Prediction of emissions and performance of a diesel engine fueled with waste cooking oil and C8 oxygenate blends using response surface methodology

Extracting energy from waste and utilizing it as a transport fuel is a sustainable option to reduce fossil fuel dependency that could also give a solution to waste management. In the present study, used cooking oil from restaurant is collected and converted to biodiesel was later tested in a diesel engine along with three oxygenates viz., di-n butyl ether (DNBE), 2-ethyl-hexanol (TEH) and 1-octanol (OCT). This study aim to minimize the emissions of a diesel engine with these C8 oxygenates and also to provide a comparative analysis on the effects of their addition to the biodiesel individually on performance and emission of a single cylinder diesel engine. A response surface methodology (RSM) based optimization using a 3-factor x 3-level full factorial experimental design was employed to find the optimum combination of compression ratio, exhaust gas recirculation (EGR) and oxygenates with an objective to minimize NOx and smoke opacity with maximum performance. Three compression ratio (16:1, 17.5:1 and 19:1), three EGR rates (0%, 10% and 20%) and three fuel blends D80-WCOME15-DNBE5 (b) D80-WCOME15-TEH5 (c) D80-WCOME15-OCT5 were used. Multiple regression models developed using RSM for NOx, smoke opacity and BTE were found to be statistically significant. Interactive effects between compression ratio and EGR on responses for all blends were compared. From desirability approach, D80-WCOME15-OCT5 injected at compression ratio 19:1 with 10% EGR rate delivered optimum performance and emission characteristics with maximum desirability of 0.967.1-Octanol was found to be the best among di-n butyl ether and 2-ethyl-hexanol for this purpose. Confirmatory tests validated the models to be adequate with an error in prediction within 6%. With reference to diesel, D80-WCOME15-OCT5 injected at compression ratio 19:1 with 10% EGR rate reduced smoke opacity by 29.38% and increased NOx emissions by 4.07% with an improvement in BTE by 1.22%. With respect to D80-WCOME20, the same blend reduced smoke opacity by 34.7% and increased NOx emissions by 5.1% with 1.3% lower BTE.

Automated summary

This study focuses on utilizing used cooking oil as biodiesel along with different oxygenates in a diesel engine. The goal is to reduce emissions and improve performance by optimizing the parameters using response surface methodology. The results show that D80-WCOME15-OCT5 has the best performance and emission characteristics under specific conditions.