In general, the introduction of EGR influences diesel
engine combustion in three different ways: thermal,
chemical and dilution. The thermal effect is related to the
increase of inlet charge temperature that affects volumetric
efficiency (thermal throttling) and the increase of charge
specific heat capacity due to the presence of CO2 and H2O.
On the other hand the chemical effect is related to the
dissociation of species during combustion, while dilution is
related to the reduction of O2 availability. In the present we
focus mainly on the first, i.e. thermal effect, considering the
effect of recirculated exhaust gas temperature on performance
and emissions. Based on previous studies, cooled
EGR is beneficial for engine operation and emissions but
an important issue remains to examine the effect of EGR
gas temperature on performance and emissions for various
EGR rates.