干煤粉弥散特性的实验研究与数值模拟

Experimental Study and Numerical Simulation of Dispersion Characteristics of Dry Coal Powder

通过改变操作参数、粉体物性和喷嘴结构参数对干煤粉进行弥散特性实验研究,并结合弥散相模型(DPM)对喷嘴出口弥散过程进行数值模拟,获得了干煤粉浓度、气体流量及喷嘴结构等参数对粉体弥散特性的影响规律。结果表明:中心气流速度从175m/s增大到275m/s有助于气固两相流充分混合,改善弥散参数,促进颗粒分布均匀,明显改善弥散质量。当外环气固两相流速度由6m/s增加到10m/s时,对下游弥散质量的改善不明显;固体质量流量由30kg/h增大到70kg/h会导致下游弥散质量逐渐恶化,出现颗粒均匀性下降、重力沉降加强等现象。当内部旋流角度由30°增加到60°对下游颗粒弥散特性的影响较小,但是颗粒分布比内部无旋流弥散场的均匀性有明显改善。

The effects of operation parameters, the powder properties and the nozzle struc- ture parameters on dispersion characteristics of dry pulverized coal were studied experimental- ly, the discrete phase model （DPM） was used to numerically simulate the nozzle dispersion characteristics, and the influence of the dry pulverized coal concentration, gas flow rate and the nozzle structure on powder dispersion law were obtained. The results showed that in- crease of center air velocity from 175 m/s to 275 m/s enhanced the mixing of gas-solid two phase, improved the dispersion parameters and promoted the uniform distribution of the par- ticles, which can significantly improve the quality of dispersion. When the velocity of outer ring gas-solid two phase flow is increased from 6 m/s to 10 m/s, the downstream dispersion quality improvement was not obvious. As solid mass flow rate is increased from 30 kg/h to 70 kg/h, dispersion quality gradually deteriorated in downstream, such as particle uniformity declining, gravity settling enhancement and so on. When the angle of internal rotational flow is increased from 30°to 60°, the effect on the dispersion characteristics of particles in down- stream is smaller, compared with dispersion of internal irrotational flow, the uniformity of the particle size distribution was more obviously improved.