| Highway tunnels occupy an important position in the construction of highways in China.The problem of large dust concentration and difficult to reduce during tunnel construction still exists.Dust particles suspended in tunnels not only cause serious damage to the health of operators,but also affect the progress of construction.The dust emitted from the entrance of the tunnel has caused secondary pollution to the surrounding environment of the tunnel.Therefore,it is particularly necessary to study the reduction of dust.This paper proposes a new type of dust removal method-negative ion dust removal.Previously,negative ion dust removal technology was used in indoor and ventilation ducts,and related research was also concentrated here.There was a lack of research on the large-space and high-pollution environment of such tunnels during the construction period.In this paper,through the combination of theoretical analysis,numerical simulation and field test,the influence of variable factors on the dust removal efficiency of negative ion systems is analyzed.The main contents include the following:1.The theoretical analysis section describes the generation of negative ions and the role of negative ions.The mechanism of negative ions in tunnels to reduce dust particles is analyzed.The effects of dust characteristics and tunnel environment on the dust removal efficiency are analyzed.2.Numerical simulation UDF is written in C++ programming,and secondary development of Fluent is performed.According to the investigation and actual measurement,the tunnel model calculation parameters were selected to establish a three-dimensional model of the tunnel and negative ion system.The model has a large span,from the smallest 2cm to the largest 320 m.The finite-volume method based on structured grids is used to solve the electric discharge field.The RNGk-ε dual-equation turbulence model is used to solve the current field by the momentum equation adding electric field force source term.The SIMPLE algorithm was used to simulate the electric field distribution,flow field distribution,particle motion,discrete phase and fluid phase and phase coupling.The potential distribution,currentfield distribution and particle motion of the negative ion system during tunnel construction were simulated..3.The numerical simulation was performed by changing the parameters of the influencing factors,ie selecting four dust particle sizes,four inlet wind speeds,four working voltages,four dust initial concentrations,and three installation positions,and obtaining different parameters under different conditions.The movement of the dust particles and the change of the dust removal efficiency obtained the effects of dust particle size,inlet wind speed,working voltage,installation position and initial dust concentration on the dust removal efficiency of the negative ion system during the construction period.4.Multivariate linear regression analysis of influencing factors using SPSS software,combined with numerical simulation results to determine the effect of dust particle size,inlet wind speed,working voltage,installation position and initial dust concentration on the dust removal efficiency of the negative ion system in the tunnel during construction period.Size relationship.5.By using the negative ion system in the tunnel of the project,a comparative test was conducted and the test results were analyzed and compared with the numerical simulation results.The results obtained from the test results and the numerical simulation results are consistent. |
