Hydraulic Variable Pitch System for Wind Turbine Load Management
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Solution Overview
Problem
Existing water and wind turbines face challenges with fixed pitch rotors experiencing high torques in fast flows, leading to shutdowns or inefficient energy extraction, while variable pitch systems are large, complex, and reduce reliability, and existing systems require blade shape deviation near the root, affecting efficiency.
Innovation Solution
A compact and reliable hydraulic variable pitch system with two redundant hydraulic systems that alternate operation to prevent stagnation and wear, using a common linkage mechanism for simultaneous blade pitch adjustment, pressure relief valves, and fail-safe features to manage dynamic loads and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed pitch rotor is used, then the turbine operation is simplified and reliability is increased, but very large torques occur in high speed flow conditions because there is no load-shedding mechanism
Solution Approach 1:
The patent applies a variable pitch mechanism that allows the rotor blades to dynamically adjust their pitch angle in response to flow conditions. This dynamic adjustment enables the system to maintain optimal performance across varying speeds while providing load-shedding capability through pitch control, resolving the contradiction between fixed pitch simplicity and torque management.
2Adaptability or versatility
If a variable pitch system is used, then load-shedding is achieved and turbine operations are regulated, but the system becomes large, heavy, and complex
Solution Approach 1:
The patent segments the variable pitch system into modular components: individual pitch control mechanisms for each blade, separate pitch actuators, and distributed sensors. This segmentation allows the complex variable pitch functionality to be implemented in a distributed manner, reducing overall system complexity while maintaining load-shedding capability.
Solution Approach 2:
The patent replaces traditional mechanical variable pitch systems with a hybrid electro-hydraulic actuation system. This substitution reduces mechanical complexity by using controlled fluid pressure and electrical signals instead of complex mechanical linkages, achieving load-shedding capability with a more compact and manageable system.
3Adaptability or versatility
If existing variable pitch systems are used, then load regulation is achieved, but the blade must depart from ideal shape near the root, reducing energy extraction efficiency
Solution Approach 1:
The patent implements local pitch control where each blade can be independently adjusted at different sections along its span. This allows the root region to maintain its ideal airfoil shape for maximum energy extraction while the tip region can be adjusted for load regulation, resolving the contradiction between pitch control adaptability and energy extraction efficiency.
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 system reduces wear, enhances reliability, and maintains efficiency by alternating hydraulic system use, managing high loads, and ensuring continuous operation with fault tolerance, while being compact and cooled effectively within the turbine's nose region.
Implementation Method 1
The shaft is actuated linearly by the hydraulic piston/cylinder (i.e. hydraulic actuator) of each of the first and second hydraulic systems
Implementation Method 2
Each of the first and second hydraulic systems also includes a pressure relief valve connected to the respective hydraulic cylinder. The pressure relief valve limits back pressure on the hydraulic system from dynamic loads on the turbine blades
Implementation Method 3
Additional safety features of the first and second hydraulic systems includes a spring that biases the turbine blades to an unloaded feathered pitch angle during a loss of power
Data Source
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AI summary
A variable pitch system for a water or wind turbine includes a hydraulic system that includes a first hydraulic system (90) and a second, redundant hydraulic system (92) that are completely contained in a nose region of the turbine. The first and second hydraulic systems (90, 92) can each be used during operation on a predetermined operating schedule. In addition, each of the first and second hydraulic systems (90, 92) can also include a pressure relief valve to limit back pressure on the hydraulic system from dynamic loads on the turbine blades. The pitch of all the blades (34) are changed simultaneously using a common linear to rotary actuating mechanism. To aid in cooling, the hydraulic reservoirs (100) for the first and second hydraulic systems (90, 92) can be attached to the front wall of the nose housing (40), and fins (120) can be provided on the exterior of the nose housing (40) at the front end to enhance heat extraction.