Wind Turbine Gear Research Articles

Fault diagnosis of wind turbine gears based on OCSSA-VMD and WOA-CNN-BiLSTM

Fault diagnosis of wind turbine gears based on OCSSA-VMD and WOA-CNN-BiLSTM

Analysis of rolling contact and tooth root bending fatigue in a new high-strength steel: Experiments and micromechanical modelling

To find materials that meet the future requirements of increasing load density in wind turbine gear structures, the commonly used reference material, 18CrNiMo7-6, and another high-strength steel were analysed. Their fatigue properties were studied through rolling contact fatigue (RCF) and gear tooth root bending fatigue (TRBF) tests. The reference steel exhibited better fatigue performance under RCF conditions compared to the new steel; however, it was outperformed by the new steel under TRBF conditions. This study aims to understand gear contact fatigue at the microscopic level, moving beyond the macroscopic focus that dominates current research literature. To establish the causal link between the varied fatigue performance observed in these materials, we proposed a multiscale modelling workflow based on crystal plasticity. This crystal plasticity framework is combined with the fatigue indicator parameter (FIP) to explore the fatigue resistance of materials subjected to RCF and TRBF conditions. Emphasis has been placed on the role of retained austenite (RA) in fatigue performance. Utilizing representative elementary volumes (REVs) generated based on statistically representative crystallographic features and measured size distribution of RA, we examined the effects of various RA levels on fatigue resistance. Our findings reveals that the fatigue damage accumulation is significantly influenced by the level of RA. Different fatigue damage accumulation behaviours were observed under RCF and TRBF conditions. These insights offer new perspectives on RA’s role in fatigue resistance and highlight its complex influence under varied loading conditions.

Refined composite multiscale dynamic causality diagram: a novel time-series analysis approach and its application in fault diagnosis of rotating machinery

Entropy-based feature extraction methods have been widely used in the fault diagnosis of rotating machinery, but the entropy-based methods still have the defects of poor noise robustness, weak feature extraction, and low computational efficiency. To solve this problem, this article proposes a fault diagnosis method based on refined composite multiscale dynamic causal diagram (RCMSDCD) and local receptive field extreme learning machine (LRFELM). First, a novel feature extraction method, named dynamic causal diagram (DCD), is proposed to comprehensively quantify static and dynamic complexity. DCD is obtained by combining generalized inverse fractional order entropy with complexity–entropy causal plane. Then, combined with the coarse-graining process, DCD is extended to a multiscale analysis called RCMSDCD to complement the feature description at cross-time scales. Third, RCMSDCD features are input into LRFELM classifier for fault recognition of rotating machinery. The effectiveness of the proposed RCMSDCD-LRFELM method is verified by the Paderborn University bearing test and real wind turbine gear signals. The results show that this method has the highest classification accuracy of 100% with high computational efficiency, good stability, and strong generalization ability.

Dynamics characteristics of wind turbine gear pairs considering lubrication and tooth surface roughness

Dynamics characteristics of wind turbine gear pairs considering lubrication and tooth surface roughness

Reliability based design optimization of a two-stage wind turbine gearbox

This paper describes a multi-objective reliability-based design optimization (MORBDO) of a two-stage wind turbine gearbox. The optimization process incorporates the gear's reliability of accounting for the uncertainty of its internal geometric parameters. It also ensures that constraints relating to the gear's reliability index and efficiency are respected. The objective functions are to minimize both the total volume and the center distance. A specific reliability target is established, and to address the multi-objective reliability-based design optimization (MORBDO), the hybrid method (HM) in conjunction with the constrained non-dominated sorting genetic algorithm (C-NSGA-II) is employed. The outcomes demonstrate that applying C-NSGA-II to solve the multi-objective reliability-based design optimization problem yields dependable Pareto solutions that are well-distributed in relation to the desired reliability level. The optimization using C-NSGA-II with a population size of 300 particles and 1000 generations produced the most favorable outcomes. This research significantly contributes to the multi-objective design optimization of wind turbine gear while simultaneously considering their reliability.

