基于CFD-DEM的打叶后烟叶风分运动特性分析与试验

为研究打叶后烟叶在离心风分仓内的运动特性及受力变化，基于CFD-DEM耦合方法分析了不同进风风速下，物料在风分仓内的运动过程及受力变化规律。仿真结果表明:随着进风风速增大，风分仓内压力逐渐增大，片烟间碰撞次数增加，流场均匀性变化较小；当进风风速为11、13、15 m/s时，片烟与仓体壁面产生的最大平均碰撞力分别为0.155、0.164、0.378 N，叶含梗率分别为2.46%、2.37%、3.12%。以叶含梗率作为风分效率评价指标进行试验，结果表明:当进风风速为11、13、15 m/s时，叶含梗率分别为2.27%、1.84%、2.54%，试验结果与仿真结果误差 < 1百分点，验证了仿真模拟的合理性。该研究可为优化风分仓结构和工艺参数提供理论支持。      

风选工艺参数对梗丝结构的影响

为降低梗丝在后加工工序中的造碎率,对风选后输送风速和烘后梗丝含水率两个主要参数变化对梗丝结构的影响进行了测试。结果表明:①风选后的输送风速越高,梗丝的造碎率越大;②烘后梗丝含水率越高,梗丝造碎率越低;③在实际生产中,烘后梗丝含水率宜控制在13 5%左右;风选后的输送风速应在保证风分箱风选效果良好的前提下尽量调低。     

ZJ17卷烟机悬浮腔外形及内部挡块的设计优化——基于梗签分离效果的研究

  目的  研究ZJ17型卷烟机悬浮风分系统悬浮腔形状和内部结构对风分气流的影响,确定能够实现最佳梗签分离效果的悬浮腔设计方案。  方法  利用ANSYS Workbench中的Fluent模块对不同形状、不同内部结构的悬浮腔进行仿真分析,对比内部气流的压力图、速度图及运动轨迹图。通过上机实验验证仿真模拟结果。  结果  1）压力云图、速度矢量图显示“三角形型挡块+方形悬浮腔”中气流形成漩涡较多,有利于梗签分离。2）轨迹图显示“三角形型挡块+方形悬浮腔”气流运动主要呈螺旋状,可使梗签和烟丝的运动更加充分。3）上机实验表明“横置三角形型挡块”设计分离效率均值为80.91%,碎丝率均值为2.74%,优于其他两种设计,与仿真模拟结果吻合。  结论  方形悬浮腔+三角形型挡块的设计方案分离效果更好,可使梗签和烟丝分离的更加彻底。      

Drying kinetics and quality of okara dried in a jet spouted bed of sorbent particles

Okara or soy residue is a byproduct of soymilk and tofu production process. Okara has high protein content and can be used as an ingredient in many food products or can be used as animal feed. However, okara deteriorates rapidly; hence raw okara must be dried as early as possible under appropriate conditions. Drying could also help eliminating undesirable antinutritional factors in okara. The present study investigated the feasibility of drying okara using a combined convection-sorption drying, i.e., the use of a jet spouted bed of sorbent particles. The effects of various parameters such as drying air temperature and velocity, mass ratio of sorbent particles to okara, and initial bed height of okara on the drying kinetics were investigated. Also, various quality attributes of okara viz. color, oxidation level, rehydration ability, urease activity and protein solubility as well as the specific energy consumption during drying were investigated in both low- and high-temperature ranges.     

基于DEM离散元技术的玉米直线振动筛仿真分析

目的：分析物料颗粒在直线振动筛面上的运动情况,以便直线振动筛的机构优化。方法：基于离散单元法,采用EDEM软件对直线振动筛面上物料颗粒的运动情况进行仿真分析。以堆积角为响应,采用批处理的形式对仿真物料颗粒的离散元仿真参数进行校准;采用SolidWorks软件建立直线振动筛的三维模型,以物料在筛网面的下落高度、物料颗粒的形状尺寸为变量,以物料颗粒在筛网面上运动的平稳程度为指标,通过仿真,观察物料颗粒在晒网面的运动速度及位置分布情况。结果：单球形颗粒的速度分布相对较大,在达到振动筛分平稳阶段,单球形玉米颗粒的速度分布相对稳定,颗粒跳动现象明显减少。双球形玉米颗粒的速度分布相对较小,在达到筛分的稳定阶段,双球形玉米颗粒的位置跳动比较明显。双球形玉米颗粒在振动筛面的速度明显低于单球形玉米颗粒,不同下落高度的单球形玉米颗粒对振动筛分有一定的影响。结论：在对直线型振动筛分设计过程中,不同的高度,不同的颗粒形状对筛分的效率都有较大的影响,基于离散元法可以有效地分析物料振动筛分情况。     

Fractionation of Distillers Dried Grains with Solubles (DDGS) Through a Narrowing of Particle Size Distribution Followed by Aspiration

Distiller's dried grains with solubles (DDGS) may have more value and utility if they can be separated into high protein and high fiber fractions. A variety of such separation processes have been proposed; two of the most promising processes involve three screening and three air classification unit operations. In the present study, an alternative process involving fewer unit operations is demonstrated. DDGS are subjected to a single screening, and the oversize particles are processed in a mill setup so that it narrows the particle size distribution of the oversize fraction. The milled DDGS is then processed in an air classification device known as an aspirator, which separates it into high and low terminal velocity fractions. The combination of the undersize fraction and the low terminal velocity fraction were substantially enriched in protein. The separation achieved by this process compares favorably to other reported processes while being less complex.     

