Main Shaft Bearings Research Articles

Study on accelerated life tests for main shaft bearings in wind turbines

Study on accelerated life tests for main shaft bearings in wind turbines

Research on Real Working Condition Simulation and Performance Test of Wind Power Main Bearing Based on Test Bench

As a renewable energy source, wind energy has received more and more attention, and the wind power industry has also been advocated and developed by countries all over the world. In the production and use of wind turbines, the design and manufacturing technology of wind turbine bearings is very important. In order to ensure the reliable operation of the wind power main bearing after installation and realize the longest life of it, this paper designs a bearing test bench that can test the performance of the wind power main bearing. It can analyze the temperature, displacement, load, and moment of the key parts of the 5 MW wind power main shaft bearing. The solid modeling of the experimental platform was carried out using the 3D modeling software SolidWorks. Hydraulic loading system and test monitoring system are designed to realize the drive and control of the test bench. Through the established mathematical model, the central load of the hub is converted into the axial cylinder load and the radial cylinder load of the test bench to simulate the actual working conditions of the tested bearing. The test results show that the test bench meets various loading requirements and can reliably complete the task of testing wind power main bearings.

Deep domain adversarial residual neural network for sustainable wind turbine cyber‐physical system fault diagnosis

AbstractAs a popular renewable energy generation technology, wind turbine system has become a critical enabler for building the sustainable cyber‐physical system (CPS). The main shaft bearing is an important part of the wind turbine CPS and often runs under variable working conditions. Thus, the reliable bearing diagnosis method can timely discover the main shaft bearing fault, which reduces the maintenance cost of wind turbines. Inspired by the idea of domain adaptation, we combined domain adversarial neural network and residual network and proposed a novel deep domain adversarial residual neural network (DDA‐RNN) for diagnosing bearing fault and improving model performance on the unlabeled dataset. This proposed software and hardware co‐design method was evaluated by our bearing dataset, which was collected from two wind turbine CPSs from Sanmenxia in Henan Province. Besides, F1 score and accuracy are served as model metrics, which reflect the diagnosis performance. Compared with other methods, the experimental results show that DDA‐RNN can improve model performance. Meanwhile, DDA‐RNN extracts diagnosis knowledge from labeled dataset and improves the model performance on the unlabeled dataset under different working condition. Therefore, the proposed method can be potentially used to benefit many practical scenarios in the future.

Research on Life Prediction of Fan Spindle Bearing Based on Gated Recurrent Unit Neural Network

In order to solve the problems of redundancy calculation and inefficiency of traditional machine learning algorithm in dealing with large amount of historical data of fan, a new predictive algorithm based on gated recurrent unit (GRU) is proposed to predict the remaining service life of fan spindle bearing. Firstly, the vibration history data of the main shaft bearing of the fan is analyzed to find out the relationship between the characteristic value and the remaining life, and the characteristic parameters which can reflect the remaining life are selected; Then, GRU is used to build the remaining service life prediction model of spindle bearing, and the main parameters of the model are adjusted to improve the prediction accuracy of the model. Compared with long short term (LSTM) algorithm, GRU is an effective tool to deal with a large number of data sets.

Analysis of skid damage to cylindrical roller bearing of mainshaft of aeroengine

Skid damage to mainshaft bearings on aeroengines severely reduces aircraft reliability. In this study, a batch of cylindrical roller bearings extracted from mainshaft of inservice aeroengines with, skid damage after a certain service period, were collected, and damage features of the bearings were characterized and compared with those of the undamaged bearings and the new ones. Microscopic feature evaluation, elemental analysis as well as the composition distribution of the bearings were conducted using scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffractometry, X-ray photo-electron spectroscopy, transmission electron microscopy and surface profilometry. Analysis results reveal that skidding itself is a very complex process initiated by the action of different mechanisms, and manifest in different wear types. The damage mechanism of skid damaged bearings was the joint consequence of abrasive wear, oxidation wear and delamination wear. All the aforementioned damage and wear led to severe aircraft failures.

