1、英文原文Numerical simulation of the factors inuencing dust in drilling tunnels: Its applicationNiu Wei, Jiang Zhongan, Tian DongmeiKey Laboratory of Ministry of Education for High Efciency Exploitation and Safety of Metal Mine, Beijing University of Science and Technology, Beijing 100083, ChinaAbstract:
2、 Gas-solid two-phase ow theory was used to predict dust distribution and movement at the working face of a mine. The software package FLUENT was used to numerically simulate dust motion and the results were compared to observed data. The simulation agrees with the data taken from an actual working f
3、ace, which conrms the choice of mathematical model and numerical simulation method. Using the model we predict a set of conditions optimum for reducing dust concentrations at the mine working face.Keywords: drivage working face, dust concentration, the gas-solid two-phase ow, ventilation method1 Int
4、roductionDust in a mine seriously endangers safe production and the mine workers health. The driving face is one of the major dust generating locations. The airow and the ow eld distribution at the driving site of the roadway directly inuence the process of gas exchange and dust movement. This is a
5、hot topic among scholars at home and abroad. Since the 1980s, scholars have carried out airow experiments at the driving face1,2.In 1993, Rao and others from Australia used hydrodynamic calculations to simulate the wind ow distribution at a long-wall working face and the effect of ow on dust reducti
6、on. Heerden and Sullivan from South Africa used CFD to simulate and test airow and dust distribution patterns next to a driving machine. Nakayama and some other scholars from Japan have simulated the wind ow at a working face3,4.An accurate understanding of dust movement and gas collection requires
7、a discussion of wind ow at a driving face that is partially aerated.2 Basic hypotheses and the solution of the gas-solid two-phase ow equation1) Basic hypotheses model dust movement at the working face will be simplied. The driving roadway is modeled as a 4m by 3m rectangle with a length of 12m. The
8、 ventilation pressure in the roadway was measured by hanging a 0.6m diameter wind canister 1.8m long on one sidewall. The distance between the exit of the wind canister and the working face was 7m. Gambit was used to establish a geometric model and to mesh the calculation area, and to check the grid
9、; see Fig. 15,6.2) Establishment of the two-phase ow equationDust movement in the airow is in essence a kind of two-phase ow. We take airow as the background phase and describe it using Euler methods. Dust arising from the various sources is the other phase (the dust is dispersed in the background o
10、w). The dust movement is described by Lagrange methods6.2.1 Airow equation and its solutionWe assume the ow to be non-compressible Navier-Stokes ow with steady incompressible in three dimensions. The ow equation is taken as a double k- equation, which is the most widely used model in this engineerin
11、g eld. In this model only momentum transfer is considered and heat transfer is neglected.(a) Geometric model (b) Grid diagramFig. 1.Geometric model and net diagram of the driving roadwayWe can then derive the following equations7,8:The continuity equation:(1)The equation of motion:(2)The k equation:
12、(3)The equation:(4)where(5)and(6)where Gk is the rate of change in ow momentum caused by changing cutting force; k the turbulent ow momentum, m2/s2; the laminar ow viscosity coefcient, Pas; t the turbulent ow viscosity coefcient, Pas; p the effective pressure of turbulent ow, Pa; the gas density, kg
13、/m3; xi the coordinates in the directions x, y and z, m; ui the ow velocity in the x, y or z direction, m/s; and, C1, C2, C, , and k are the constants that are assumed to be 1.44, 1.92, 0.09, 1.30 and 1.00 in this model.2.2 Dust equation of motion and its solutionA discrete phase model treats dust m
14、ovement in the roadway by a differential equation in a Lagrangian reference frame9.(7)Where mp is the quantity of the dust, kg; up is the dust velocity, m/s; and,F is the resultant force, N. This resultant is comprised of Fd, drag forces, N; Fg, the force of gravity; Ff, buoyancy, N; and, Fx all the
15、 other forces, N, including the added mass force, the ascending force of Magnus, the ascending force of Saffman, and the force of Brown. These latter forces are too small to be considered in this treatment.It is true that(8)where Cd is the drag coefcient; Cp a form coefcient, obtained from experimen
16、tal data on the dispersion and is set equal to 1 here; Ap the cross sectional area of the particle, m2; ug the airow velocity, m/s; and, up the dust velocity, m/s. Cd may be obtained from the Reynolds number of the dust:(9)(10)where Rep is the Reynolds number and dp the diameter of the dust, m.Although af
