Wind Turbine Blade Root Structure for Friction Load Transfer
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Solution Overview
Problem
Current methods for connecting wind turbine blades to the pitch bearing result in over-engineering and inefficient load distribution, limiting the ability to increase blade length and energy extraction, and are prone to material failure due to unsuitable adhesive and bolt connections.
Innovation Solution
A wind turbine blade assembly featuring a metal section at the root, with thin metal sheets that are stiff and capable of bearing higher loads, allowing for closer positioning of carbon fibre spar caps and optimized load distribution through radially extending bolts and friction connections, enhancing stiffness and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional adhesive and bolt connections are used to attach blade root to pitch bearing, then the connection can be implemented with conventional methods, but the adhesive is subject to constantly varying tensile forces which it is not optimally suited for, and bolts bear tensile and bending loads rather than shear loads, resulting in over-engineering and large safety factors
Solution Approach 1:
The patent replaces the traditional adhesive-bolt mechanical connection system with a friction-based mechanical connection. The blade root is equipped with friction surfaces that directly bear against the pitch bearing, eliminating the need for adhesive bonds and reducing bolt loads. This substitution allows the connection to function through friction and direct bearing rather than tensile adhesion, resolving the mismatch between adhesive properties and loading conditions.
Solution Approach 2:
The patent changes the loading parameters on the bolts by introducing friction surfaces that convert tensile and bending loads into shear loads. The friction connection creates a load path where bolts primarily experience shear forces, which is the optimal loading condition for bolted connections. This parameter change eliminates the need for oversized bolts designed to withstand tensile and bending stresses.
2Productivity
If the length of wind turbine blades is increased to extract more energy from the wind, then energy extraction capability is improved, but the current method of blade/hub connection limits the extent to which this can be achieved due to fatigue and load distribution issues
Solution Approach 1:
The patent segments the load path from the blade through the root to the hub by introducing distinct friction surfaces and load-bearing interfaces. This segmentation creates separate zones for load distribution (friction surfaces) and load transfer (bolts and pitch bearing), allowing each component to be optimized for its specific function. This enables longer blades to be supported without compromising connection fatigue performance.
Solution Approach 2:
The patent employs a composite connection structure combining friction surfaces, bolts, and pitch bearing components working together. The friction surfaces provide distributed load bearing, while the bolts provide mechanical fastening, creating a composite connection system that handles the increased loads from longer blades more effectively than traditional single-method connections.
3Strength
If bolts are used to connect pitch bearing to blade root, then the bolts bear tensile and bending loads which they are not well-suited for, but using larger bolts with larger safety factors results in over-engineering
Solution Approach 1:
The patent inverts the traditional load path by using friction surfaces to bear the primary loads and redirecting forces into shear loading on the bolts. Instead of bolts directly承受ing tensile and bending loads, the friction connection interface carries these loads and transfers them as shear forces to the bolts, which are then properly sized for their actual loading conditions.
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
The solution enables the design of wind turbine blades with increased load capacity, reduced material usage, and improved fatigue performance, facilitating larger blade lengths and efficient energy extraction while minimizing stress concentrations and material failure.
Implementation Method 1
friction connections, enhancing stiffness and reducing material usage
Data Source
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AI summary
A wind turbine blade having a tubular root portion with a proximal end defining the root end of the blade, and a distal end located at a spanwise distance from the proximal end. The root portion comprises a metal section which extends from the proximal end towards the distal end of the root portion, a fibre composite section which extends from the distal end towards the proximal end, and a transition section located between the metal section and the fibre composite section. The metal section comprises one or more metal sheets which extend beyond the metal section into the transition section. The portion of the metal sheet(s) located in the transition section are encapsulated within fibre composite material which is continuous with the fibre composite material of the fibre composite section. The metal section is connectable to a pitch bearing of a wind turbine hub.