Numerical experiments based on computational fluid dynamics methods were carried out to investigate the effect of pitch-diameter ratio on the flow field and particle separation process in spirals. Firstly, the longitudinal evolution of the secondary circulation in spirals was systematically investigated when pitch-diameter ratio was adjusted. Secondly, the migration behaviour of hematite and quartz particles was investigated. The variation of particle motion with fluid evolution and the influence of pitch-diameter ratio were discussed. Finally, The separation efficiency was predicted and the influence mechanism of pitch-diameter ratio on the particle separation process and results was identified. The results show that the increase of the pitch-diameter ratio can form the overall continuous secondary circulation spatial distribution faster, enhance the inner circulation velocity in the central region, weaken the equilibrium velocity of the inner and outer circulation in the outer area, and reduce the relative stability and volatility of the radial flux in the outer circulation. The larger the pitch-diameter ratio, the more the outward migration of hematite. However, at r=100 mm, the migration tends to be balanced, and the enrichment is formed in the middle. The outward migration of quartz in the area outside r=100 mm increases, and the position difference between quartz and hematite enrichment areas expands. The predicted separation efficiency is positively correlated with the pitch-diameter ratio. The maximum separation efficiency reaches 75.03% at the trough of the end of the third turn when the pitch-diameter ratio increases to 0.8, and the optimal splitter position is 94 mm. It is consistent with the evolution characteristics of the secondary circulation and the migration law of particles. © 2024 Central South University. All rights reserved.