风力送丝系统的优化

为解决烟丝风送过程中风速控制的不稳定问题,利用流体动力学原理和自动控制技术对风送系统进行研究分析。通过测算风送管网相关参数,调整除尘风机变频和末端补风控制,使管网风压风量得到合理匹配,并消除了风机喘振。文章研发了新的风速检测装置,优化改进了单台卷烟机风速控制程序。实际应用效果表明:稳定的烟丝风速控制系统可以使整丝率和碎丝率指标有较明显地改善,其中整丝率可以提高3.27%,碎丝率降低了0.669%;卷烟机的不良烟支剔除量可以降低2.793支/万支。     

小麦粉多点供料气力输送系统的研究

为企业设计小麦粉给料系统时,针对企业提出的物料在混料工艺前需要存储一段时间的特定要求,为保证连续供料,通过多储料罐进行小麦粉的存储与供料,设计了小麦粉多罐供料气力输送系统,确定了系统管道直径、风速、料气混合比等参数以及系统运行所需风机的风量与功率,同时通过组态王对系统运行进行监控,大大提高了企业生产过程自动化的程度。     

Monte Carlo simulation of the collective behavior of food particles in pneumatic drying operation

Although most of the time drying operation aims at controlling the mean batch behavior, the quality of the final product is often related to the individual behavior of the supplied materials in a batch. The mean batch models provide limited information for quality evaluation studies. Since the initial physical and thermal properties of rice powder in a batch influence the final condition of product dried with a pneumatic dryer, a Monte Carlo simulation with initial random parameters is useful to investigate the individual behavior of rice particle during pneumatic drying. In this study, we analyzed the influence of initial moisture content and particle diameter of rice powder on the conditions of the final product in pneumatic drying process. Samples of initial moisture content and particle diameter distributions were generated by means of the covariance decomposition algorithm and Monte Carlo simulations with 5000 runs based on momentum, energy and mass balances between drying air and rice particles were performed to obtain the profiles of the response variables, rice powder temperature, moisture content and particle diameter, in a pneumatic dryer. The developed pneumatic conveying drying (PCD) model could describe the complex behavior of rice particles in a batch.     

Enhancing the potential use of microparticulate insecticides through removal of particles from raw grain

The current study presents the design and evaluation of a laboratory device combining mechanical motion of wheat grain and turbulent air streaming inside a positive pneumatic conveyor system. The device recovers microparticulate nano-engineered alumina insecticide powders (NAIP) from treated grain. The particle removal efficiency of the conveying system was experimentally quantified by using a laboratory prototype assembled by attaching an electrostatic filter (EF) to the conveyors exhaust. Then, the NAIP particles detached from the grain inside the conveyor were drawn by the conveyors’ exhaust air stream into the EF, where particles bound to the electrodes due to electric charge differences. The NAIP particle load bound to the EF electrodes was removed and weighed to determine the efficiency of the wheat grain cleaning process. Our experimental results, under laboratory conditions, show that the recovery efficiency of the prototype averaged 98.0% (±1.4). Thus, the present study provides an innovative strategy to remove NAIP insecticide particles after storage, once their role as insecticide in stored grain has been fulfilled. This technology provides advancement in grain technology allowing the possibility to provide insecticide-free grain to the food market.     

Use of Positron-Emission Particle Tracking (PEPT) Technique for Velocity Measurements in Model Food Fluids

ABSTRACT Positron-emission particle tracking (PEPT) is a method of following particles in opaque fluids inside metal equipment. Comparison of experimental and theoretical velocity distributions obtained in aluminum pipes indicated that PEPT can be used to measure velocity distributions in viscous fluids for conditions of relevance to the food industry. Velocities were also measured for a fluid containing starch particles using 2 tracers having diameters of 600 and 240 μm. Velocity profiles were not significantly different, but the smaller tracer passed closer to the flow boundaries. PEPT was also used to quantify the effect of headspace on the velocity distributions of rotating cans containing soup. While in fully filled cans, fluid moved in circular motion, addition of air altered this, resulting in D-shape velocity contours.     

风分器中气流抛料器的设计应用

目前打叶复烤生产线中风分器采用的拨叶辊抛料器产生的造碎大,高速皮带抛料存在着抛料角度不可调、回带料严重等问题,为此,采用气流抛科技术设计了气流抛料器.该装置由高压风机、分流管、金属软管路、气流腔及调节装置等组成,将打后烟叶落到气流腔形成的高速气流面上,利用高压气体将烟叶抛入风分器仓体内.相对于拨叶辊抛料器,气流抛料器将机械抛料改为流体柔性吹抛,有效降低了抛料过程中的造碎,大中片率提高近2.7个百分点,碎片率下降近0.8个百分点,叶中含梗率下降0.1个百分点;相对于高速皮带抛料,气流抛料器抛料角度可根据不同等级、不同产地烟叶进行调整,提高了风分效果,也避免了回带料、皮带跑偏等问题.     

