Ignition and Combustion of Nickel Coated and Uncoated Aluminum Particles in Hot Post-Flame Gas Environment

Open Access
Author:
Boyd, Eric R.
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Kenneth K Kuo, Thesis Advisor
Keywords:
  • Nickel Coating
  • Gas Burner
  • Combustion
  • Aluminum
Abstract:
An experimental study of ignition and combustion of isolated, Ni-coated, and uncoated aluminum particles was conducted. Ni-coated Al particles are of particular interest for two reasons. The Ni-coating prevents the particles from forming agglomerates due to the protective nickel layer. Intermetallic reactions between the nickel and aluminum are exothermic, giving an additional energy feedback to start the Al particle ignition. Two particle sizes (nominally 32 μm and 9 μm in diameter) were examined in this study. Since the coated and uncoated particles are from the same batch any differences between the ignition and combustion behaviors can be directly attributed to the effect of the Ni-coating. The ignition and combustion properties of the aluminum particles were examined in the post-flame zone of a multi-diffusion flat-flame (a modified Hencken burner) at atmospheric pressure. Isolated, single particles are burned in this experimental setup so the exothermic heating from the Ni-Al intermetallic reaction is of particular interest. This study shows that the applied nickel coating decreased the ignition temperature of the Al particles by 750 K on average for 32 m particles and by 300 K for smaller 9 m particles. These results are plotted against an effective oxidizer factor that takes into account the strength of O2, H2O, and CO2 in the oxidation reaction of aluminum. Combustion times were measured by optical techniques to determine how the applied nickel coating would affect the combustion time. While there was significant data scatter, due to a broad particle size distribution, the results still showed that the combustion times for different sized particles were not noticeably affected by Ni-coating.