Effect of compression ratio variation and waste cooking oil methyl ester on the combustion and emission characteristics of an engine

In this research, a thermodynamic zero-dimensional model has been done to predict performance characteristics (in-cylinder pressure, heat released, and the thermal efficiency) of a diesel engine with the use of biodiesel–diesel fuel blends (B0, B20, B50, B80, and B100) at different compression ratios (14, 15, 16, 17, and 18). The corresponding mathematical and thermodynamic relationships have been solved in MATLAB. Based on the experimental tests, it was found that the developed model can predict the engine variables sufficiently. According to the results, the heat release rate and the cylinder pressure increased for all fuel blends by an increase in the compression ratio. Moreover, with the increasing biodiesel amount in the fuel blend (up to 50%) heat release rate and the cylinder pressure increased but these variables have a reduction when biodiesel percentage increases from 50 to 100 due to the lower heating value of waste cooking oil methyl ester in comparison with neat diesel fuel. Moreover, according to the experimental tests, carbon monoxide emission was reduced when biodiesel proportion increased in the fuel blend but the nitrogen oxides emitted from the engine enhanced when biodiesel amount in the fuel mixture increased. According to the results, it can be concluded that B50 has better combustion characteristics among all fuel blends.