Abstract: In order to study the combustion characteristics of jet flames formed by natural gas pipeline leakage fires, a CH4 laminar combustion system was independently constructed and the morphology, temperature and charged particle concentration transport law of the flame above the jet outlet were analysed by comparing the response characteristics of the flames with different nozzle sizes under the conditions of 0.48~0.72 L/min jet flow. The results show that for the same nozzle size, the geometry of the jet flame and the average temperature of the measurement point increase with the increase of the jet flow rate, but the jet exit temperature for different nozzle sizes decreases with the increase of the nozzle flow rate. In addition, the value of the ionic current at the flame root increases the closer to the nozzle region, but the maximum value does not exceed 1.0 μA, and the rate of change of the flame axial ionic current decreases with the increase of the flow rate, and the value of the ionic current at the flame edge decreases with the increase of the distance between the measurement point and the nozzle.

Key words: jet flame, combustion characteristics, flame form, flame temperature, ionic current