A New Method of Calculating the Attainable Life and Reliability in Aerospace Bearings

The aviation industry made significant progress improving reliability, efficiency and performance throughout the last decades. Especially aircraft engines and helicopter transmission systems contributed significantly to these improvements. The kerosene consumption decreased by 70 % and the CO2 emissions due to air transport decreased by 30 % per passenger kilometer within the last 20 years. Simultaneously, the flight safety was increased with aircraft engine in-flight-shut-downs as low as 1 ppm and „unscheduled engine removals” as low as 4 ppm. Flight safety is equal to the reliability of the systems in service. Failure of these systems directly leads to exposure of human life. Among the most critical aviation systems are aircraft engines including the rolling element bearings which support the rotors. A serious damage to the aircraft engine main shaft bearings during flight requires shout-down of the engine to avoid a further damage escalation subsequently leading to engine fire. Today, it is a requirement for aircraft to operate with one engine shut down. However, each in-flight-engine-shut-down typically is connected with flight diversion or abort and immediate landing. Inflight-shut-downs translate into increased risk for passengers and crew and substantial on cost. Therefore, rolling element bearings for aircraft engines are developed – similar to other aircraft engine components – targeting a reliability of nearly 100 % over an operation time of more than 10 000 hours prior to overhaul. To achieve this requirement despite the extreme operating conditions such as high speed and temperatures occurring in gas turbines, special high-performance materials are used for the rolling bearing components which are partially integrated in surrounding engine parts like shafts and housings. These special conditions - deviating from conventional industrial rolling element bearing applications - are currently not sufficiently considered in the standardized method of calculating the bearing life per ISO 281. A new method of calculating the attainable life of rolling elements bearing in aerospace applications is presented. This method considers the special aerospace conditions and materials and thus enables a higher reliability of the theoretical analysis and life prediction.

New Method of Calculating the Attainable Life and Reliability in Aerospace Bearings

The aviation industry made significant progress improving reliability, efficiency and performance throughout the last decades. Especially aircraft engines and helicopter transmission systems contributed significantly to these improvements. The kerosene consumption decreased by 70 % and the CO2 emissions due to air transport decreased by 30 % per passenger kilometer within the last 20 years. Simultaneously, the flight safety was increased with aircraft engine in-flight-shut-downs as low as 1 ppm and „unscheduled engine removals” as low as 4 ppm. Flight safety is equal to the reliability of the systems in service. Failure of these systems directly leads to exposure of human life. Among the most critical aviation systems are aircraft engines including the rolling element bearings which support the rotors. A serious damage to the aircraft engine main shaft bearings during flight requires shout-down of the engine to avoid a further damage escalation subsequently leading to engine fire. Today, it is a requirement for aircraft to operate with one engine shut down. However, each in-flight-engine-shut-down typically is connected with flight diversion or abort and immediate landing. Inflight-shut-downs translate into increased risk for passengers and crew and substantial on cost. Therefore, rolling element bearings for aircraft engines are developed – similar to other aircraft engine components – targeting a reliability of nearly 100 % over an operation time of more than 10 000 hours prior to overhaul. To achieve this requirement despite the extreme operating conditions such as high speed and temperatures occurring in gas turbines, special high-performance materials are used for the rolling bearing components which are partially integrated in surrounding engine parts like shafts and housings. These special conditions - deviating from conventional industrial rolling element bearing applications - are currently not sufficiently considered in the standardized method of calculating the bearing life per ISO 281. A new method of calculating the attainable life of rolling elements bearing in aerospace applications is presented. This method considers the special aerospace conditions and materials and thus enables a higher reliability of the theoretical analysis and life prediction.

