异纤分拣机输棉通道结构对气流稳定性的影响

针对异纤分拣机输棉通道内部出现气流波动导致后续棉花异纤的检测与剔除效果不佳等问题,对异纤分拣机输棉通道结构与气流稳定性之间的关系进行了研究。利用流体仿真软件Fluent分别对原始输棉通道结构、不同弯管角度与通道入口段长度以及在通道入口增设不同类型面扩散器进行模拟分析,探讨输棉通道在不同方案改进下其内部气流速度分布、压力分布及直通道中心线位置的速度衰减曲线的规律。仿真结果表明:原始输棉通道由于弯管处产生流动方向突变和离心力,导致内外壁面存在压力差使得通道内部流速波动较大;减小弯管角度、增大入口段长度有利于减小压力不均衡分布区域,提升内部气流稳定性;在输棉通道入口增设局部阻力系数最小的双圆弧相切流线型面的缩扩型扩散器,不仅可以减小因型面突变产生的局部阻力,同时可将气流集中在管道中间位置,相较于原始输棉通道气流的波动距离缩短0.3 m。

FBCDZ-10-No36型通风机进气风道气流稳定性分析

根据某矿压入式轴流主通风机在进气风道入口安装片式消声器,在运行1个月后,第1级部分叶片表面出现裂纹的情况,探讨了影响叶轮入口气流不稳定的主要因素,据此对吸声片尾部和进气风道结构进行了改进,并对改进前后风道内的流场进行数值模拟。结果表明:进气风道入口安装消声器后,在吸声片尾迹中卡门涡街阵列、弯曲风道内流动和风道拐弯处分离流动的共同作用下,叶轮入口截面主流速度分布不均匀程度增强、截面气流压力脉动明显加剧,成为引起叶片疲劳破坏的主要原因;结构改进显著提高了风道内以及叶轮入口截面气流的均匀性和稳定性,从而保证了叶片工作的安全性。

矿井局扇风机气流稳定器的改进实验

对在气流稳定器中设置导流叶片对矿井局扇风机性能的影响进行了实验研究,其结果为改进气流稳定器的设计,提高矿井局扇风机不稳定工况特性提供了参考依据。

润东煤业矿井气流稳定性与通风系统优化研究

针对润东煤业矿井通风气流稳定性差、风力小、系统复杂,巷道或工作面温度高、湿度大,有害气体无法排除等问题,分析了矿井对角通风系统的缺点及关键影响因素。为了满足巷道及工作面通风需要,设计了矿井通风系统优化方案,通过在工作面增加21 kW风力机、更换通风机和优化气流的有效截面等措施,实现了矿井通风系统的升级改造,满足了矿井通风的需要。

不稳定气流影响下多卫星抗干扰混合定位方法的研究

不稳定的气流会导致信号传播路径的扭曲和延迟变化,从而导致接收到的卫星信号的延迟和失真。这将导致定位系统的测距和寻向误差增大,影响定位结果的精度和准确性。因此,提出了一种新型的在不稳定气流影响下的多卫星抗干扰混合定位方法。对高空不稳定湍流数据进行预处理,快速验证湍流数据的真实性。基于动量守恒定律构建流场描述方程。通过运用载波相位观测和卫星天线相位中心坐标建立多卫星运动方程,并构建抗干扰混合定位模型。引入全球导航卫星系统(GNSS)技术,利用多颗卫星的信号来计算接收器的位置、速度和时间,从而解决多卫星混合抗干扰模型。实验结果表明,对于静态目标,该研究方法在目标方向N(北)、S(南)和E(东)的定位偏差较小;采用近地卫星、中等高度卫星和地球同步卫星混合定位时,定位误差的均方值始终低于0.002 cm。对于动态目标,该方法不受杂波干扰,能够稳定地定位目标。此外,所提出的方法具有更低的定位延迟和更高的定位效率。

圆锥形扰流器对室内风蚀风洞气流均匀性与稳定性的影响

【目的】寻求风蚀风洞最合适的扰流器组合,调整截面气流以满足正式模拟试验对截面气流的要求,为风蚀风洞的设计提供参考。【方法】对12个扰流器(3层,每层前后2组,每组并排2个)的位置从左至右进行编号,用每排4个扰流器的位置编号代表该层的组合情况,每一种扰流器组合包含了3层的组合情况,设定每种组合中的3层组合情况一致。从所有组合中选取11种(C1～C11,其中C11为对照),测试每种组合截面上24个测点的10个等时距气流流速值,用以评价气流的均匀性与稳定性。【结果】(1)组合C1、C4、C6、C9、C10对截面气流的均匀性有积极的改善作用。(2)C4、C5、C6、C7 4种组合在改善截面各测点气流稳定性方面有积极的效应。(3)根据试验的具体情况,适当提高设定的风速值,保证气流的稳定性,有利于增加模拟试验的可靠性,且不影响气流均匀性。【结论】C4组合在各个风速档下对截面气流均匀性和稳定性的综合影响均是正向的,且影响显著,并优于其他组合。

电除尘器内气流的稳定性

本文从气流稳定性的角度,讨论电除尘器内气流的品质.气流的稳定性是以时间作为自变量来研究气流的脉动状况,它与以空间坐标作为自变量的气流均匀性本是两个不同的概念.但对实验测到的数据进行分析和归类,发现这两者有一定的对应关系.在气流分布比较均匀的截面上,各测点上的气流也相应的比较平稳;而在气流分布不均匀的截面上,大多数测点气流的脉动相当强烈.这是一个很有趣的问题,可作更深入一步的研究.

