流化床颗粒流动混合特性实验与数值研究

发布时间：2018-07-05 12:00

本文选题：内循环流化床 + 颗粒混合　；参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：内循环流化床在处理垃圾衍生燃料(RDF)燃烧方面具有独特的优势,床内气固两相流动特性直接影响相间传热传质以及化学反应速率。本文着重研究了冷态隔板式内循环流化床中单组分颗粒流动机制和双组分颗粒混合特性,并通过计算流体力学耦合离散单元方法(CFD-DEM)对床内颗粒运动的流场及混合进行了数值模拟。其中欧拉方法处理连续气相场的同时用拉格朗日方法直接跟踪离散颗粒场的单个颗粒运动,从多组分颗粒层面对内循环床内混合机制进行了研究。本文首先以Goldschmidt等人建立的三维矩形喷动流化床为实验基础,对圆柱状RDF颗粒的混合机制进行了CFD-DEM数值模拟,验证了计算结果与实验结果的吻合性。然后自主设计并搭建了冷态隔板式内循环流化床实验台,利用高速摄像机进行了可视化观测,重点讨论了示踪颗粒特性以及高低进气配风比对于孔口处颗粒循环量的影响。最后进行了相同工况下的CFD-DEM数值模拟,结果表明,合理的高低进气配风比是实现颗粒内循环混合的关键因素,同时指出双组分颗粒混合度会随着孔口处颗粒循环量的增大而得到有效改善。内循环流化床能够进一步改善床内的物料混合状态,通过内循环流化床进行的实验和数值模拟取得的研究成果,将对今后燃料颗粒在床内混合提供实际应用价值。
[Abstract]:The internal circulating fluidized bed has a unique advantage in the treatment of garbage derived fuel (RDF) combustion. The gas-solid two-phase flow characteristics in the bed directly affect the heat and mass transfer between phases and the chemical reaction rate. In this paper, the flow mechanism of single component particles and the mixing characteristics of two components particles in a cold partition type inner circulating fluidized bed are studied. The flow field and mixing of particles in the bed are simulated by the coupled discrete element method (CFD-DEM). The Euler method is used to deal with the continuous gas phase field and the Lagrangian method is used to directly track the single particle motion of the discrete particle field. The mixing mechanism in the inner circulating bed is studied from the multi-component particle level. In this paper, the mixing mechanism of cylindrical RDF particles is numerically simulated by CFD-DEM based on the 3D rectangular spouted fluidized bed established by Goldschmitt et al, and the agreement between the calculated results and the experimental results is verified. Then we design and build the cold partition type inner circulating fluidized bed test bed, and make visual observation with high speed camera. The characteristics of tracer particles and the effect of high and low intake air distribution ratio on the particle circulation at the orifice are discussed in detail. Finally, the numerical simulation of CFD-DEM under the same working condition is carried out. The results show that the reasonable ratio of high and low intake air distribution is the key factor to realize the cycle mixing in particles. At the same time, it is pointed out that the mixing degree of two-component particles will be improved effectively with the increase of particle circulation at the orifice. The internal circulating fluidized bed can further improve the material mixing state in the bed. The research results obtained through the experiment and numerical simulation of the inner circulating fluidized bed will provide practical application value for the future mixing of fuel particles in the bed.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X705

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