupling of Translations and Rotations Full Coupling of the Stationary and Rotating Parts Time-Dependent Terms of Equations Finite Element Analysis of Rotating Structures Potential Energy of Structure Dissipative Forces Non-dissipative Forces Finite Element Equation Assembly Coupled Equilibrium Equation Assembly Analysis Equilibrium Equations Computational Solution Techniques Direct Time Domain Solution of the Equilibrium Equation Direct Frequency Domain Solution Direct Free Vibration Solution Modal Solution Technique Static Condensation Dynamic Reduction Numerical Solution Techniques The Lanczos Method Orthogonal Factorization The Block Lanczos Method Solution of Periodic Equations Part II: Engineering Analysis of Rotating Structures Resonances and Instabilities Analysis Type vs. Modeling Approach Resonances and Instabilities Critical Speed of Rotating Mass The Laval Rotor Influence of Damping Unsymmetric Effects of Bearing and Rotor A Rotating Tube Rotating Model with Flexible Arms The Ground Resonance Dynamic Response Analysis Frequency Response without Rotation Frequency Response with Rotation Transient Response without Rotation Transient Response with Rotation A Finite Element Case Study Turbine Wheel with Shaft and Blades Engineering Analysis Computational Statistics The Journal Bearing Active External Loads Analysis of Aircraft Propellers A Propeller Blade Quasi-steady Aerodynamics of Blade Unsteady Aerodynamics of Blade Propeller with Four Blades Analysis of Wind Turbines An Example Wind Turbine Modeling and Analysis of Wind Turbine Blade Wind Turbine with Three Blades Response Analysis of Wind Turbines Horizontal Axis Wind Turbines with Two Blades

Vertical takeoff and landing aircraft

Abstract: The purpose of the present invention is to provide a vertical takeoff and landing aircraft which takes off and lands vertically with the plane of rotation of a rotor facing to the lower side of a main wing and moves forward with the plane of rotation of the rotor facing to the back side of the main wing, the vertical takeoff and landing aircraft achieving a reduction in the length of a rotor shaft by a lightweight and simple structure. In this vertical takeoff and landing aircraft, the position of the center of gravity (G) of the body of the aircraft is set in an area (BA) on the trailing edge side from the chord center (C) of the main wing (3), a rotor shaft (2) is extended downward from the position of the center of gravity (G), and the rotor shaft (2) is rotated between a vertical attitude in which the leading end (2a) thereof faces to the lower side of the main wing (3) and a horizontal attitude in which the leading end (2a) thereof faces to the trailing edge side of the main wing (3). Since the rotor shaft (2) is extended downward from the position of the center of gravity (G) set in the area (BA) on the trailing edge side of the main wing (3), when the rotor shaft (2) is brought into the horizontal attitude by being rotated backward, the length of rotor shaft (2) required to locate the plane of rotation of a rotor (7) on the back side from the trailing edge of the main wing (3) can be decreased.

Ground Resonance Instabilities Analysis of a Bearingless Helicopter Main Rotor

Abstract: The ground resonance instability of a helicopter with bearingless main rotor hub were investigated. The ground resonance instability is caused by an interaction between the blade lag motion and hub inplane motion. This instability occurs when the helicopter is on the ground and is important for soft-inplane rotors where the rotating lag mode frequency is less than the rotor rotational speed. For the analysis, the bearingless rotor was composed of blades, flexbeam, torque tube, damper, shear restrainer, and pitch links. The fuselage was modeled as a mass-damper-spring system having natural frequencies in roll and pitch motions. The rotor-fuselage coupling equations are derived in non-rotating frame to consider the rotor and fuselage equations in the same frame. The ground resonance instabilities for three cases where are without lead-lag damper and fuselage damping, with lead-lag damper and without fuselage damping, and finally with lead-lag damper and fuselage damping. There is no ground resonance instability in the only rotor-fuselage configuration with lead-lag damper and fuselage damping.

Method for de-icing the rotor blades of a helicopter and device for performing the method on the helicopter

Abstract: The method involves performing deformation of frozen-surfaces (12) of rotor blades (1) with certain frequency by planar actuators (5, 6) in order to remove ice from the frozen-surfaces, where the frequency is greater than rotational frequency of the rotor blades. The rotor blades are twisted during deformations of frozen-surfaces with the actuators around longitudinal axes (9) of the actuators. Torsional resonance vibrations of the rotor blades are stimulated with the actuators, where the actuators are integrated in layers (4) of the rotor blades. An independent claim is also included for a device for defrosting rotor blades of a helicopter.

Method for influencing flight path of rotor blades of helicopter rotor of helicopter, involves controlling swash plate assembly such that collective change of setting angle of rotor blades is effected

Abstract: The method involves controlling a swash plate assembly such that a collective change of setting angle of rotor blades is effected through a collective adjustment of the swash plate assembly. The collective change of setting angle of the rotor blades have a frequency per revolution of a rotor that corresponds to a fractional part of the number of rotor blades. The collective change of setting angle of the rotor blades is effected, such that adjacent blades characterize different trajectories. An independent claim is included for a helicopter rotor assembly for influencing a flight path of rotor blades of a helicopter rotor of a helicopter.