Optomec, Inc., 2575 University Avenue, #135, St. Paul, Minnesota, 55114, USA
To gain insights into ink material deposition behavior during Aerosol Jet® printing, particle deposition patterns on the plate of inertial impactor with circular laminar jet are investigated numerically with a lagrangian solver implemented within the framework of the OpenFOAM® CFD package. Effects of taper angle of the nozzle channel and jet-to-plate distance are evaluated. The results show quite different particle deposition patterns between tapered nozzle and straight nozzle. At jet Reynolds number Re = 1132, a tapered nozzle deposits particles to form a pattern with a high density ring toward the deposition spot edge, especially when the particle Stokes number St > St50, which is absent with a straight nozzle. Increasing the jet-to-plate distance tends to reduce such particle density peak. Reducing Re to 283 yields particle deposition patterns without the high density ring near the spot edge, with the same tapered nozzle. The particle deposition patterns with the straight nozzle at Re = 283 exhibit further reduced particle density around the spot edge such that the particle density profile appears more like a Gaussian function. In general, the effect of reducing Re on particle deposition pattern seems to be similar to increasing the jet-to-plate distance. The computed particle deposition efficiency η shows the fact that those particles around the jet axis, even with very small values of St, always impact the center of plate, as indicated by the nonvanishing value of η with substantial reduction of St. Such a “small particle contamination” typically amounts to ~10% of small particles (with < 0.1) at Re ~ 1000 and ~5% at Re ~ 300, which may not be negligible in data analysis with inertial impactor measurement.