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Machine Dynamics - Acoustics
at the Institute for Thermal Turbomachinery and Machine Dynamics
Head of Department:
     Dr. Andreas Marn
Address and contact:
     TUG / TTM / AV
     Inffeldgasse 25 A
     A 8010 Graz
     Tel. +43(0)316 873-7726

General Machine Dynamics and Acoustics

Machine dynamics deals with the external and internal forces that work in machines as well as the vibration processes in the entire field of mechanical engineering. Computation of vibration modes, journal bearing damping and amplitude calculations are the mean value for secure vibration tuning to avoid resonances and overstrain in the involved machine elements.
The non-linear elements like the oil film in journal bearings represent the greatest computational difficulty in that way but now it is possible to predetermine the entire oscillation behaviour and the sound radiation of a diesel engine with numeric methods correctly. The same applies to the quietness and the vibration safety of the rotors and turbine blades and for short-circuit resistance of the turbo sets.
However, appropriate experiments are necessary in the case of complicated forms concerning the vibration behaviour but also the damping parameters. The research works of the institute are occupied with short-circuit states in turbo sets, the rotor dynamics and internal shaft cooling of high frequency motors, vibrations and the functional behaviour of string stranding machines, calculations of vibrating foundations, functional behaviour and vibration behaviour of rock milling, the study of the sound radiation from power plant components and the sound attenuation by active sound control as well as the reduction of the sound radiation of vibrating surfaces.
At present an experimental turbine is built up where the flow phenomenon and the vibration behaviour of rotor and blades may be tested under special conditions. With rotor dynamic monitoring devices these processes can be analysed and the comparison of the measurement with computational solutions will be possible. In this way, an improvement in the analytical models for vibration monitoring in rotating machines and the diagnosic methods required is made possible.
The results will cause a vibration reduction and therefore a service life increase as well as a safety increase and will show possibilities of an effective noise control. With the projects mentioned above, the institute participates in the European research activity COST Action F3 "Structural Dynamics". There is participation in the work groups 2: "Health Monitoring and Damage Detection" and 3: "Identification of Non-linear Systems" and 3: Active Control of Structures.

Rotor-Dynamics in Steam- and Gasturbines, Turbocompressors and other Turbomachinery

Rotor dynamic investigations to predict the behaviour of large rotors and fast running rotors providing exact description of the properties of the bearings are inevitable in order to ensure low shaft vibration amplitudes and to secure the safe operation of blading under the condition of very narrow clearances which are prescribed in these machines.
Additional questions have to be solved as stability in situation of oil film instability, of fluid flow clearance instability and proper running of rotors has to be ensured with special design as squeeze film damped roller bearings, which are applied to jet engines and modern power plants. Computer programs for the simulation of these rotor dynamic effects have been developed and successfully applied by the institute since quite some time and also vibrational investigations regarding disc vibrations have been conducted in conjunction with industry.
Another part of this work area is concerned with the torsional vibrations which may happen when synchronising large power shafts and especially during short circuit which result in large exciting electrical moments causing torsional vibrations being transmitted through the shafts of steam and gas turbine plants. Especially fast running steam and gas turbines with gears in the shaft train pose a difficult problem since non-linearity due to the clearances in gears an couplings have to be properly accounted for. By automatic synchronising the action of governing systems causes quick actions and response of shafts which have to be investigated and simulated in the course of torsional vibrations. The institute has an intensive cooperation not only with machine building industry but also with owners of power stations especially regarding the question of resistance to short circuits, which requires intensive calculations in order to supply the safety and security of operation.

  TTM - TU Graz // Inffeldgasse 25A // A-8010 Graz // Phone: +43 (316) 873 7226 // Fax: +43 (316) 873 7239
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