Green-synthesized Al₂O₃ Nanoparticle-enhanced Rubber Seed–Avocado Seed Hybrid Biodiesel for CI Engine Performance: Experimental Investigation and CatBoost-based Machine Learning Prediction
J. Environ. Nanotechnol., Volume 15, No 3 (September 2026) pp. 308-322
Abstract
The relatively high viscosity and lower heating value of biodiesel can reduce brake thermal efficiency and increase fuel consumption in compression ignition (CI) engines. The novelty of this study lies in integrating rubber seed–avocado seed hybrid biodiesel, green-synthesized Al₂O₃ nanoparticles, and CatBoost-based prediction within a single experimental framework. Hybrid biodiesel was prepared from equal proportions of rubber seed and avocado seed oils, while Al₂O₃ nanoparticles were synthesized using Syzygium cumini leaf extract and aluminium nitrate nonahydrate as the precursor. Nanoparticle formation was preliminarily supported by a UV–visible absorption band near 350 nm and an Al–O vibration near 595 cm⁻¹ in the FTIR spectrum, while DLS indicated an average particle size of 30 ± 5 nm. The reported engine-performance analysis focused on B25 and B50 blends, with and without 40 ppm Al₂O₃ nanoparticles, using a single-cylinder CI engine operated at 1500 rpm, compression ratios of 15:1, 17:1, and 19:1, and loads of 2, 5, 8, and 11 kg. Engine performance was evaluated using brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC). At 11 kg load, B25 + Al₂O₃ increased BTE by 6.10% and reduced BSFC by 6.13% at 19:1. B50 + Al₂O₃ produced a maximum BTE improvement of 6.05% at 17:1 and a maximum BSFC reduction of 7.12% at 19:1. Separate CatBoost models were developed using biodiesel percentage, Al₂O₃ concentration, compression ratio, engine load, lower heating value, and brake power. The models achieved R² values of 0.9967 for BTE and 0.9918 for BSFC. Within the investigated operating conditions, 40 ppm Al₂O₃ improved the measured performance of B25 and B50, while CatBoost accurately predicted their BTE and BSFC. Therefore, the developed nano-biodiesel and CatBoost framework has potential application in predicting and improving the performance of biodiesel-fuelled CI engines under comparable operating conditions.
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