上吸风环形风道碾米机设计与试验

针对卧式碾米机收集到的米糠混有碎米的缺陷,设计一种具有环形风道的上吸风式碾米机,可直接对米糠和碎米进行分离收集.运用Fluent对该新型碾米机流场进行分析,采用多孔介质模型模拟碾白室内糙米对气流的阻碍作用,并搭建样机利用PIVlab软件进行观测,结果表明:当上吸风口与喷风机风速分别为6 m/s和10 m/s时,环形风道内形成环形绕流,流速分布均匀、流场稳定,平均风速为4.1～4.6 m/s,垂直方向分速度为2.0～6.5 m/s,介于米糠与碎米悬浮速度之间;气压隔板形成狭管效应,上升气流从1.4 m/s加速至3～4 m/s;喷风槽附近米筛网内外压差最大约5550 Pa;试验证明碎米与米糠的分离效果良好.     

印刷车间风速及温度分布规律研究

针对西安市某印刷车间生产运行时对风速的特殊要求,为确定较优送风速度,借助FLUENT前处理软件Gambit绘制模型,完成网格划分,设置初始边界条件,对不同风速工况时,即出风口速度分别为5.0和5.5 m/s时,印刷车间室内不同水平面及垂直面的温度场和速度场分布规律进行模拟分析,得出风速为5 m/s的工况下,风速分布均匀性指标较优,温度分布有利于车间内污染物的排出。研究结果可为印刷车间正常运行提供良好的室内空气环境。     

LEY生产工艺的探讨

通过超高速纺丝,可以获得高取向、结构稳定的可织LEY,而且纺丝速度越高,其物理性能越好。在纺制LEY中,当侧吹风风速在0.4m/s、单体抽吸风速在1.2m/s时最为理想。为确保丝饼成形良好,要求在纤维冷却成形前提高纺丝张力,而在纤维冷却成形后要尽可能降低卷绕张力。     

多温区冷藏车厢体内温度场和速度场的数值模拟及优化设计

对多温区冷藏车厢的温度场、速度场进行数值计算,并数值模拟蒸发器出风口风速及厢内不同的堆货形式对流场的影响,从而对出风风速、堆货方式进行分析及优化设计。试验得出从冷冻厢与冷藏厢内都存在中心回流区,为合理利用冷量和空间,应该使用带风道的冷藏车厢,冷藏厢降温初始阶段为保证降温速度可以用较高的风速,而等温度稳定后建议将风速调小到6m／s。     

吸尘系统中总管—收集器配置最优化

在实际设计通用吸尘系统中会遇到总管—收集器确定最佳位置的问题,这时系统的能源损失为最小。合乎逻辑地提出了所述任务的下述数学解:已知吸尘系统中压力损失的关系式:P=λ((l/d)·(ρ/2))v~2(1)式中:=P-圆形管道中的压力损失;λ-摩擦阻力系数;l-风管的长度,m;ρ-空气的密度,kg/m~3d-风管的直径,m;v-空气的线速度,m/s。已知通过它所运输的空气体积和速度,确定出风管的直径:     

基于烟丝风速比控制的丘堆状风力喂丝工艺

为解决风力喂丝工艺风速过高、烟丝速度不可控带来的烟丝分层、造碎较大等问题,采用基于烟丝风速比控制的丘堆状风力喂丝方法,对风力喂丝系统进行了升级改造。以龙岩烟草工业有限责任公司在制品"七匹狼(红)"为对象进行测试,引入烟丝风速比△VAT作为控制参量,增大喂丝流量,增加自动防堵料模块。结果表明:(1)烟丝风送速度控制在7～11 m/s时,能实现低风速的丘堆状风力喂丝,烟丝不会与送丝管道产生过多摩擦,可有效保护烟丝。(2)将△VAT值比例控制在0.70至0.85之间,可以达到最好的烟丝输送状态。(3)风力喂丝系统改进后实现了低风速的丘堆状风力喂丝,风速由不可控降低至11.32 m/s,烟丝速度降低至9.5 m/s,烟丝风速比为0.84,有效解决了原系统烟丝风送速度过快带来的烟丝分层问题,提升了生产的工艺质量。(4)系统改进后烟丝的混合均匀度由5.41%降低至5.16%;同时风速降低有效减少了烟丝消耗,烟丝整丝率下降绝对值由1.27%降低至0.74%,烟丝消耗由32.17 kg·(50 000支)-1降低至31.34 kg·(50 000支)-1。     

