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
...
