| 1. |
- Evertsson, Magnus, 1967, et al.
(författare)
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Control systems for improvement of cone crusher yield and operation
- 2014
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Ingår i: Proceedings of Comminution '14.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Gyratory and cone crushers are regaining interest and are becoming more frequently used in order to create more energy efficient comminution circuits. A typical example is found in coarse comminution circuits were HPGRs are used as a first milling stage. In this case the preparation of a suitable feed with a well-defined width of the particle size distribution and a controlled top size are of high importance. In turn, this emphasizes the importance of a stable and controlled operation of the preceding crushing stages. Control systems for cone and gyratory crushers were first introduced during the early 60ths. The common opinion is that if these systems are able to compensate for the wear of the crushing liners the production yield can be increased with 20-25%. Over the years these types of systems have been widely used but the theory behind the principles have not been thoroughly scientifically scrutinized and presented. Of special interest is the capability to protect the crushers from long term overloading commonly defined as fatigue.With developments in electronics and plant control the crusher control systems have become more refined over the years. Though, there are sometimes conflicting interests in the control strategies between process requirements and crusher protection. In the paper an overview of the challenges, opportunities and existing control systems for cone and gyratory crushers is presented. A requirement specification for a system that is possible to fully integrate into modern plant control systems is outlined.
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| 2. |
- Evertsson, Magnus, 1967, et al.
(författare)
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Monitoring and validation of life time prediction of cone crusher with respect to loading and feeding conditions
- 2016
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Ingår i: Comminution 16. - 9781510826670 ; 904 (1 Vol)
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Konferensbidrag (refereegranskat)abstract
- The interest and need for compressive crushing in gyratory, cone and HPGR crushers are increasing since ores become more competent and more difficult to break. Compressive crushing is energy efficient as a consequence of the crushing principle and the imposed stress-state. The stress variations can be described by stress amplitudes and it is a known fact that many different materials, components and machines suffer from cyclic loading which shortens the service lifetime. This phenomena is explained by density variations of the particle beds in the equipment which in turn originates from particle segregation and feeding alignment. The phenomena is often called fatigue and the consequence is premature breakdowns and a relatively shorter lifetime than expected. In this paper, a previously developed theory for lifetime assessment of cone crushers will be used as a foundation for evaluation of full-scale operating cone crushers in minerals processing plants. Lifetime is calculated as a consequence of the load spectrum. The data shows that improper feeding conditions will substantially decrease the lifetime of the crusher equipment leading to excessive operating costs. An adequate control system should be able to recognise the hazardous lifetime decreasing overloads and to warn the operator. There are sometimes conflicting interests in the control strategies between production yield (process requirements) and crusher protection.
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| 3. |
- Bhadani, Kanishk, 1991, et al.
(författare)
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Application of Structural Optimization for an Early Stage Product Development
- 2017
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Ingår i: NAFEMS World Congress 2017, A World of Engineering Simulation, Stockholm, Sweden. - 9781910643372 ; , s. 13-
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Konferensbidrag (refereegranskat)abstract
- In today’s automotive industry there is a growing demand for more fuel efficient vehicles and reduced development times. These trends are driven by stricter environmental regulations, a growing environmental awareness, and increasing technological development and competitiveness. Finding an optimized and balanced component that fulfils the requirements in an early phase of the product development is a prerequisite for enabling more competitive lead times, costs, weights and minimizing the risk for late design changes. The aim with this paper is to show a process capturing CAE driven development for an early stage development of components in a complex system. The process utilizes structural optimization techniques to generate knowledge, optimize and balance packaging volumes of adjacent components in complex systems. The paper also highlight the organizational challenges and technical challenges involving the use of structural optimization for realizing the process completely. The paper will illustrate the simultaneous use of topology and shape optimization to generate knowledge for the optimized design volume for multiple adjacent components linked together. The linking of the multiple component is carried out using morphing technique and the design space between the multiple components is dynamic in nature during simulation. The mesh in one component is allowed to change according to the mesh of the other component during the simulation. The result from the simultaneous topology and shape optimization simulation generates the knowledge if it is feasible to change design volume to meet the weight and performance targets. The process also indicates how much performance increase is possible if the design volume is allowed to change and thus generating a trade-off between the components performance.The new process has a potential to be extended to other conflicting scenarios in adjacent components which exists in early stages of development process especially, cases involving conflicting structural requirements in various industries.
