| 1. |
- Asadi, Saeed, 1987, et al.
(författare)
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STRUCTURAL DYNAMICS OF A WIND TURBINE DRIVE TRAIN HIGH SPEED SUBSYSTEM: MATHEMATICAL MODELLING AND VALIDATION
- 2015
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Ingår i: In Proc. of the International Conference on Engineering Vibration, Ljubljana, 7 - 10 September ; [editors Miha Boltežar, Janko Slavič, Marian Wiercigroch]. - EBook. - Ljubljana: Faculty for Mechanical Engineering, 2015. - 9789616536974 ; , s. 553-562
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Irfan, Muhammad, 1986, et al.
(författare)
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Modelling of Heavy Vehicle Transmission Synchronizer using Constrained Lagrangian Formalism
- 2015
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Ingår i: In Proc. of the International Conference on Engineering Vibration, Ljubljana, 7 - 10 September ; [editors Miha Boltežar, Janko Slavič, Marian Wiercigroch]. - EBook. - Ljubljana: Faculty for Mechanical Engineering, 2015. - 9789616536974 ; , s. 28-37
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Konferensbidrag (refereegranskat)abstract
- Robust and efficient synchronizers are keys elements to ensure good gear shift in heavy vehicles. In order to improve existing as well as develop new synchronizers, efficient simulation tools are needed. In this contribution, a mechanical system with 5 degrees of freedom modelling a generic synchronizer consisting of engaging sleeve, synchronizer ring and gearwheel are considered.Due to the design of the different components and their interactions the synchronizing process is described in terms of different steps or phases; presynchronization, main synchronization, blocker transition and engagement. The four main phases are further divided into sub-phases.To study the whole process in a unified manner, Constrained Lagrangian Formalism (CLF) turns out to be a suitable method in which the interactions between components (sleeve,synchronizer ring and gearwheel) are described by unilateral or/and bilateral constraints imposed on generalized coordinates of the system during different phases. Using CLF a mathematical model of a generic synchronizer is developed and represented by the system of differential-algebraic equations. Kinematics and kinetics of the generic synchronizer are modelled for each sub-phase. The sleeve is considered as a master and thegearwheel is considered as a slave. The statement of the dynamics problem for a generic synchronizer is given and the numerical algorithm is implemented in Matlab for solving the differential-algebraic equations resulting from CLF. The generic synchronizer computational model is adapted to available experimental setup and validated using obtained measurement data. Sensitivity of the synchronization time is studied varying the cone angle, coefficient of dry friction and sleeve force. Effect of driveline vibrations on synchronization performance isalso studied.
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| 3. |
- Lindell, Hans, 1962, et al.
(författare)
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NONLINEAR DYNAMIC ABSORBER TO REDUCE VIBRATION IN HAND-HELD IMPACT MACHINES
- 2015
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Ingår i: In Proc. of the International Conference on Engineering Vibration, Ljubljana, 7 - 10 September ; [editors Miha Boltežar, Janko Slavič, Marian Wiercigroch]. - EBook. - Ljubljana: Faculty for Mechanical Engineering, 2015. - 9789616536974 ; , s. 1530-1539
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Konferensbidrag (refereegranskat)abstract
- Hand-held impact machines have been used since the early 20th century. Up to day still a little has been changed in their fundamental design. Despite them being robust and efficient,vibration, noise, dust and poor ergonomics cause a large number of injuries to the operators, especially in the stone industry. In this paper, vibration dynamics of a pneumatic hand-held impact machine (HHIM) equipped with a nonlinear tuned vibration absorber (NLTVA) is in focus. The considered HHIM has the same parameters as the existing conventional one with respect to piston weight, impact energy and operating frequency. The paper presents the mathematical and computational models of vibration dynamics of the HHIM with NLTVA as well as the experimental set-up developed for model validation. The advantage of using a nonlinear spring is shown and how the effective vibration reduction frequency of the NLTVA can be made to follow the excitation frequency and thereby in principal achieving thesame conditions as is the case for tuned pendulum absorbers for torsional vibrations where the resonance frequency follows the engine order. Using the verified and validated computational model, the sensitivity analysis of vibration dynamics has been performed in a broad set of feasible operational scenarios with respect to structural parameters of the HHIM equipped with NLTVA. Sensitivity analysis results have formed the base for optimisation of the parameters of NLTVA. It was shown by simulations as well as it was proved by experiment that the vibration of the HHIM equipped with NLTVA can be reduced significantly in a broader range of operating frequencies compared to the vibration of the same machine equipped with linear tuned vibration absorber. The results obtained confirm the possibility to design a user friendly low vibration impact machine efficiently operating in a broad frequency range. Optimised NLTVA combined with vibration isolation has shown to significantly reduce the vibration on the operator.
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| 4. |
- Shoja, Siavash, 1982, et al.
(författare)
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Investigating the Application of Guided Wave Propagation for Ice Detection on Composite Materials
- 2015
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Ingår i: In Proc. of the International Conference on Engineering Vibration, Ljubljana, 7 - 10 September ; [editors Miha Boltežar, Janko Slavič, Marian Wiercigroch]. - EBook. - Ljubljana : Faculty for Mechanical Engineering, 2015. - 9789616536974 ; , s. 152-161
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Konferensbidrag (refereegranskat)abstract
- Wind turbines operating in cold regions face icing problems. At the same time these regions are one of the best places to install the wind turbines. To minimize this problem and optimize the de-icing system it is very important to have an efficient ice detection system. Application of guided wave propagation has been previously considered in aircraft industries. To study this application for wind turbines, guided wave propagation should be investigated in composite materials. In the current work, first the guided wave propagation in multi-layered anisotropic materials is mathematically modelled and dispersion curves were obtained. Moreover the composite plate was homogenized to an anisotropic plate in order to simplify the calculations. Comparison of dispersion curves shows changes in group velocity when a second layer as ice is added on top of the first layer. Next, a finite element model was made to observe the effects of ice accretion on top of a composite plate. An experimental set-up was also developed at a cold climate lab on a composite test object used in wind turbine industry. The guided wave propagation was studied experimentally to see the effect of temperature and ice on the material and measurement data was obtained to validate the computational model. Both numerical and experimental results show that a patch of ice on top of a composite plate reflects the propagated guided waves with an amplitude that raises by increasing the thickness of theice layer. Furthermore, ice accumulation affects the group velocity of the guided waves and it proves that the use of guided waves is a promising method to detect ice on turbine blades.
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