Integrated multi-objective optimization, MCDM, and bias modelling of Al2O3/TiO2 nano-additives with HHO enrichment in diesel engine fuelled with waste tire pyrolysis oil

Waste tire was converted into pyrolysis oil; however, its elevated density, viscosity and aromatic content may adversely affect engine emissions and performance. Impact of TiO 2 and Al 2 O 3 nano-additives with oxyhydrogen (HHO) addition on performance and emissions of diesel engine operating on pyrolysis oil and diesel blends was demonstrated. Pyrolysis oil was blended with diesel fuel at 20% volume ratio to create T20 base blend. Al 2 O 3 and TiO 2 nanoparticles were individually scattered in an oil mixture at proportions of 25, 50, and 100 ppm. An alkaline dry electrolyser was used to produce HHO at a rate of 0.5 L/min. The diesel engine was run at 3000 rpm under various loads. Mixtures of T20A100+HHO and T20T100+HHO increased thermal efficiency by 23 and 29%, respectively. When 100 ppm of Al 2 O 3 and TiO 2 were added to the oil-oxyhydrogen mixture, CO decreased by 16% and 23%, respectively, compared to T20. The drops in smoke were 40% and 52% for T20A100 + HHO and T20T100 + HHO, and the HC decreases were 33% and 43%. When oxyhydrogen was added to an oil combination containing 100 ppm of titanium oxide and alumina, NOx was dropped by 29% and 39%, respectively. Mathematical models were built for the different responses using regression-based response modeling. Fuzzy multi-objective optimization and multi-criteria decision-making, including AHP and entropy, are used to obtain optimal operating conditions, which are experimentally validated. Sensitivity analysis was performed using a set of biased mathematical models to assess the relationship between the optimal solution and the decision-maker's bias. The Pareto front was plotted for the different predicted biased responses; in addition, TOPSIS was used to rank them. The quality of the predicted optimal operating conditions shows a strong relationship with decision-maker bias. Integration of Al 2 O 3 /TiO 2 nano-additives and HHO enrichment enhanced engine performance and emissions of waste-tire pyrolysis oil–diesel blend under the specified testing conditions.