Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part I: Combustion, Performance, and Emission Studies

In this study, a single-cylinder research engine was used to investigate the comparative combustion, performance, and emissions characteristics of the engine in a 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 mineral diesel. For both combustion modes, experiments were performed at constant fuel injection pressure (FIP, 700 bar), engine speed (1500 rpm), and fuel energy input (0.7 kg/h diesel equivalent). PCCI mode combustion experiments were performed at four different start of main injection (SoMI) timings using two different pilot 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). Results showed that advancing SoMI timing for both CI and PCCI combustion modes resulted in knocking; however, the DPI strategy resulted in relatively lesser knocking compared with the SPI strategy. The performance of PCCI mode combustion was relatively inferior compared with baseline CI mode combustion; however, biodiesel blends slightly improved the performance of PCCI mode combustion. Overall, this study shows that the PCCI mode combustion operating load range can be improved by using the DPI strategy.