Machine Dynamics - Acoustics
at the Institute for Thermal Turbomachinery and Machine Dynamics
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.