Numerical Simulation of the Effect of Nozzle Angle on the Mixing Process of Glass Fiber Raw Materials

In order to solve the problems of stratification, segregation, and insufficient mixing uniformity of glass fiber raw materials in the process of pneumatic mixing, the binary particles of pyrophyllite and limestone, the core raw materials of E-glass fiber, were taken as the research object, and the influence of nozzle inclination angles (0°, 45°, 60°, 75°) on the gas–solid flow, particle motion and mixing performance in the pneumatic mixing tank was systematically investigated by using the CFD-DEM coupling method. The flow field evolution and mixing mechanism at different inclination angles were compared and analyzed by visualization of particle motion, gas flow streamlines, turbulent kinetic energy distribution, and quantitative characterization of Lacey mixing index (LMI) and particle axial concentration distribution. The results show that the nozzle inclination angle significantly regulates the flow field structure in the tank, the 0° vertical nozzle forms a single axial jet, with a low-speed dead zone at the top and particle accumulation, and the mixing index stabilizes only at 0.92. The 45°~75° inclined nozzle can induce the formation of a stable and symmetrical double-vortex circulation flow field, which strengthens the radial mixing of particles and the turbulent disturbance in the whole region. The LMI is stable above 0.97, and the mixing uniformity and stability are significantly improved. In particular, under the 45° inclination angle, the volume-averaged turbulent kinetic energy shows a counter-trend increase, with a relatively low flow dead zone and a uniform axial concentration distribution. The advantages of the oblique jet in reducing segregation, optimizing flow field, and improving mixing efficiency are clarified. It can provide a theoretical basis and numerical reference for the pneumatic mixing of glass fiber raw materials and the improvement of relevant equipment structure and process optimization.