Date of Award
December 2021
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Committee Member
Phanindra Tallapragada
Committee Member
Amin Bibo
Committee Member
Richard Figliola
Committee Member
Shyam Panyam
Abstract
As the wind energy field continues to grow, reducing component failures will be of top priority to reducing the cost of power production. The high speed shaft (HSS) bearings are one of the leading causes of failure in wind turbines, if improvements in the operating life of turbines are to be made HSS bearing failure is one area with large growth potential. In industry, engineers use modeling and simulation techniques to better understand the potential failure modes of the turbine. Utilizing these models, turbine manufacturers can improve designs and implement control strategies to eliminate failure modes and extend the operating life of the turbine. Some of the worst loading conditions in a turbine are produced as a result of electrical events in the generator, this coupling of mechanical and electrical systems is often referred to as electromechanical interaction and is one of the leading areas of study in wind turbines. Understanding how NTL impacts HSS bearing failure modes during grid interruption events can lead to reductions in turbine failures and improvement in turbine availability. This will be studied through the use of multi-body dynamic models developed to replicate the loading in wind turbine drivetrains. Electromechanical interaction in a wind turbine drivetrain is typically studied using dynamic models of 3 distinct types. High fidelity full gearbox models, simplified torsional gearbox models, and isolated component lumped parameter models. The first objective of this work is to outline the benefits and drawbacks of each model type and determine the appropriate model for studying the effect of non-torque loading (NTL) on high speed shaft (HSS) bearing failure modes during a transient electrical event. It was determined that the high fidelity full gearbox model was necessary to capture all the effects NTL could present in the HSS bearing failure modes. With the appropriate model selected, analysis was then performed to determine the effect of NTL on skidding and impact loading in the HSS bearings during a grid interruption event. The application of NTL in the high fidelity drivetrain model resulted in substantial differences in bearing failure modes. Applying NTL resulted in a static shift in the bearing force away from 0, potentially alleviating concerns of skidding in the bearing during a grid interruption event. Additionally, applying NTL was seen to cause a decrease in the total impact loading seen in the bearings. To achieve the benefits of adding NTL in the drivetrain, an offset to the generator was used to create a reaction force from the high speed shaft coupling (HSC) mimicking the NTL applied previously at the rotor connection point. This method was tested for its ability to replicate the NTL applied at the rotor and was found to do so to a high degree of accuracy. NTL was then implemented to align the HSC when the turbine is operating at full power. This new process offsets the generator to account for the torque induced misalignment in the HSC. This alignment method was shown to increase the minimal radial loading seen in each of the bearings while slightly increasing the impact loading in the 2 MW DW bearing and the 5 MW UW bearing. The minimum radial loading for the 2 MW model increased by roughly 14% and 6% of the steady state conventionally aligned radial load for the DW and UW bearings respectively. The 5 MW model saw increases of 13% and 5% in the DW and UW bearings respectively. These improvements are significant when considering the high rate of speed during the grid interruption any improvements in skidding can go a long way for the life of the turbine. Future study is needed on the potential drawbacks of the added loading but reduction in potential skidding cases could result in significant improvements in the lifespan of bearings.
Recommended Citation
Roulier, Joseph Scott, "Impact of Non Torque Loading on Wind Turbine High Speed Shaft Bearing Failure Modes During a Grid Interruption Event" (2021). All Theses. 3634.
https://tigerprints.clemson.edu/all_theses/3634