转筒颗粒流崩塌前后的颗粒温度和体积分数测量  

Measurements of solid volume fraction and granular temperature at granular avalanches in a drum

作　　者：陈泉 杨晖[1] 李然[1] 韩韧[1] 孙其诚[2] CHEN Quan;YANG Hui;LI Ran;HAN Ren;SUN QiCheng(School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;State Key Laboratoiy of Hydroscience and Engineering,Tsinghua University',Beijing 100084,China)

机构地区：[1]上海理工大学光电信息与计算机工程学院,上海200093 [2]清华大学水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《中国科学：物理学、力学、天文学》2019年第6期54-66,共13页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11572201,11572178,91634202)资助项目

摘　　要：转筒中的颗粒流在工业生产中广泛应用,准确描述颗粒流规律对于调控生产中的换热效率和混合效率极为重要,颗粒温度和颗粒体积分数是影响颗粒流的主要参数.本文搭建了基于面阵CCD相机的图像测量装置,以及基于线阵CCD相机的同轴双散斑能见度光谱法(Speckle Visibility Spectroscopy, SVS)测量装置,选取均值粒径为0.5 mm的球形颗粒和等效粒径为0.5mm的不规则颗粒.通过测量转筒中颗粒体系的侧表面轮廓,计算得到颗粒体系崩塌前后的体积分数.发现在崩塌过程中,球形颗粒体系和不规则颗粒体系都发生膨胀;在崩塌前,不规则颗粒体系发生压缩,而规则颗粒体系不发生压缩?进一步,测量了颗粒体系自由表面上不同位置的颗粒温度发现球形颗粒与不规则颗粒的崩塌发生在同一个位置;不规则颗粒体系的压缩首先发生在体系上半部分,并且在一个崩塌周期时间内,压缩现象仅发生一次.最后,根据颗粒体系的侧表面轮廓和颗粒温度大小,确定了休止角和特征时间参数,发现球形颗粒体系休止角与崩塌时间的关系与Davidson提出的模型一致,并发现崩塌前不规则颗粒体系的压缩会缩短颗粒的崩塌时间.实验结果揭示的转筒内颗粒流规律,为完善工业生产中颗粒材料流动与传热的控制技术提供参考数据.A granular flow in the drum has high heat exchange efficiency and mixing efficiency, and is widely used in industrial productions. Accurately describing the flow properties is extremely important for industrial production. In this work, an image measuring device based on area array CCD camera and a Speckle Visibility Spectroscopy (SVS) measuring device based on linear array CCD camera were established. Spherical particles having a mean particle diameter of 0.5 mm and irregular particles having an equivalent particle diameter of 0.5 mm were used. By measuring the profile of the side surface of the granular system in the drum, the volume fractions before and after the avalanche of the granular system were calculated. It was found that both the spherical particle system and the irregular particle system expanded during the avalanche process;before the avalanche, the irregular particle system was compacted, while the spherical particle system did not compact. Furthermore, granular temperature at different locations on the free surface of the granular flow was measured. It was found that the avalanche of the spherical particles and the irregular particles occurred at the same position;the compaction of the irregular particle system first occurred in the upper half of the system, and the compaction phenomenon occurred only once during one avalanche cycle time. Finally, based on the side surface profile and granular temperature, the angle of repose and characteristic time parameters were measured. It was found that the relationship between the angle of repose of the spherical particle system and the avalanche time was consistent with the model proposed by Davidson, and the compaction of the irregular particle system before avalanche would shorten the avalanche time of the particles. The experimental results obtained in this work provide reference data for improving the precise control technology of the flow and heat transfer of the granular materials in industrial productions.

关 键 词：颗粒流 散斑能见度光谱法 颗粒温度 体积分数 阻塞转变(Jamming) 

分 类 号：O347.7[理学—固体力学]