Abstract:
Ethanol fuelled homogenous charge compression ignition
engine (HCCI) offers a better alternative to tackle the problems
of achieving higher engine efficiency and lower emissions.
Numerical simulations were carried out for a HCCI engine
fueled with ethanol by stochastic reactor model using newly
developed reduced ethanol oxidation mechanism consists of
47 species and 272 reactions. Reduced mechanism used in this
study is validated by measured engine cylinder pressure
curves and measured ignition delays in constant volume
reactors in the previous study. Simulations are conducted for
engine speeds ranging from 1000 to 3000 rpm at different
intake temperatures (range 365-465 K) by varying the air-fuel
ratio. Parametric study for combustion and emission
characteristics is conducted and engine maps are developed
at most efficient inlet temperatures. The HCCI operating range
is defined using combustion efficiency (>85%) and maximum
pressure rise rate (<5 MPa/ms). Areas of operation where
excessive exergy destruction occurred were recognized using
analyses of availability losses from exhaust, heat transfer,
unburnt species and destruction due to combustion using
engine operating maps. Availability destruction due to
combustion is found to be maximum at high engine loads and
high engine speeds. The maxima of losses of availability due
to heat transfer and unburnt species are observed at low engine
speeds and loads. In contrast to the mentioned losses, exhaust
based loss of availability has its vertex at the highest achieved
engine loads.
