Performance evaluation of a diesel engine fuelled with waste plastic pyrolysis oil, 1-butanol, and CeO2 additives under varying injection pressures

This research examines the effects of various injection strategies using a fuel composition of 90% diesel, 7% waste plastic oil, 3% 1-butanol, and 25 ppm of CeO 2 nanoparticles. The novelty in this work includes the addition of limited percentages of cerium oxide with limited percentages of 1-butanol to achieve better performance, combustion, and emission characteristics. A detailed statistical investigation is carried out using Response Surface Methodology, followed by optimization using powerful desirability optimization techniques. Furthermore, advanced Machine Learning (ML) techniques are employed for modeling, enabling precise prediction and analysis of engine behavior under varying operating conditions.The injection pressure tested include 180 bar (low pressure), 200 bar (standard pressure), 220 bar (high pressure), and 240 bar (very high pressure). The findings reveal that the machine learning model outperformed RSM, with predicted R 2 values consistently ranging from 0.9 to 0.999 across all tests evaluating engine performance and emissions. Notably, at an injection pressure of 220 bar, there were significant improvements in key combustion metrics, including a 5.32% increase in cylinder pressure, a 5.11% increase in heat release rate, and a 3.42% increase in cumulative heat release rate, indicating enhanced combustion efficiency and superior atomization. Moreover, a maximum brake thermal efficiency of 35.6% was achieved, along with a reduced brake-specific energy consumption of 10.12 MJ/kWh at this pressure level. The 220-bar injection pressure also effectively lowered harmful emissions of CO, HC, and smoke by 7.23%, 18.72%, and 5.08%, respectively, although it resulted in a slight increase in CO 2 and NOx emissions by 3.91% and 3.94%. These outcomes are attributed to improved spray penetration and more efficient fuel-air mixing, yielding an optimal mean fuel droplet size. Overall, the 220-bar injection pressure demonstrated superior performance compared to the standard 200-bar, higher 240-bar, and lower 180-bar injection pressures, particularly when using a 10% waste plastic pyrolysis oil blend.