Experimental Study of Gliding Arc Plasma-Assisted Combustion in a Blast Furnace Gas Fuel Model Combustor: Flame Structures, Extinction Limits and Thermoacoustic Characteristics

A gliding arc plasma was employed to assist the blast furnace gas /air combustion with different equivalence ratio. Flame chemiluminescence, the pressure and heat release rate pulsation were recorded simultaneously for showing the combustion characteristics of blast furnace gas. The experimental result demonstrates that there are six flame structures in the combustion process of blast furnace gas fuel: A stable flame with short U-shaped (SS-Flame), a vertical oscillating flame (VO-Flame), a stable flame with long U-shaped (SL-Flame), a special gourd-shaped flame (SG-Flame), a lifted flame (L-Flame) and a continuous extinct flame (CE-Flame). According to characteristics of flame structures before flameout, all cases can be divided into three types of extinction modes: I: Direct extinction, II: Oscillation extinction, III: Lifted extinction. The equivalence ratio of extinction limits at the low volume flow rate of air is more likely to be extended by gliding arc plasma than those at the high volume flow rate of air. The pressure and heat release rate pulsation experiment result shows that the violent oscillation of the heat release can be one of the prediction indexes of the flameout of blast furnace gas fuel. In all cases, the pressure pulsation of blast furnace gas fuel combustion is ±10 Pa, and there is no obvious dominant frequency of heat release pulsation. The amplitude of heat release rate decreases from 0.04V to 0.01V with gliding arc plasma addition at ϕ = 0.7 (E-1 case). Meanwhile, the flame structure of blast furnace gas fuel changes from VO-Flame to SS- Flame due to the gliding arc anchoring the flame root.