导向管喷动床内单相流场及声波对流场影响的数值模拟

为阐明超细粉在声场导向管喷动流化床内的流化机理,并为进一步优化和完善床层结构及操作条件提供基础,采用标准k-ε湍流模型计算了导向管喷动流化床内的单相气体流场,考察了进口流化气速和射流气速对气体流动规律的影响,以及声场对导向管喷动流化床内气体轴向速度分布及其脉动均方根的影响。结果表明:在高速射流条件下,导向管喷动流化床内气体呈内循环流动,气体循环流量随流化气速度的增加而减小,但随射流气速度的增加而增加;外加声场使环隙区和喷泉区的气体流动更加均匀,显著增加环隙区和喷泉区气流的湍动程度,且湍动程度随声压级的增大而显著增大,随声波频率的升高而小幅度降低。

Numerical Simulation of Single-Phase Flow and Influence of Acoustic Field in a Spouted-Fluidized Bed with a Draft Tube

In order to elucidate the fluidization mechanism of ultrafine powder in the spouted-fluidized bed with a draft tube and establish the foundation for further optimization and improvement of the fluidized bed structure and operating conditions, the numerical simulation of the flow field in the spouted-fluidized bed with draft tube was carried out using the standardk-ε turbulence model. The effects of inlet fluidizing gas velocity and ejecting gas velocity on the flow field and velocity distribution were investigated. Meanwhile the effects of sound pressure level and sound frequency on distribution of axial gas velocity and root mean square (RMS) in annulus and fountain areas were investigated, respectively. The results showed that the gas flow in the spouted-fluidized bed with draft tube was characterized by the internal circulation at high velocity jet flow. The gas flow rate decreased with the increase of the fluidizing gas velocity and increased with the ejecting gas velocity. The introduction of sound field made the distribution of the gas flow in annulus area and fountain area more uniform, which significantly increased the intensity of turbulence in annulus and fountain area. The intensity of turbulence increased with the increase of sound pressure level and decreased slightly with the increase of sound frequency.