旋风除尘器减阻节能技术的研究与应用

通过安装在旋风除尘器内适当位置处的减阻杆,可以在保证分离效率的前提下降低流动阻力,实现设备的节能增产。分别采用五孔球形探针、激光多普勒测速仪和粒子图像测速仪对旋风除尘器内安装减阻杆前后的时均流场与湍流场进行了测量,发现减阻杆降低了流场中于粉尘分离无益的内旋流切向速度,削弱了中心区域的湍流强度,使湍流耗散减弱,从而实现减阻。工业应用实例表明旋风除尘器减阻杆技术是可行的,而且取得了显著的经济效益。     

旋风分离器排气管内流动分析及减阻机理

利用激光多普勒测速仪(LDV)对旋风分离器排气管内流场进行了全面系统的测量,发现气流的高速旋转、回流区的存在及湍流脉动是排气管内产生流动阻力损失的重要原因. 安装减阻杆改变了排气管内流场分布规律,使旋转动能降低、回流区消失以及湍流脉动减弱,从而降低了排气管内流动阻力损失. 减阻杆迎风截面宽度越大,绕流边缘越尖锐,排气管内切向速度就越小,轴向速度分布越均匀,分离器的减阻幅度也越大.     

带有减阻杆的旋风分离器内气体流动分析

利用激光多普勒测速仪(LDV)对装有减阻杆的旋风分离器内流场进行了详细测量,根据流场分布的特点发现在减阻杆后存在明显的绕流尾涡区.对比实验的结果表明不同结构型式的减阻杆后绕流尾涡区的流动分布不同,其中减阻杆的迎风宽度及形状对减阻杆后绕流尾涡区的流动分布有明显影响.由于减阻杆的迎风宽度及形状与减阻性能有关,因此通过对减阻杆后绕流尾涡区的流动分析可以进一步揭示旋风分离器内减阻杆的减阻机理.     

螺旋型减阻器对旋风分离器减阻作用的研究

本文根据对旋风分离器内流场中切向速度及全压压降分布特性的分析，认为旋风分离器压降主要集中在对分离无效的内旋涡区和出口带走的气流旋转功能损失。据此提出一种抑制内旋涡流动并回收出口气流旋转动能的螺旋减阻装置。本文研究了这种装置的减阻特性，获得了降低压降４０％、而对分离效率影响＜１％的显著效果。     

旋风分离器内筒减阻装置的试验研究

以理论研究为基础,通过冷模试验研究了不同操作条件下旋风分离器压力损失的变化规律,开发设计了一种针对旋风分离器的内筒高效减阻装置,并对安装内筒减阻罩的旋风分离器的阻力损失和分离效率进行了试验研究,探讨了不同入口风速、不同固气比条件对旋风分离器的性能影响.对结果进行了理论分析,结果表明:对于相同规格的旋风分离器,内筒减阻罩能起到优化旋风分离器阻降且把分离效率控制在合理数值范围内的作用,不同风速,不同固气比条件下,内筒减阻罩的最大减阻幅度为43.36％,而分离效率最大降幅只有8.78％.     

蜗壳式旋风分离器减阻实验研究

根据蜗壳式旋风分离器环形空间流场研究结果,在分离器排气管特定位置上加装减阻片。加装直片减阻片后,最大减阻幅度达59%,但由于减阻片对环形空间内的切向速度影响较大,分离效率下降约5%,综合效率因子降低了2.2%;在排气管外壁周向270o处加装改进型减阻片对切向速度的影响较小,同时可以大幅度提高分离器中心部分的静压,从而可使分离器压降降低22%,效率仅下降0.3%,综合效率因子提高25%。     

一种新型两性界面活性剂的减阻特性

对一种新合成的两性界面活性剂N,N,N-三甲胺-N′-油酸酰亚胺在二维通道内的减阻特性进行了实验研究.为了能进行低温测试,以20%的甘醇不冻液为溶剂.溶液质量浓度范围为（5×10^-5）～（1×10^-3）,测试温度为-5℃和25℃.用粒子成像测速仪对减阻流动的湍流特性进行了测量.实验表明,这种新型界面活性剂溶液呈现明显减阻特性,且减阻特性与浓度和温度均有很大的关系,最大减阻值可高达83%.该界面活性剂中加入NaNO₂,在低温和低浓度条件下能有效改善减阻效果,而在常温和高浓度条件下反而降低减阻效果.添加界面活性剂抑制了湍流速度脉动和湍流涡脉动,使雷诺剪切应力完全消失.     

旋风分离器防磨减阻性能机理研究

为了提高旋风分离器的防磨减阻性能,运用计算流体动力学方法研究了常规和防磨减阻旋风分离器的防磨减阻机理。结果表明:常规旋风分离器容易发生严重的局部冲蚀,而防磨减阻旋风分离器冲蚀磨损区域较为均匀。在同一粒径下,防磨减阻旋风分离器的壁面冲蚀磨损远小于常规旋风分离器。两者的壁面冲蚀磨损速率随粒径增大而逐渐增大,当粒径大于15μm时,冲蚀磨损速率变化不大。两者的压降损失随着入口速度的增加而增大,当入口速度为15 m/s时,防磨减阻旋风分离器的压降为297 Pa远小于常规旋风分离器的821 Pa。防磨减阻板不会改变旋风分离器的流场特性,分离小粒径颗粒效率略小于常规旋风分离器,但粒径大于5μm时,防磨减阻旋风分离器具有很高的分离效率。     

导叶式旋风管整流罩减阻的实验研究

研究开发了一种新型减阻结构——整流罩,安装在排气管的入口处。此减阻元件可以减弱旋风管内旋流的旋转强度,而对外旋流基本没有影响,从而可以在保证总效率基本不变的情况下,较大程度地降低旋风管的压降,达到减阻的目的。     

旋流数为1.0的强旋湍流两相流动的PDPA实验

采用相位多普勒颗粒测速仪 (PDPA)对旋流数为 1 0的轴向和切向进风的圆柱形旋风筒内强旋湍流气粒两相流动进行了测量研究 ,并与旋流数为 0 47、 1 5和 2 0 8的实验结果进行了对比分析 ,指出了旋流数变化对两相流场及两相湍流特性的影响 .     

