Available data on critical energies for sustained ignition of black alpha-cellulose paper in the absence of forced convective heat losses are correlated against exposure time on a nondimensional basis. Investigations cover a range of irradiance from 2 to 25 calsq cm sec, exposure time from 0.1 to 4 seconds, and paper thickness from 2 to 30 mils. Ignition energies for papers of two nominal densities were determined. Results are presented in terms of an energy modulus and the Fourier modulus for a constant value of ERT sub o equal to 44. For Fourier moduli less than 0.4, the energy modulus approaches a constant value of approximately 0.11. As the Fourier modulus increases, the energy modulus decreases to a minimum value of 0.068 at a Fourier modulus of 0. 8. For Fourier moduli above 0.8, the energy modulus increases with exposure time according to a given equation. Regions of ignition, transiet flaming, destruction without flame, and nondestruction are illustrated in terms of the above-mentioned dimensionless moduli.
Interim technical rept.,
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