Asymmetric Wind Turbine Coupling for Torque Reversal Damping
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Solution Overview
Problem
Wind turbine gearbox bearings experience premature failure due to axial cracking caused by torque reversals, leading to high maintenance costs, as existing coupling systems are inadequate in managing the high strain rate and impact stress during these events.
Innovation Solution
A wind turbine coupling system with asymmetric torsional behavior, featuring high torsional wind-up and displacement ability in the reverse direction, combined with a high frictional slip capability to absorb and dissipate the energy of torque reversals, while maintaining minimal wind-up and slippage during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torsional wind-up of the system is increased to lower the natural frequency and reduce torque reversal impact, then the bearing damage is mitigated, but resonant frequency issues in other parts of the turbine may occur and recertification is required
Solution Approach 1:
The coupling system is divided into separate functional elements: a friction element for energy dissipation and a wind-up element for frequency adjustment. This segmentation allows independent optimization of each component's function without affecting the entire system's complexity
Solution Approach 2:
The coupling system acts as an intermediary between the gearbox and generator, providing torsional flexibility and energy dissipation. This mediator absorbs the adverse effects of torque reversals before they reach the bearings, protecting the critical components
2Productivity
If a rigid coupling system is used to maintain precise alignment between gearbox and generator, then transmission efficiency is high, but torque reversal impact loads are amplified causing bearing failure
Solution Approach 1:
The coupling system dynamically changes its torsional stiffness parameter based on operating conditions. During normal operation, it maintains high stiffness for efficient power transmission. During torque reversals, the friction element engages and the wind-up element flexes, reducing stiffness to absorb impact energy
3Reliability
If frictional slip capability is increased to absorb torque reversal energy, then bearing damage is reduced, but slippage during normal operation causes energy loss and wear
Solution Approach 1:
The frictional slip capability is made dynamic rather than constant. The friction element remains engaged during normal operation to maintain precise torque transmission, and only slips when torque reversal exceeds a threshold level, providing protection without continuous energy loss
Solution Approach 2:
The effective friction coefficient changes based on the torque direction and magnitude. During normal forward operation, friction is minimized. During reverse torque events, friction increases to dissipate energy and protect the bearings
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 coupling system effectively reduces the magnitude and rapidity of torque reversals, mitigating damage to gearbox bearings by allowing significant slippage only during transient events, thus extending the lifespan of wind turbine components and maintaining normal operation without affecting the system's forward torsional characteristics.
Implementation Method 1
a frictional slip component set in the forward direction to at least 10% of the rated turbine torque
Implementation Method 2
a torsional spring component with an asymmetric rate such that the spring rate in reverse is lower than the spring rate in the forward direction
Data Source
AI summary
A wind turbine power generating system, including a wind turbine connected to a speed-increasing gearbox having an output shaft. An electrical generator having an input shaft is also provided. A coupling interconnects the input and output shafts. The coupling includes a high torsional wind-up and/or displacement ability in parallel with a high frictional slip ability, such that during normal operation there is little or no frictional slippage and during a transient torque reversal the loads in the turbine drive system are decreased, thus decreasing the impact loads on the gearbox bearings.