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| 4. |
- Gantasala, Sudhakar, et al.
(författare)
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Aeroelastic simulations of wind turbine using 13 DOF rigid beam model
- 2016
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Ingår i: Open archives of the 16th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery. - : Symposia on Rotating Machinery.
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Konferensbidrag (refereegranskat)abstract
- The vibration behavior of wind turbine substructures is mainly dominated by their first few vibration modes because wind turbines operate at low rotational speeds. In this study, 13 degrees of freedom (DOF) model of a wind turbine is derived considering fundamental vibration modes of the tower and blades which are modelled as rigid beams with torsional springs attached at their root. Linear equations of motion (EOM) governing the structural behavior of wind turbines are derived by assuming small amplitude vibrations. This model is used to study the coupling between the structural and aerodynamic behavior of NREL 5 MWmodel wind turbine. Aeroelastic natural frequencies of the current model are compared with the results obtained from the finite element model of this wind turbine. Quasi-steady aerodynamic loads are calculated considering wind velocity changes due to height and tower shadow effects. In this study, vibration responses are simulated at various wind velocities. The derived 13 DOF simplified model of the wind turbine enables to simulate the influence ofchange in parameters and operating conditions on vibration behavior with less computational effort. Besides that, the results of the simplified models can be interpreted with much ease.
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| 5. |
- Bengtsson, Magnus, 1973, et al.
(författare)
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Model of banana screen for robust performance
- 2016
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Ingår i: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 91, s. 66-73
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Tidskriftsartikel (refereegranskat)abstract
- Screens are an important production unit in crushing plants. The performance of the screen is essential to the performance of the crushing plant. In this paper a mechanistic model of a banana screen is described and a novel model for screen deck configuration is presented. The developed model can be used for optimization of a screen so that it has the best possible performance with respect to different feeding conditions, in order to obtain a desired separation. The simulation results were compared to full scale test data and the conclusions from this comparison is that the screen model needs further parameters to handle the necessary screen deck configuration. An initial static model was derived to explain how the screen deck configuration will affect the screen efficiency. The modification of the screen deck parameters resulted in a better correlation both regarding size distribution and predicted capacity.
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| 6. |
- Gantasala, Sudhakar, et al.
(författare)
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Identification of ice mass accumulated on wind turbine blades using its natural frequencies
- 2018
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Ingår i: Wind Engineering. - : Sage Publications. - 0309-524X .- 2048-402X. ; 42:1, s. 66-84
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Tidskriftsartikel (refereegranskat)abstract
- This work demonstrates a technique to identify information about the ice mass accumulation on wind turbine blades using its natural frequencies, and these frequencies reduce differently depending on the spatial distribution of ice mass along the blade length. An explicit relation to the natural frequencies of a 1-kW wind turbine blade is defined in terms of the location and quantity of ice mass using experimental modal analyses. An artificial neural network model is trained with a data set (natural frequencies and ice masses) generated using that explicit relation. After training, this artificial neural network model is given an input of natural frequencies of the iced blade (identified from experimental modal analysis) corresponding to 18 test cases, and it identified ice masses’ location and quantity with a weighted average percentage error value of 17.53%. The proposed technique is also demonstrated on the NREL 5-MW wind turbine blade data.
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| 7. |
- Gantasala, Sudhakar, et al.
