Theoretical Analysis of Multi-Zone and Transported Probability Density Function Approaches Applied to Low Temperature Combustion Process

Electrification of transport, together with the decarbonization
of energy production are suggested by the
European Union for the future quality of air. However,
in the medium period, propulsion systems will continue to
dominate urban mobility, making mandatory the retrofitting
of thermal engines by applying combustion modes able to
reduce NOx and PM emissions while maintaining engine
performances. Low Temperature Combustion (LTC) is an
attractive process to meet this target. This mode relies on
premixed mixture and fuel lean in-cylinder charge whatever
the fuel type: from conventional through alternative fuels with
a minimum carbon footprint. This combustion mode has been
subject of numerous modelling approaches in the engine
research community. This study provides a theoretical
comparative analysis between multi-zone (MZ) and
Transported probability density function (TPDF) models
applied to LTC combustion process. The generic thermokinetic
balances for both approaches have been analyzed in
term of similarities. Only onion-skin for MZ models have
been considered in this study. The governing assumptions
linked to sub-models for each approach to describe mixing
process for TPDF and interzonal heat and mass transport for
MZ are discussed. This step identifies the calibrated model
parameters for each approach and their effects on the accuracy
in predicting LTC mode simulations. This work shows that
the transported probability density function model has fewer
parameters to calibrate compared to multi-zone model.
Transported probability density function seems easier to use
for LTC process.