Optimisation of Water, Surfactant and Dual-Biodiesel Concentration for a Least-Phase-Separation Emulsified Neem–Palm Blend in a Diesel Engine: Stability, Performance and Emission Study
Authors
Mechanical Engineering Department, Gandhinagar Institute of Technology, Gandhinagar University, Moti Bhoyan, Gandhinagar 382721, Gujarat, India (India)
Mechanical Engineering Department, Gandhinagar Institute of Technology, Gandhinagar University, Moti Bhoyan, Gandhinagar 382721, Gujarat, India (India)
Mechanical Engineering Department, Gandhinagar Institute of Technology, Gandhinagar University, Moti Bhoyan, Gandhinagar 382721, Gujarat, India (India)
Mechanical Engineering Department, Gandhinagar Institute of Technology, Gandhinagar University, Moti Bhoyan, Gandhinagar 382721, Gujarat, India (India)
Article Information
DOI: 10.51244/IJRSI.2026.1306000181
Subject Category: Sustainable Development
Volume/Issue: 13/6 | Page No: 2465-2476
Publication Timeline
Submitted: 2026-06-09
Accepted: 2026-06-14
Published: 2026-06-29
Abstract
Fossil-fuel depletion and the harmful exhaust emissions of compression-ignition (CI) engines have intensified the search for cleaner alternative fuels. Emulsification of water into biodiesel–diesel blends is an attractive technique because the micro-explosion of dispersed water droplets improves atomisation and lowers the peak combustion temperature, simultaneously enhancing performance and reducing oxides of nitrogen. This study optimises the water, surfactant and dual-biodiesel content of a least-phase-separation emulsified fuel and evaluates it in a single-cylinder CI engine. A B30 blend of Neem and Palm biodiesel (15% Neem + 15% Palm + 70% diesel, denoted N15P15D70) was selected as the base fuel. Water-in-oil emulsions were prepared with water concentrations of 1–5 v/v %, surfactant (SPAN 80 / TWEEN 80) of 1–2 v/v %, and hydrophile–lipophile balance (HLB) values of 4.3, 5.3 and 6, using a mechanical stirrer. Emulsion stability was assessed from the phase-separation percentage over six hours, and the optimum formulation was tested for engine performance and exhaust emissions against neat diesel. The emulsion with 5% water, 2% surfactant and HLB 6 (W5S2HLB6) gave the best stability, with only 8% separation after six hours. Relative to diesel, this fuel delivered about 14% higher brake thermal efficiency, 42% higher carbon dioxide (indicating more complete combustion), and roughly 60% lower carbon monoxide and 61% lower NOx, although brake specific fuel consumption rose by about 16.7% and smoke increased marginally. The study concludes that an emulsified fuel of 30% dual biodiesel, 2% surfactant, 5% water and HLB 5.3–6 markedly reduces harmful emissions while improving engine performance, and can be used in existing engines with little or no modification.
Keywords
CI engine; Alternative fuel; Dual biodiesel; Neem; Palm; Emulsification; Emulsion stability; Engine performance; Emission analysis; Micro-explosion
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