Gas Turbine Response on Seismic Load

Abstract eng:
Investigation of stationary gas turbine power unit behavior at seismic load is performed. Methodology for developing of gas turbine power unit system “rotor – fluid film bearings – casing – foundation frame” reduced finite-element (FE) models is presented. Nonlinear stiffness and damping characteristics of lubrication layer in fluid film tilting-pad and multilobe bearings are taken into account in presented models. Calculation of bearing stiffness and damping characteristics involves coupled solution of problem of incompressible lubrication flow in gap between shaft journal and pad surfaces and problem of each pad equilibrium position definition with elastic deformations of sliding surfaces taken into account. Natural frequencies and modes of vibration for gas turbine power unit are determined for two cases: with and without gyroscopic moments taken into account. Verification between different reduced FE models of rotor is carried out. Investigation of gas turbine power unit with rotating rotor dynamic response at seismic load is carried out by direct integration using Newmark scheme. Rotor orbits in bearings and disks orbits are calculated both at operational loads and at seismic load applied. Calculated orbits full spectrum analysis is performed. Conclusion regarding to fluid film bearings working capacity at seismic load is performed. Rotor and casing parts stress-strain state is calculated. During analysis of gas turbine power unit response on seismic event with amplitude of 9 by the MSK-64 scale the evaluation of static and dynamic reactions in rotor supports and casing mounting points is performed. Rotor orbits and casing parts deformations at seismic load in comparison with similar results for stationary operation conditions allows to evaluate gaps changing in gasdynamic path and in bearings and make a conclusion regarding to working capacity of gas turbine power unit at seismic load. The evaluation of lubrication layer stiffness in fluid film bearings in rotor supports influence on gaps in gasdynamic path at seismic load is carried out. Shown that gyroscopic moments of rotating rotor changing gas turbine natural frequencies and leads to sufficient rotor and casing reciprocal displacements that changing values of gaps in gasdynamic path at seismic load.

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