口罩泄漏性检测仓气流稳定性研究

针对口罩泄漏性检测仓结构不合理,导致颗粒浓度不均匀以及检测仓内空气流速不稳定的问题,将检测仓顶部和底部气道设计为喇叭口状,同时,顶部和底部气道喇叭口都设计开孔板,用以调节检测仓颗粒浓度与均匀性。在顶部和底部气道喇叭口以及底部开孔板不变的情况下,改变顶部开孔板的圈距和孔数,设计了三种开孔板,通过试验选择最优结构。试验表明,设计三的开孔板能使仓内气流稳定和颗粒物均匀性达到测试要求。

基于稳定气流的两级安德森采样器

目前Andersen采样器是国际通用的测定空气细菌和真菌粒子浓度的标准仪器,闭环控制可以获得可调节的稳定气流,实现了基于稳定气流下的全自动两级安德森采样器,其轻巧、便携、操作方便、可远程控制。并通过与标准采样器的对比实验(t检验统计分析),对全自动采样器的性能以及采样效果进行验证,采样效果满足需求。

进气加温模拟装置对涡扇发动机进气流场稳定性影响试验

为分析新设计的进气加温模拟装置对涡扇发动机进气流场稳定性的影响,对试验设备、测试方案、进气流场的稳定性评估方法和试验方案进行设计研究。通过开展气源供气温度、供气流量和发动机状态多因素匹配工况下涡扇发动机与进气加温模拟装置的联合试验,确定发动机进口气流稳定性指标的最高值。对不同试验工况数据进行计算分析,结果表明:进气加温模拟的稳压进气道对发动机进口压力场影响较小,发动机状态稳定时进口温度场只有1个高温区,T_(1)升高以及发动机状态提高,温度场及压力场不稳定性增大,多工况下发动机温场周向不均匀度最大为0.6907%,压力场周向畸变指数最大为0.0187%。进气加温模拟装置条件下,发动机压力场和温度场稳定性情况满足发动机试验要求,可为后续开展发动机进气加温试验提供参考。

基于稳定气流法对莱氏现象的探究

本文利用稳定气流来模拟液滴下蒸汽层的方法,实现了莱顿弗罗斯特现象。对不同黏度的液滴,观察了其稳定状态、不规则振动、星形振荡和液滴的破裂(烟囱现象:指液体下方的气泡上涌,突破液滴的中心,导致液滴破碎的现象)。通过实验数据分析总结,给出了液滴体积与气体流速的关系,以及不同黏滞系数液滴对气流流速的影响。同时,由计算机软件建立模型,模拟了实验过程。通过实验可以发现,莱顿弗罗斯特现象的产生只依赖于纯流体动力学机制,而与热效应无关。

Experimental and Numerical Investigation of Micro Tip Injection in a High‑Speed Axial Compressor Rotor

A series of experiments and numerical simulations are carried out in a high-speed axial compressor to systematically investigate the influence and underlying flow mechanisms of micro tip injection on enhancing compressor stability.Different geometric structures of micro tip injection have been investigated,including the axial positions of injector port,injected mass flow rate and injector diameter.First,seven designed micro tip injection structures and one solid wall casing are tested in the compressor test rig to elucidate the influence of different micro tip injection parameters on the compressor stability.Then,numerical simulations are conducted to analyze the underlying flow mechanisms of micro tip injection with different design parameters on enhancing the compressor stability.The experimental and numerical investigation reveal that when the injection port is located upstream of the low-speed region,the compressor stability is significantly enhanced.The tip injection with larger injected mass flow can obtain higher stall margin improvement.Smaller injector diameter produces higher injection momentum and velocity,contributing to greater improvement on the compressor stability.

