Comparison of multibody simulations and measurements of wind turbine gearboxes at Hansen’s 13 MW test facility

Continuous up-scaling of wind turbine size into the multi-megawatt class, together with developments for off-shore installation are calling for new wind turbine configurations and technologies. High product reliability is a key factor in these developments, cascaded down to each component manufacturer in the supply chain. Increasing the reliability of wind turbine drive trains for wind turbines with ever increasing size requires dedicated simulation models which can provide more insight in the internal gearbox dynamics in the early stages of the design process. However, simulation models can only add value to the design process if their results prove to be representative and reliable. Therefore validation based on measurements on real multi-megawatt wind turbine gearboxes is an absolute necessity. For this reason, Hansen Transmissions developed a back-to-back 13MW test rig set-up capable of dynamically testing gearboxes and validating their dynamical models. This validation is based on three foundations: validation of model parameters, validation in the frequency domain and validation in the time domain. The initial results of the validation of model parameters, validation in the frequency domain and validation in the time domain already demonstrate the added value of multibody gearbox models. Therefore the confidence level in the applicability of multibody simulation models in gearbox design is increased.status: publishe

David Margrett : a black missionary in the revolutionary Atlantic

David Margrett was a black missionary sent by the Countess of Huntingdon to preach to slaves in South Carolina and Georgia in 1774. Margrett did not confine his preaching in America to spiritual matters, instead speaking out against the system of slavery itself, and offering himself as a “second Moses.” Margrett's message was not well received by authorities in South Carolina, indeed he was fortunate to escape with his life. This article argues that Margrett was a product both of his evangelical training, where speaking out on important matters was encouraged, and also of his British environment, where anti-slavery voices were becoming increasingly prominent. The story of David Margrett demonstrates how black Britons received and interpreted the message of Christianity, and in particular how they used their faith as a means to attack slavery

Isolation and characterisation of rye starch

Starch was isolated from rye flour by alkaline extraction or Pronase treatments. Both procedures led to starches of comparable purity. The present first report on the use of proteolytic enzymes in rye starch isolation showed that such treatment resulted in the highest starch yields. The rye starches had A-type granules with average particle size of 31 mum. The Pronase isolated starch had lower differential scanning calorimetry gelatinisation temperatures than the alkaline extracted starch. Defatted rye flour resulted in a Pronase isolated starch with lower peak and higher end viscosities. Wheat and rye starches isolated by the Pronase procedure were of comparable purity, but a higher yield of the former was obtained. The wheat starch had lower levels of A-type granules with an average particle size of 26 mum. When compared pairwise to the rye starches, the wheat starches had higher gelatinisation temperatures, a higher pasting temperature, a higher peak viscosity and a lower end viscosity. (C) 2003 Elsevier Ltd. All rights reserved.status: publishe

Multibody modelling of varying complexity for modal behaviour analysis of wind turbine gearboxes

In the currently booming market of wind turbines, a clear focus is put on the design of reliable and cost-effective subsystems, such as the gearbox. A requirement for reliable gearbox design calculations is sufficient insight in the dynamics of the entire wind turbine drive train. Since traditional wind turbine design codes reduce the drive train to just a few degrees of freedom, considerable research effort is spent in advanced modelling and simulation techniques to gain more insights in the dynamics at hand. This work focusses on the gearbox modal behaviour assessment by means of three more complex modelling techniques of varying complexity: the purely torsional-, rigid six degree of freedom with discrete flexibility- and flexible multibody technique. Both simulation and experimental results are discussed. Typical mode categories for traditional wind turbine gearboxes are defined. Moreover the challenge of the definition of an accurate approach to condense finite element models for representing the flexible components in the flexible multibody models is overcome. Furthermore the interaction between the structural modes of the planet carrier and planetary ring flexibility with the overall gearbox modes is investigated, resulting in the definition of two new mode categories: the planet carrier modes and planetary ring modes.status: publishe

Multibody modelling of varying complexity for modal behaviour analysis of wind turbine gearboxes

In the currently booming market of wind turbines, a clear focus is put on the design of reliable and cost-effective subsystems, such as the gearbox. A requirement for reliable gearbox design calculations is sufficient insight in the dynamics of the entire wind turbine drive train. Since traditional wind turbine design codes reduce the drive train to just a few degrees of freedom, considerable research effort is spent in advanced modelling and simulation techniques to gain more insights in the dynamics at hand. This work focusses on the gearbox modal behaviour assessment by means of three more complex modelling techniques of varying complexity: the purely torsional-, rigid six degree of freedom with discrete flexibility and flexible multibody technique. Both simulation and experimental results are discussed. Typical mode categories for traditional wind turbine gearboxes are defined. Moreover the challenge of the definition of an accurate approach to condense finite element models for representing the flexible components in the flexible multibody models is overcome. Furthermore the interaction between the structural modes of the planet carrier and planetary ring flexibility with the overall gearbox modes is investigated, resulting in the definition of two new mode categories: the planet carrier modes and planetary ring modes. © 2011 Elsevier Ltd.status: publishe

Experimental assessment of gear meshing excitation propagation throughout multimegawatt gearboxes

Gearboxes consisting of both planetary and helical gear stages are increasingly used in helicopters, wind turbines and vehicles. A requirement for reliable gearbox design calculations is sufficient insight in internal gearbox dynamics. Excitation frequencies and excitation levels play an important role. Main objective of this work is to investigate the influence of internal gear meshing excitation on the overall gearbox dynamics. Experiments are conducted on a dynamic 13.2MW test facility on which two multi-megawatt wind turbine gearboxes are placed back to back. A dedicated dynamic load case representing realistic drive train excitation is applied and the role of the meshing orders in spreading this excitation over a broader frequency range is determined by means of waterfall spectra from measurement signals of bearing displacement sensors, torque sensors, encoders and accelerometers throughout the gearbox. Moreover the propagation of the meshing excitation throughout the gearbox is of interest. Relating the orders to the corresponding excitation source allows the definition of order influence regions within the gearbox. These insights will be used to prove the need for accurate gear mesh order excitation representation within the corresponding flexible multibody simulation model. Moreover the meshing order influence regions offer the opportunity to tune order excitation to the gearbox modal properties and reduce vibration levels.status: publishe

Updated wind turbine gearbox multibody model with optimized flexible housing to deliver inputs for acoustic calculations

Wind turbine design requirements are increasingly focussing on vibration and noise emission levels. In addition to the rotor and blades also the drive train is a contributor to the overall noise and vibrational behaviour of the wind turbine. Therefore good dynamic design of the drivetrain is highly important. With regard to acoustic radiation both excitations at gearbox input and output as internal excitations originating from the gears are important. Two acoustic phenomena are investigated: structure borne excitation past by/comming from the gearbox through the nacelle to the receiver and airborne noise directly radiated from the gearbox housing. This work discusses the use of a flexible multibody in combination with a Boundary Element Model (BEM) to asses these phenomena. The multibody model is used to calculate the housing vibrations. A method is discussed to convert these deformations at the structural mesh nodes to the nodes of the BEM mesh.status: accepte