风速对甜玉米棒冻结速度影响的研究

目前国内甜玉米棒冻结加工多以冻结库为主,冻结温度和风速直接影响产品的冻结速率。通过甜玉米棒在-18℃和-16℃低温下,冻结时间的观察以及风速对于冻结速度的影响,阐明了降低温度对加快产品的冻结速度有显著的影响外,由0 m/s风速提高至3.5～4.5 m/s,对加快产品的冻结速度也有极大的影响。在-16℃的冰柜中,棒芯初始温度从22.2℃降至-15℃,3.5～4.5m/s风速的处理用了165 min,而0 m/s风速用了430 min;在-18℃的低温冷藏间,3.5～4.5 m/s风速的处理,棒芯初始温度从22.2℃开始,经过120 min降至-15℃,而0 m/s风速的处理在相同的时间内,棒芯温度仅降至-1.1℃。试验结果还表明,经过烫漂玉米棒芯的冻结曲线呈现典型的先快后慢再快的特征。在-18℃的低温冷藏间,风速3.5～4.5 m/s的处理,经过120 min,玉米棒芯和玉米粒中心几乎同时达到-15℃,但是玉米粒达到0℃的时间要远远快于玉米棒芯,玉米粒冻结时其冰点温度没有明显的显示出来;经过烫漂玉米棒棒芯的冰点温度平均为-0.45℃,在通过冰点时,温度保持恒定一段时间。     

基于CFD的新型加香加料机布风系统的设计及改进

在新型烟草加香加料设备研制过程中,为解决多管送风导致孔板布风不均的问题,采用计算流体力学(Computational Fluid Dynamics,CFD)软件Fluent对原设计结构中的流场进行了仿真研究.仿真结果表明,布风室内气流合流产生的漩涡和筒内不良气泡特性的产生是导致布风不均的主要原因,对此提出了加装隔板分割布风室、对各布风室独立送风的改进措施.试验数据表明,改进后布风室两侧进风管道的风速差由2.1,1.5,14 m/s降低到0.5,1.3,1.0 m/s,阻止了布风室内涡流和加香加料筒内不良气泡特性的产生,改善了筒内气固两相混合的均匀性和规律性.     

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。      

高效节能型MH633热风烘燥机

对连续轧染设备中的关健单元热风烘燥机进行升级改造。改进后的MH633型热风烘燥机喷风盒左中右风温风速均匀一致,导布辊左中右温差±1℃,狭缝式风嘴风速16~20 m/s,烘燥效率提高15%,废气净化余热利用节能达25%,能提高活性染料轧染生产的产品质量。     

硬脂酸及辅助气流对熔体微分静电纺的影响

为得到细化的纳米纤维,利用自制的熔体微分静电纺丝装置,在聚丙烯（PP）中添加硬脂酸进行熔体微分静电纺丝,讨论硬脂酸含量对纤维的细化作用,同时探究在纤维下落时,气动抽风装置中的气流速度对纤维牵伸细化作用。实验结果表明：在纺丝温度为260 ℃,添加质量分数为2%~10% 的硬脂酸有助于降低PP熔体的黏度和细化纤维直径;当硬脂酸质量分数为4%时纤维细化效果最好。当通入的气流速度从13m/s 增加到29m/s时纤维直径明显细化（气流最大速度为29m/s）。当硬脂酸质量分数为4%,气流速度为29m/s时,纤维直径大都小于500nm,平均直径可达420nm。     

