Effects of EGR Rate and Temperature on Combustion and Emissions Characteristics of Compression Ignition Engines Fueled with Hydrotreated Vegetable Oil

This study investigates the effects of varying exhaust gas recirculation (EGR) rates and temperatures on the combustion and emissions characteristics of a compression ignition engine fueled with hydrotreated vegetable oil (HVO). Understanding these effects is essential for optimizing renewable fuel applications in compression ignition engines, contributing to cleaner combustion, and supporting sustainable transportation initiatives. The experiments revealed that increasing the EGR rate to 20% not only reduces NOx emissions by approximately 25% but also increases smoke by around 15%, highlighting a trade-off between NOx and particulate matter control. When EGR temperature is increased from 130 to 220 °C, NOx emissions rise by about 10%, accompanied by a 12% increase in smoke emissions, indicating that elevated EGR temperatures can counteract the NOx-reducing benefits of EGR by raising the overall combustion temperature. Additionally, a higher EGR rate shifts particle size distributions, reducing nucleation mode particles by about 30% while increasing accumulation mode particles, with peak concentrations moving toward larger diameters. These findings suggest that precise control of EGR parameters is essential for optimizing emissions performance and ensuring the feasibility of HVO as an alternative fuel in compression ignition engines.