Efficiency study of low calorific value high momentum turbulent jet combustion flame

The industrial torch system is used to handle large amounts of flammable, toxic, and corrosive gases emitted during accidents or normal production processes. It utilizes open flames to burn off the gas pollutants. This study employs computational fluid dynamics (CFD) to investigate the combustion characteristics and efficiency of flames under high-velocity jet, aiming to address the issue of low combustion efficiency under high-velocity jet conditions. A three-dimensional flame model was established using methane and air as fuel, in order to investigate the variations and impact mechanisms of the combustion flame temperature field and carbon dioxide mass fraction distribution under different jet velocities, pilot component temperatures, and equivalence ratios. The reasons for low combustion efficiency under high-velocity jet conditions were analyzed. It was proposed to increase the combustion efficiency of the flame by raising the temperature of the pilot component, which differs from the traditional method of adding combustion-assisting gases. The combustion efficiency of flames under various operating conditions was evaluated. The results showed that as the jet velocity (v) increased from 49.6 m/s to 65 m/s, the height of the combustion flame in the vertical direction decreased continuously. Additionally, the high-temperature region at the center of the flame gradually decreased, leading to a 5.26% decrease in the highest flame temperature and a 3% decrease in combustion efficiency. When v = 70 m/s, the high-velocity fuel flow penetrated the ignition source, causing a large amount of methane to escape into the atmosphere without combustion, resulting in flame extinction. Elevating the temperature (T) of the pilot component can reduce the impact of high-velocity jet on combustion efficiency. When T = 2000 K, the flame reignites with a combustion efficiency of 94.1%. As the mass flow rate of the fuel composition inlet is reduced from 33.45 x 10-5 kg/s to 12.74 x 10-5 kg/s, the highest temperature of the combustion flame drops from 2072 K to 1451 K. As the equivalence ratio (phi) increases from 1.05 to 1.2, the height of the combustion flame in the vertical direction decreases continuously, resulting in a 0.7% decrease in the highest flame temperature and a 10.5% decrease in combustion efficiency.