MADYN 2000 is a leading rotordynamics software
developed by DELTA JS. One of its unique features
is the hot spot stability analysis, which
allows assessing the risk of thermally induced
rotor instabilities. In this video we analyse
a double overhung rotor for hot spots in the
fluid film bearings, also known as Morton
effect.
Both the Campbell diagram of the damped eigenvalues
and the resonance curves of the unbalance
response analysis proved that the rotor has
its lowest critical speed significantly above
the operating speed range, which is marked
with a blue area.
The hot spots are applied at the two shaft
stations with the fluid film bearings. For
a hot spot due to the Morton effect the length,
the heating type and the coefficients for
heat input and heat dissipation can be calculated
from the bearing parameters by the program.
In the shaft model plot the hot spot locations
are marked with red flash symbols.
As the first step of the analysis procedure
the thermal shaft bending due to a unit temperature
difference across the shaft diameter at the
hot spot location is calculated for the free
shaft. As an example the deformation plot
for heating at the left bearing is shown.
In the hot spot stability analysis the eigenvalues
of a system that is extended by the thermal
equations for the hot spots are calculated
as a function of the speed - similar to a
Campbell diagram. The influence of all hot
spots is considered simultaneously. The number
of hot spot modes is equal to the number of
specified hot spots. The use of a fine speed
step in the analysis ensures smooth curves
in the result plots.
Various hot spot result plots are available.
In the stability threshold plot the green
and red stability thresholds of the two hot
spot modes are shown. Instability occurs if
the actual heat ratio curve in black is above
the lowest threshold curve.
In the stability threshold factor plot the
factor is shown by which the actual heat ratio
must be multiplied to reach the lowest stability
threshold. If the factor is less than one
instability occurs.
The shapes of the two hot spot modes can be
plotted. The rotation frequency of the hot
spot on the shaft surface as well as its direction
are also available in the results.
The hot spot stability analysis in MADYN 2000
offers full flexibility to model virtually
any hot spot mechanism. Are you interested
in our advanced rotordynamics software? Feel
free to contact us for more information.
