Effect of inlet area on the performance of a two-stage cyclone separator

The cyclone separator is an important separation device.This paper presents a new type of embedded two-stage cyclone,which includes a 2 nd-stage cyclone(internal traditional cyclone)with multiple inlets and a 1 st-stage cyclone(outer cylinder)that unifies the 2 nd-stage cyclone inlets into one inlet.The Taguchi experimental method was used to study the two-stage cyclone separator’s inlet area on its performance.Studies have shown that the increase of the 1 st-stage cyclone inlet area and the increase in the number of 2 nd-stage cyclone inlets(N)positively affect reducing the pressure drop and a negative effect on efficiency.It is recommended to use 2 S(the original 1 st-stage cyclone inlet area)of the 1 st-stage cyclone inlet area and 2 N of the 2 nd-stage cyclone inlets when separating fine particles.Compared with a traditional cyclone,the pressure drop is reduced by 1303 Pa,the mass separation efficiency(Eq)is increased by 0.56%,and the number separation efficiency(En)is increased by 2.05%.When separating larger particles,it is recommended to use 2 S of the 1 st-stage cyclone inlet area and 4 N of the 2 nd-stage cyclone inlets.Compared with a traditional cyclone,although Endecreases slightly,the pressure drop is reduced by 3055 Pa,and the Eqis increased by 0.56%.The research results provide new insight into the design of the cyclone.

Dust pollution during shotcrete process in high-altitude tunnel based on numerical simulation

The surrounding rock needs shotcrete support after drilling and blasting excavation in the tunnel;the high concentration of dust generated in the process will endanger workers'occupational health.Therefore,to ensure the cleanness and safety of the tunnel construction process,a full-scale model of the tunnel was established based on field data of a high-altitude tunnel of the Sichuan-Tibet railway.The dust production mechanism is summarized by combing the whole process of shotcrete.The Computa-tional Fluid Dynamics(CFD)method was used to study the diffusion and transport of dust under different conditions.The grey relational analysis was applied to investigate the correlation values of the influ-encing factors on dust diffusion in the shotcrete operation area.The results show that the dust gener-ation mechanism of shotcrete includes the sudden change of particle velocity in the jet area leading to escape and particle impact dust generation,where fine dust is easily dispersed in the tunnel.During continuous dust production,the dust concentration is higher near the wet spraying machine and on the backflow side of the working face.Increasing the air supply volume and shortening the distance between the air duct and the working face is conducive to diluting the dust concentration in the tunnel.In the high-altitude environment,the dust concentration in the tunnel decreases,the diffusion distance be-comes smaller,the settlement proportion of dust particles increases,and the risk of secondary pollution increases.The simulation results and the field measurement data are consistent,which can provide theoretical support for the construction site dust control.