Energy and exergy analysis and multi-objective optimization of a biodiesel fueled direct ignition engine

•Taguchi analysis was carried out to find the optimized engine condition.•Combined action of peanut oil biofuel and CNT significantly enhances the engine performance and emission characteristics.•20% of biofuel blend with 25 ppm of CNT nanoparticles proved to be the optimal condition.•Fuel energy and exergy for carbon nanotubes blended peanut oil biodiesel were almost unchanged. The analysis of optimum engine conditions was carried out with the help of Taguchi technique by fuelling the engine with carbon nanotubes blended peanut oil biodiesel with various engine operating conditions by L16 array approach. The effects of peanut oil biodiesel and CNTs with different fuel blends is studied at different engine loading conditions of 25%, 50%, 75%, and 100%. In addition, operating condition is examined by varying the ignition pressure (180 bar, 200 bar, 220 bar, and 240 bar) and ignition timing (21° bTDC, 23° bTDC, 25° bTDC, and 27° bTDC). According to combinations of array such as load, blend, nanoparticle, ignition pressure and ignition timing with four optimal levels, Taguchi L16 array was designed and analysed. Results from L16 Taguchi method were used to find out the optimal operating condition of the engine in terms of higher performance with reduced emissions. When compared with neat diesel, peanut biofuel blend with CNTs has a greater influence in both performance and emission characteristics. Fuel energy and exergy analysis depicted that the readings for carbon nanotubes blended peanut oil biodiesel were almost unchanged or slightly lower than neat diesel.