Optimisation design for wind turbine mainshaft bearing based on lubrication reliability

The lubrication of the mainshaft bearing has a great influence on the safe operation of wind turbines. In this paper, an optimal design model of the mainshaft bearing of a wind turbine is established on the lubrication reliability analysis. The maximum rated dynamic load is set as the design objective. The roller number, roller diameter, roller length and wall thicknesses are design parameters. Constraints are formulated mainly based on lubrication reliability and structure consideration. In the lubrication reliability constraint model, the lubrication reliability criterion was determined by solving the minimum film thickness of numerical calculation model of grease EHL. The reliability of bearing lubrication is calculated by Monte Carlo Simulation, and uncertain variables based on sensitivity analysis are selected to improve calculation precision. In the structure constraints, range for the design variables is determined in terms of requirements of geometric structure and strength. Finally, the mainshaft bearing was optimised and analysed by genetic algorithms. The analysis results show that the rated dynamic load of bearing is improved from 1.3e6 N to 2e6 N. Meanwhile the lubrication reliability is improved about 10%. The model presented shows great advantages and practical usefulness in the mainshaft bearing research of wind turbines.

Optimisation design for wind turbine mainshaft bearing based on lubrication reliability

The lubrication of the mainshaft bearing has a great influence on the safe operation of wind turbines. In this paper, an optimal design model of the mainshaft bearing of a wind turbine is established on the lubrication reliability analysis. The maximum rated dynamic load is set as the design objective. The roller number, roller diameter, roller length and wall thicknesses are design parameters. Constraints are formulated mainly based on lubrication reliability and structure consideration. In the lubrication reliability constraint model, the lubrication reliability criterion was determined by solving the minimum film thickness of numerical calculation model of grease EHL. The reliability of bearing lubrication is calculated by Monte Carlo Simulation, and uncertain variables based on sensitivity analysis are selected to improve calculation precision. In the structure constraints, range for the design variables is determined in terms of requirements of geometric structure and strength. Finally, the mainshaft bearing was optimised and analysed by genetic algorithms. The analysis results show that the rated dynamic load of bearing is improved from 1.3e6 N to 2e6 N. Meanwhile the lubrication reliability is improved about 10%. The model presented shows great advantages and practical usefulness in the mainshaft bearing research of wind turbines.

Effects of Flexibility and Suspension Configuration of Main Shaft on Dynamic Characteristics of Wind Turbine Drivetrain

The current research of wind turbine drivetrain is mainly concentrated in dynamic characteristics of gearbox with a specific suspension of main shaft, such as one-point and two-point suspension. However, little attention is paid to the effects of these suspension configurations on the dynamic responses of wind turbine gearbox. This paper investigates the influences of suspension configurations of main shaft on the dynamic characteristics of drivetrain. For evaluating the dynamic behaviors of drivetrain with multi-stage transmission system more realistically, a dynamic modeling approach of drivetrain is proposed based on Timoshenko beam theory and Lagrange’s equation. Considering the flexibility and different suspension configurations of main shaft, time-varying mesh stiffness excitation, time-varying transmission error excitation and gravity excitation, etc., a three-dimensional dynamic model of drivetrain is developed, and the dynamic responses of drivetrain are investigated. Results show that with the one-point suspension of main shaft, the resonance frequencies in gearbox, especially at the low-speed stage, obviously shift to the higher frequency range compared to the gearbox without main shaft, but this trend could be inversed by increasing main shaft length. Meanwhile, the loads in main shaft, main shaft bearing and carrier bearing are greatly sensitive to the main shaft length. Hence, the load sharing is further disrupted by main shaft, but this effect could be alleviated by larger load torque. Comparing to the one-point suspension of main shaft, there occurs the obvious load reduction at the low-speed stage with two-point suspension of main shaft. However, those advantages greatly depend on the distance between two main bearings, and come at the expense of increased load in upwind main shaft unit and the corresponding main bearing. Finally, a wind field test is conducted to verify the proposed drivetrain model. This study develops a numerical model of drivetrain which is able to evaluate the effects of different suspension configurations of main shaft on gearbox.

