Predicting And Improving The Dynamic Behavior Of Multistage High Performance Pumps

Abstract

Good rotordynamic behavior, implying sufficient stability margin and low sensitivity to unbalance forces, is mandatory for modern high pressure multistage pumps. Stiffness, damping and mass matrices describing the forces acting on a rotor at bearings, seals, balancing device and impeller is discussed. Comparisons are made between calculated natural frequencies from coupled damped models and “wet critical speeds” calculated from undamped uncoupled models. The effect of design changes on the stability limit at increased clearances is shown experimentally, and a simplified mathematical model is presented, showing the effect of the various coefficients on the stability limit. Finally, results are shown from experiments and calculations on coupled rotor casing pedestal systems.