In this work an exhaust gas temperature and a piston damage model are coupled,
with the aim to develop an innovative model-based strategy for the calibration
of the lambda map and to actively control the spark advance (SA). In this way,
the lambda value needed to reach a target exhaust gas temperature evaluated at
the turbine inlet is determined. In the first part of the article, some
empirical and semi-physical models for the calculation of the exhaust gas
temperature, the combustion phase, the maximum in-cylinder pressure, and the
knock intensity are developed and presented. A piston damage model previously
developed by the authors determines the SA to reach a target piston erosion for
the knock-limited operating conditions, increasing the combustion efficiency and
lowering the temperature of the exhaust gases with respect to the standard spark
timing map. The exhaust gas temperature model allows to estimate the lambda
value that returns the maximum temperature at the turbine inlet, exploiting the
gained combustion efficiency to extend the stoichiometric area of the engine
operating field.
In the last part of the work, the lambda map calibrated through the proposed
algorithm is validated for both the transient and steady-state conditions,
reproducing a real vehicle maneuver at the engine test bench. The results
finally demonstrate that a combustion efficiency increase equal to 8% can be
reached by managing the SA with a piston damage-based controller, and this
number can be increased up to 16% by applying the recalibrated lambda map, with
respect to the standard engine calibration.