An Investigation on the Teeth Crowning Effects on the Transient EHL Performance of Large-Scale Wind Turbine Spur Gears

Crowning is applied to wind turbine gears, including spur gears, to ensure adequate stress distribution and contact localization in wind turbine main gearbox gears to improve the gear performance in the presence of misalignments. Each gear tooth is crowned along the face width using a parabolic curve that graduates from a maximum height at the edges and vanishes at the center of the tooth flank. This crowning transfers the elastohydrodynamic contact problem from a line to a point contact case where the surface curvatures and pressure gradient are considered in both directions of the solution space. A wide range of longitudinal crowning heights is considered in this analysis under heavily loaded teeth for typical large-scale wind turbine gears. Furthermore, the variation in the velocities is considered in the analysis. The full transient elastohydrodynamic point contact solution considers the non-Newtonian oil behavior, where the numerical solution is based on the finite difference method. This work is focused on the evaluation of the effectiveness of teeth’s longitudinal crowning in terms of the consequences on the resulting pressure distribution and the corresponding film thickness. The modification of the tooth flank significantly elevates the film thickness levels over the zones close to the tooth edges without a significant increase in the pressure values. Moreover, the zone close to the tooth edges from both sides, where the pressure is expected to drop to the ambient pressure, is extended as a result of the flank modification.

Enhancing tribological properties of 18CrNiMo7-6 through grain refinement incorporating Al2O3 particles

Wind turbine gears are critical components within the internal gearbox of the wind turbines. However, the vulnerability of gears to wear adversely affects their operational lifespan. Here, we propose a novel approach utilizing ultrasonic shot peening to incorporate Al2O3 particles onto the surface of the 18CrNiMo7–6, termed the USG treatment. The tribological test shows that the coefficient of friction and wear rate of the USG-treated sample decreased by 14.4% and 58.3% respectively, as compared to the untreated sample. Experiments and detailed analysis reveal that 18CrNiMo7–6 not only undergoes grain refinement on its surface but also forms a wear-resistant layer enriched with Al2O3. The findings here provide a new insight into the design of wear-resistant layers on gear steel surfaces.

A Review—Effect of Accelerating Methods on Gas Nitriding: Accelerating Mechanism, Nitriding Behavior, and Techno-Economic Analysis

Gas nitriding, as a surface modification technology to improve the wear resistance of workpiece surfaces, is widely used in wind turbine gears, pressure vessel gears, high-precision die casting abrasives, and other areas. However, the gas nitriding time is too long, reaching 40–60 h, which reduces the efficiency of nitriding and hinders the development of gas nitriding. Therefore, various accelerating methods are born accordingly. This review first introduces the basic principle, microstructure, and process parameters of conventional gas nitriding. Then, five common accelerating methods are summarized: process parameter optimization, surface mechanical nano-crystallization, surface-active catalysis, surface pre-oxidation, and surface laser treatment. Then, the effect of acceleration methods on gas nitriding is analyzed for the acceleration mechanism, nitriding behavior, and nitriding efficiency. Finally, the technical economy of the acceleration methods is compared for three aspects: energy consumption, carbon dioxide emission, and cost. And, the technical maturity of the acceleration methods is compared according to technology readiness level (TRL) technology. Based on the above content, the advantages and disadvantages of the five accelerating methods are reviewed, and the concept of a multi-technology collaborative processing acceleration method is proposed.

The contributions regarding to the behavior of bearings in wind turbines

With the growth of the wind industry in the world and the commissioning of turbines with powers higher than 1 MW, higher loads and increased stresses have a strong effect on the durability of the bearings that equip the main shaft and the kinematic transmission of wind turbine gears. As a result, the wind industry is demanding greater durability of the bearings that equip the main shaft and the kinematic transmission with gears, and manufacturers are striving to come up with solutions for these requirements. The novelty in this work consists in the identification of some solutions, as well as improvements of the existing solutions for the construction of some mechanical systems for the existing wind turbines. We present below some constructive bearing solutions that are effective in the wind turbine industry. The research in the paper consists of: stress analysis of the load- bearing structure for the axial radial bearing with straight rollers with single ring, some aspects about lubrication of blade bearing in wind turbine and defects in blade bearings.

