Contribution to the dynamic study of a rotor by finite elements
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Date
2025-01-07
Journal Title
Journal ISSN
Volume Title
Publisher
University Mohamed Boudiaf-M’sila
Abstract
Rotor dynamics is an important aspect of the design or analysis of any type of rotating
machine, as various types of vibrations appear in this mechanical system when the rotor is
turned on, which can limit performance or easily lead to disaster. Therefore, the dynamic
analysis of the rotor is necessary to ensure proper operation by providing accurate knowledge
of the vibration behavior of the rotor system. In this study, scientific techniques for
modeling and simulating the vibrations of a rotating system are presented. The equations
of vibration motion of the rotor are determined using the Lagrange energy method.
The centrifugal fan installed at the cement factory was selected to be of the FN280
type, equipped with a single wheel with blades mounted on the shaft supported by two
bearings. Due to the fact that the manual solution of the equations of motion characterizing
the dynamic analysis is considered a difficult task, the dynamic analysis of the
cement fan FN280 using the finite element method was performed by the code ANSYS.
The various components of the fan are designed using SolidWorks, except for the blade.
Due to the lack of design data for it, we resorted to reverse engineering technology, which
is also called reverse design. To obtain a 3D model of the blade, we used a CMM machine
to scan the blade, and the fan was assembled and a dynamic analysis of the rotor
was performed using the ANSYS Workbench. We determined the natural frequencies,
extracted the critical speed by means of the Campbell diagram and mode shapes, and
also studied the effect of the worn blades on dynamic behavior. In addition, a harmonic
response analysis was performed in both cases.
FSI simulation was also applied to the fan to estimate the loads resulting from
unsteady flow. This simulation process is carried out using the ANSYS Workbench, which
integrates flow simulation and transient analysis simulation using a one-way coupling
approach. This approach was chosen because there is very weak interaction between the
structural domain and the fluid. The purpose of this simulation is to verify the ability to
make a preliminary estimate of the fatigue limit and the effect of pressure loads applied
to the structure resulting from unsteady flow on the life of the fan. Results showed that
air loads have a negligible effect on fan life.