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Rotordynamic model of a fibre refinery in BEAST
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

A fibre refiner is a rotating machine that cut wood chips into fibres, which are used for example to produce panel boards. The aim of this thesis has been to implement a rotor dynamical model of a fibre refiner into SKF own computer program BEAST in order to study the dynamical behaviour of the system and what effect it will have on the bearings. This thesis starts with an introduction to linear rotor dynamics by a study of four degrees of freedom overhung rotor model with gyroscopic effect. This model has been solved in two different ways namely by a direct method and by FFT analyse. The FFT analysis is one way to threat rotordynamical problems when doing experiments on real machines. The analytical tool has in this case been the Campbell diagram which is a method for plotting eigenfrequencies as a function of the spin speed. In rotordynamics the sign of eigenfrequencies has dependence because of the connection to the spin speed via the gyroscopic matrix. A routine has therefore been developed for creation of Campbell diagram constructed from signals by FFT analysis in Matlab (see Appendix B for code description). Then this thesis continues with introduction to BEAUTY and BEAST. Three models of the fibre refiner have been studied during this thesis. Model A is an overhung rotor that has been compared to the analytical model, the aim of studding this model was to see if BEAST could handle the gyroscopic term in the equation of motion. In BEAST implemented with the analytical stiffness matrix directly onto the disk. Model B is modelled with rigid body rested on two flexible supports in x and y direction. This result is then compared to an analytical model B. Model C is the final concept of the refinery. Here are bearings and pressure chambers introduced in the model and possibility to ad clearance in the model. The creation of model C take one month, therefore analysis as lifetime calculations on the bearings hasn’t been done. This been the future work on this model. The results from model B shows that BEAST could handle the gyroscopic term in the equation of motion. The result from model C shows that the largest force was on bearing C closest to the rotor and that the shape of the bearing forces change when clearance where added in the simulations.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Rotordynamics
Keyword [sv]
URN: urn:nbn:se:ltu:diva-53964ISRN: LTU-EX--06/138--SELocal ID: af1bb1ee-0732-4b02-99e9-174683fc7c47OAI: diva2:1027343
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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