New rotordynamics data item helps reduce vibration problems
New rotordynamics data item helps reduce vibration problems
ESDU International's latest design engineering data item (No. 95023) is designed to increase understanding of the role played by bearings in the dynamic behaviour of rotors.
Turbomachines, such as compressors, turbines and turbopumps, may suffer from levels of vibration which can seriously affect plant profitability. Vibration-related problems can delay the development and commissioning of such machines, or can result in reduced output or unplanned shutdowns.
The data item provides a user manual for a computer program (ESDUpac) entitled: "Dynamics of a simple flexible rotor supported in axial groove hydrodynamic journal bearings" and can be used to determine the response to imbalance and the onset of oil-whip instability. The simple model employed provides insight into the dynamics of operation. It can also be used as an education tool for assisting in the interpretation of output from the vibration measurements of a machine or an equivalent computer simulation. 
Turbine rotor subject to vibrations
The program is capable of determining the out-of-balance response of the rotor for either constant rotational speed or constant acceleration, with or without speed dependent external loading. A complete working cycle of the rotor can be simulated,starting with a run-up to operating speed, followed by a period of constant speed and concluded with a final coast-down. During the whole process, selected parameters such as deflections or bearing forces may be recorded in a form suitable for plotting.
Three types of analysis are carried out: dynamic simulation of the rotor/bearing system with constant acceleration or deceleration; stability analysis to provide the oil-whip frequency together with the rotational frequency on the boundary of stability;and unbalance response analysis to determine the synchronous harmonic response orbits.
More details from ESDU International plc, 27 Corsham Street, London N1 6UA. Tel: 0171 490 5151; Fax:0171 490 2705.