小型直流式风力机实验风洞的流场特性研究

同济大学新建的小型直流式风力机实验风洞,送风段包括进风稳定段、风机段、过渡段和蜂窝器段。本文实验段流场特性的研究是根据测量风速,以风速均匀性、稳定性为指标,分析风洞性能的评价方法。实验采用杯式风速计测量风速,根据计算所得的风速均匀性以及风速稳定性,确定了距风洞出口5m处为最佳的实验断面。进一步测量5m处截面的风速-电机频率的关系,结果表明气体流速随风机工作频率呈直线变化。

Turbulence regime near the forest floor of a mixed broad leaved/Korean pine forest in Changbai Mountains

The measurement and observation for this study were carried out by using a three-dimensional (u, v, w) Sonic anemometer (IAP-SA 485), at Forest Ecosystem Opened Research Station of Changbai Mountains (12828扙 and 4224?N, Jilin Province, P. R. China) in August 2001. The basic characteristics of turbulence, such as turbulence intensity, atmospheric stability, time scales, and convection state, near the forest floor were analyzed. It is concluded that the airflow near forest floor is characterized by high intermittence and asymmetry, and the active and upward movement takes the leading position. Near forest floor, the vertical turbulence is retained and its time scale and length scale are much less than that of u, v components. The eddy near forest floor shows a flat structure and look like a ’Disk’. Buoyancy plays a leading role in the generation and maintenance of local turbulence

中阳钢铁1780 m^(3)高炉操作制度优化

中阳钢铁1 780 m^(3)高炉在2018年采取“焦包矿”的布料模式,常出现气流稳定性差、出现出格铁、炉温大幅波动、压差升高就会悬料等炉况不稳现象,且利用系数偏低,自开产以来年平均日产不超过3 800 t,故在2019年从入炉原料、装料制度、风口布置上不断地进行攻关突破,实施操作制度优化措施,经多次反思、尝试后,在2022年终于取得可喜的成就,连续一个月日均铁水产量达到4 500 t,且炉况压差下降、气流稳定性增加,2023年平均日产基本在4 400 t左右。

Study on the instability of airflow in mine hoisting-shaf

In order to discover the airflow pattern in mine shaft which outfitted with hoist equipment （HE）, this paper set up the physical model and anatomized the piston-wind caused by hoist equipment, and researched the flow field and velocity field around the hoist equipment during its moving process, and analyzed the airflow around single and couple hoist equipment as well as decisive range of piston effect and additional effect of hoist equipment to ventilation system. Research conclusion indicate that during hoist equipment movement, airflow pattern changes repeatedly because of the influence of pis-ton effect from hoist equipment, and the study of airflow stability in shaft is the foundation for the stability of ventilation in mine.

Instability and breakup of cavitation bubbles within diesel drops

A modified mathematical model is used to study the effects of various forces on the stability of cavitation bubbles within a diesel droplet. The principal finding of the work is that viscous forces of fluids stabilize the cavitation bubble, while inertial force destabilizes the cavitation bubble. The droplet viscosity plays a dominant role on the stability of cavitation bubbles compared with that of air and bubble. Bubble–droplet radius ratio is a key factor to control the bubble stability, especially in the high radius ratio range. Internal hydrodynamic and surface tension forces are found to stabilize the cavitation bubble, while bubble stability has little relationship with the external hydrodynamic force. Inertia makes bubble breakup easily, however, the breakup time is only slightly changed when bubble growth speed reaches a certain value(50 m·s-1). In contrast, viscous force makes bubble hard to break. With the increasing initial bubble–droplet radius ratio, the bubble growth rate increases, the bubble breakup radius decreases, and the bubble breakup time becomes shorter.

Stability of Stratified Gas-Liquid Flow in Horizontal and Near Horizontal Pipes

A viscous Kelvin-Helmholtz criterion of the interfacial wave instability is proposed in this paper based on the linear stability analysis of a transient one-dimensional two-fluid model. In thismodel, the pressure is evaluated using the local momentum balance rather than the hydrostatic approximation. The criterion predicts well the stability limit of stratified flow in horizontal and nearly horizontal pipes. The experimental and theoretical investigation on the effect of pipe inclination on the interfacial instability are carded out. It is found that the critical liquid height at the onset of interfacial wave instability is insensitive to the pipe inclination. However, the pipe inclination significantly affects critical superficial liquid velocity and wave velocity especially lor low gas velocities.

Direct Numerical Simulation of Particle Dispersion in Gas-Solid Compressible Turbulent Jets

A numerical method was developed to directly simulate the compressible, particle-laden turbulent jets.The fourth order compact finite difference schemes were used to discretize the space derivatives. The Lagrangian method was adopted to simulate the particle motion based on one-way coupling. It is found that the turbulent intensity profiles attain self-similar status in the jet downstream regions. At the Stokes number of 1, particles are concentrated largely in the outer boundaries of the large-scale vortex structures with the most uneven distribution and the widest dispersion in the lateral direction. Particles at the much smaller Stokes numbers are distributed evenly in the flow field, and the lateral dispersion is also considerable. Distribution of particles at much larger Stokes numbers is more uniform and the lateral dispersion becomes small. In addition, the inflow conditions have different effects on the particle dispersion. The direct numerical simulation (DNS) results accord with the previous experiments and numerical studies.

The stability indexes of branched airflow of ventilation network in coal mine

The stability of branched airflow of ventilation network is guarantee of safety in production of coal mine. Two indexes which stand for the stability of branches of ventilation network in coal mine were put forward in this paper, that are airflow intensity and sta- bility index of branched airflow, The airflow stability of working place was divided into different grade according to the stability index. The conclusion has great significance for safety in production of coal mine.