Residual Strength Modeling and Reliability Analysis of Wind Turbine Gear under Different Random Loadings

A novel method is proposed to investigate the pattern of variation in the residual strength and reliability of wind turbine gear. First, the interaction between loads and the effect of the loading sequence is considered based on the fatigue damage accumulation theory, and a residual strength degradation model with few parameters is established. Experimental data from two materials are used to verify the predictive performance of the proposed model. Secondly, the modeling and simulation of the wind turbine gear is conducted to analyze the types of fatigue failures and obtain their fatigue life curves. Due to the randomness of the load on the gear, the rain flow counting method and the Goodman method are employed. Thirdly, considering the seasonal variation of load, the decreasing trend of gear fatigue strength under multistage random load is calculated. Finally, the dynamic failure rate and reliability of gear fatigue failure under multistage random loads are analyzed. The results demonstrate that the randomness of residual strength increases with increasing service time. The seasonality of load causes fluctuations in the reliability of gear, providing a new idea for evaluating the reliability of the wind turbine gear.

Demonstration of Sensor Monitoring of Lubricants

Due to the spread of carbon neutral, the effective use of lubricant has been drawing attention. Since the main component of lubricant is petroleum-derived hydrocarbon oil, reducing the amount used by 1 kg will reduce CO2 by approximately 3 kg. The value of CO2 reduction is very important. In order to reduce the amount of lubricant used, there is a movement to reduce the frequency of lubricant exchange or continue to use lubricant without exchanging it. However, it is known that lubricant-induced mechanical failures occur. For this reason, equipment condition monitoring using oil sensors has been spread. The color of the lubricant, also called machine blood, indicates the condition of the machine. The oil sensor measures contamination, which has a fatal effect on machine failure, and oxidation degradation, which is related to the performance of lubricant and the machine failure. Contamination includes water and wear debris, and oxidative degradation includes consumption of additives and oxidation of base oil. By digitizing the hue of wind turbine gear oil through color diagnosis using an oil sensor, the oil contamination and degradation is identified. Additives in the gear oil were quantified by liquid chromatography-mass spectrometry, and it was found that the color change of gear oil was highly correlated with the depletion of the extreme pressure additive. It is known that the depletion of the extreme pressure additive is correlated with the useful life of the gear oil. Using the technique, the remaining life diagnosis of the gear oil was shown. Demonstration in the gearbox with the oil sensor was succeeded by avoidance of the effects of air bubbles in the gear oil.

Wind turbine gear reliability analysis considering dependent competing failure

AbstractTo more precisely assess the reliability of wind turbine gears, a competing failure model is established with consideration given to the degradation of internal fatigue strength and external random shocks. Firstly, the nonlinear Gamma process is adopted to depict the degradation of fatigue strength, and the strength‐stress interference theory is used to establish the threshold of degradation failure that changes over time. Also, the non‐homogeneous Poisson process is employed to depict the arrival of the shock, and classification of the shocks. Secondly, the correlation between degradation and shock is described, while the effect of shocks on degradation is demonstrated as a sudden increase in the extent of degradation. Besides, the decline rate of residual strength curve is introduced to describe the change in intensity parameters of the Poisson process, and then the effect of degradation on shocks is described. Finally, the sun gear in the wind turbine gearbox is an example. Monte Carlo simulation is used to calculate the reliability of the dependent competing failure model. This is then compared with the conventional stress‐strength interference model. The results verify that when the relationship between degradation and the shock process is disregarded, the reliability of gears may be overestimated.

