Experimental investigation of particle distributions in particle-laden coaxial jets

Abstract

The characteristics of particle distribution and fluid velcotiy were investigated in a particle-laden coaxial jets. Simultaneous measurements were taken of the mean velocity and concentration of the small traces (1 µm) and large particles (42.5 µm) in a particle-laden flow. Velocity characteristics of small tracers and large particles was obtained using particle image velocimetry (PIV) and particle tracking velocimetry (PTV), repectively. Particle concentration was obtained by counting the number of particles in each interrogation cell of the PIV/PTV images. The experimental results reveal the significant influence of the solid particle mass loading on the flow charactersitcs. The gas-phase velocity in the developing region, which is lower than a single-phase velocity, increases as a loading ratio, but there is a higher mean velocity in the developed region due to the momentum exchange between particles and fluid. The deviation difference of particle local mean concentration maximized at the edge of the shear flow region. It was also observed that vortical structure influence on the non-random concentration fluctuations of particle and as particle mass loading increases intensity of vorticity decreased than deviation parameter also decreased. Nomenclature u t = terminal velocity τ s = relaxation time = density of particle = density of fluid = dimeter of particle St0 = Stokes number at the nozzle exit Re p = particle Reynolds number ϕ = particle mass loading ratio D = deviation parameter Rein = Reynolds numder of inner gas flow Reout = Reynolds number of outer gas flow 0 = Drag coefficient at the nozzle exit = gas phase vleocity = particle velocity = particle mean number density = tracer mean number density