【作者】 王天宇；

【导师】 何玉荣；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2013， 硕士

【摘要】 流化床系统是利用固体流态化技术，使颗粒悬浮于流体介质中而改变颗粒之间的接触形式，使颗粒具有拟流体性质的工业设备。流化床最早出现于化工工业，随后引入能源行业，并引发了巨大的技术变革。鼓泡流化床是流化床设备中重要的一类，在能源、化工、冶金、制药和生物工程等行业内具有广泛的应用，对鼓泡流化床运行机理的探索一直是研究的热点。经过近几十年的发展，鼓泡流化床内气固两相流动的研究已经取得了初步的成果，并得到了流场结构及部分颗粒动力学特性，奠定了一定的理论基础。随着研究的深入，更多的问题呈现了出来，比如对颗粒小尺度上的动力学特性的研究及相关模型参数的影响等。本文针对以上问题进行了相关的模拟研究，主要分析了颗粒的动力学特性。本文依据欧拉-拉格朗日模型的基本原理，建立了气固两相流动的计算模型，气相采用连续模型，直接求解体积平均的纳维-斯托克斯方程，并加入大涡模拟方法，对Smagorinsky亚格子模型中的Smagorinsky常量进行了改进，采用函数形式的Smagorinsky常量；固相采用离散颗粒硬球模型，并研究了单组份和双组份固相在鼓泡流化床内的不同颗粒行为。对颗粒平移和旋转动力学特性进行了分析，着重研究了颗粒的平移和旋转速度脉动情况，考察了入口空气速度、床层高度、双组份固相份额和不同弹性恢复系数等参数对颗粒动力学特性的影响。对单组份固相的鼓泡流化床气固两相流动的模拟结果显示，采用欧拉-拉格朗日法的离散颗粒模型（DPM）模拟并选用Beetstra曳力模型和0.97的法向弹性恢复系数的模拟结果与Müller等人的实验结果符合较好，而不同的模型参数对颗粒的动力学特性具有不同的影响：曳力模型主要影响颗粒的宏观运动特性，表观气速全面影响颗粒的运动特性，而法向弹性恢复系数对颗粒运动特性虽然有较大影响，但规律性不强。对双组份固相的鼓泡流化床气固两相流动的模拟结果表明，采用欧拉-拉格朗日法进行模拟，固相应用离散颗粒硬球模型，气相采用大涡模拟方法，其中Smagorinsky亚格子模型应用了变化的Smagorinsky常量形式，其模拟结果与Lu等人的实验数据吻合良好。由于大小颗粒的存在，床内的颗粒碰撞较为复杂，其颗粒动力学特性的变化规律也更加复杂。颗粒的平移速度、气泡颗粒温度和颗粒平移温度等参数会随着床层高度的升高而增加，但对颗粒旋转特性的影响规律性不强。改变颗粒的固相组份对颗粒动力学特性规律影响不大，但影响大小。法向弹性恢复系数主要影响颗粒的小尺度速度脉动，即对颗粒平移温度和颗粒旋转温度有较大影响，而对颗粒速度和旋转速度的影响不大。更多还原

【Abstract】 A fluidized bed is a system using the solid fluidized technology, making theparticles suspended in the fluid medium, thereby changing the contact form ofparticles and giving the particles fluid-like properties. Fluidized bed was firstused in the chemical industry, followed by the energy industry and sparked ahuge technological change. Bubbling fluidized bed is kind of fluidized beds, andhas a wide application in energy, chemical, metallurgical, pharmaceutical andbio-engineering and other industries. The research on the bubbling fluidized bedhas also been one of the hot research fields.For decades of development, some basic rules of bubbling fluidized bedwere found including the flow structures and particle characteristics. Withfurther researches, however, there had also been some more problems, includingtranslational motion and rotational motion characteristics and the characteristicsof the model parameters related to its specific impacts. Therefore, this work isfocused on the microscopic dynamics of particles, and trying to solve theproblems mentioned above.The simulation in this work is based on the Eulerian-Lagrangian model, andthe basic principles of the gas-solid two-phase flow were formed. A continuousmodel was used for the gas phase, which solved the volume-averagedNavier-Stokes equations directly and added large eddy simulation method withthe mutative Smagorinsky constant in Smagorinsky sub-grid model. The discreteparticles hard sphere model and the one-component and binary solid phase wereused for the solid phase. Particle dynamic characteristics, including thetranslation and rotation movement were investigated, and focused on themicroscopic scale of particle translational and rotational speed pulsations. Thecharacteristics of the model parameters such as inlet air velocity, bed height,different component of solid phase and the coefficient of restitution wereinvestigated.For the one-component solid phase bubbling fluidized bed, the approach ofDPM model with the Beetstra drag model and normal restitution coefficient of0.97can simulate the experiment of Müller et al. Drag model mainly affects the macroscopic particle motion characteristics, the superficial gas velocity has aninfluence on all of the particle motions, while the normal coefficient ofrestitution has a greater impact on particle characteristics, but there is no obviouspattern.For the binary solid phase bubbling fluidized bed, the approach of DPMmodel with large eddy simulation method with the mutative Smagorinskyconstant in Smagorinsky sub-grid model can simulate the experiment of Lu et al.Because of the presence of big and small particles, the mechanism of particlecollision is more complex. Particle translational velocity, bubble granular andparticle translational granular temperature will increase as the bed heightincreases, but for the particle rotation characteristics there is no law. Thedistribution of the particle dynamic characteristics will not be changed by thedifferent component of solid phase, but the magnitude will be changed. Normalrestitution coefficient can affect the small-scale velocity fluctuations such asparticle rotational granular temperature and particle translational granulartemperature, while there is little effect on the particle translational and rotationalvelocity.更多还原