A novel accurate model for tracking irregular particles: Development, implementation, and impact on biomass combustors.

Multiphase flows with irregular solid particles are ubiquitous in engineering applications, where particle rotation critically influences dynamics, mixing, phase interactions, and chemical reactions. Conventional particle-tracking models often neglect rotation, focusing solely on translational motion. Recent advances in drag, lift, and torque coefficients for irregular particles, derived from particle-resolved direct numerical simulations, underscore the need of models that account for both translational and rotational motion. This study bridges this gap by developing a novel model that accurately couples these motions. Leveraging drag, lift, and torque coefficients derived from thousands of particle-resolved simulations and an advanced analytical discretization scheme, this model ensures high accuracy, numerical robustness and broad applicability. The model's capabilities are demonstrated through computational fluid dynamics (CFD) simulations of a natural gas/biomass co-fired burner, with biomass particles represented as prolate ellipsoids. The results reveal that biomass particles predominantly rotate around their minor axes, with rotation intensifying as particle size decreases. For equi-volume diameters decreasing from 16.5 mm to 165 µm, peak angular velocities around minor axes surge from approximately 4 to 6,600 rad/s, while those around major axes remain 1-2 orders of magnitude lower, rising from 0.03 to 71 rad/s. Compared to conventional models, this model provides unprecedented insights into particle rotation and significantly improves simulation outcomes without compromising computational efficiency. Notably, it extends particle residence times (∼20 % longer in the 10-meter-long burner chamber), enhances mixing and lateral particle dispersion, and intensifies phase interactions, making it a valuable tool for simulating particle-laden multiphase flows in engineering applications.