Structure of coal water slurry sprays

Abstract

A model of coal water slurry (CWS) sprays is presented with new experimental data for CWS viscosities and surface tension. The model is based on the aerodynamic theory of spray atomization that has been successfully used for diesel sprays. However, the higher CWS viscosity makes their behavior different from diesel sprays. For comparison with experiment the following spray parameters are identified; spray angle, intact core length, drop diameters, and velocities of drops and gas. The results from the computations have been compared with experimental measurements reported in the literature. Computed spray angles and penetration rates agree well with experimental measurements. Computed drop sizes show the right trend when the injection pressure and the axial location at which the Sauter mean diameter is measured are varied. Nomenclature A = function in Taylor's analysis AV = constant of the initial spray angle B = function in Taylor's analysis B({ = constant of the initial drop size equation C, Cc = constants of the intact core length Cd = coefficient of discharge of the nozzle /)„ = nozzle diameter d() = initial drop diameter calculated from Eq. (2) /*, = dimensionless frequency of fastest growing wave Im = imaginary part k = wave number L = length of the nozzle Pa =. ambient gas pressure Re = real part S = spray tip penetration distance s = real part of nondimensiona l temporal growth rate Ta = Taylor number p,a2lpg^V^ t = time th = breakup time U = average axial centerline velocity of drops/gas U{} = average injection velocity u' - axial perturbation velocity of the CWS jet Kinj = ideal injection velocity VT = relative velocity between the liquid and gas v' = radial perturbation velocity of the CWS jet Xi = length of the CWS spray intact liquid core x = axial distance y = radial distance a = temporal growth rate of the CWS velocity perturbation