CASE STUDY USING PISDYN OF THE EFFECT ON ... - Ricardo

with the PISDYN simulations used in designing the skirt profile and contour. Consequently,
when the major car manufacturer that the piston was to be produced for, asked ACL to determine
the feasibility (in terms of piston performance) of using a 7.9% longer connecting rod in the
engine, while maintaining the same piston design, all that was required for an initial study was to
change the connecting rod geometry and inertial data in the PISDYN input deck and to repeat the
simulations.
OPTIMISATION OF PISTON SKIRT TO BE USED IN ORIGINAL
ENGINE
To optimise the skirt profile and contour, PISDYN simulations were performed to model three
engine operating conditions:
1) At 1000 RPM and 2.5% of maximum engine power to simulate conditions when
"Croaking" noise would be approximately at its greatest.
2) At 2800 RPM and 13% of maximum engine power to simulate conditions when
"Rattling" noise would be approximately at its greatest.
3) At maximum power operating conditions to simulate conditions when skirt wear and
skirt-liner friction would be expected to be greatest.
Noise minimisation
To simulate worst case conditions in the "Croak" and "Rattle" simulations:
1) The simulations are performed using piston thermal expansion data (from
computations performed by TRIBFE) assuming a cold engine operating in a -20° C
environment.
2) Another simulation parameter was modified to simulate start-up conditions.
4 of 13