Dynamic modeling and simulation of bottom outlet air flow field in wide slot positive pressure spunbonding drawing process

The air jet flow has an important influence in wide slot positive pressure spunbonding process that not only includes the filament fiber diameter, crystallinity, and birefringence, but also the fiber web evenness. In this work, the air drawing model and the air jet flow field model of bottom outlet in spunbonding process are established and studied. The characteristics and regularities of the plane air jet flow in wide slot positive pressure spunbonding process are also demonstrated. It is simulated by means of the finite difference method. The numerical simulation computation results of distribution of the air velocity match quite well with the experimental data. The air drawing model of polymer is solved with the help of the distribution of the air velocity. The predicted filament fiber diameter, crystallinity, and birefringence agree well with the experimental data. It was found that higher initial velocity and initial temperature of air can yield finer fibers, and its effect was very significant. The results also reveal the great potential for this research in the computer-assisted design of spunbonding technology and equipment.     

基于随机算法的纤维材料过滤特性仿真分析

为分析纤维空气过滤材料的流场演变情况,综合过滤效率及颗粒流动轨迹,基于随机算法建立了纤维空气过滤材料的三维模型,并采用计算流体力学中的欧拉-拉格朗日离散相模型,在雷诺相似准则的基础上研究了微米纤维介质中的气固流动特性。结果表明:入口速度变化对流场压力与速度场分布有明显影响,随着入口速度增大,阻滞区域面积增加,流场空隙处更易形成高速流动与速度漩涡,同时流场整体速度差增大,压力损失与入口速度呈正相关;纤维模型对平均粒径为8~18 mm颗粒的过滤效率较为稳定,均在80.4%~84%,在入口速度为2 m/s工况下,过滤效率与粒径接近正比例关系。     

Determination of optimum hazelnut roasting conditions

The objective of this study was to test the hypothesis that the roasting conditions used for hazelnuts, such as the air temperature, air velocity and roasting time (independent variables), could be optimized by using Response Surface Methodology. Effects of independent variables on sensory and physical characteristics were determined. A consumer test was used to determine the acceptable samples. Very dark and very light roasted samples, corresponding to 165 °C, 3 m/s, 25 min and 125 °C, 1 m/s, 15 min process conditions, respectively, were unacceptable. Superimposed contour plots were used to determine the values of independent variables and these showed the process conditions where all product characteristics were acceptable to consumers. At low velocity (0.3 m/s), acceptable products were produced at about 165–179 °C for 20–25 min. When air velocity increased, air temperature shifted to lower temperatures. Samples roasted at 145 °C, 2 m/s, 28 min, 165 °C, 1 m/s, 25 min and 145 °C, 3.7 m/s, 20 min produced the most acceptable products. The sample roasted at 165 °C, 1 m/s, 25 min required the least air velocity and was the most economical in terms of energy consumed among the samples rated most acceptable by consumers.     

Numerical simulation and experimental investigations of air drawing model and air jet flow field model in wide slot positive pressure spunbonding process

An air drawing model of polymers and a model of the air jet flow field model in wide slot positive pressure spunbonding process are established. The air jet flow field model is solved by means of the finite difference method. The numerical simulation computation results of distributions of the air velocity match quite well with the experimental data. We find that the variation of the density and the specific heat capacity of polymer melt at constant pressure with polymer temperature have much effects on fiber diameter. The newly developed formulas were incorporated into a spunbonding theoretical model to predict the fiber diameter of nonwoven web. The air drawing model of polymer is solved with the help of the distributions of the air velocity measured by a Particle Image Velocimetry (PIV). The predicted fiber diameters agree with the experimental data well. It can be concluded that the higher air pressure, higher air velocity and air temperature can yield the finer fibers diameter. The higher inlet pressure and smaller jet angle will all cause higher x-axis position of air velocity and air pressure, which are beneficial to the air drawing of the polymer melt and thus to reducing the fiber diameter.     

