Combustion Characteristics of an Indirect Injection (IDI) Diesel Engine Fueled with Ethanol/Diesel and Methanol/Diesel Blends at Different Injection Timings

Abstract

In this study, the influence of methanol/diesel and ethanol/diesel fuel blends on the combustion characteristic of an IDI diesel engine was investigated at different injection timings by using five different fuel blends (diesel, M5, M10, E5 and E10). The tests were conducted at three different start of injection {25, 20 (original injection timing) and 15 CA before top dead center (BTDC)} under the same operating condition. The experimental results show that maximum cylinder gas pressure (Pmax) and maximum heat release rate (dQ/dθ)max increased with advanced fuel delivery timing for all test fuels. Although the values of Pmax and (dQ/dθ)max of E10 and M10 type fuels were observed at original injection and retarded injection (15 CA BTDC) timings, those of the diesel fuel were obtained at advanced injection (25 CA BTDC) timing. From the combustion characteristics of the test fuels, it was observed that ignition delay (ID), total combustion duration (TCD) and maximum pressure rise rate (dP/dθ)max increased with advanced fuel delivery timing. The ID increased at original and advanced injection timings for ethanol/diesel and methanol/diesel fuel blends when compared to the diesel fuel. It was also found that increasing methanol or ethanol amount in the fuel blends caused to increase in ID and to decrease in TCD at all injection timings. At original injection timing, the (dP/dθ)max increased with increasing methanol or ethanol amount in the fuel blends. To see the cycle to cycle variation, the fifty cycles of each fuel were also investigated at the different injection timings. It was found that, at the advanced injection timing, cyclic variability of the test fuels was higher when compared to the original and retarded injection timings. The maximum cyclic variability was observed with the M10 at the advanced injection timing.