不同STOKES数和初始条件对炉内固体颗粒弥散的影响

ANALYSIS OF THE EFFECT OF STOKES NUMBER AND INITIAL CONDITION ON THE DISPERSION CHARACTER FOR THE SOLID PARTICLES IN BOILER FURNACE

采用Eulerian-Lagrangian随机轨道模型方法,对四角切圆炉膛内不同Stokes数的固体颗粒运动进行了分析。通过对比3种粒径颗粒在燃烧器区、炉膛出口等处颗粒速度、体积分数等,显示出由于惯性、跟随性和湍流扩散能力的差异,在炉内的弥散运动也存在不同特点。文中讨论了颗粒运动特性及差异与结渣和烟温偏差等的关系。另外,通过分析起始于不同一次风口的颗粒轨道,发现由于燃烧器区气流变化剧烈,致使不同颗粒在炉膛内飞行距离和停留时间明显不同。模拟结果与3D-PDA测量的颗粒速度进行对比,结果较为吻合。

Gas-solid two-phase flow in a tangentially-fired boiler(TFB) is simulated with Eulerian-Lagrangian stochastic model. Dynamics of the particles with different Stokes number are analyzed by comparing particulate velocities, void fraction of volume and trajectories at burner region and exit of the furnace. Due to such different dynamical properties as inertia, responsiveness to gaseous flow and turbulent diffusiveness, particles with different Stokes number show evident variance of dispersion characters, based on the gas flow pattern in the boiler. The impact of particle dispersions on the problems of TFB such as slagging and gas-side-temperature-imbalance are discussed. It is also found that due to strongly non-uniformity of gaseous velocities on the burner region, the resident time and trajectory length of the particles are sensitive to its starting positions. Predicted results are compared with particulate velocities measured by 3D-PDA, the general good agreement is achieved.