Flammability characteristics and structure of a pulverized coal, laminar opposed jet diffusion flame

Abstract

A novel use of the opposed jet diffusion flame in an experimental study of laminar, pulverized coal flames is described. The opposed jet configuration has previously only been used to study gaseous diffusion flames stabilized either between two jets or off evaporating surfaces. In those cases it yielded information on fuel pyrolysis and so its extension to pulverized coal seems well motivated. It is shown, both theoretically and experimentally, that the p.f. laminar opposed jet flameis one dimensional in species concentration and temperature. Particle size segregation does occur but, provided Stokes drag is applicable, the one dimensionality holds for particle size and number density even when particles do not follow gas streamlines. In general, the opposed jet configuration allowed investigation of the effects of non-premixingof pulverized fuel and oxygen on flame structure and characteristics. Although fundamentally different, this flame possessed some surprising similarities to premixed pulverized coal-air flames. Because of its one dimensionality in temperature and species concentrations and because of apparent similarities in propagation mechanisms, the opposed jet flame can be viewed as the diffusion flame analog to more traditional premixed flame studies.