Crank-Angle resolved exergy analysis of ethanol fueled HCCI engine using newly reduced ethanol oxidation mechanism

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.