Processing of the Heat Resistant Bearing Steel M50NiL by Selective Laser Melting

Abstract Additive manufacturing (AM) methods become more and more important due to improvements in the printing technology and availability of printers. As additive manufacturing is still a very expensive technology, it is predominantly used for complex parts in aerospace or medical applications. Especially in such demanding applications the properties of the parts are very important. In case of M50NiL, a carburizing heat resistant steel typically used for mainshaft bearings in aero engines, the development of an AM process and the properties of AM processed parts are shown. By comparison with specimens manufactured from conventional M50NiL it is demonstrated, that properties determined by optical microscopy, hardness testing, tensile testing, and rolling contact fatigue testing of M50NiL AM and M50NiL conventional manufactured are comparable.

Conceptual study of a gearbox fault detection method applied on a 5‐MW spar‐type floating wind turbine

AbstractIn this paper, a model‐based fault detection method for fault detection of gearboxes in offshore wind turbines is presented. The main aim of this paper is to support conceptual studies with more emphasis on early fault detection methods for floating wind turbines. The method is introduced and applied on a 5‐MW reference gearbox installed on a spar‐type floating wind turbine. Faults applied on the main bearing, high and intermediate speed shaft bearings, and the planet bearing are examined with this method. The gearbox is modelled in a multibody simulation environment with high fidelity. The 5‐MW gearbox model used in this study is an offshore reference gearbox that consists of 3 stages, 2 planetary and 1 parallel stages, which is supported in a 4‐point configuration layout. The bearing faults are detected through the angular velocity error function. The angular velocity measurements are performed at input, output shafts, and 2 additional sensors inside the gearbox. The aim of the method is also to detect the fault through the external sensors—input and output shafts—measurements, which can be embedded in the existing control system. The results reveal the possibility of early fault detection by this method for large floating wind turbines.

The Sliding Wear and Frictional Behavior of M50-10 wt.%(Sn-Ag-Cu) Self-Lubricating Materials at Elevated Temperatures

As the main steel used in the aero-engine main shaft bearings, the tribological properties of M50 can directly affect the performance of aero-engine. The purpose of this study is to design the reasonable composition of Sn-Ag-Cu alloy and investigate the wear mechanisms of M50-10 wt.%(Sn-Ag-Cu) composites (MSACC) prepared by SPS sliding against Si3N4 ball from 25 to 550 °C at 12 N-0.25 m/s. XRD, EPMA, FESEM and EDS mappings are conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MSACC. The results indicate that MSACC with different specifications of Sn-Ag-Cu alloy shows excellent friction and wear properties from 25 to 550 °C compared to M50. M50-10 wt.%(50Sn40Ag10Cu) (MSACC-2) shows the distinguished tribological performance for the lower friction coefficients of 0.22-0.61 and less wear rates of 1.7-4.1 × 10−6 mm3 N−1 m−1, which is attributed to the formed excellent lubricating structure consisting of the lubricating film with massive Sn-Ag-Cu alloy and intermetallic compounds formed during the friction process, as well as the underneath mixed layer who can well support the lubricating film due to the good intersolubility between the designed Sn-Ag-Cu alloy and M50 (Fe).

Simulation and experimental analysis of rolling element bearing fault in rotor-bearing-casing system

Abstract The rotor-bearing-casing system is an important structural form in aero-engines, where the main shaft bearing plays an important role in the safe and efficient operation of the whole engine. To study the performance of rolling element bearing faults and their transmission characteristics, a dynamic model of rotor-bearing-casing system with a nonlinear rolling element bearing is established in this paper. The rotor and the casing are modelled by finite element method and the rest parts are modelled by lumped mass method. The casing part is built using a kind of 2-D curved beam element. Single and mixed localized bearing defects are simulated in this dynamic model and also introduced in the rotor-bearing-casing system test system, then vibration signals from the bearing pedestal and the casing are obtained and analyzed. The simulation has a good prediction in components of bearing fault characteristic and modulation frequencies, which could be extracted from the experimental signals. Results are compared between the bearing pedestal and the casing, also between the simulation and the experiment. And sensitivity analysis could be conducted based on fault feature extraction and analysis at different locations on the flexible casing.

