Numerical and experimental studies of irregular-shape biomass particle motions in turbulent flows

Abstract

This paper discusses numerical and experimental studies of biomass micro scale particles motion in turbulent flows. The biomass micro size particles are extremely anisotropic and typically of irregular shape with sizes varying between 200–6000 μm in length and 125–1400 μm in diameter. Four different types of biomass micro size particles from different sources are applied. Ten different numerical modelling tools for simulation of the biomass micro size particles motion in turbulent flow are presented and validated against experiments. The experiments are carried out using three different techniques: an aerodynamic classifier, vibrating sieve and microscopic image analysis. Results showed considerable discrepancy between the models and the experiments. In consequence, a comprehensive new shape factor correlation for the irregular-shape particles is proposed, which enhances significantly the model results. Parametric studies are also carried out, including influence of particle shape, size, and anisotropy criteria. Moving orientation of the irregular-shape particles in turbulent flow is addressed as well. Results demonstrated that the key issue for modelling of biomass micro size particle motion in turbulent flow is both drag coefficient and particle-projected area. Small size of biomass particle is quickly accelerated and it tends to follow airflow; larger biomass micro size particle is slowly accelerated and it decelerated rapidly because of less response to air stream. Additionally, both small and large biomass micro size particles tend to orient themselves to one preferable direction.