Shock Wave Ignition of Pulverized Coal,
MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
Pagination or Media Count:
Heating and ignition delay times behind an incident shock of small clouds of coal dust-particles of three different size ranges were measured in a shock tube. Four different compositions of O2-N2 mixtures were used as the oxidizer and the incident shock Mach number varied from 4.1 to 4.8. Observed delay times were in the range 10 to 150 microsec, decreasing with increasing Mach number and O2 concentration. The theoretical analysis is based on the numerical solution of the one-dimensional transient heat equation for a single spherical particle. Particle acceleration has an important effect on heat transfer and is considered in the model. Heating due to gas phase and heterogeneous reactions is represented with appropriate volumetric or surface source terms. The results show that volatilization is insufficient to account for the short delay times observed. The main mechanism for ignition in these short times appears to be heterogeneous surface reaction both on the outside and within the porous particle.