Effect of low bioethanol fraction on emissions, performance, and combustion behavior in a modernized electronic fuel injection engine

This study examined the effects of low content rates of Mbwazirume bioethanol blends (5%, 10%, and 15%) with gasoline in a modernized electronic fuel injection (EFI) engine. The results showed that the E15 fuel ratio induced an increase in combustion duration with minimum premixing combustion duration, hence exhibited low emissions, high indicated power, and efficiency with low fuel consumption (at 12 to 18° CA aTDC). These results are due to the low content of carbon in bioethanol, which eliminates the occurrence of soot formation and requires less air to burn fuel blends with low luminosity and radiation. In E10 and E15 fuel, when the engine operated at 2700 rpm, the engine emissions were relatively low with a slight increase in performance, except for E5. The rate of NO_X formation rose higher with E5 and E10; this was due to the combustion advanced which led to higher temperature and in-cylinder pressure than that of E0 and E15. However, when the exhaust gas temperature (T_eg) was at 192 °C for 21.7 s fuel drain time (F_dt), the CO and CO₂ emissions decreased with E15 and increased rapidly with E5 and E10. In addition, the HC emissions decrease at all injection timings for E5, E10, and E15, except that of 10° CA bTDC which did not follow this trend. When the combustion phases are the same, the model results suggest that a little modification in the heat-transfer parameter has a great impact on the thermal efficiency.