بحث بعنوان Vibration Analysis of Bladed Disc Assemblies

بحث بعنوان
Vibration Analysis of Bladed Disc Assemblies
C. Minas, S. Kodiyalam
GE Corporate Research and Development
P.O. Box 8, Kl, EP123
Schenectady, New York 12301
ABSTRACT
The dynamic behavior of a bladed disc
assembly was determined by developing a finite
element model @‘EM). The object of this work
is to develop an understanding of the dynamic
behavior of the system with respect to the
various boundary conditions. The analysis
included variation of the boundary conditions at
the blade-disc interface, between adjacent
blades, and the shroud. It was clearly shown
that only certain mode patterns are affected with
respect to a particular boundary condition,
leaving the remaining modes unchanged. The
quantitative effect of the various boundary
conditions was calculated by finite element
analysis of a cyclic symmetric model. A
methodology is also presented where the
associated modes of the higher harmonics
resonant frequencies of the assembly, are
identified in a systematic and automated way
without being plotted and viewed. This
methodology which uses the cross-orthogonality
equations, is valuable to systems with a large
number of nodal diameters, where the complete
set of the associated mode shapes can be
analyzed in an efficient and systematic way.
The technique is illustrated through an example,
where a complete analytical Campbell diagram
for the lower order modes is developed.
CONCLUSIONS
The dynamic behavior of a bladed disc
assembly was determined by developing a
cyclic symmetric FEM The object of this work
was to develop an understanding of the dynamic
behavior of the system with respect to the
various boundary conditions. The analysis
included variation of the boundary conditions at
the blade-disc interface, between adjacent
blades, and the shroud. It was clearly shown
that modification of the boundary conditions at
the blade-disc interface affected only the axial
modes of the system. On the contrary,
modifying the boundary conditions between
adjacent blades and the shroud affected only the
tangential modes. The quantitative effect of the
aforementioned boundary condition
modifications was demonstrated through an
example. A methodology is also presented
where the associated modes of the higher
harmonics resonant frequencies of the assembly,
are identified in a systematic and automated way
without being plotted and viewed. The
technique was illustrated through a cyclic
symmetric bladed-disc assembly with 24
identical sections.
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