Analysis of particle cloud height dynamics in a stirred tank

Local and temporal variations of the particle cloud formed in a cylindrical mixing vessel were investigated experimentally. Different particle sizes (0.5, 1, and 2 mm) and volumetric concentration up to 20 vol % were evaluated at different impeller speeds. The time‐averaged cloud height was linear with impeller frequency and with volume concentration. Suspensions with larger particles had a lower average cloud height, while the standard deviation for the temporal cloud height variation was larger. Two strong periodic phenomena were identified to be dominating the particle cloud height variations. The frequencies were linear with impeller speed, resulting in dimensionless frequencies of S₁=0.02–0.03 and S₂=0.05–0.06. The frequencies were affected by neither the particle size nor the volumetric concentration. The amplitude showed no dependency on the particle size, but the S₂ amplitude significantly decreases and S₁ increases with increasing solid concentration. The results were compared to LES/discrete element method simulations and showed a fair agreement. © 2015 American Institute of Chemical Engineers AIChE J, 62: 338–348, 2016     

阀笼式调节阀套筒窗口形状设计与流量特性分析

我国的阀笼式调节阀技术起步晚,传统的设计过程常常依赖经验公式,产品的实验结果与设计要求存在较大误差。因此,以阀笼式调节阀套筒为设计对象,基于阀笼式调节阀的孔板流量计原理,推导得到套筒横截面积的通用公式和4种流量特性(直线型流量特性、等百分比型流量特性、抛物线型流量特性和快开型流量特性)不同开度下套筒的横截面积,建立模型并用FLUENT软件进行仿真模拟,将调节阀在不同开度下相对流量的实验值与理想设计值进行对比。结果表明:此设计方法在调节阀开度为30%～80%时具有可靠性,不仅有效满足设计要求,而且该方法设计周期短、成本低、精度高。此外,通过推导的阀笼式调节阀套筒的通用面积公式,可改变套筒进口处和出口处的压力值和不同固有流量特性要求,得到符合特定要求的套筒,故具有一定的工程应用价值。     

压力脉动作用下管道的流固耦合瞬态分析

针对液压输流管内的压力脉动研究,提出流体压力脉动的计算方法和管道流固耦合分析的计算模型。对流体压力脉动进行编程,得到压力脉动作用产生激振力的变化。建立管道和流体实体模型,采用UDF技术将脉动压力编译到流体中,从而进行流固耦合瞬态力学分析,得到异径管和弯管处流体压力变化以及管道的应力和变形情况。研究结果表明:压力脉动沿管道传播发生衰减,其产生的激振力对弯管破坏较大;弯管段流体产生压力集中,进而引起弯管段变形大于异径管段。将压力脉动加载到管道中,对输流管道研究具有一定参考价值。     

流体网络理论在地下矿压风系统中的实践

流体网络理论是由流体力学和电路网络理论结合起来的一门应用科学，是流体力学和电学两大学科交叉的边缘学科。本文采用流体网络理论对地下矿压风系统进行优化，控制空压机的供风量，提供足够的风量；再通过控制闸阀状态从而改变网络结构，使整个系统处于最佳状态。     

液力偶合器在惯性圆锥破碎机的应用研究

简述惯性圆锥破碎机的结构特点、运动分析及限矩型液力偶合器的结构传动原理，讨论了加装液力偶合器后所具有的功能。在此基础上，探讨其推广应用的可行性。     

An initial study on feasible treatment of Serbian lignite through utilization of low-rank coal upgrading technologies

Despite benefiting from vast fuel reserves, combustion of low-rank coals is commonly characterized by low thermal efficiency and high pollutant emissions, partly due to high moisture content of the coals in question. Thus, removal of moisture from low-rank coals is deemed an important quality upgrading method. The paper provides an overview of the current status of low-rank coal upgrading technologies, particularly with respect to utilization of drying and dewatering procedures. In order to examine the influence of relevant parameters on the moisture removal process, a model of convective coal drying in a packed, as well as in a fluid bed combustion arrangement, is developed and presented. Product-specific data (intraparticle mass transfer, gas–solid moisture equilibrium) related to the coal variety addressed herein (lignite) are obtained through preliminary investigations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlünder is used to define heat transfer mechanisms occurring in the packed bed. Similar two-phase fluidization model has been validated for different types of biomaterials.     

A comparison of local phosphorescence detection and fluid dynamic gauging methods for studying the removal of cohesive fouling layers: Effect of layer roughness

The performance of industrial cleaning in place (CIP) procedures is critically important for food manufacture. CIP has yet to be optimised for many processes, in part since the mechanisms involved in cleaning are not fully understood. Laboratory tests have an important role in guiding industrial trials, and this paper introduces and compares two experimental techniques developed for studying CIP mechanisms: local phosphorescence detection (LPD), and scanning fluid dynamic gauging (sFDG).To illustrate the comparison, each technique is used to investigate the influence of soil topology on the cleaning of pre-gelatinised starch-based layers from stainless steel (SS 316) substrates by aqueous NaOH solutions at ambient temperature. The roughness of the soil surface is varied by incorporating zinc sulphide particles with different particle size distributions (range 1–80 μm) into the starch suspensions. The soil roughness increased with the use of larger particles, increasing the 3D arithmetic mean roughness (S_a) of the dry layers (range 0.37–3.33 μm). Rough layers were cleaned more readily than those containing small inclusions, with a good correlation between the cleaning rates observed during LPD and FDG measurements. The LPD technique, which is an instrumented CIP test, gives a better indication of the cleaning time, while sFDG measurements provide further insight into the removal mechanisms.     

流体传热场中的守恒定律及其解法

流体传热场[1,2]中的传热是自然过程或过程工业中常见的单元操作[3,4]之一,而套管式换热器[5]是一类典型的换热设备;在套管式换热器中的流体传热场涉及了流体运动[6],这些流体质点可能匀速直线运动(层流)、也可能波动运动(过渡流或湍流),所以确定流体质点运动的速度侧形(=■+■)成为了确定流体传热场的基础,本文中基于守恒定律探讨了流体质点运动速度侧形的求解方法。