FX6型就地风选器在梗签风选中的应用

为降低生产成本,有效地回收利用梗签中夹带的游离烟丝,应用FX6型就地风选器进行了梗签风选试验。结果表明,最佳风选风速为0.8~2.0m/s,除尘风门开度为1.5~2.5格,风选后的梗签含丝率比风选前降低了3.5%~4.0%;风选后的烟丝结构、填充值及纯净度与回收的残烟烟丝相近。将其以≤6%的比例掺配到成品烟丝中,对卷烟的总体质量无负面影响。     

Effect of pneumatic conveying parameters on physical quality characteristics of infant formula

The geometry and operating conditions of a pneumatic conveying rig for infant formula were varied according to an L₁₈ orthogonal array, with the goal of minimising variations in four product quality characteristics: bulk density, volume mean diameter, particle density and wettability. A modular pneumatic conveying rig was fabricated from 316L stainless steel components. The factors that were varied in these experiments included mode of conveying, air velocity, number of rig passes, bend radii and vertical rig section length. A factorial analysis of variance showed that the mode of conveying, air velocity and number of passes had a statistically-significant effect on bulk density. The optimum settings to minimise variability were dense phase conveying with a 50 mm plug length, 960 mm vertical section, 3 m/s air velocity, 2 passes and 50 mm bend radii, assuming a linear model. The bulk density change at these optimum settings was negligible at 0.9%.     

风力烟丝输送系统的改进

为解决使用过程中存在的烟丝造碎大和烟丝组分分离及烟丝填充能力降低等问题,对风力烟丝输送系统进行了改进:确定合理的风速;采用变频调速技术,以及设置瞬间补风装置削减风速峰值等方式,提高风速的稳定性;吸丝管风速实现独立调节;改进吸丝管的用料;采用无振动转塔式喂料机,防止烟丝分层;提高电控系统的自动化程度。改进后风力烟丝输送过程中烟丝造碎率降低了0.94%,每年可节约成本约500万元。     

卷烟机风分除杂系统的改进

卷烟机吸丝成形过程中利用风分原理将烟梗杂物从烟丝中分离剔除 ,由于二次风分风速存在波动 ,即风分除梗除杂率波动 ,根据风分除梗原理 ,对二次风分除梗除杂风速自动控制系统进行了改进 ,在二次风分风道中增装了风速传感器 ,改造了二次风分风道调整机构 ,通过PLC对二次风分风速进行自动控制 ,从而提高了风分除梗、除杂效     

熔喷工艺中纤维运动的研究

利用“球—弹簧”纤维模型,模拟计算了熔喷过程中纤维断裂后的运动情况,模拟计算的结果与实验拍摄到的纤维运动状况定性地符合;研究了空气的初始速度和气流的角度对纤维运动的影响。     

Evaluation of drying models of apple (var. McIntosh) dried in a convective dryer

Drying behaviour of apple particles was investigated in a laboratory type dryer. The effect of drying air temperature, airflow velocity, initial height of layer, particles shape and size on the dehydration characteristics of apples was investigated. Increase in drying air temperature and increase in the airflow velocity caused a decrease in the drying time and an increase in drying rate. Increase in initial height of layer and increase in the sample thickness caused an increase in the drying time and decrease in drying rate. Drying time of the cubes was shorter and their drying rate was higher than for slices. The experimental dehydration data of apple particles obtained were fitted to the semi‐theoretical, empirical and theoretical models. The accuracies of the models were measured using the correlation coefficient (R), mean bias error (MBE), root mean square error (RMSE), reduced chi‐square (χ²), and t‐statistic method. All models described the drying characteristics of apple particles satisfactorily (R > 0.9792). The Logarythmic model can be considered as the most appropriate (R > 0.9976, MBE = ?10^?11?4.5 × 10^?6, RMSE = 0.00287–0.01746, χ² = 8.5 × 10^?6?3.1 × 10^?4, t‐stat = 7.3 × 10^?9?1.2 × 10^?3). The effect of drying air temperature, airflow velocity, characteristic dimension of the particle and initial height of layer on the drying models parameters were also determined.     

纬纱与气流粘附性测试方法的评价

喷气引纬需要大量的压缩空气，所需的压缩空气量取决于织机的参数设置和纬纱的规格。通过确定不同纱线在恒定气流中的速度或气流指数，就有可能更加精确地设置织机参数。本文将研究不同纱线在气流中的速度，并将这些结果与不同的纱线性能及喷气织机参数作对比。同时，设计了不同的测试方法来比较这些参数，并研究了纬纱气流指数与织机参数之间的相互关系。结果表明，随着织机参数设置精确性的提高，所需的压缩空气量减少。比较性的测试在其他研究中进行。