Studying the Effect of Engine Parameters and Cetane Number on NOx and Particulate Matter Emissions

Emission characteristics (NOx and particulate matter) of a CI engine are influenced by fuel properties, engine operating conditions and the type of engine technology used. The current study is focused on analyzing the effect of fuels (blend of 50% hexadecane with 50% petro-diesel (HD50), hydro-processed renewal diesel (HRD) and petro-diesel) possessing different cetane number and operating parameters of the engine on NOx and particulate matter (PM). The design of experiment (DOE) technique was employed to identify the most dominant parameter among CN, speed and torque that affect NOx emissions significantly. An empirical correlation between NOx emissions and CN, engine speed, torque and in-cylinder peak pressure was developed using Rayleigh’s method. Combustion analysis (in-cylinder pressure, heat release, combustion temperature and mass fraction burn) of the engine fueled with these fuels was also undertaken to corroborate the emission results. PM emissions were reduced by around 44% and 30% with the use of HRD and HD50 fuel over petro-diesel. HRD fueled engine showed 18% lower NOx emissions than petro-diesel. Interestingly, it also showed 8% lower NOx than HD50 fuel despite 9% higher CN of HD50 as compared to HRD. DOE analysis revealed that the engine torque is the most dominant parameter that influences NOx emissions significantly. It may be concluded that higher CN does not always assure a reduction in NOx emissions, and it is highly dependent on engine operating parameters.