Experimental And Numberical Studies On Flow Field Of A Coal Burner With Bumping Separator And Pre-combustion Chamber

As the most widely combustion equipment in the energy industry, there still exist a lot of problems in pulverized coal fired boilers, such as low efficiency, low load stable combustion ability, serious pollution of combustion. Burners are key combustion devices in boilers, and play a very important role. It is important for the safe and economic operation to study the performance of burners. Based on the mechanism of stationary combustion in burners the thought is put forward about the burner with a bumping separator and pre-combustion. The author studies the flow characteristics of the burner by numerical simulation, and optimizes the burner structure. In order to further explore the flow characteristics, the experimental system has been designed and built used for measuring combustion performance. The system has been used for exploring the characteristics of the burner with a bumping separator and pre-combustion.For the burner with a bumping separator and pre-combustion, the physic and mathematic models as well as the boundary and convergence conditions are defined. By Fluent the author studies the effect of the baffle location, the velocities of the primary and secondary air on the recirculation zone. If the spacing between the primary air outlet and the baffle is80mm, the recirculation zone behind the baffle increases when the velocity of the primary air rises. The radial length of the recirculation region at the outlet is proportional to the swirl strength, and the axial length of the recirculation region is proportional to the velocity of the primary air. When the swirl intensity is2and the velocity of the secondary air is30m/s, the radial and axial length of the recirculation zone are respectively390mm and980mm. The recirculation length of the secondary air has a peak with the change of the ratio of the primary air to the secondary air. Because of condensation and function there is a high concentration zone in the pipeline for the primary air and near the baffle.Experimental system has been designed and built, and it has been used for exploring the characteristics of the burner with a bumping separator and pre-combustion. The experimental results have been compared with the results from numerical simulation. The experimental results indicated that the distribution of the tangential and axial velocities at the burner exit depends mainly on the velocity of the secondary air. The velocity of the primary air has almost no any effect on the distribution. When the spacing between the primary air outlet and the baffle is80mm and the axial and tangential angles for the radial holes are respectively30°, the spread angle and the swirl strength are27°and0.99separately. The distributions of the tangential and axial velocities are in accordance with the results by numerical simulation. The axial length in the recirculation region has a certain error compared with the result by numerical simulation due to the accuracy of the measuring apparatus and the tightness of the experimental system.