| Popis: |
The objective of this study was to investigate experimentally the effect of adding ethanol at different proportions (0 to 85%) on the combustion behaviour of a SI direct injection engine. Although the effect of ethanol on combustion behaviour was studied by several researchers, the variation in the results among those researches illustrated a need for a better understanding of ethanol effects. Combustion behaviour has a significant effect on engine’s emission and performance. There is an agreement among researchers that faster burn rate is a favourable characteristic. Shorter burn duration produce more robust and repeatable combustion pattern. In addition to changing fuel content, experimental data was obtained for different running conditions including different speeds, loads, spark timing, equivalence ratio and exhaust gas recirculation. The Rassweiler and Withrow method was used to estimate the burn duration in the engine. Furthermore, the effect of increasing ethanol concentration on combustion stability and EGR tolerance was evaluated. Results show that combustion duration decreases significantly at high ethanol content (85% by volume). However, there is not a linear relationship between increasing ethanol and combustion duration, comparable durations were obtained for gasoline and low ethanol contents. This advantage of decrease burn duration manifests itself through increase in tolerance to dilution and EGR |
