Two-dimensional model of laser-sustained plasmas in axisymmetric flowfields

Abstract

A two-dimensional numerical model of laser-sustain ed plasmas in flowing argon has been developed. Real-gas properties and a complete radiation loss mechanism have been included, but radial velocities in the flowfield are neglected. Calculated plasma size, peak temperatures, global absorption characteristics, and thermal efficiencies are in good agreement with experiment. Radiation loss is found to be the dominant process at high laser powers, although thermal conversion efficiencies in excess of 40% (at 20 kW) can be realized by operating at high flow velocities. Nomenclature c = speed of light Cp = specific heat, J/kg - K D - focus spot diameter, mm e = electronic charge / = optical / number h = Planck constant / = laser intensity, W/m2 K = thermal conductivity, W/m-K kB = Boltzmann constant ne = electron number density, m~ 3 me - electron mass r = radius, m t =time, s T = temperature, K u,v = axial and radial velocity components, respectively, m/s z = axial position, m Zeff = radiation loss correction factor a = absorption coefficient, 1/m e = emission coefficient, W/m3 p = density, kg/m3 vc = continuum cutoff frequency, s~*