High-energy Nd:YAG laser ignition of coals

摘要

Abstract: the main purposes of the present study is to explore the use of laser radiation to initiate and support combustion of coals. Within this context, some experiments were conducted to study the interaction of the Nd-Yag laser radiation with four different coals. Laser intensities ranging from 0.5 $MUL 10$+3$/ to 1.5 $MUL 10$+4$/ W/cm$+2$/ at 1.064 $mu@m wavelength and the pulse duration of 5 ms were used. For laser intensities less than 800 W/cm$+2$/, no ignition was observed for all coals. For laser intensities above this value, two ignition mechanisms were observed: the surface ignition followed by the gas phase ignition when Wyoming subbituminous, Indian lignite and North Dakota lignite coals were used. For the same range of the laser intensities, however, only the gas phase ignition was observed when Pittsburgh bituminous coal was used. It was also noted that a significant amount of the external laser radiations were absorbed by the pyrolysis products during the early stages of the ignition period.!8