Investigation of the effects of biodiesel/2-ethylhexyl nitrate (EHN) fuel blends on diesel engine performance and emissions by response surface methodology (RSM)

•Biodiesel ratio, EHN ratio and load have been chosen as input parameters.•Proposed RSM model are capable for mapping engine performance-emission paradigms with high accuracy.•RSM was applied to optimize the engine performance and exhaust emissions.•Trade-off study based on RSM technique showed the optimal engine operating condition for biodiesel/EHN blends. In this study, the effect of biodiesel (97%, 98%, 99% and 100%) which is a mixture of canola, safflower and waste vegetable oil blends completed with transesterification and 2-ethylhexyl nitrate (EHN) (3%, 2%, 1% and 0%) on compression ignition engine performance and emissions were examined experimentally and by response surface methodology (RSM). Engine experiments were carried out at four different engine loads (500, 1000, 1500 and 2000-W) with biodiesel/EHN fuel blends obtained with different mixing ratios. According to the results obtained from the experiments, RSM model was created. Biodiesel ratio, EHN percentage and load are chosen as input factors, while brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC) and smoke emissions are selected as response parameters to be examined. In the created RSM, Box-Behnken design (BBD) type was chosen with three number of continuous factors. ANOVA supported Pareto charts were created and it was determined how effective the selected input factors are. The optimum values of the engine parameters were biodiesel percentage of 100%, EHN percentage of 1.1% and, load of 1515-W. According to optimum input parameters, the optimum responses of BTE, BSFC, NOx, CO, HC and smoke were 19.782%, 385.790 g/kWh, 436.951 ppm, 0.0272%, 33.639 ppm and 0.167%, respectively. The obtained outcomes demonstrate that the RSM can be effectively utilized for optimizing compression ignition engine performance and exhaust emissions powered by biodiesel/EHN combines by saving time and reducing engineering effort.