Influence of Rotor-Induced Airflow on Particle Fragmentation in an Impact Crusher: A Computational Fluid Dynamics-Discrete Element Method Study.

Abstract

Impact crushers are essential equipment in mineral processing, where improving their efficiency is crucial for resource utilization. In this study, a CFD-DEM two-way coupled numerical model was developed to simulate gas-solid interactions within the crushing chamber, focusing on the influence of rotor-induced airflow on particle motion and fragmentation under varying operational conditions. Simulation results reveal that particles exhibit three distinct trajectorieshigh-speed, low-speed, and circulating flowsdepending on their location relative to the rotor. At a rotor speed of 400 rpm, particles reach a maximum velocity of 11.6 m/s during crushing, while low-speed particles remain below 4.63 m/s. As the rotor speed increases from 200 to 600 rpm, the maximum stress experienced by particles rises from 603.4 to 1062.5 N, indicating higher collision forces and increased crushing probability. However, excessive rotor speeds lead to significant energy dissipation, where a substantial fraction of the collision energy is consumed in nonfracturing impacts and shell wear, rather than effective particle breakage. The airflow velocity in the crushing chamber also increases notably with higher rotor speeds, reaching up to 7.21 m/s near the hammer head at 600 rpm while remaining as low as 0.721 m/s in the discharge area. Additionally, the number of broken particle bonds increases dramatically between 0.25 and 0.34 s of simulation time, with up to 104,470 broken bonds recorded at 1 s under high-speed conditions. These findings provide quantitative insights into the complex interplay among rotor speed, airflow, and particle dynamics, offering a theoretical basis for optimizing the design and operating parameters of impact crushers to achieve improved crushing performance and energy efficiency.