The increased demand in fuel economy and the reduction of CO₂
emissions results in continued efforts to downsize engines. The
downsizing efforts result in engines with lower displacement as
well as lower number of cylinders. In addition to cylinder and
displacement downsizing the development community embarks on
continued efforts toward down-speeding. The combination of the
aforementioned factors results in engines which can have high
levels of torsional vibrations. Such behavior can have detrimental
effects on the drivetrain particularly during the development phase
of these. Driveshafts, couplings, and dynamometers are exposed to
these torsional forces and depending on their frequency costly
damages in these components can occur.
To account for these effects, FEV employs a multi-body-system
modeling approach through which base engine information is used to
determine optimized drivetrain setups. All mechanical elements in
the setup are analyzed based on their torsional behavior. Bending
and axial vibration are considered in the analysis as well. During
the early stages of engine development, very little information is
available to ensure proper drivetrain layout. To ensure highest
possible usefulness of the modeling tool, the developed algorithms
can function with very limited input data. The moments of inertia,
stiffness, and dampening of the five major groups - crankshaft,
piston assembly, flywheel, driveshaft, dynamometer - are required
to ensure successful processing. A large database with known
components can support the process in case precise target data is
not available. Cylinder pressure information allows to further
increase the accuracy of the results. All available information is
processed and the natural frequencies and Eigen modes are
determined. This basis allows further optimization of the
drivetrain through modifications of the critical parameters of
flywheel and driveshaft. The optimized result allows robust and
reliable engine testing under all operating conditions.