Predicting the effect of biodiesel composition on the performance and emission of a compression ignition engine using a phenomenological model

•Biodiesel-composition effects on combustion-NO emission captured using a phenomenological model.•NO emission correlates well with biodiesel composition through a short chain saturation factor (SCSF)•Biodiesel with high SCSF reduces NO emission at identical injection schedule.•Poor correlation between NO emission and SCSF in engines with mechanical injection system. The renewable biodiesels have been under active consideration for replacing fossil diesel due to the proximity of their properties and minimum engine hardware modifications. Biodiesels derived from fatty acids of plant or animal origin exhibit significant composition variations depending upon the feedstock used for production. The oxides of nitrogen (NOx) emission from biodiesel are higher than diesel and remain a significant concern. In the present work, combustion and nitric oxide (NO) emission characteristics of any generic biodiesel are predicted using a phenomenological modeling approach. The developed model accounts for biodiesel composition effects on physical properties, spray, auto-ignition, combustion and emission formation. The model predictions are validated with measurements done in a turbocharged multi-cylinder heavy-duty engine fuelled with two biodiesel fuels having significantly different compositions, viz. Karanja having a higher proportion of unsaturated methyl esters, and Palm having a higher proportion of saturated methyl esters. The cylinder pressure histories and peak pressures are predicted within an error of 5% and 3%, respectively. The model shows a reasonable qualitative agreement in heat release rate predictions. The NO emission is predicted within 23% error using the extended Zeldovich mechanism. The model is efficient in predicting the engine characteristics at high loads for any generic biodiesel with minimal run time (~2 min). The validated model is then used to examine the relationship between biodiesel composition and NO emission, wherein a better correlation is obtained between biodiesel composition-based parameter, viz. short-chain saturation factor (SCSF) with maximum spray temperature and NO emission.