Experimental study of ignition and combustion characteristics assisted by laser-induced plasma during oxy-coal atmosphere by optical emission spectroscopy

Abstract

This investigation aims to understand the enhancement characteristics of plasma-assisted combustion in oxy-coal combustion. A 1064 nm Nd:YAG laser was added into a laminar flow reactor to produce laser-induced plasmas (LIPs). The high-speed visualization of the coal flame was used to reveal combustion's progress and evolution following laser-induced breakdown. To the best of our knowledge, this is the first time LIP has been applied to the optimization of pulverized coal combustion. The optical emission spectroscopy (OES) demonstrats that LIPs can generate adequate free electrons and ions during combustion. When the laser's pulse interval exceeds 60 ms, the LIP has a beneficial impact on combustion. For the heterogeneous reaction, the thermal effect generated by LIP only improves the intensity of flame radiation by 11–33 %. In contrast, the combination of chemical and thermal effects of plasma can result in significant enhancements of radiation intensity for high-volatile coals, with improvements of 76–203 %. Following laser-induced breakdown, the ignition delay time also decreases from lignite to anthracite, and the flame's peak intensity occurs earlier.