Wind Turbine Pitch Actuator Clevis Opening Geometry
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Solution Overview
Problem
As wind turbine blades increase in size to capture more wind energy, the pitch system components, such as bearing rings and actuators, also grow in size, leading to increased mass, which is undesirable for reducing overall component weight.
Innovation Solution
The pitch actuator features an actuator rod with a clevis fork arrangement that includes flared perimeter sections in the clevis openings, providing enlarged clearance zones to avoid contact with the clevis pin, thus reducing stress and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If wind turbine blade size is increased to capture more wind energy, then energy capture capability is improved, but pitch system component mass increases
Solution Approach 1:
The patent modifies the geometric parameters of the clevis opening by incorporating flared perimeter sections that create enlarged clearance zones. This parameter change allows for reduced actuator rod diameter while maintaining structural integrity and load-bearing capacity, thereby reducing pitch system component mass without compromising the ability to handle larger blade loads
2Weight of moving object
If actuator rod diameter is reduced to decrease mass, then component weight is reduced, but stress concentrations increase
Solution Approach 1:
The patent applies local quality by creating flared perimeter sections at specific locations around the clevis opening. These flared sections locally increase the clearance zone where stress concentrations would otherwise occur, providing stress relief at critical points while maintaining the overall compact diameter of the actuator rod
Solution Approach 2:
The flared perimeter sections incorporate curved geometries that transition smoothly from the nominal circular opening. These curved transitions eliminate sharp corners and create enlarged clearance zones that distribute stress more evenly, reducing stress concentrations while allowing for reduced actuator rod diameter
3Ease of manufacture
If clevis opening is made circular for simplicity, then manufacturing is easier, but wear and fatigue increase
Solution Approach 1:
The patent maintains a generally circular clevis opening for ease of manufacture while incorporating localized flared perimeter sections at critical areas. This local modification creates enlarged clearance zones that reduce wear and fatigue without requiring complete redesign of the entire opening geometry
Solution Approach 2:
The flared perimeter sections use curved geometries that are extensions of the nominal circular opening. These curved transitions are straightforward to manufacture using standard machining operations while providing superior stress distribution and wear resistance compared to sharp corners or complex non-circular shapes
Data Source
AI summary
A pitch actuator for a wind turbine pitch system, the pitch actuator having an actuator rod, a drive end of which is defined by a clevis fork arrangement having first fork member and a second fork member that extend in a direction along a rod axis and terminate at a tip end. The first and second fork members define respective clevis openings for receiving a clevis pin therethrough, said clevis openings each having an opening perimeter profile comprising: a first perimeter section defined by a leading circular arc that is centred on the rod axis and oriented in the direction of the tip end of the fork members, the circular arc defining a nominal radius and a central angle of less than 120 degrees, and second and third flared perimeter sections that flank respective sides of the first perimeter section, each of which define an enlarged clearance zone with respect to at least part of an imaginary circle defined by the nominal radius of the first perimeter section. A benefit of the invention is that the enlarged clearance zones defined by the flared perimeter sections create an area where there is no contact between the perimeter of the openings and the outer surface of the clevis pin. This provides a stress relieving function since deformation of the openings in use, due to force applied along the axis of the actuator rod, does not create a point of stress combined with sliding or rubbing movement with the sides of the clevis pin, thereby reducing wear and fatigue. The invention extends to a pitch system including such a pitch actuator and a wind turbine incorporating such a pitch system.