Clearinghouse for Federal Scientific and Technical Information Cfsti Document Management Branch 410.11 Limitations in Reproduction Quality

Available data on critical energies for ffostained ignition of black alpha-cellulose paper in the absence of forced convective heat losses are correlated against exposure time on a nondimenslonal basis. Investigations cover a range of irradiance from 2 to 25 cal/cm^sec, exposure time from 0.1 to ^ 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, QR/pcLE and the Fourier modulus, at/L for a constant value of F/RT0 equal to 44For 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 the equation ^ = 0.080 at 0.5 pcLE ' L These results are valid for paper moisture contents of 4 to 5 percent, initial paper temperatures between 0 and 60C, and irradiance levels above the critical irradiance, estimated to be 2 jal/cnrsec. Presented correlations are within a maximum error of ±15 percent. Regions of ignition, transient flaaiing, destruction (without flame), and nondestruction are illustrated in terms of the abovementioned dimensionless moduli.