Investigation on the impact of electrical faults on the loads and exposures of wind turbine gears

For the design of a wind turbine, it is necessary that the design process takes into account the stresses of real operation to a high degree of detail so that targeted dimensioning can be carried out. Depending on its design, the drivetrain of a wind turbine includes a gearbox that connects the rotor to the generator. During operation of a wind turbine, transient load conditions can occur due to loopback from the power grid and faults in the frequency converter. The influence of the resulting stress and possible damage to the gears used in the gearbox is unclear in the design phase. While the stresses on the gears can often be simulated with a high degree of accuracy for constant operating conditions and can thus be integrated into the drivetrain design, this is not the state of the art for dynamic load conditions. The objective of this report is a method for considering dynamic loading events in the design of the cylindrical gear stage used in wind turbine gearboxes using a coupled multi-body simulation and a finite element based tooth contact analysis. Afterwards the method is used to quantify the stress on the tooth flank and tooth root due to special electrical events such as short circuits between the frequency converter and generator or power grid faults for various converter designs. The simulation analyses show that different converter concepts have different effects on the resulting gear load during electrical faults, but are not significantly decisive for the accumulated damage due to elastic material behavior between generator and gear.

Fault diagnosis of wind turbines with generative adversarial network-based oversampling method

Due to the complex working environment, effective fault data from wind turbine gears are often difficult to obtain. Aiming at this practical issue, a generative adversarial network (GAN)-based oversampling method is proposed in this paper, which can achieve fault classification with a small dataset. In the initial stage, wavelet packet transform is applied to generate and extract features. Then, the optimal discriminator and generator trained by GAN are used to generate data to compensate for the imbalanced fault dataset. Random forest, eXtreme gradient boosting and support vector machines are chosen to classify a real dataset, imbalanced dataset and generated dataset, respectively. Experiments indicate that the data generated by the proposed method stay at the same distribution as the real data. Therefore, for small or imbalanced dataset situations, the proposed method could be a solution to compensate for the dataset.

Mesoscopic dynamic characteristics and RCF damage evolution of high-speed transmission gear in wind turbine

For the gears utilized in wind turbines, the main reason leading to malfunction is the crack initiation and propagation under cyclic loading. In the gear engagement process, the fatigue damage accumulates gradually and formulate visible microcrack if the fatigue parameter reaches to specified threshold. In order to simulate the fatigue evolution in wind turbine gears, a mesoscopic model is established, in which the Voronoi tessellation and cohesive elements are integrated, such that the crystal structure and grain boundary can be modeled. The dynamic stress distribution and fatigue evolution phenomenon are then investigated under different working conditions. The loading in the meshing region is simplified as moving load on a semi-infinite plane, so the shear stress distributions for per loading cycle are obtained. Furthermore, bilinear traction-separation law (TSL), Jump-in-Cycles (JIC) loading methodology and multi-axial fatigue criterion are involved to fulfill the damage accumulation simulation. As a result, the initiation location and propagation pattern of the fatigue crack are predicted, and the fatigue life curve is also obtained. Thereafter, the influence of wind speed and lubrication condition on fatigue damage evolution is also discussed. The results have shown that the wind loading mainly influences the magnitude of the maximum shear stress, whereas the contact width will determine the location of the maximum shear stress. When the whole fatigue evolution procedure is finished, the first two cracks initiate at the depth of 0.13 mm and 0.27 mm beneath the surface respectively, and then propagate into the substrate. Through comparative analyses of fatigue life curves, it can be concluded that higher wind speeds and poor lubrication conditions will reduce gear service life significantly.

Study on gear bending fatigue considering gradient characteristics: Numerical analysis and experiments

The bending fatigue of the case hardened gear, one of the essential components used in high-end equipment such as helicopters, wind turbines and automobiles, significantly limited the safety, reliability and service life of such equipment. In this work, we proposed a novel gear bending fatigue model incorporating gradient characteristics of hardness and residual stress based on the continuum damage theory to evaluate the bending fatigue behavior of case hardened wind turbine gear. The damage equations involving the residual stress and hardness gradients and damage coupled constitutive equations are derived. This model is then experimentally validated on the bending stress, bending fatigue failure position, mechanical properties deterioration and bending fatigue life. The evolutions of damage, stress response and mechanical properties are investigated. Results show that the predicted gear bending fatigue lives of different case hardened gears are within the 1.5 scatter factor bond.

