Mathematical and physical modeling of the coal–water fuel particle ignition with a liquid film on the surface

Abstract

The results have been presented of the theoretical and experimental research of the ignition processes of single drops of coal–water fuel (CWF). Their surface is covered by a water film. The temperature of the environment Tehas also been recorded and the main characteristics of the process — the times of complete evaporation of the water film (tewf)) and the ignition delays (tign). The errors in determining Tehave not exceeded 5%.According to the results of the detailed analysis of the video recordings of the investigated process of ignition, the mathematical models have been developed. They describe the interrelated complex of the thermophysical and thermochemical processes. The approximate analytical solutions of the multistage nonlinear problem of ignition of a coal–water particle have been obtained using the asymptotic procedures.According to the results of the experimental and theoretical studies, it has been established that the thickness of an aqueous film is one of the parameters determining the conditions and characteristics of the CWF ignition. Moreover, under the conditions of the experiments it has been established that the characteristic evaporation time of the near-surface layer can be from 45 to 60% of the total induction period. They depend on the thickness of the film.

Keywords

• Ignition
• Coal-water fuel
• Water film
• Asymptotic procedures
• Particle