What are the reasons for the deviation of the airflow in a direct-fired burner with a four-corner configuration and how does it affect combustion?
What are the reasons for the deviation of the airflow in a direct-fired burner with a four-corner configuration and how does it affect combustion?
The reason for the deviation of the airflow is mainly:
(1) The pressure difference causes the airflow to be pushed to one side. Due to the fact that the four-corner jet of a direct-fired burner intersects the center imaginary circle of the combustion chamber or the cross-sectional area of the combustion chamber is not square, the angle between the two sides of the jet and the wall of the combustion chamber is different. The side with a larger angle has a larger space and the high-temperature flue gas replenishes the space more fully; while the side with a smaller angle replenishes the gas insufficiently, causing the static pressure of the larger angle side to be higher than that of the smaller angle side. Under the action of the pressure difference, the jet deviates towards the smaller angle side. The difference in the width-depth size of the combustion chamber, the larger the diameter of the circular cut, the greater the difference in the two angles, the greater the pressure difference, and the greater the deviation of the jet.
(2) The transverse thrust of the jet from the upstream corner burner forces the airflow to deviate.
(3) The rigidity of the jet also affects the deviation of the airflow. The higher the velocity of the jet, the greater the momentum, the larger the area of the nozzle opening, and the smaller the ratio of the height to the width of the nozzle, the greater the rigidity, and the smaller the deviation of the jet. On the contrary, the rigidity is worse, and the airflow deviation is greater.
When the deviation of the airflow is small, it can improve the gas flow condition in the combustion chamber, so that some high-temperature flue gas can replenish the root of the airflow from the adjacent burner, not only ensuring the rapid ignition and stable combustion of the coal-air flow, but also avoiding slagging. This is a relatively ideal gas dynamic condition in the combustion chamber. However, when the deviation of the airflow is too large, it will form an airflow clinging to the wall, causing wall slagging and tube bank erosion, and there is a large no-blow area in the center of the combustion chamber, and the degree of flame filling is reduced.