Energy and Exergy Analysis of Biodiesel Combustion in a DI Compression Ignition Engine Using Single-Zone Model

In the present work, the energy and exergy analysis was carried out for a diesel engine fueled with soybean oil biodiesel and its blends at different temperature and two speeds (1200 and 1600 rpm). To simulate the combustion process, a single-zone combustion model was developed. A comprehensive MATLAB-based simulation tool incorporating multiple combustion by-products was developed to perform detailed energy and exergy evaluations. Simulated in-cylinder pressure profiles for pure diesel fuel were benchmarked against experimental observations, demonstrating strong correlation and reliability. The model also provided insights into both instantaneous and cumulative forms of energy and exergy at various crank angles for three biodiesel blend ratios—B20, B40, and B100. The results show that the exergy efficiency increases as biodiesel increases by volume and blends from 20% to 100%. At the same time, the accumulative irreversibility decreases considerably. For the fuel blend containing 20% biodiesel, the system exhibited greater values of indicated exergy output, thermal exergy losses, chemical exergy input from combustion, and entropy-related inefficiencies compared to those observed with B40 and B100 mixtures. An increase in the engine speed caused total exergy and irreversibility to increase. In addition, the indicated work exergy, the heat loss exergy decreased. Furthermore, the increase in the inlet mixture temperature caused total exergy and heat loss exergy to increase, whereas the indicated work exergy and irreversibility decreased.