RSM Optimized Feasibility Assessment of Hybrid Algae-Plastic Oil Blended Diesel Fuel with Binary Additives CuO–MgO on Performance and Emissions in CRDI Diesel Engine

Abstract

This study was carried out to analyze the feasibility of a less-explored alternative fuel blend combination for diesel engines comprising third-generation biofuel (algae oil (AO)) and fuel derived from waste plastic. Combining these two oils in equal proportions, hybrid algae-plastic oil (HAPO) blends were formed. For this study, waste plastic oil (WPO) was produced through a lab-scale thermal pyrolysis process. The impact of different blend ratios (0–40 vol %) of HAPO-blended diesel fuel along with input engine load (20–100%) and fuel injection pressure (FIP) (300–700 bar) is experimentally tested for its performance and emission characteristics in a single-cylinder common-rail direct-injection (CRDI) diesel engine. The impact of combined total binary (CuO + MgO) metal oxide nanoadditives (0–300 ppm) in a 1:1 fixed mass ratio formulation with HAPO blends, along with engine key input variables, has also been assessed. The response surface methodology (RSM) technique was applied for optimization by developing trials using a four-factor central composite design (CCD) approach, and output responses were analyzed using surface plots. The R2 values of estimated outputs for brake thermal efficiency (BTHE), exhaust gas temperature (EGT), nitrogen oxide (NOx), smoke, and unburned hydrocarbon (HC) were determined to be nearly approaching 90–99.9%, except for the limited predictive R2 for the carbon monoxide (CO) model. The outcomes from the input parameters were optimized for maximum performance and minimum emissions. RSM-predicted optimized input value settings at 40 vol % HAPO blend, 300 ppm of total binary additive with 441.4 bar of FIP, and 52.32% engine load have given a significant RSM-predicted response of 20.27% of BTHE and 459.36 K of EGT with noticeable reduction in smoke by 11.5%, HC by 16.1 ppmv, NOx by 358.33 ppmv, and CO by 0.0927 vol % with an overall composite desirability of 81.98% within the investigated experimental domain. Final tests were conducted for experimental verification of optimized conditions by fixing the input parameters to optimized values to confirm authenticity. The percentage error between RSM-predicted values and experimental values for BTHE, EGT, smoke, and CO output responses was less than 5%, whereas for HC and NOx, the errors were 5.93 and 5.21%, respectively. The results demonstrate the short-duration laboratory-scale technical feasibility and promising performance of characterized HAPO-blended diesel as a candidate fuel for CRDI diesel engines with significant tailpipe emission reduction potential.