Study and optimization of flow field in a novel cyclone separator with inner cylinder

This paper presents a study of gas-solid flow in a novel cyclone separator with inner cylinder, compared with that in a conventional cyclone. The Reynolds stress model (RSM) is used to simulate fluid flow, and the discrete phase model (DPM) is selected to describe the motion behavior of particles. The experimental data measured by particle image velocimetry (PIV) is used to verify the reliability of the numerical model. The results show that in the novel cyclone, the cleaned gas can be quickly discharged from the vortex finder, the movement distance and residence time of fine particles are prolonged, the short-circuit flow and vertical vortex under the vortex finder are eliminated, the mutual interference between upflow and downflow in the cylinder is eliminated, and the region of quasi-free vortex in the cone is enlarged. Compared with the conventional cyclone, the novel cyclone has higher collection efficiency and lower pressure drop.     

直径30cm圆柱的气动力参数和绕流特性研究

为研究光滑圆柱的气动力系数和绕流特性,在均匀流中进行不同风速下的测压风洞试验,试验获得了阻力系数、升力系数、表面风压分布、风压相关性系数、斯托罗哈数等随雷诺数的变化特征,并将试验结果与以往结果进行比较。研究表明:升力系数的脉动值大于阻力系数的脉动值,说明涡脱造成的横风向激励比顺风向紊流激励剧烈;雷诺数位于临界区域时,圆柱表面风压分布呈现出对称-不对称-对称的变化过程,反映了由层流分离转化为湍流分离的全过程;在雷诺数为352000时呈现一侧为层流分离、另一侧为湍流分离的临界流态,风压呈现出左右不对称的单边泡形式;获得层流分离和湍流分离时的表面风压相关性分布特征,层流分离时圆柱同一侧的风压测点均呈较强的正相关,而湍流分离时在分离点前的区域相关性较强,分离点之后的区域相关性较弱;层流分离的升力系数谱有显著的峰值,表明尾流是规则的漩涡脱落,而湍流分离的升力系数谱没有明显峰值,表明尾流是随机的漩涡脱落。     

小直径附加圆柱对圆柱涡激振动抑制的参数优化

采用基于迭代嵌入式浸入边界法对后方对称布置两个小直径圆柱的单圆柱涡激振动进行了数值模拟研究,对涡激振动抑制进行了参数优化。雷诺数和圆柱直径比分别为Re=100和d/D=0.125,其中D和d分别为大、小圆柱直径。通过改变控制角度(θ)、主圆柱与小圆柱的间隙比(G/D)、小圆柱旋转角速度和旋转方向(α)和阻尼比(ζ)确定的最优控制参数组合为θ=25°、G/D=0.125、α=-2.2和ζ=1.02。小圆柱的旋转角速度和旋转方向对圆柱振幅有一定的影响,其中内向反转会进一步抑制圆柱的振动,外向反转则恰好相反。随着阻尼比的增加,圆柱振幅先增后减,但影响程度较小。     

Al₂O₃ and γAl₂O₃ Nanomaterials Based Nanofluid Models with Surface Diffusion: Applications for Thermal Performance in Multiple Engineering Systems and Industries

Thermal transport investigation in colloidal suspensions is taking a significant research direction. The applications of these fluids are found in various industries, engineering, aerodynamics, mechanical engineering and medical sciences etc. A huge amount of thermal transport is essential in the operation of various industrial production processes. It is a fact that conventional liquids have lower thermal transport characteristics as compared to colloidal suspensions. The colloidal suspensions have high thermal performance due to the thermophysical attributes of the nanoparticles and the host liquid. Therefore, researchers focused on the analysis of the heat transport in nanofluids under diverse circumstances. As such, the colloidal analysis of H₂O composed by γAl₂O₃ and Al₂O₃ is conducted over an elastic cylinder. The governing flow models of γAl₂O₃/H₂O and Al₂O₃/H₂O is reduced in the dimensionless form by adopting the described similarity transforms. The colloidal models are handled by implementing the suitable numerical technique and provided the results for the velocity, temperature and local thermal performance rate against the multiple flow parameters. From the presented results, it is shown that the velocity of Al₂O₃–H₂O increases promptly against a high Reynolds number and it decreases for high-volume fraction. The significant contribution of the volumetric fraction is examined for thermal enhancement of nanofluids. The temperature of Al₂O₃–H₂O and γAl₂O₃–H₂O significantly increases against a higher ϕ. Most importantly, the analysis shows that γAl₂O₃–H₂O has a high local thermal performance rate compared to Al₂O₃–H₂O. Therefore, it is concluded that γAl₂O₃–H₂O is a better heat transfer fluid and is suitable for industrial and technological uses.     

