NOx reduction of biodiesel engine using pongamia ester with oleic acid and optimization of operating conditions using particle swarm optimization

Biodiesel is comprised of 36–75% oleic fatty acid (OA) that has the molecular formula, C₁₈H₃₄O₂ and is an excellent carrier of hydrogen and oxygen. OA has proven to have a positive effect in curbing NOx from biodiesel combustion. In this work, the effect of varying concentrations of OA in Pongamia ester is studied on a compression ignition engine that is again varied at different loads and compression ratios. Design of experiments is carried out with brake thermal efficiency and NOx emissions as responses. Regression equations for these responses are developed and optimized using multi-objective particle swarm optimization (MOPSO). It is found that the best operating regime for maximum efficiency and minimum NOx is by adding 10% OA, with a compression ratio of 17.5 running at an engine load of 81%. Experimental validation of the prediction made by the optimization model is also carried out.