Diagnostic investigation of devolatilization, ignition, and flame fluctuation during laminar oxy-coal combustion

The rapid development of measurement technology has created possibilities for the advancement of intelligent combustion diagnostics. The high-speed OH-PLIF was used to investigate homogeneous ignition and combustion characteristics of gas-solid two-phase flame in a laminar flow reactor of oxy-coal combustion. The primary focus is to investigate the physico-chemical processes of gas-solid interaction during the early stages of combustion. The image processing was employed to analyze the flame features and then obtain the ignition mechanism, OH distribution, species radiations, and fluctuation frequency. Results show that the homogeneous reaction dominates the ignition and volatile combustion at the early stages of oxy-coal flame. The ignition delay time and volatile burning time decrease with the increasing gas temperatures and oxygen concentrations. The fluctuation dominant frequency increases from 190.5 Hz to 243.2 Hz at the ambient temperature from 1200 to 1800 K. The dominant frequency stabilizes between 243.2 Hz and 243.5 Hz at the ambient temperature from 1500 to 1800 K. The dominant frequency undergoes a shift to a maximum limit of 243.5 Hz from 1200 to 1800 K. When the oxygen concentration increases from 20 % to 40 %, the dominant frequency continues to rise from 244.8 Hz to 268.7 Hz.