【作者】 陈博；

【导师】 范浩杰；

【作者基本信息】 上海交通大学 ， 动力工程（专业学位）， 2016， 硕士

【摘要】 内循环流化床在现代工业生产中得到了广泛应用,然而由于高温导致的床料结焦结渣问题会使床料流化运动受阻,时常对安全生产造成影响。床料的运动总体上具有内部循环的特点,但是具体而言,床内的气固两相流在颗粒冷态、粘性态以及发生团聚后这三种状态下都具有很高的复杂性,深入研究颗粒在内循环流化床内的运动规律对于合理设计和改进内循环流化床很有意义。为研究颗粒在内循环流化床内的运动规律,本课题利用具有低温粘熔特性的模拟物,在二维半热态流化床实验台上进行冷态、粘熔态及团聚态的流化实验,运用CCD摄像技术、粒子图像测速技术(Particle Image Velocimetry,PIV)及DEM模拟对内循环流化床内流化特性进行研究。论文进行了内循环流化床内颗粒流化的实验模拟,总结了颗粒运动的总体规律,分析了流化风速和温度对颗粒运动的影响,并与床内气泡的运动规律以及DEM模拟得出的颗粒运动规律进行了比较。实验结果表明:气泡在床内运动路径为倾斜向上,可以概括为“两个过程,四个阶段”。气泡首先经历长大过程,该过程分底部长大阶段和中部长大阶段,底部阶段气泡长大快,运动快,中部阶段长大慢,运动慢;之后经历衰减过程,分为拉长阶段和爆破阶段,拉长阶段气泡长大慢,运动较快,爆破阶段气泡减小迅速,运动速度最快。高低风速比和温度因素都对气泡运动有明显影响。合理的高低风速配比可以使气泡运动更为充分,提升床内流化效果;较低的温度,可以减小颗粒粘性,阻止颗粒团聚,对提高以气象为动力的床内气固两相流流化效果有明显作用。颗粒在内循环流化床内的运动总体上具有循环性,在床中部形成循环运动;非均匀布风可以加强颗粒的横向运动;高低风速比和温度因素对颗粒在内循环流化床内的运动有显著影响。高低风速大小对循环运动方向有影响,当高速风不够大时,颗粒循环方向为顺时针,当高低风速比增大2:1后,循环方向变为逆时针;另外,倾斜布风板带来的床层压力差异也对循环方向有影响;温度升高后,颗粒会产生粘性,当粘性力增大到一定程度后,在特定工况下,会使床内颗粒循环运动方向发生改变。更多还原

【Abstract】 Internal circulating fluidized bed in modern industrial production has been widely used,however,due to the high temperature caused by the bed agglomeration problems can make the bed material flow movement is blocked,often affect production safety.The movement of bed material has the characteristics of internal circulation,but it is very important to study the motion law of the particles in the bed,which is a very important part in the design and improvement of inner circulation fluidized bed.In order to study the motion of particles in the inner circulation fluidized bed,this paper uses Particle Velocimetry CCD(PIV)and particle image velocimetry(Image)and DEM to simulate the particle movement in the internal circulating fluidized bed.In this paper,the experimental simulation of particle flow in internal circulation fluidized bed is carried out,and the general rule of the particle motion is summarized.The influence of the flow velocity and temperature on the particle motion is analyzed,and the motion law of the bubble in the bed is compared with that of DEM simulation.The experimental results show that the moving path of the bubble in the bed is four stages,which can be summarized as "two processes".The process of bubble growth,the growth of the process,the growth of the bottom and the middle of the growth stage,the bubble at the bottom of the stage,moving fast,slow motion,slow motion,and then through the process of decay,which is divided into elongated and explosive.High and low wind speed ratio and temperature have obvious effects on the bubble movement.The reasonable ratio of high and low wind speed can make the bubble movement more fully,improve the flow of the bed,lower temperature,can reduce the particle viscosity,prevent particle agglomeration,improve the gas and solid two phase flow in a fluidized bed with the weather as the driving force.The movement of particles in the circulating fluidized bed is generally circular,in the middle of the bed to form a circular motion;the wind can strengthen the lateral movement of the particles;The high and low wind speed ratio and temperature have significant influence on the movement of particles in the inner circulation fluidized bed.The high and low wind speed has effect on the direction of the circular motion,when the speed of the particles is not large enough,the direction of the particle circulation is clockwise,and the ratio of the high and low wind speed increases,and the pressure difference of the bed layer is also affected by the temperature rise.When the temperature rises,the particles will be changed to a certain extent.更多还原