Investigation on reduction of emission in PCCI-DI engine with biofuel blends

Immense potential is seen in Homogenous Charge Compression Ignition (HCCI) engines as an alternative to conventional Compression Ignition (CI) engines as it can simultaneously reduce oxides of nitrogen (NOx) and soot while maintaining high efficiency. The challenges are predominantly control of combustion and limited operating ranges. Mitigation of these challenges using PCCI-DI is explored in this work. A pilot injector is used to supply a small quantity of premixed charge of fuel and air to the engine followed by direct injection through the main injector. An added advantage is dual fuel capability and improvement of combustion characteristics. Two fuels namely diesel and a blend of ethanol and diesel (containing 15% of ethanol by volume, called E15D) are used in four different combinations for the pilot and main injection. The emission characteristics of each combination were then compared with the conventional mode of operation. The four combinations or modes of operation with PCCI setup were Diesel-Diesel (pilot-main fuel), Diesel-E15D, E15D-Diesel, and E15D-E15D. The results of the experiment indicate that the Diesel-E15D mode is comparatively the best mode of operation due to its lower NOx and smoke emissions.