Accession Number : AD0669489

Title :   EXPERIMENTAL BURNING RATES AND COMBUSTION MECHANISMS OF SINGLE BERYLLIUM PARTICLES,

Corporate Author : PURDUE UNIV LAFAYETTE IND PROJECT SQUID HEADQUARTERS

Personal Author(s) : Macek,Andrej ; Semple,J. McKenzie

Report Date : MAR 1968

Pagination or Media Count : 28

Abstract : Single spherical beryllium particles from two powder samples having average particle diameters of 32 microns and 25 microns respectively were injected into oxidizing gases, both moist and dry, at atmospheric pressure and at temperatures ranging from 2600 to 2950K. The purpose was accurate measurement of metal burning rates and a study of parameters affecting these rates. Ignition efficiencies, burning rates, and flame diameters of particles were found to vary both with particle diameters and with ambient gas properties. It is concluded that beryllium particles may burn by several distinct modes. One is rapid vapor-phase diffusion flame, favored by high partial pressures of oxygen and high temperatures of the gaseous environment. The burning times corresponding to this mode, measured with accuracy of plus or minus 0.1 msec and ranging from 1.3 to 4.5 msec. were found to be proportional to the square of the particle diameter and inversely proportional to a power of oxygen pressure slightly less than unity. As the partial pressure of oxygen is decreased below a certain value which is usually between 0.1 and 0.2 atm, the metal flame temperature decreases and vapor-phase combustion gradually changes over into slow surface reaction. There is also evidence of a third mode in which combustion is only moderately slower than the rapid vapor-phase burning. This mode, favored by low temperature and by the presence of water vapor in the environment, may be vapor-phase combustion hindered by a heavy coating of beryllia accumulated on the particle during the pre-ignition surface reaction. (Author)

Descriptors :   (*BERYLLIUM, *COMBUSTION), SOLID ROCKET PROPELLANTS, ADDITIVES, POWDER METALS, IGNITION, BURNING RATE, FLAMES, VAPORS, OXIDIZERS, OXYGEN, BERYLLIUM OXIDES

Subject Categories : Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE