Influence of ethanol blending ratios on in-cylinder soot processes and particulate matter emissions in an optical direct injection spark ignition engine

Soot volume fraction distribution of ethanol blended fuels (ethanol volume fraction 0%, 20%, 40% and 60%, named as E0, E20, E40 and E60) were measured in an optical direct injection spark ignition (DISI) engine by combined laser induced incandescence (LII) and two-color (2C) method. Exhaust particulate matter (PM) emissions were measured by a Combustion DMS500 Fast Particulate Analyzer. For DISI engines, pool fire and the resulting diffusion flame are the main sources of soot in the cylinder. Choosing a suitable measurement plane and detection time, laser induced incandescent can be used to quantitatively measure the soot concentration produced by the pool fire. This research explores the effect of ethanol blending on engine particulate matter by comprehensively analyzing the soot process in the cylinder and exhaust particulate emissions. According to the two-dimensional quantitative soot volume fraction results, the maximum average soot volume fraction of the same fuel on the 10 mm plane is greater than the 5 mm plane; on the same plane, E20 shows the highest soot concentration compared to the other fuel blends which could be the physical properties of the ethanol become apparent. For exhaust particle emissions, ethanol can significantly reduce the total particle number and accumulation mode particle number. E0, E40 and E60 show fairly similar behavior between the exhaust particle emissions and the soot-LII imaging measurements. For E20, however, this is in poor agreement when comparing the soot-LII imaging results to the results of exhaust particle emission measurements.