Abstract This study investigates the feasibility of ternary fuel blends consisting of B20 cottonseed biodiesel combined with oxygenated alcohols (ethanol, isoamyl alcohol, and tert‐butyl alcohol) to improve performance and reduce emissions in a common rail direct injection (CRDI) diesel engine. A structured experimental plan based on the Taguchi L25 orthogonal array was used to examine the influence of three key variables: injection timing (19–27°CA bTDC), injection pressure (180–260 bar), and alcohol concentration (5–25% by volume) on engine performance and emission behavior. To address the trade‐off between enhancing brake thermal efficiency (BTE) and lowering emissions (NOₓ, CO, HC, and smoke), a hybrid optimization strategy was implemented. Gray Relational Analysis (GRA) was initially applied to transform the multi‐response problem into a single optimization index and determine the optimal parameter combination for each alcohol blend. The results consistently indicated a preference for advanced injection timing (27°CA bTDC), while the optimum alcohol share and injection pressure varied with fuel type. Subsequently, the VIKOR multi‐criteria decision‐making method was used to rank all tested fuels based on a combined performance–emission metric. The findings showed that neat B20 operated at 27°CA bTDC and 260 bar provided the best overall balance. Among the ternary blends, the fuel containing tert‐butyl alcohol achieved the highest ranking, indicating an improved compromise between efficiency and emissions. An initial economic evaluation further demonstrated that the optimized ternary fuels remain cost‐competitive, with prices within ±8% of conventional diesel. Overall, the study validates optimized biodiesel–alcohol blends and highlights the effectiveness of the integrated Taguchi–GRA–VIKOR framework for sustainable engine fuel development.
Yadav et al. (Fri,) studied this question.