Effect of water-emulsive biodiesel/diesel blend with alumina nanoparticles on diesel engine performance and emissions: experiments and optimization

Fossil fuel depletion and consequential environmental pollution have spurred concerns about alternative, environmentally friendly fuels like biodiesel from various feedstocks, which regrettably results in high nitrogen oxide (NO_X) emissions. On the contrary, water emulsion effectively lowers the combustion temperature, resulting in subsequent NO_X levels depletion. Nevertheless, introducing water into the system poses additional challenges of higher carbon monoxide (CO) and hydrocarbon emissions. Therefore, this work studies the influence of various Alumina nano additives and water-emulsion biodiesel dosages on diesel engine emissions and performance. Experimental designs are obtained based on the orthogonal array of the Taguchi method for three influencing parameters with three levels, and the experiments are carried out at distinct brake loads. Grey relational analysis, Taguchi S/N ratio, and principal component analysis are employed to maximize engine heat release rate and thermal efficiency while minimizing brake-specific fuel consumption, CO, NO_X, and smoke opacity. The optimal fuel combination is a 10% vol biodiesel blend with 1% water emulsion and 150 mg/l Alumina nanoparticles (B10A150W1). This combination was tested for validity and fair agreement and illustrated a BTE enhancement compared to baseline diesel by 9.1%, with around 40%, 26%, and 22% reductions in CO, smoke, and NO_X, respectively.