The Load Distribution of the Main Shaft Bearing Considering Combined Load and Misalignment in a Floating Direct-Drive Wind Turbine

The main shaft tapered double-inner ring bearing (TDIRB) of floating direct-drive wind turbine system (FDDWT) is one of the most critical components in FDDWT, and its failure accounts for a large proportion of wind turbine malfunctions and faults. Over the past decades, a significant number of methods have been proposed to calculate the contact load distribution along the roller length in TDIRB, since the contact load distribution of roller is the key factor of fatigue life of TDIRB. Most of methods, however, neglected the misalignment of inner ring with respect to outer ring and friction force. In this paper, with the help of comprehensive and accurate quasi-static mathematical method, the contact load distribution of internal loads in TDIRB are analysed by considering the effects of combined loads, angular misalignment and friction force at different wind speeds for FDDWT. The simulation results show that the amount of combined load has an apparent effect on the contact load distribution along the TDIRB raceways and flanges in both rows. Furthermore, the slight change of tilted misalignment has a great influence on the contact load distribution. In addition, the slight angular misalignment easily produces noncontact zone for the bearing raceway in both rows, which is significantly disadvantage for the external load uniform transmitting to each roller.

Diagnostic monitoring of drivetrain in a 5 MW spar-type floating wind turbine using Hilbert spectral analysis

The objective of this paper is to investigate the frequency-based fault detection of a 5MW spar-type floating wind turbine (WT) gearbox using measurements of the global responses. It is extremely costly to seed managed defects in a real WT gearbox to investigate different fault detection and condition monitoring approaches; using analytical tools, therefore, is one of the promising approaches in this regard. In this study, forces and moments on the main shaft are obtained from the global response analysis using an aero-hydro-servo-elastic code, SIMO-RIFLEX-AeroDyn. Then, they are utilized as inputs to a high-fidelity gearbox model developed using a multi-body simulation software (SIMPACK). The main shaft bearing is one of the critical components since it protects gearbox from axial and radial loads. Six different fault cases with different severity in this bearing are investigated using power spectral density (PSD) of relative axial acceleration of the bearing and nacelle. It is shown that in severe degradation of this bearing the first stage dynamic of the gearbox is dominant in the main shaft vibration signal. Inside the gearbox, the bearings on the high speed side are those often with high probability of failure, thus, one fault case in IMS-B bearing was also considered. Based on the earlier studies, the angular velocity error function is considered as residual for this fault. The Hilbert transform is used to determine the envelope of this residual. Information on the amplitude of this residual properly indicates damage in this bearing.

Effect of Ti3SiC2 on Tribological Properties of M50 Matrix Self-Lubricating Composites from 25 to 450 °C

The tribological performance is a key factor for M50 steel that is widely used in aero-engine main-shaft bearings. In this study, the tribological properties of M50 matrix self-lubricating composites with different contents of Ti3SiC2 against Si3N4 ceramic counterpart are investigated at 15 N-0.2 m/s from 25 to 450 °C. The results showed that M50 with 10 wt.% Ti3SiC2 (MT10) exhibits the lower friction coefficients (0.21-0.78) and less wear rates (1.78-3.14 × 10−6 mm3 N−1 m−1) at 25-450 °C. Especially at 350 °C, MT10 shows the lowest friction coefficient and wear rate owing to the formation of smooth lubricating layer containing Ti3SiC2 and oxides. Ti3SiC2 and compacted Ti-Si-oxides are uniformly distributed in the lubricating layer, which can well improve the anti-friction and anti-wear performance of MT10. The mechanically mixed layer containing massive Ti3SiC2 can sustain the lubricating layer, resulting in the increase of anti-wear performance of MT10. MT10 could be applied under the practical conditions of friction and wear for its outstanding anti-friction and anti-wear performance.

