Due to collisions between ice and propeller the drive train of ice breakers in artic
conditions is a highly stressed system. Aim of the ArTEco ‘Arctic Thruster Ecosystem’ project is to
increase the reliability of vessels when overloads and torsional vibrations occurs.
To achieve this aim different load scenarios will be analysed on a test rig located in Tuusula
(Finland). Here the WST14 azimuth thruster, which is equipped with measuring instruments, is
operated by the VTT and Wärtsilä. To investigate the behaviour of the test rig and the thruster
different simulation models are created. These multibody system simulation (MBS) and finite element
models (FE) are required to understand the behaviour of the thruster and investigate improvement
strategies. Targets of these investigations are the dynamic behaviour during ice contact and the
optimization of bevel gears in prospect of safety and efficiency. Therefor estimated
propeller loads that occur during ice contact of the gear box housing or loads occur by hitting the
propeller blades are used.
The simulation models of the thruster regards the flexible structure of the housing and shafts.
Using this information the comparison considers natural eigenfrequency correlates to the test rig
in Tuusula and the misalignment of the bevel gear can be investigated, validated and an
optimisation achieved. For further analysis a simulation model is assembled by TU Dresden and
verified by several time based data sets and modal analysis of the test rig. That
way overloads and high dynamic loads which can’t be applied on the test rig are evaluable. Besides
the dynamic analysis a progress in design phase for bevel gear stages is done. This is achieved by
using complex FE models including the elastic bevel gear contact, bearing stiffness,
clearances and the support of the flexible housing. The complex load and temperature condition lead
to different displacements of the gears. Using simulation based displacement data and the software
BECAL [1] a precise contact pattern can be investigated to determine safety factors, damage sum and
efficiency.
To investigate the possible efficiency improvements of a bevel gear a design process is
described. Therefor a variation of macro- and micro geometry were made. Point of interest is to
shift the theoretical pitch cone relative to the contact pattern, to reduce the local sliding
speed. The combination of profile shifting 𝑥𝑥ℎ𝑚𝑚1 , pressure ang e 𝛼𝛼 and
profile crowning 𝑐𝑐𝑃𝑃𝑃𝑃
modification leads to a significant efficiency improvement.
