The uniform removal of the bran layer significantly enhances the nutritional and economic benefits of rice. However, the influence of parameter conditions on the uniformity of milling in the abrasive milling process remains unclear. This is not conducive to improving the quality of rice milling. In this study, the effects of rotational speed and filling volume on milling uniformity in abrasive milling were investigated by combining experimental methods and simulation. The results showed that the higher the rotational speed, the more uniform the milling. The higher the filling volume, the more non-uniform the milling. The main reason for the variation in milling uniformity is the axial and radial position exchange of the rice particles in the milling chamber. The more frequent the exchange, the higher the milling uniformity. Subsequently, the frequency of position exchange was quantitatively characterised using axial and radial exchange rates, respectively. The rotational speed and filling volume change the position exchange frequency by affecting the rotational kinetic energy of the rice particles and the degree of dense rice population, respectively. These findings are useful in promoting rice loss reduction and nutritional balance.

Eccentric silo is an extremely common type of silo, but it is still unclear how to accurately control the discharge by adjusting eccentric orifices, limiting the application and development of eccentric silo. In this study, the rice particle discharging process on silos with different eccentricities was simulated by the discrete element method (DEM), and the influence mechanism of orifice eccentricity on silo discharge rate was analyzed. The results show that eccentricity has a direct influence on the particle volume fraction and vertical velocity that determine the discharge rate of the silo. In fully eccentric silo, it is not easy for particle flow to achieve balance, particles will pass through outlet with more kinetic energy. Moreover, continuous force network cannot be formed between particles with shear resistance, resulting in weak interlocking action between particles. The orientation of particle in fully eccentric silo is more vertical, especially near the silo wall, which will produce larger local particle volume fraction above the orifice. When the eccentricity exceeds the critical eccentricity, the sparse flow area on the discharge orifice becomes larger, and the particle acceleration area increases accordingly. Research findings may offer valuable insights for the accurate control of discharge rate of eccentric silo, as well as for optimizing silo design.

The impact velocity of the grains is a critical factor affecting the hulling efficiency in centrifugal hullers. However, significant differences in velocity are observed among paddy grains following acceleration by the impeller. Therefore, elucidating the mechanism responsible for these velocity differences is essential for improving hulling performance. This study employed coupled CFD-DEM simulations to analyse the kinematic behaviour of paddy grains. The results demonstrate that velocity differences among grains are prevalent within centrifugal hullers and adversely affect hulling efficiency. These differences primarily arise from tangential collisions between grains and blades prior to acceleration, as well as axial collisions during the acceleration phase. The jumping degree (S_v) quantifies the relative motion between paddy grains and blades in the normal direction. Velocity differences decrease significantly as the jumping degree approaches unity. Furthermore, a tilted curvature blade was developed to mitigate velocity differences. Computational analysis and simulation determined that a blade curvature of 300 mm combined with a 20° tilt angle achieved the most substantial reduction in velocity differences. This optimised configuration improves hulling efficiency by 4.5% compared to the original blade design. This modification is expected to substantially facilitate the optimisation of centrifugal huller designs.