CFD Simulation of Combustion and Emission Characteristics of Pure Spirulina Microalgae Biodiesel in a Single-Cylinder DI Diesel Engine

This study examines the combustion and emission characteristics of pure Spirulina microalgae biodiesel (B100) in a single-cylinder direct-injection (DI) diesel engine using computational fluid dynamics (CFD) in ANSYS Fluent. A 2D axisymmetric sector model of the engine was developed and simulated with a moving mesh to capture dynamic piston motion throughout the engine cycle. The Discrete Phase Model (DPM) was applied to simulate spray atomization and droplet evaporation, while a non-premixed combustion model and RNG k-ε turbulence model were used to resolve in-cylinder combustion dynamics. The thermophysical properties of Spirulina biodiesel were defined from literature data to accurately model fuel injection, vaporisation, and ignition phenomena. The study focused on analysing in-cylinder pressure, temperature, and emission characteristics such as NOx, CO, and soot, and compared the results with those of conventional diesel fuel. Simulation results indicated that Spirulina biodiesel produced a more diffuse flame front, faster vaporization due to its higher oxygen content, and lower carbon-based emissions. However, a moderate increase in NOx was observed, attributed to elevated combustion temperatures. The findings support the potential of Spirulina biodiesel as a clean-burning, renewable alternative to fossil fuels and demonstrate the capability of CFD tools in optimizing alternative fuel performance in engine applications. Keywords: Spirulina biodiesel, CFD simulation, direct injection diesel engine, Alternative fuels, Renewable energy, Microalgae fuel.