Non-symmetric approach to single-screw expander and compressor modeling

Single-screw type volumetric machines are employed both as compressors in refrigeration systems and, more recently, as expanders in organic Rankine cycle (ORC) applications. The single-screw machine is characterized by having a central grooved rotor and two mating toothed starwheels that isolate the working chambers. One of the main features of such machine is related to the simultaneous occurrence of the compression or expansion processes on both sides of the main rotor which results in a more balanced loading on the main shaft bearings with respect to twin-screw machines. However, the meshing between starwheels and main rotor is a critical aspect as it heavily affects the volumetric performance of the machine. To allow flow interactions between the two sides of the rotor, a non-symmetric modelling approach has been established to obtain a more comprehensive model of the single-screw machine. The resulting mechanistic model includes in-chamber governing equations, leakage flow models, heat transfer mechanisms, viscous and mechanical losses. Forces and moments balances are used to estimate the loads on the main shaft bearings as well as on the starwheel bearings. An 11 kWe single-screw expander (SSE) adapted from an air compressor operating with R245fa as working fluid is used to validate the model. A total of 60 steady-steady points at four different rotational speeds have been collected to characterize the performance of the machine. The maximum electrical power output and overall isentropic efficiency measured were 7.31 kW and 51.91%, respectively.

The Evolution of Reliability and Efficiency of Aerospace Bearing Systems

The worldwide air traffic underwent a rapid development in recent decades. Between the early 70s and the late 90s of the last century civil air traffic doubled every 15 years. The civil aviation market will continue to grow with 4% - 5% each year within the next 20 years. This enormous growth represents major challenges for airframers, engine makers, suppliers, airlines, air traffic management and ground infrastructure. In addition, the public debate on the worldwide civil air traffic is dominated by environmental and climate issues, even though only 2% of the man-made carbon dioxide (CO2) emissions are due to air transportation. Therefore the aerospace industry will have to focus on a low-emission and quite air traffic, and on the conservation of natural resources and our environment. The end-use consumer and environmental policy requirements for aircrafts of the next generation translate into components with improved efficiency and reliability. Rolling bearings are one of these components which significantly determine the reliability and mechanical efficiency of aerospace applications such as aircraft and rotorcraft engines and transmission systems. They have to withstand very demanding operating conditions. Especially main shaft bearings in modern aircraft engines experience high rotational speeds andtemperatures. Furthermore aerospace bearings have to meet the highest reliability standards and require low-weight design solutions. These operating conditions and requirements present a continuous challenge for improvements in all fields of bearing technology. This article presents solutions in aspects of materials, design, analysis, and surface technologies in order to meet the environmental, reliability, and economical requirements of advanced aerospace bearing systems. State of the art bearing analysis and advanced bearing design solutions contributing to lower friction power losses and increased systems efficiency are discussed. Weight, functional, and maintenance benefits are presented with the example of highly integrated aircraft engine main shaft bearings. It is also shown that the progress in bearing materials and surface technology development is the basis for weight and friction energy reduction in aerospace bearing systems.

Comparison of Power Losses and Temperatures between an All-Steel and a Direct Outer Ring–Cooled, Hybrid 133-mm-Bore Ball Bearing at Very High Speeds

ABSTRACTNext-generation aircraft engines will have to face more stringent requirements for reliability, thrust to weight, efficiency, environment protection, and profitability. These requirements affect all engine modules and components, including rolling element bearings. To cope with the above-mentioned requirements, next-generation aircraft engine main shaft bearings will operate under higher loads, speeds, and temperatures and increased reliability. In addition, lighter weight components are desirable. Hence, new material and cooling technologies including weight- and stress-optimized designs need to be developed.In this article, the experimental investigation results of a novel main shaft ball bearing featuring ceramic balls, direct outer ring cooling, squeeze film damping, as well as surface-nitrided raceways are presented. Bearing rig testing under typical aircraft engine flight conditions has been performed. Savings for oil flow quantity of more than 45% and for power loss of more than 15% were identified. Outer ring temperature reductions of more than 20 K were achieved due to the use of ceramic ball material and the direct outer ring cooling concept. The ultra-high-speed capability of the bearing was demonstrated. Rotational speeds of 24,000 rpm were achieved at bearing temperatures below 200°C. The fundamental experimental results including oil and bearing temperature distribution, power dissipation, and bearing efficiency are presented. In addition, experimental power loss and temperature results are compared with data for a conventional all-steel bearing.