Identifying the influence of dimensional parameters on the stresses and deformations of two helical gears

In this research paper, focusing on the basic variables of the gear modeling process and setting its dimensions to see which gears are capable of withstanding transmission operations and its rigidity was done. Because one of the most prominent transmission mechanics is gears, as the types of gears are numerous and common, and one of the most prominent types of gears is the helical gear. The helical gear is one of the most widely used and widespread gears in mechanical fields due to the increase in the contact area during the interlock process, as this increase reduces noise during gear rotation. Three main variables were used to establish the results. The first of which is the pressure angle, the helix deflection angle, and the module number, and they made a number of cases to see which one was able to withstand the movement operations with a proven torque. The results proved that the distortion value in the first case at module 1 was 87×10-6 m, while in module 2 the distortion value was 3.75×10-6. The data are useful and important because the values of the stresses that affect the gears must be known by changing the module due to it gives a stronger concept of the extent to which the gears can withstand movement. Pressure angle is one of the basic variables that change the dimensions of wind turbine gears. The value of the greatest stress was 2.13×108 Pa, but at the pressure angle of 20 degrees, the stress value was 1.93×108 Pa. It affects the diameter, stiffness and tensile strength of a wind turbine. The study of this research paper depends on helical gears. It is known that the angles of the helical teeth increase the large contact area between two gears. From the resulting deformation values, it is noted that the deformation value is 4.26×10-6 m when the helix angle is 20 degrees.

An improved fault model of wind turbine gear drive under multi-stage cracks

Considering the real crack propagation paths using the fracture mechanics theory, a novel simulation dynamic model for the two-stage cracked gear drive of the wind turbine is established. The mesh characteristics (time-varying mesh stiffness, contact stress) are obtained with the finite element method. The mesh stiffness under the single-stage and multi-stage cracks is imported into the two-stage cracked gear drive dynamic model to solve the dynamics. The results of the simulation and experiment are performed to verify the proposed dynamic model. The dynamic characteristics and statistical indicators under different cracks are discussed. The results reveal that the crack has a significant influence on the mesh stiffness of the single-tooth contact zone. A rotating periodic impact is found on the time-domain response for the cracked gear drive. Under the single-stage crack, the components of rotating sideband frequencies also appear in the other-stage healthy gear drive. The gear acceleration amplitudes under the multi-cracks are larger than that under the single-stage crack. Therefore, the single-stage crack has an influence on the other-stage gear in the coupling system. This developed result can be applied well to vibration measurement and fault diagnosis.

Research on Scanning Induction Heating Process of Wind Turbine Gear: Dynamic Evolution of End Temperature

Research on Scanning Induction Heating Process of Wind Turbine Gear: Dynamic Evolution of End Temperature

Lifetime extension of gears and main bearings in wind turbines, scientific calculations and practical implementation

REWITEC, as a part of Cargill Bioindustrial, is a developer and manufacturer of an innovative particle-based surface treatment phyllosilicate-technology for increasing the reliability and the lifetime of wind turbine gears and bearings. The active particles are compatible to all common oils and greases and use lubricants as a carrier to build through their adsorption a protective and repairing phyllosilicate-based coating on the surface. The modified surface has a significantly lower surface roughness, which ensures a better load distribution, lower local pressure and lower tribological stress. Additionally, due to the special layered material structure the particles can be sheared in the tribological contact, which leads to a reduction in friction. All in all, when applying the products systems can run better with reduced friction, wear, surface roughness and temperature. These effects lead to higher reliability and a longer lifetime and thus to cost savings for operators. We would like to show our new scientific study about the lifetime calculation of a grease-lubricated wind turbine main bearing (1.5 MW) with and without the use of technology. The project is a cooperation between REWITEC and Sentient Science who performs lifetime calculations using digital clone method based on real friction coefficient and surface roughness data. The project includes data generation using MTM test bench, in a wind turbine bearing and subsequent simulation based on this data and bearing geometry. The simulation shows that with REWITEC the probability for a bearing failure significantly decreases which leads to a lifetime extension of up to 17.3 years.