A significant advancement in understanding self-sustaining pulsatile injector dynamics: Effects of numerics, nozzle geometry, gas feed rate, and non-newtonian slurry

The performance of a rather large-scale self-exciting coaxial three-stream airblast injector was studied experimentally and computationally by Strasser [1] and the computational method was validated using an air-water test stand (AWTS). Frequency domain analyses revealed distinct changes in spray character and pulsations as a function of air feed rates. Since that work, efforts have progressed in studying the effects of injector geometry, including inner nozzle retraction, stream meeting angle, outer annulus gap, and nozzle diameter. Changes to retraction produce the most profound, but not always monotonic, responses in the energy content and nature of the spray pattern. Later, the use of slurry and a high-density gas (SH) as replacements for air and water is investigated, revealing that the nature of the SH flow is dramatically different from its AW counterpart. As with AW, inner nozzle retraction and stream meeting angle prove to be the most influential geometry variables. Strong geometry, materials, and gas flow rate interactions are found among the metrics considered. Estimated droplet length scales of the SH system are not much different than those of the AW system. Attempts to further stimulate the spray via modulating the inner gas provide marginal influence for both sets of flowing materials. Lastly, swirling feeds and a multitude of modeling issues are addressed.