Abstract: A theoretical investigation on the effects of both
steady-state and dynamic deformations of the foils on the dynamic
performance characteristics of a self-acting air foil journal bearing
operating under small harmonic vibrations is proposed. To take into
account the dynamic deformations of foils, the perturbation method is
used for determining the gas-film stiffness and damping coefficients
for given values of excitation frequency, compressibility number, and
compliance factor of the bump foil. The nonlinear stationary
Reynolds’ equation is solved by means of the Galerkins’ finite
element formulation while the finite differences method are used to
solve the first order complex dynamic equations resulting from the
perturbation of the nonlinear transient compressible Reynolds’
equation. The stiffness of a bump is uniformly distributed throughout
the bearing surface (generation I bearing). It was found that the
dynamic properties of the compliant finite length journal bearing are
significantly affected by the compliance of foils especially whenthe
dynamic deformation of foils is considered in addition to the static
one by applying the principle of superposition.
Abstract: Analysis of reciprocating equipment piston rod leads
to nonlinear elastic-plastic deformation analysis of rod with initial
imperfection under axial dynamic load. In this paper a new and
effective model and analytical formulations are presented to evaluate
dynamic deformation and elastic-plastic stresses of reciprocating
machine piston rod. This new method has capability to account for
geometric nonlinearity, elastic-plastic deformation and dynamic
effects. Proposed method can be used for evaluation of piston rod
performance for various reciprocating machines under different
operation situations. Rod load curves and maximum allowable rod
load are calculated with presented method for a refinery type
reciprocating compressor. Useful recommendations and guidelines
for rod load, rod load reversal and rod drop monitoring are also
addressed.