Study On Structure Optimization Of Impact Pre-combustion Chamber Pulverized Coal Burner

There are many problems to influence the boiler operation, such as multivariate fuels, the difference between the designed and used fuels, frequent change of the loads. The pulverized coal burners play an important role in the safe and economic operation for boilers. So it is important to develop a kind of burner which may satisfy the requirements of steady combustion and adjustment at the low loads, flexibility, low emission.Based on the analysis of the design idea of the impact pre-combustion chamber of pulverized coal burner, this thesis discussed the characteristics of the burner and determined the structure parameters by the cold model. The author optimized the structure of the burner by numerical simulation and the flow characteristics measured in the experiment system.In this thesis the parameters of the original model were confirmed by the cold modeling calculation. The parameters included the exit diameter, the tangential and axial angles of secondary air intakes, etc. The author studied the flow field distribution features of the original model. The research results show that there was an open air in the filed. In order to optimize the structure of the burner, the author established the physical model, mathematical model, boundary conditions and convergence condition for the burner, The flow field distribution, concentration distribution and particle trajectories were simulated by Realizable k-epsilon turbulence model. Simulation results show that the exit diameter, the tangential and axial angles of secondary air intakes greatly influence the burner performance. The vortex and entrainment ability of the burner are strengthened with the increase of the burner diameter. The larger the tangential angle is, the bigger the vortex intensity is. The axial angle of the secondary air intake has little influence on the vortex intensity.Numerical simulation for the optimization shows that the reflux area, the concentration field and the particle trajectory may be a good match for the burner with320mm in exit diameter,5°in tangential angle and30°in axial angle. At this time, the reducing atmosphere insided the burner may reduce NOx formation.the high temperature flue gas entrained by the reflux area might maintain the stable combustion.The author simulated the concentration field for the optimized structure. The results show that many particles stagnated in the corner bend when the particles enter the pre-combustion chamber with the primary air. When the particles pass through the baffle, they are concentrated and the performance is helpful to combustion.