STP1197

    Modeling of Al And Mg Igniters Used in the Promoted Combustion of Metals and Alloys in High Pressure Oxygen

    Published: Jan 1993


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    Abstract

    NASA determines flammability of metal and alloy samples in high pressure oxygen by Test 17 of NHB 8060.1C. An aluminum or magnesium promoter, releasing at least 3.0 kJ, is used as the sample ignition source. This ignition system is modelled using lumped-parameter mathematical equations and solved using the MATLAB computer code. Model parameters were obtained from the combustion of Al and Mg promoters on copper rods in the standard flammability instrument system. The copper rod is non-flammable under test conditions, that is, pure oxygen pressures of 3.44, 6.89, 20.7, 34.4 and 68.9 MPa. At test conditions, both aluminum and magnesium alloyed with the copper rod and burned in liquid phase reactions. The following heterogenous kinetic reaction rate functions were obtained: for Al: RAl=0.102Po21.+0.186Po2,g/m2s for Mg: RMg=0.067Po21.+0.146Po2,g/m2s.

    The model is validated by comparing ‘time-to-ignition’ values for iron samples with measured experimental time-to-ignition for this material. Model predictions are between −5 to +28% of measured values. This work also provides ‘burn-rates’ for bulk aluminum and magnesium as functions of oxygen pressure.

    Keywords:

    metal ignition model, kinetic reaction rate Al/Mg, liquid phase metal combustion, time-to-ignition


    Author Information:

    Steinberg, TA
    Principal scientists, Lockheed-ESC, White Sands Test Facility, Las Cruces, NM

    Wilson, DB
    Principal scientists, Lockheed-ESC, White Sands Test Facility, Las Cruces, NM

    Benz, FJ
    Laboratory Chief, NASA, White Sands Test Facility, Las Cruces, NM


    Paper ID: STP24859S

    Committee/Subcommittee: G04.02

    DOI: 10.1520/STP24859S


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