双槽熔喷工艺中外沿长度对空气流场的影响

用数值方法研究了双槽熔喷工艺中外沿长度对空气流场特征的影响。首先,在双槽熔喷工艺模头的气槽外沿添加2片一定长度的附件,然后用数值方法对添有附件的双槽熔喷工艺的空气流场进行模拟计算;最后,分析了外沿长度对纺丝中心线上的空气速度、压力和温度分布的影响。结果表明,随着外沿长度的增加,空气速度和压力最大值都减小,而空气温度最大值基本不变,速度和压力的衰减程度增加,而温度的衰减程度减小。     

网格圈集聚纺纱系统三维流场表征与分析

通过建立流体动力学模型,利用标准κ-ε湍流模型及并行计算技术对网格圈集聚纺纱系统集聚区流场进行了模拟与表征,分析集聚区域内气流的流动状况,解析吸气斜槽入口曲面上气流的静压分布及速度分布规律,并讨论速度分布对须条的作用效果。研究结果表明：网格圈集聚纺纱系统是利用负压效应来产生集聚气流;斜槽入口曲面上的负压使网格圈向异形管内凹;X、Y、Z轴向的速度分量对须条的作用效果各不相同;集聚区产生附加捻度的区域主要靠近吸气斜槽的S1端。     

Different air velocity drying impacts on browning reaction and antioxidant activity of apple cube and its storage counterparts

The colour quality and functional activity of dried fruits are important quality indexes. The purpose of this study was to evaluate the effects of heat pump drying with different air velocity on browning-related reactions and antioxidant activities of products and their storage counterparts. The results showed that apple cubes possessed different Maillard reaction levels, polyphenol and pectin variation, and antioxidant capacity, which could be controlled by different drying air velocity when the temperature is constant. In present work, high air velocity (2.0–2.5 m/s) drying (HHD) apple cubes possessed 22.58% more browning comparing to low air velocity (0.02–0.50 m/s) drying (LHD), which correlated with its 8.13 μg/g, 132.35 μg/g and 6.21% more of 5-HMF, chlorogenic acid and DE level of pectin, respectively. Interestingly, the b value of HHD and LHD samples decreased after storage, which was related to the DE, GalA, structural properties (Ratio1, Ratio2 and Ratio3) and conformational properties (PDI, RG and RC) of pectin in samples. Besides, HHD treatment promoted higher DPPH and FRAP capacity than LHD, which significantly involved Mw of pectin. The research would provide a new insight from the perspective of pectin for regulating the browning and antioxidant activity in apple thermal process.     

牵伸速度对PET纺粘纤维凝聚态结构的影响

在纺粘非织造布加工过程中,通过调整牵伸风的速度,制得不同结构的聚对苯二甲酸乙二醇酯(PET)纤维,研究了牵伸风速度对纺粘PET纤维外观形貌、直径、结晶度和取向度的影响。结果表明:牵伸风速度对纤维表观形貌没有影响;随着牵伸风速度的增加,PET纺粘纤维的直径逐渐减小,当牵伸风速度达到一定值后其对纤维直径的影响较小;PET纺粘纤维的结晶度低于15.0%,牵伸风速度对其影响不大;随着牵伸风速度的增加,PET纤维晶区的取向度逐渐增加,当牵伸风速度达到一定值后对其晶区取向度影响较小。     

旋风磨研磨效率优化设计

为了解决旋风磨研磨效率低的问题,通过数值计算和Fluent模型分析,研究其研磨机理,发现旋风磨的风道结构设计不合理,从而导致旋风磨研磨的样品容易在风道堆积甚至发生阻塞。重新设计了风道,风道进气口段与研磨腔体的圆心共线,在风道中间位置设计1个135°的拐角,此结构使腔体内气流速度从88.7 m/s提升到107.0 m/s,而且消除了风道内不良湍流,显著地提高了旋风磨的研磨效率。