(författare)
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Influence of Icing on the Modal Behavior of Wind Turbine Blades
- 2016
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Wind turbines installed in cold climate sites accumulate ice on their structures. Icing of the rotor blades reduces turbine power output and increases loads, vibrations, noise, and safety risks due to the potential ice throw. Ice accumulation increases the mass distribution of the blade, while changes in the aerofoil shapes affect its aerodynamic behavior. Thus, the structural and aerodynamic changes due to icing affect the modal behavior of wind turbine blades. In this study, aeroelastic equations of the wind turbine blade vibrations are derived to analyze modal behavior of the Tjaereborg 2 MW wind turbine blade with ice. Structural vibrations of the blade are coupled with a Beddoes-Leishman unsteady attached flow aerodynamics model and the resulting aeroelastic equations are analyzed using the finite element method (FEM). A linearly increasing ice mass distribution is considered from the blade root to half-length and thereafter constant ice mass distribution to the blade tip, as defined by Germanischer Lloyd (GL) for the certification of wind turbines. Both structural and aerodynamic properties of the iced blades are evaluated and used to determine their influence on aeroelastic natural frequencies and damping factors. Blade natural frequencies reduce with ice mass and the amount of reduction in frequencies depends on how the ice mass is distributed along the blade length; but the reduction in damping factors depends on the ice shape. The variations in the natural frequencies of the iced blades with wind velocities are negligible; however, the damping factors change with wind velocity and become negative at some wind velocities. This study shows that the aerodynamic changes in the iced blade can cause violent vibrations within the operating wind velocity range of this turbine.
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| 8. |
- Gantasala, Sudhakar, et al.
(författare)
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Investigating How an Artificial Neural Network Model Can Be Used to Detect Added Mass on a Non-Rotating Beam Using Its Natural Frequencies : A Possible Application for Wind Turbine Blade Ice Detection
- 2017
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Structures vibrate with their natural frequencies when disturbed from their equilibrium position. These frequencies reduce when an additional mass accumulates on their structures, like ice accumulation on wind turbines installed in cold climate sites. The added mass has two features: the location and quantity of mass. Natural frequencies of the structure reduce differently depending on these two features of the added mass. In this work, a technique based on an artificial neural network (ANN) model is proposed to identify added mass by training the neural network with a dataset of natural frequencies of the structure calculated using different quantities of the added mass at different locations on the structure. The proposed method is demonstrated on a non-rotating beam model fixed at one end. The length of the beam is divided into three zones in which different added masses are considered, and its natural frequencies are calculated using a finite element model of the beam. ANN is trained with this dataset of natural frequencies of the beam as an input and corresponding added masses used in the calculations as an output. ANN approximates the non-linear relationship between these inputs and outputs. An experimental setup of the cantilever beam is fabricated, and experimental modal analysis is carried out considering a few added masses on the beam. The frequencies estimated in the experiments are given as an input to the trained ANN model, and the identified masses are compared against the actual masses used in the experiments. These masses are identified with an error that varies with the location and the quantity of added mass. The reason for these errors can be attributed to the unaccounted stiffness variation in the beam model due to the added mass while generating the dataset for training the neural network. Therefore, the added masses are roughly estimated. At the end of the paper, an application of the current technique for detecting ice mass on a wind turbine blade is studied. A neural network model is designed and trained with a dataset of natural frequencies calculated using the finite element model of the blade considering different ice masses. The trained network model is tested to identify ice masses in four test cases that considers random mass distributions along the blade. The neural network model is able to roughly estimate ice masses, and the error reduces with increasing ice mass on the blade.
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| 9. |
- Elled, Anna-Lena, et al.
(författare)
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The fate of zinc during combustion of demolition wood in a fluidized bed boiler
- 2007
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Ingår i: Energy & Fuels. - : American Chemical Society. - 0887-0624 .- 1520-5029. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- Demolition wood can be used as a fuel in heat and power plants. However, it may contain elevated amounts of zinc, originating from white paint, which can cause problems related to deposit formation and corrosion on heat transfer surfaces. In this work, combustion tests with zinc addition were carried out in a fluidized bed boiler to investigate its effect on deposit formation. Thermodynamic equilibrium calculations were performed to complement the experimental data. The results show that combustion of demolition wood only contaminated with zinc generates a modest amount of deposit. Combustion of demolition wood contaminated with both zinc and chlorine promotes the deposit formation due to the increased amount of submicron particles in the flue gas. The thermodynamic equilibrium analyses show further that reducing conditions increase the release of zinc to the flue gas. On the other hand, in the case of oxidizing conditions, the retention of zinc in the ash is strong. Zinc, in combination with chlorine, gives rise to formation of zinc chloride in the flue gas. The formation is, at reducing conditions, thermodynamically favored between 450 and 850 °C. At oxidizing conditions, the formation is initiated at 400 °C and gradually increased with the temperature.
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| 10. |
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