Burner nozzle structural design is a key factor influencing flame stability. It directly determines the sustainability and safety of the combustion process by regulating the fuel-air mixing process, airflow velocity distribution, and flame anchoring mechanisms. As the starting point of fuel injection, the nozzle's geometry, dimensional parameters, and internal flow channel design significantly influence airflow entrainment, vortex formation, and combustion reaction rate at the flame root, thereby affecting the flame's anchoring and diffusion characteristics.
Nozzle outlet diameter is a key parameter for controlling fuel flow rate and injection momentum. A smaller outlet diameter increases the fuel injection velocity, enhancing its ability to entrain the surrounding air and forming a more uniform fuel-air mixture near the nozzle outlet. This design helps shorten flame length and minimize flame interaction with the burner wall, thereby reducing the risk of flame failure. Conversely, an excessively large outlet diameter reduces fuel flow rate and uneven mixture concentration, which can lead to locally rich or lean flames, causing flashback or flame failure.
The nozzle's internal flow channel structure plays a decisive role in fuel atomization. By optimizing the flow path geometry, such as using a swirl or Venturi tube structure, the fuel can be spun or accelerated during injection, enhancing the shear interaction between the fuel and air, thereby breaking the liquid fuel into finer droplets. These fine droplets not only increase the contact area between the fuel and air, but also shorten evaporation and mixing time, resulting in more uniform flame propagation and effectively suppressing flame pulsation caused by localized poor mixing.
The matching design of the nozzle and the combustion chamber head structure is crucial for maintaining flame stability. The nozzle must work in conjunction with the burner holes, flame stabilization disk, and other components in the combustion chamber head to ensure that the fuel-air mixture enters the burner holes at the appropriate velocity and angle. For example, in a swirl burner, the coordinated design of the nozzle and swirler generates tangential velocity in the airflow, creating a stable swirl field and enhancing the flame's resistance to interference. Furthermore, the spacing and arrangement of the burner holes must be aligned with the nozzle's characteristics to avoid insufficient flame overlap due to excessively large burner hole spacing, or flame competition due to too small a spacing.
The side holes in the nozzle are an effective means of regulating the primary air volume. For fuels prone to yellowing flames, such as liquefied petroleum gas, circular side holes in the nozzle's sidewalls can introduce additional primary air, optimizing the mixture concentration and reducing soot generation. The size and number of the side holes must be precisely designed based on the fuel's characteristics. If the side holes are too large, excessive primary air may result in a lean mixture and misfire; if the side holes are too small, they may not meet the requirements for complete combustion. This design dynamically adjusts the air-to-fuel ratio to maintain a stable flame under various operating conditions.
The nozzle's geometry guides the direction and location of the flame's propagation. For example, compared to a circular nozzle, an elliptical nozzle can modify the axial and radial velocity distribution of the airflow, slowing the flame's rise and increasing its peak temperature while reducing heat radiation to the surrounding environment. This design optimizes the flame shape, enhancing heat exchange efficiency between the flame and the combustion chamber walls, and improving overall combustion stability.
The nozzle's material selection and manufacturing precision also influence flame stability. In high-temperature environments, the nozzle must possess excellent heat and corrosion resistance to prevent material deformation that could cause the spray direction to shift. Furthermore, nozzle machining accuracy must be strictly controlled to ensure that parameters such as outlet diameter and side hole position meet design requirements. This prevents uneven airflow distribution caused by manufacturing errors, which in turn affects flame stability.
Burner nozzle structural design plays a key role in improving flame stability by regulating fuel injection characteristics, the mixing process, and the flame anchoring mechanism. Proper nozzle design not only optimizes combustion efficiency and reduces pollutant emissions, but also enhances the burner's adaptability to different fuels and operating conditions, providing a fundamental guarantee for the reliable operation of industrial combustion equipment.
