New Dynamic Participation Factor for Turbine-Generator Foundations

Abstract

This paper proposes a new dynamic participation factor (DPF) for analysis and design of structures supporting rotational machines, especially large turbine generators. The new DPF takes into account the distribution patterns of the machine unbalanced forces and addresses the phase lags among the forces at different bearings and between the different force components. An example of a real turbine-generator foundation is presented and the new and traditional DPFs are compared along with examination of the vibration modes. The results show that the new DPF can clearly identify the local vibration modes that cause severe resonance. Using the traditional DPF could cause engineers to ignore these modes and, consequently, result in unsafe design. The common misconceptions of dominant fundamental modes and low tuning are clarified. Harmonic analyses (frequency sweeps) are also performed and the results are compared with the results of the new DPF analyses. The new DPF analysis has clear advantages over the harmonic analysis in that it provides a complete picture of the dynamic behavior of the whole structure and does not need the engineer to anticipate the local vibration points. The new DPF analysis can also be used to guide the selection of locations for vibration amplitude check and provides an alternative method to consider the different phasing of bearing loadings, which produces responses to real loading cases.