Multibody dynamic modelling of a direct wind turbine drive train

Wind turbines normally have a long operational lifetime and experience a wide range of operating conditions. A representative set of these conditions is considered as part of a design process, as codified in standards. However, operational experience shows that failures occur more frequently than expected, the costlier of these including failures in the main bearings and gearbox. As modern turbines are equipped with sophisticated online systems, an important task is to evaluate the drive train dynamics from online measurement data. In particular, internal forces leading to fatigue can only be determined indirectly from other locations’ sensors. In this contribution, a direct wind turbine drive train is modelled using the floating frame of reference formulation for a flexible multibody dynamics system. The purpose is to evaluate drive train response based on blade root forces and bedplate motions. The dynamic response is evaluated in terms of main shaft deformation and main bearing forces under different wind conditions. The model was found to correspond well to a commercial wind turbine system simulation software (ViDyn

A Ronkin type function for coamoebas

The Ronkin function plays a fundamental role in the theory of amoebas. We introduce an analogue of the Ronkin function in the setting of coamoebas. It turns out to be closely related to a certain toric arrangement known as the shell of the coamoeba and we use our Ronkin type function to obtain some properties of it

A Ronkin type function for coamoebas

The Ronkin function plays a fundamental role in the theory of amoebas. We introduce an analogue of the Ronkin function in the setting of coamoebas. It turns out to be closely related to a certain toric arrangement known as the shell of the coamoeba and we use our Ronkin type function to obtain some properties of it

Wind turbine drive train vibration with focus on gear dynamics under nondeterministic loads

In present-day, the engineering challenge around a drive train design for a wind turbine is not only to enhancesystem reliability but also to reduce the turbine top mass. These requirements together with the trend of upscaling affect many system characteristics and parameters. The proposed contribution presents a model tostudy torsional drive train vibration dynamics of a generic indirect drive multi-MW wind turbine. The mainfocus lies on developing a fully parameterized computational model of a multi-stage gearbox which fulfillsthe requirement of a proper gear dynamic representation appropriate for multibody formalism as well asthe requirement to be computationally efficient. Two different strategies for modeling the gear contact arestudied and compared in time domain. An analysis of a multi-stage gearbox together with a generator load and a turbine specific nondeterministic excitation was carried out. It is believed that the obtained results will help designer to improve drive train components and to enhance wind turbine reliability and cost efficiency

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well-known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their rolling contact fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well-known that these premature failures are attributed to surface damages such as white surface flaking (WSF), white etching cracks (WECs) and axial cracks. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied to demonstrate their TTR mitigation capabilities. Then, a novel idea of open-loop high-speed shaft mechanical brake control is proposed. The results presented here show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high-speed shaft and reducing the risk of bearing slip by actuating the high-speed shaft brake at the onset of the transient event. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time applied to it. This novel approach allows the wind turbines to protect the gearbox bearings from TTRs using the existing hardware on the turbine

Effects of in-company quality awards on organizational performance

The relationship between total quality management (TQM) practices and improved performance has been frequently discussed in the literature. In this paper, the costs and the effects of in-company quality awards on performance are discussed and analysed. The paper covers a survey of Swedish companies that use or have used in-company quality awards to stimulate TQM efforts and thereby to improve performance. The study cannot show any strong evidence of improved performance for units that applied for the in-company quality award. However, in contrast to units that have not applied, some units that have applied for the in-company quality award considered that the results related to performance have improved greatly. One large positive effect perceived by the participating units was increased customer orientation while the largest costs were put on the description of activities and the improvement work itself

