Impact of damper seal coefficients in rotor dynamics : uncertainties and optimization

Abstract

Damper seals can have a significant impact on rotor dynamics, but the calculation of the stiffness and damping coefficients for this component can be challenging and has a high uncertainty. In the present work, a probabilistic model is proposed to model the seal coefficients, which are frequency-dependent. We develop a stochastic process (frequency indexed) so that the uncertainty in the model is taken into account. The impact of these uncertainties on the rotordynamic behavior of a compressor is analyzed. The deterministic coefficients of the seal are determined considering a bulk-flow model and values calculated by a compressor vendor based on the extrapolation of experimental data. The obtained results show that the uncertainty of these coefficients have a considerable impact on the compressor rotordynamic behavior, affecting the stability margin and the unbalance response. Based on this analysis, a procedure for the robust optimization of the compressor rotordynamic behavior is proposed. This procedure considers the seal geometric parameters as design variables. The results for the robust optimization show that the seal length and the cell hole depth can be modified to improve the unbalance response.