Combustion of aluminum particles in solid rocket motor flows

J. C. Melcher, Rodney L. Burton, Herman Krier

Research output: Contribution to conferencePaperpeer-review


The time-resolved diameter history of combusting aluminum particles was studied in a solid-rocket chamber flow-field as a function of pressure and oxygen concentration. Rocket motor chamber conditions were generated directly from a solid propellant combustion products flow field, and the aluminum particle source was an aluminized solid-propellant sample. Injecting additional oxygen gas into the chamber varied the oxygen concentration over a range of 0.8% to 10.4%. The experimental test conditions were 13 -22-atm pressure and -2300 K temperature. The burning aluminum particles were recorded as streaks on photographic film using an open-shutter 35mm camera and chopper wheel. Using a narrow band filter for AlO emission at 486-nm, it was determined that the thermal emission from the hot oxide smoke particles dominates the emitted light. The images are analyzed digitally by a background subtraction / high-pass filter technique to measure the apparent diameter of the two-dimensional image of the A12O3 smoke cloud surrounding the particle. Burning particles were quenched on glass in the chamber and found to be typically the same size as the loaded aluminum particles, 106 microns, implying that propellant-surface aluminum agglomeration is minimal. The initial diameter of the outer smoke cloud to the particle surface radius is found to vary experimentally with pressure by (r / Is) ∝ p-2.3, but varies weakly with oxygen concentration. Not every particle bums identically, and the data, interpreted statistically, show that the diameter dependence Dn law does not strictly follow the classically predicted n = 2, but instead follows n =1.65 ± 0.55. The burning rate slope, k, defined in the equation Dn = Don -kt, is found to vary little with oxygen concentration, but does increase linearly with pressure over the range of study. The weak dependence of ‘k’ with oxygen concentration indicates that oxygen is probably not the primary oxidizer for aluminum combustion in the solid-propellant combustion-product flow-field, which is supported by calculations that show faster reaction rates for H2O and CO2 over O2.

Original languageEnglish (US)
StatePublished - 1999
Event35th Joint Propulsion Conference and Exhibit, 1999 - Los Angeles, United States
Duration: Jun 20 1999Jun 24 1999


Other35th Joint Propulsion Conference and Exhibit, 1999
CountryUnited States
CityLos Angeles

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Mechanical Engineering
  • Control and Systems Engineering
  • Aerospace Engineering

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