Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part II: Particulate Studies

Abstract

In this study, experiments were performed in a single-cylinder research engine to investigate the particulate matter (PM) characteristics of the engine operated in premixed charge compression ignition (PCCI) mode combustion vis-a-vis baseline compression ignition (CI) mode combustion using three test fuels, namely, B20 (20% v/v biodiesel blended with mineral diesel), B40 (40% v/v/ biodiesel blended with mineral diesel), and baseline mineral diesel. The experiments were carried out at constant fuel injection pressure (FIP) (700 bar), constant engine speed (1500 rpm), and constant fuel energy input (0.7 kg/h diesel equivalent). PM characteristics of PCCI mode combustion were evaluated using two different fuel injection strategies, namely, single pilot injection (SPI) (35 deg before top dead center (bTDC)) and double pilot injection (DPI) (35 deg and 45 deg bTDC) at four different start of main injection (SoMI) timings. Results showed that both PCCI mode combustion strategies emitted significantly lower PM compared to baseline CI mode combustion strategy. However, the blending of biodiesel resulted in relatively higher PM emissions from both CI and PCCI combustion modes. Chemical characterization of PM showed that PCCI mode combustion emitted relatively lower trace metals compared to baseline CI mode combustion, which reduced further for B20. For detailed investigations of particulate structure, morphological characterization was done using transmission electron microscopy (TEM), which showed that PM emitted by B20-fueled PCCI mode combustion posed potentially lower health risk compared to baseline mineral diesel-fueled CI mode combustion.