Medium-speed natural gas industrial burners reduce flame licking by optimizing the combustion chamber structure. This requires systematic optimization in three areas: flow field organization, flame stabilization, and coordinated design of geometric parameters.
Combustion chamber flow field organization is key to controlling flame shape. Traditional straight-cylinder burners are prone to flame deflection due to uneven air velocity decay. However, a converging-diverging structure creates a uniform recirculation zone. In the converging section, the airflow is accelerated, creating negative pressure, inducing high-temperature flue gas to flow back to the burner outlet, providing a stable anchor point for the flame. The diverging section, through its deceleration effect, extends the flue gas residence time, ensuring thorough mixing of the fuel and air. This structure prevents the flame from directly contacting the furnace wall while maintaining combustion stability through heat feedback from the recirculation zone. For example, after implementing this structure in an industrial boiler retrofit, flame licking frequency was reduced by 60%, and the furnace wall temperature fluctuation range was narrowed to ±15°C.
Optimizing flame stabilization devices requires a consideration of burner power and fuel characteristics. For medium-speed burners, the combined design of a swirler and flame stabilization disk can significantly enhance flame rigidity. A swirler generates a tangential velocity component, creating a swirling airflow that thoroughly mixes fuel and air under centrifugal force. Simultaneously, the swirling airflow creates a low-pressure zone that stably captures high-temperature flue gas, forming an internal recirculation zone. A flame stabilization disk redirects the airflow, creating an external recirculation zone at the burner outlet. The synergistic effect of these internal and external recirculation zones broadens the flame stability range. During a furnace renovation at a petrochemical company, the use of an adjustable swirler combined with a conical flame stabilization disk reduced flame length by 20%, completely eliminated licking, and increased thermal efficiency by 3.2%.
The matching design of combustion chamber geometric parameters must adhere to the principles of fluid dynamics. The length-to-diameter ratio (L/D) of the combustion chamber is a critical parameter. An excessively small L/D will result in the flame contacting the furnace wall before full development, while an excessively large L/D may cause flame pulsation. Medium-speed burners typically adopt an L/D design of 3 to 5, which ensures complete combustion of the fuel while preventing excessive flame elongation. Furthermore, the combustion chamber inlet angle must precisely match the direction of fuel injection, typically with an inclination of 30° to 45°. This allows the airflow to enter the combustion chamber tangentially, minimizing interference with the main flow field. During a steel mill's rolling mill reheating furnace renovation, adjusting the combustion chamber inlet angle from 15° to 40° and reducing the flame deflection angle from 25° to 8° eliminated the number of furnace wall overheating alarms.
Material selection and surface treatment also play a supporting role in reducing furnace licking. A high-temperature alloy substrate combined with an alumina coating significantly reduces the thermal conductivity of the furnace wall, reducing the heat flux in the flame contact area by over 40%. Furthermore, ceramic fiber insulation layers applied to key areas of the combustion chamber not only reduce heat transfer to the furnace wall but also suppress localized flame overheating through their low thermal conductivity. During a ceramic kiln renovation, adding a 5mm-thick ceramic fiber layer to the combustion chamber sidewall reduced the furnace wall surface temperature from 320°C to 180°C, and the equipment failure rate due to furnace licking decreased by 75%.
Through optimized flow field structure, improved flame stabilization devices, precise matching of geometric parameters, and upgraded materials, the medium-speed natural gas industrial burner systematically addresses the flame licking problem. In actual projects, the optimal structural parameters must be determined based on specific operating conditions through a combination of CFD simulation and experimental verification, ultimately achieving both improved combustion efficiency and equipment safety.
