Marie-Ange Andrianoely

Balancing of machinery with a flexible variable-speed rotor

The balancing procedure of machines composed of a flexible rotating part (rotor) and a non-rotating part (stator) mounted on suspensions is presented. The rotating part runs at a variable speed of rotation and is mounted on bearings with variable-speed-dependent characteristics. Assuming that the unbalance masses are relatively well defined, such as in the case of a crank-shaft, the procedure is based on a numerical approach using rotordynamics theory coupled with the Finite Element and Influence Coefficient Methods. An academic rotor/stator model illustrates the procedure. Moreover, the industrial application concerns a refrigerant rotary compressor whose experimental investigation permits validating the model. Assuming that the balancing planes are located on the rotor, it is shown that reducing the vibration level of both rotor and stator requires a balancing procedure using target planes on the rotor and on the stator. In the case of the rotary compressor, this avoids rotor-to-stator rubs and minimizes vibration transmission through pipes and grommets.

Effect of Rotor-Stator Contact on the Mass Unbalance Response

In turbo-engines the sudden increase of mass unbalance, due for example to a blade-loss, can generate rotor-stator contacts in different zones of the motor architecture: turbine blade/flange, centrifugal compressor wheel/shroud, seals, stop-end bearing. The aim of this paper is to analyse the influence of such rotor-stator interactions on the dynamic behaviour of two types of academic rotors. Several contact laws combined with smoothing methods are investigated in order to implement them in rotor dynamics models. The full annular rub and a finite impact series in forward whirl are exhibited.

An analysis of rotor-stator interaction

The aim of this paper is to investigate the influence of rotor-stator interaction on the dynamic behaviour of a rotor-bearing system. First the model of a SDOF system with two stop-ends is established. The analytical solution permits testing the stability and the robustness of the penalty contact law combined with two numerical schemes. Second, a three-disk rotor in bending equipped with two bearings is subject to a disk-stator contact. The two numerical algorithms analytically validated are again used and associated to four contact models: three types of smooth penalty methods and the Lagrange multiplier method. Spectrograms of time history responses are presented and permits analysing the spectral evolution of the rotor behaviour.

Nonlinear Dynamics of a Rotary Drill-String Immersed in a 3D Geometry Well

Oil or geothermic rotary drilling is composed with a very slenderness drill-string which is subjected in particular to the tool-bit excitations. Therefore a great number of vibratory phenomena concerned with the axial, lateral and torsional behavior are exhibited: whirling, bit bouncing, stick slip to cite just a few. In order to predict the rotordynamics of such a structure, the model proposed is based on Timoshenko beam elements immersed in a 3D geometry well. A constant rotation speed in imposed at the top of drill-string. A fluid-structure interaction model that takes into account the drilling mud is used. The effect of drilling mud in drill-string vibration is studied by varying the well trajectories.

Experimental Variability on Modal Characteristics of an In-Situ Pump

Considering that experimental data, usually considered as the reference in test-analysis correlation and model updating purpose, must also be concerned with uncertainty quantification, the experimental variability on modal characteristics of two nominally-identical pumps in industrial environment is observed, via a benchmark between 5 independent teams. Free choice is let to determine the number and the type of sensors, the excitation means, the number of excitation points and the modal identification method. Variabilities relative to the operator and pump specimen are addressed; moreover specific variability relative to the modal identification phase can be quantified using the same experimental test runs.