Multicriteria Optimization of Performance and Emission Characteristics of Diesel Fuel, Waste Tire Pyrolysis Oil and Waste Transformer Oil Ternary Blends Using Response Surface Methodology

This study aims to experimentally investigate the effects of fuel mixtures containing waste transformer oil (WTRO) and waste tire pyrolysis oil (WTPO) on engine performance and exhaust emissions in a single-cylinder diesel engine and to determine the most suitable operating conditions using response surface methodology (RSM)-based multicriteria optimization. Experiments were conducted at different engine speeds between 1200 and 2400 rpm. In addition to pure diesel (D100) as fuel, binary and ternary mixtures such as WTRO30, WTRO10WTPO20, WTRO20WTPO10, and WTPO30 were used. Brake Thermal Efficiency (BTE), Brake Specific Fuel Consumption (BSFC), Carbon Monoxide (CO), and Nitrogen Oxides (NOx) emissions were measured as the main response parameters. Second-order RSM models were created by considering engine speed and fuel mixture ratios as independent factors. The best operating point was selected using a multi-criteria desirability score function to optimize multiple performance and emission targets simultaneously. According to the main findings, the optimum operating conditions were determined to be an engine speed of approximately 1900 rpm and a fuel mixture with a WTRO ratio of 17.50% and a WTPO ratio of 12.50%. The values predicted by the model at this optimum point were: 22.00% for BTE, 396.79 g/kWh for BSFC, 7287 ppm for CO emission, and 471 ppm for total NOx emission. The results showed that the optimization algorithm minimizes emissions by pulling the engine speed to a medium-high level (1900 rpm) while keeping the total waste oil ratio at the maximum level of 30% within the constraints. Under the tested steady-state conditions, the WTRO-WTPO ternary blend demonstrated promising short-term operability as a fuel alternative for diesel engines without requiring immediate modifications to the engine setup, accompanied by slight improvements in output parameters.