Abstract
In this paper, a new method for the balancing of rotor-bearing systems supported on fluid film bearings is proposed. The influence coefficients necessary for balancing are calculated using a novel simulation method called the Numerical Assembly Technique. The advantages of this approach are quasi-analytical solutions for the equations of motion of complex rotor-bearing systems and very low computation times. The Numerical Assembly Technique is extended by speed-dependent stiffness and damping coefficients approximated by the short-bearing theory to model the behavior of rotor systems supported on fluid film bearings. The rotating circular shaft is modeled according to the Rayleigh beam theory. The Numerical Assembly Technique is used to calculate the steady-state harmonic response, influence coefficients, eigenvalues, and the Campbell diagram of the rotor. These values are compared to simulations with the Finite Element Method to show the accuracy of the procedure. Two numerical examples of rotor-bearing systems are successfully balanced by the proposed balancing method.
Highlights
Many test runs are necessary to determine the influence coefficients, which may be very time consuming and expensive. This can be avoided with calculated influence coefficients, as long as a very accurate model for the rotor-bearing system is used, including all rotor dynamic effects [6]
The critical speeds, Campbell diagram, and frequency response function (FRF) were compared with the well-known Finite Element Method (FEM) code by Friswell et al [37] to show the accuracy of the Numerical Assembly Technique (NAT) simulation
The displacements of the rotor-bearing system were calculated with the Friswell code in this paper. With these displacements and the influence coefficients calculated by NAT, the balancing weights were found, and the balancing success was analyzed
Summary
Rotary machines are always subject to imbalances, leading to an excitation of the rotor and the surrounding structure. The modal balancing method requires only a small set of test runs and is accurate up to higher modes [3]. Many test runs are necessary to determine the influence coefficients, which may be very time consuming and expensive. This can be avoided with calculated influence coefficients, as long as a very accurate model for the rotor-bearing system is used, including all rotor dynamic effects [6]. NAT is an efficient, quasianalytic method to calculate the steady-state harmonic response, influence coefficients, eigenvalues, and the Campbell diagram of rotor-bearing systems. Wu and Chen extended the method to the Timoshenko beam theory [8]
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