Advanced prediction and optimization of VCR engine characteristics using RSM with DFA for sustainable biofuel derived...

The rising demand for alternative fuels stems from fossil fuel depletion, rising crude oil prices, and environmental concerns. Diesel engines, valued for efficiency and durability, contribute to resource depletion and pollution. Biofuels offer a sustainable alternative, with waste lemon peels presenting a viable feedstock for biofuel production. Using a steam distillation process, lemon peel waste oil (LPWO) is extracted from waste lemon peels and test fuel blends of LPWO and conventional diesel have been created in ratios of 5%, 10%, 15%, and 20%. According to the ASTM standards, the properties of LPWO and its blends, along with diesel, have been assessed. The characteristics of LPWO were determined by FTIR, GC-MS, and TG/dTG analysis. The performance, combustion, and emission parameters have been evaluated for neat LPWO and LPWO blends in a variable compression ratio (VCR) engine by varying BP between 0 kW and 5.2 kW and compression ratio from 16:1 to 18:1. From experimental analysis, optimum results are observed while using the blend 5% LPWO, BP 5.2 kW and CR 18:1. LPWO5 showed an increase in BTE and EGT by 2.168% and 3.09% while minimizing BSFC by 6.54%, also improved HRR and in-cylinder pressure; a decrease of CO, NO_x, and smoke emissions by 59.42%, 30.99%, and 7.89% whereas 9.14% and 0.201% increase in HC and CO₂ when compared to diesel fuel. To model and optimize the engine responses, a multiple regression model was developed using response surface methodology (RSM) with a desirability function approach (DFA). The optimal operating conditions predicted were 6.51% LPWO blend, 1.42 kW load, and CR 18:1, which closely aligned with experimental findings. The RSM-CCD design coupled with the DFA model yielded a combined desirability value of 0.8997. The VCR engine results were validated with the RSM predictions and DFA optimization, showing an error margin of less than 5%. These outcomes indicate that the LPWO5 blend holds strong potential as a viable alternative fuel for VCR engine applications.