A numerical study on the safety belt-to-pelvis interaction

The slide of the lap belt over the iliac crest of the pelvis during vehicle frontal crashes can substantially increase the risk of some occupant injuries. A multitude of factors, related to occupants or the design of belt, are associated with this phenomenon. This study investigates safety belt-to-pelvis interaction and identifies the most influential parameters. It also explores how initial lap belt position influences the interaction between lap belt and pelvis. A finite element model of the interaction between lap belt with pelvis through a soft tissue part was created. Belt angle, belt force, belt loading rate and belt-to-body friction as belt design parameters, and pelvis angle, constitute parameters of soft tissue, and soft tissue-to-pelvis friction as occupant parameters were inspected. For the soft tissue part, subcutaneous adipose tissue with different thicknesses was created and the effect initial lap belt position may have on lap belt-to-pelvis interaction was investigated. The influential parameters have been identified as: the belt angle and belt force as belt design parameters and the pelvis angle and compressibility of soft tissue as occupant parameters. The risk for the slide of lap belt over the iliac crest of the pelvis was predicted higher as the initial lap belt positions goes superior to the pelvis. Of different submarining parameters, the lap belt angle represents the most influential one. The lap belt-to-pelvis interaction is influenced by the thickness of subcutaneous adipose tissue between lap belt and pelvis indicating a higher risk for obese occupants

STRUCTURAL DYNAMICS OF A WIND TURBINE DRIVE TRAIN HIGH SPEED SUBSYSTEM: MATHEMATICAL MODELLING AND VALIDATION

The paper studies the dynamics of a wind turbine drive train high speed subsystem, both by modelling and experiments with focus on system torsional vibration and transient events which can reduce fatigue life of functional components (gearbox, bearings, shafts, couplings,others). A scaled down drive train high speed shaft test rig has been developed. Main components of the test rig are six-pole motor with variable frequency drive controller (up to 1000rpm), shafts’ disk coupling and flexible mounting structure representing gearbox housing with output high speed bearing. The test rig is equipped with measurement system comprising a set of accelerometers and displacement sensors, strain gauges and telemeter system, data acquisition hardware and software (SKFWindCon3.0). Mathematical and computational models of the test rig have been developed and went through validation tests. The system dynamic response is studied for different operational scenarios and structural parameters (run-shut down case with and without eccentric mass). The ultimate goal of the test rig is to get insight into interactionbetween internal dynamics of drive train mechanical and electrical functional components and to develop novel methods to detect, predict and prevent faults and failures in wind turbine drive trains arising due to misalignments and transient external loads

Failure modes and optimal performance of a generic synchronizer

The gear shifting mechanism is a crucial part of the gearbox which transmits the torque from engine to wheels with different transmission ratio. For smooth and comfortable gear changing the gear shifting mechanism is still a challenge for the engineers to adapt the different driving situations. In case of heavy vehicles particularly under certain circumstances optimized performance by avoiding failure modes of the gear shifting mechanism is also a challenge. In this paper failure modes and optimized values of the system parameters are identified to contribute for this challenge. A model of the gear shifting mechanism is developed in GT-Suite software. Failure modes are identified via sensitivity analysis. Four system response characteristics are plotted against the time and used to identify the failure modes. Optimization routine of the GT-Suite is applied on the model by taking seven parameters into account as independent variables and synchronization time as an objective function. Percentage changes of the variables from their initial values are calculated and analyzed. Finding of optimal values of parameters of the gear shifting mechanism is valuable contribution to design reliable and efficient transmission system for automotive industry especially for heavy vehicles

Wind turbine drive train vibration with focus on gear dynamics under nondeterministic loads

In present-day, the engineering challenge around a drive train design for a wind turbine is not only to enhancesystem reliability but also to reduce the turbine top mass. These requirements together with the trend of upscaling affect many system characteristics and parameters. The proposed contribution presents a model tostudy torsional drive train vibration dynamics of a generic indirect drive multi-MW wind turbine. The mainfocus lies on developing a fully parameterized computational model of a multi-stage gearbox which fulfillsthe requirement of a proper gear dynamic representation appropriate for multibody formalism as well asthe requirement to be computationally efficient. Two different strategies for modeling the gear contact arestudied and compared in time domain. An analysis of a multi-stage gearbox together with a generator load and a turbine specific nondeterministic excitation was carried out. It is believed that the obtained results will help designer to improve drive train components and to enhance wind turbine reliability and cost efficiency