Wind Turbine Blade Pitching to Reduce Service-Lock Torque
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Solution Overview
Problem
Existing methods for servicing wind turbines face challenges such as excessive tower sway and high torque due to vortex shedding and wind loads, which are exacerbated by the inability to yaw the rotor to optimal orientations and limitations in rotor lock size and weight.
Innovation Solution
Adjusting wind turbine blades to differing pitch angles, maintaining one blade at a near-horizontal position, and using a self-hoisting crane system to minimize tower sway and torque during servicing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If all three blades are pitched to 90 degrees to minimize wind loads on the rotor, then torque on the rotor lock is reduced, but tower sway increases due to vortex shedding
Solution Approach 1:
The patent applies asymmetry by pitching two blades to 90 degrees (non-operational) and one blade to 0 degrees (operational), creating an asymmetric configuration that breaks the symmetry of vortex shedding patterns. This asymmetric blade arrangement reduces tower sway while maintaining acceptable torque levels on the rotor lock during servicing operations.
Solution Approach 2:
The patent applies local quality by differentiating the pitch angles of individual blades rather than uniform pitching. Specifically, two blades are pitched to 90 degrees while one blade remains at 0 degrees, creating localized differences in aerodynamic properties that reduce vortex shedding-induced tower sway while maintaining overall system stability.
2Reliability
If rotor lock size is increased to withstand higher wind forces, then wind speeds at which rotor can be locked increase, but weight increases beyond lifting capacity of available cranes
Solution Approach 1:
The patent changes the operational parameters of the blade pitch angles during servicing (two blades at 90 degrees, one blade at 0 degrees) to reduce wind loads and vortex shedding. This parameter change allows existing lighter rotor locks to withstand the reduced forces, enabling rotor locking at higher wind speeds without increasing rotor lock weight beyond crane lifting capacity.
Solution Approach 2:
The patent applies preliminary anti-action by pre-pitching two blades to 90 degrees before locking the rotor, which proactively reduces the wind forces and torque that will act on the rotor lock during servicing. This preliminary action allows the use of lighter rotor locks that can still withstand the reduced forces at higher wind speeds.
3Productivity
If rotor is locked at higher wind speeds, then serviceable window of wind speeds increases, but tower sway and vortex shedding effects increase
Solution Approach 1:
The asymmetric blade pitch configuration (two blades at 90 degrees, one blade at 0 degrees) disrupts the symmetric vortex shedding pattern that occurs with uniform blade pitching. This asymmetry reduces tower sway even at higher wind speeds, enabling expanded serviceable wind speed range while maintaining tower stability during servicing operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces tower sway and maximizes the wind speeds at which the rotor can be locked, while minimizing torque and enabling safe servicing operations.
Implementation Method 1
excessive tower sway and high torque due to vortex shedding and wind loads
Data Source
AI summary
A wind turbine (1) has three wind turbine blades (61, 62, 63), each being arranged rotatably on the rotor hub (5) about a pitch axis in order to adjust a pitch angle of the wind turbine blade. Before performing the service work, a pitch angle adjustment is performed so that a pitch angle difference between respective pitch angles of two of the wind turbine blades is between 45 degrees and 135 degrees or between 225 degrees and 315 degrees. After performing the service work, a pitch angle adjustment is performed so that there is at least substantially no pitch angle difference between pitch angles of the respective wind turbine blades of the rotor (4). During the service work, the rotor is maintained in a rotational position in which a longitudinal axis of the third wind turbine blade forms an angle of not more than 5 degrees with a horizontal axis.