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Engine Start-Up Optimization using the Transient Burn Rate Analysis
Abstract:
The introduction of CO₂-reduction technologies like Start-Stop
or the Hybrid-Powertrain and the future emission legislation
require a detailed optimization of the engine start-up. The
combustion concept development as well as the calibration of the
ECU makes an explicit thermodynamic analysis of the combustion
process during the start-up necessary.
Initially, the well-known thermodynamic analysis of in-cylinder
pressure at stationary condition was transmitted to the highly
non-stationary engine start-up. There, the current models for
calculation of the transient wall heat fluxes were found to be
misleading. Therefore, adaptations to the start-up conditions of
the known models by Woschni, Hohenberg and Bargende were introduced
for calculation of the wall heat transfer coefficient in SI engines
with gasoline direct injection.
This paper shows how the indicated values can be measured during
the engine start-up. Furthermore, the methods of deriving the
piston positions and the engine speed from the time-based data are
described. With these, the transient burn rate analysis is
performed using the introduced approaches for the wall heat
transfer calculation.
For the validation of the thermodynamic analysis start-up
behavior of 3-, 4-, and 6-cylinder SI engines is investigated and
the results are discussed. In addition to this, a 3-cylinder CI
engine start-up is analyzed to verify the novel wall heat transfer
approach for diesel engines.
Optimization of a 6-cylinder engine start-up is shown using the
transient burn rate analysis results which demonstrate the
efficiency potential for the application process.