Effect of the Fuel Injection Pressure on Particulate Emissions from a Gasohol (E15 and M15)-Fueled Gasoline Direct Injection Engine

Gasoline direct injection (GDI) engines have become popular in transportation sector off late and may possibly substitute diesel engines for various applications because of their superior power output and higher thermal efficiency. In this study, a single-cylinder, wall-guided GDI engine was investigated for its emission characteristics using a stoichiometric alcohol-gasoline mixture (gasohol) and air at 2000 rpm engine speed and 2.5-8.5 bar indicated mean effective pressure (IMEP). Gasoline blended with 15% (v/v) ethanol (E15), gasoline blended with 15% (v/v) methanol (M15), and gasoline as baseline fuel were the test fuels investigated for particulate matter (PM)/particulate number (PN) emissions in homogeneous charge mode of the GDI engine. The particle size number distributions were determined using an engine exhaust particle size analyzer (EEPS 3090, TSI) at two fuel injection pressures (FIPs, 80 and 120 bar). It was experimentally determined that FIP played a vital role in the fuel-air mixture preparation and affected particulate emissions significantly in a GDI engine. Particulate size-number, size-mass, and size-surface area distributions were reported for these test fuels under identical load conditions. PN emissions were quite high at lower IMEPs. It decreased at intermediate IMEP but increased at the highest IMEP tested. A trade-off between PM/PN was also observed. The experiment demonstrated that there is a need to control PM/PN emissions from a GDI engine in order to meet stringent emission norms. The count mean diameter gave clear statistical information that smaller particulate offers relatively higher surface area per unit mass of particulate, leading to higher adsorption of toxic compounds, making it possibly more toxic.