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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #433447
Research Project: Sustaining Productivity and Ecosystem Services of Agricultural and Horticultural Systems in the Southeastern United States

Location: Soil Dynamics Research

Title: Detailed CFD analysis of raw bio-oil atomization process inside an internally mixed air-blast nozzle using VOF to DPM model

Author
item HASAN, M - Auburn University
item KEMP, A - Auburn University
item SAPKOTA, S - Auburn University
item MITCHELL, M - Auburn University
item JALALABADI, H - Auburn University
item SCARBOROUGH, D - Auburn University
item MICHAEL, J - Auburn University
item ADHIKARI, S - Auburn University

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 3/16/2026
Publication Date: 7/26/2026
Citation: Hasan, M.J., Kemp, A., Sapkota, S., Mitchell, M., Jalalabadi, H.K., Scarborough, D., Michael, J., Adhikari, S. 2026. Detailed CFD analysis of raw bio-oil atomization process inside an internally mixed air-blast nozzle using VOF to DPM model. Proc. ASME 2026 Fluids Engineering Division. July 26–29, 2026, Bellevue, WA.

Interpretive Summary:

Technical Abstract: Atomization plays a pivotal role in achieving efficient combustion by influencing fuel-air mixing, droplet size distribution, and spray tip penetration. Bio-oil, derived from biomass pyrolysis, is a promising renewable fuel; however, its high viscosity (˜67.2 mPa·s), surface tension (˜0.037 N/m), and water content (˜25.76 wt%) make atomization challenging. This study presents a detailed 3D transient Computational Fluid Dynamics (CFD) investigation of the atomization process of 100% raw pyrolysis bio-oil inside an internally mixed air-blast nozzle which has six tip outlets. A coupled Volume of Fluid (VOF) to Discrete Phase Model (DPM) approach of ANSYS Fluent is employed to capture the transition from liquid sheet to dispersed droplets, focusing on the primary breakup inside the mixing chamber. The simulation uses a hybrid RANS-LES turbulence model, specifically Stress Blended Eddy Simulation (SBES), to resolve local turbulence and shear-driven breakup. Mesh adaptation is applied at the liquid-gas interface to accurately capture interfacial instabilities. High-performance computing on a Linux cluster is utilized to handle computational demands. Operating conditions include liquid injection pressure of 40 psi and air-assist pressure of 38 psi. Validation against experimental data confirms the accuracy of the VOF-to-DPM approach. Results are presented in terms of velocity distribution, Weber number particle gas, Q-criterion for vortex identification, breakup length throughout the y-axis, pressure field, Sauter Mean Diameter (SMD) at nozzle tip exits, and droplet trajectories. Ligament formation inside the mixing chamber is visualized, showing that it takes 0.4 ms for bio-oil to reach the bottom of the chamber. Droplet formation begins inside the mixing chamber, where strong vortical structures (Q-criterion > 1.3×103 s'²) enhance breakup. Velocity fields show that air is pushing the bio-oil inside the mixing chamber. SMD is calculated for each nozzle tip exit and presented with histogram charts. Particle tracking confirms uniform droplet dispersion and improved spray penetration. This detailed CFD analysis provides important insights into the atomization physics of high-viscosity bio-oil and establishes a robust computational framework for nozzle optimization. The findings support the development of self-sustaining pyrolysis systems by enabling efficient combustion of raw bio-oil, contributing to renewable energy advancement.