Effect of ethanol enrichment and engine parameters on the performance of an HCCI engine fuelled with biodiesel/ethanol mixtures

Based on models resulting from the merging of validated kinetic schemes, four reaction mechanisms were developed to describe the combustion of biodiesel-surrogate/ethanol blends in an HCCI engine. The proposed models were then compared to experimental data issued from a modified cooperative fuel research (CFR) engine which can be considered as an HCCI engine. The kinetic scheme displaying the best predictive capabilities, in conjunction with the single-zone HCCI code from the chemkin library, was used to investigate effects of ethanol enrichment and the variation of some important parameters, such as inlet temperature, relative air/fuel ratio and compression ratio, on the combustion and performance characteristics of the investigated HCCI engine. The blended fuels were formed by incrementally adding 10% of ethanol to the neat biodiesel mixture. The inlet temperature ranged from 320 to 420 K with a step of 20 K, whereas air/fuel and compression ratios were varied from 2 to 5 with a step of 0.5, and from 9 to 14 with a step equal to 1, respectively. The obtained data indicated that ethanol effects on the starting of combustion, combustion duration and indicated mean effective pressure were dependent on intake temperature, air/fuel and compression ratios.