Characterization of Injection Nozzles for Gas-Solid Flow Applications

Abstract

Laser phase-doppler velocimetry measurements have been used to characterize the particle-gas sprays produced by straight-tube nozzles that simulate idealized fuel injectors for solid fuel combustion systems. Tests were conducted on two nozzle sizes, for two particle sizes, two loading ratios, and two gas velocities. The Reynolds numbers was varied from 9500 to 19000, and the Stokes number from 1.9 to 61.4. It was found that the velocities of the particles in the spray decelerate more slowly, and the velocity profiles are generally more narrow, than for a single-phase free-jet. The turbulence level of the particles in the sprays was found to be less than half the turbulence level of a single-phase free-jet, and the turbulent velocity profiles were not yet fully developed at X = 40D. The hydrodynamic characteristics of the nozzles that are the most important for combustion systems were found to be: (a) the particle spray expands radially at a cone angle of 2° (measured at the radius corresponding to the peak of the particle mass flux distribution); and (b) the nozzle pressure drop and particle mass flow can be related by a correlation that depends on loading ratio, Reynolds number, Stokes number, and the pressure drop coefficient of the nozzle for a single phase flow.