波浪锥型圆柱流固耦合振动机理研究EI北大核心CSCD

为增强及控制无叶片风力俘能结构能量采集效率,该研究将表面结构斜率参数引入波浪型圆柱,发展了一种新型波浪锥型圆柱,试验研究在雷诺数Re=3900下不同波长比、波幅比、斜率参数的波浪锥型圆柱涡激振动响应特性。研究发现:在不同折合流速下,斜率k=0.05的锥型圆柱和波长比λ/D _(m)=1.75、波幅比α/D _(m)=0.10、斜率k=0.05的波浪锥型圆柱最大振幅较直圆柱分别增长26.4%和12.6%,且锁频区间得以拓展;当折合流速在锁频区间内时,在波浪锥型圆柱绕流尾流中观察到了“2S”、“2P”漩涡脱落模式,并且“2P”漩涡脱落模式在往下游发展的过程中有转变为“2C”模式的趋势。该研究可为无叶片风力俘能结构涡致振动的增大和发电效率的提升提供理论支持。     

基于热固耦合的双螺杆挤压机机筒有限元分析

目的 研究双螺杆挤压机在食品加工过程中出现卡顿、抱死的原因,为双螺杆挤压机设计及应用提供理论指导。方法 应用ABAQUS软件构建双螺杆挤压机仿真模型,通过传感器反馈的温度值设定温度载荷,同时以双螺杆挤压机运转时的低压工况、正常工况、极限工况分别设定压力载荷,运用热固耦合理论对机筒的温度分布、应力和变形进行仿真分析。结果 在最大温度工况条件下,机筒轴向热变形量为2.356 mm,总热变形量为2.358 mm,x方向上的热变形量为0.1324 mm,y方向上的热变形量为0.1592mm;在最大温度工况和极限压力耦合作用下,机筒总变形量为2.088 mm。温度引起的热膨胀是机筒变形的主要原因,机筒的轴向热变形量与总热变形量相当,并且远大于其他两方向的热变形量;与常温环境相比,在加热温度工况条件下机筒的变形量随着压力的增大而减小。结论 要充分考虑温度对挤压机性能的影响,应用过程中要合理的设置温度参数。     

钨铜聚能粒子流的侵彻特性研究

为研究钨铜聚能粒子流的侵彻特性,对钨铜多孔药型罩和紫铜板药型罩的侵彻性能进行了试验研究,测试了钨铜聚能粒子流侵彻铝板的穿深与时间关系曲线。试验结果表明:在1倍装药口径炸高下,钨铜聚能粒子流侵彻铝靶的穿深比紫铜板射流侵彻铝靶的穿深要提高31%。利用最小二乘法对穿深与时间关系曲线进行拟合,拟合结果表明穿深与时间的关系呈乘幂形式。结合侵彻试验结果,确定了钨铜聚能粒子流的最后侵彻速度为1657.8m/s。这为多孔药型罩聚能装药的设计提供一定的指导意义。     

平顶药型罩聚能射流形成过程研究

ANSYS/LS-DYNA对平顶药型罩的射流形成过程进行数值模拟,结果表明,在顶点起爆条件下,平顶药型罩的平顶中心首先下凹并拉动药型罩边壁向内汇聚,使得存在夹角的平顶与边壁整体构成环形线性聚能罩,此聚能罩在炸药爆轰作用下产生一级射流,一级射流彼此作用继而产生更高速度的二级射流。分析认为其机理是二级药型罩成型假说,尝试探索研究多级射流领域,并为提高射流速度提供一种新思路。     

铜粉末药型罩试验研究

研究粉末罩的力学性能,对聚能装药的设计和应用具有重要意义。本文对两种不同孔隙度的铜粉末药型罩进行了试验研究,并与紫铜药型罩进行了比较。试验结果表明,在给定的试验条件下,粉末药型罩的穿深随孔隙度的增加而增加;两者分别在0.7～3.0和1.1～2.2倍口径的炸高范围内,粉末药型罩穿深要比紫铜射流的深;孔隙度为9.3%的粉末射流在14μs内侵彻速度与紫铜射流几乎没有差别,14μs后很快降低。     

微结构塑件的注塑充填尺度效应

微尺度聚合物熔体流动具有明显的尺度效应,模具温度和注射速率是微注塑充填流动的关键影响因素。文中采用微细电火花铣削技术设计分别制造了一模八腔的带有200μm和300μm微孔的注塑模具。以聚丙烯(PP)进行单因素充模流动工艺实验,研究了模具温度和注射速率对直径为200μm和300μm微圆柱充填高度影响规律。结果表明,当模具温度为30℃和注射速率为60%时,直径200μm微圆柱孔的充填高度小于直径300μm微圆柱孔的充填高度,且Ⅰ型腔的微圆柱充填高度大于Ⅱ的充填高度。随着模具温度升高和注射速率增加,2种微孔充填高度差在减小,Ⅰ型腔和Ⅱ型腔之间的充填高度差值也在减小。可见,升高模具温度和增加注射速率可以减少微尺度效应对微圆柱孔充填高度的影响,同时,还可以减小流动不平衡程度。