Experimental Study and Analysis on Drag Reduction Mechanisms of Reducing Pressure Drop Stick in a Cyclone Separator

The mechanisms of mean mechanical energy losses in a cyclone separator with a Repds (Reducing Pressure Drop Stick) are studied. The results show that the energy losses are mainly caused by direct viscous dissipation, turbulent diffusion, and turbulent energy production, which is the same as in a conventional cyclone separator. In particular, the direct viscous dissipation and the turbulent energy production are of importance. Laser Doppler Velocimetry (LDV) is used to measure the flow field in the cyclone body and the exit pipe of a cyclone separator with and without a Repds, respectively. The drag reduction mechanism of the Repds is analyzed by examining the effects of the Repds on flow parameters which are related to energy loss factors. The measured results and analysis reveal that the drag reduction results from decreases of the direct viscous dissipation, turbulent diffusion, and turbulent production as a whole when a Repds is inserted into a cyclone separator. The resultant drag reduction is a tradeoff between the increase and the decrease of energy losses caused by the Repds.     

Effect of a Stick on the Flow Field in a Cyclone and the Pressure Drop Reduction Mechanism

Measurements of the flow field in a cyclone separator with and without a reducing pressure drop stick (Repds) showed that the Repds reduces the peak tangential velocity, the axial velocity gradient, and the radial gradients of static and total pressure and reverses the axial static pressure gradient. These changes reduce the energy consumed by the rotating kinetic energy, the internal friction, the turbulent kinetic energy, and the drag of the negative pressure difference. The results are used to discuss why the separation efficiency remains high while the pressure drop is reduced. The results also show that a 24% "short flow" occurs near the cyclone entrance. Analysis of the changes in the flow field and the pressure drop due to the thin stick shows that the Repds increases the pressure drop in the outer vortex zone and reduces the pressure drop in the inner vortex zone. Therefore the pressure drop reduction with the Repds is due to its wake vortex, which leads to the hypothesis that the pressure drop in turbulent flow can be reduced by adding vortexes.     

蜗壳式旋风分离器全空间三维时均流场的结构

采用激光多普勒测速系统（LDV）对蜗壳式旋风分离器全空间内三维湍流的时均流场进行了实验测定与分析,重点讨论了灰斗、环形空间和排气管的流场特点.分离空间内时均流场是外侧准自由涡与内侧准强制涡的典型结构.环形空间的入口部位有多个纵向二次涡,其他大部分空间顶部出现纵向二次环流,切向速度和径向速度的分布呈现非轴对称性,入口气量沿高度分布不均匀.灰斗的顶部也存在纵向二次环流.排气管内轴向速度分布与分离空间内的分布形态迥异.     

Hydrodynamics and velocity measurements in gas–liquid swirling flows in cylindrical cyclones

The gas–liquid swirl flow in a gas–liquid cylindrical cyclone separator has been characterized first qualitatively by flow visualizations. The emerged findings were then confirmed quantitatively by Laser Doppler Velocimetry measurements. The vortex core presents a very complex hydrodynamics, characterized by an alternation between a laminar and a turbulent state. The laminar regime is associated with velocities pointing in the same direction as the mean flow, while the turbulent state induces velocities in the opposite direction, i.e. a flow reversal. These observations give a first understanding of the origin of the double flow reversal regime that is encountered in swirl flows. It is shown that this flow structure appears for high swirl intensities, and results from a frequent laminarization of the vortex core. Results show that, contrary to the commonly assumed hypothesis, this flow structure is associated with good separation performance of the cyclone. Accordingly, we propose the use of multiple tangential inlets to generate the swirl motion in the cyclone, which is supposed to favor the double flow reversal regime, and thus, improve the separation efficiency.     

Reducing Pressure Drop in Cyclones by a Stick

It is found that a thin stick inserted into a cyclone separator can substantially reduce the pressure drop. The percentage reduction in pressure drop is dependent on the cross-section shape, size, and placed position of the stick. By using talcum powder (mass mean diameter is 10.14 mu m) as the test powder, the experiment results show that the stick can reduce the pressure drop of the cyclone by approximately 20% at the same total separation efficiency and flow rate. If the cyclone is used in a two-stage separation system and a reduction of the efficiency within 5% is permitted, the pressure drop can be reduced more than 50%.     

蜗壳式旋风分离器内的湍流特性(Ⅰ)分离空间

采用激光多普勒测速系统测试了蜗壳式旋风分离器内的流场,分析了最主要的分离空间内湍流特性.内旋流区、排尘口附近、近壁处以及上下行流交界点和内外旋流交界点等处的湍流度变化非常剧烈,而且数值上也大得多.比较轴向和切向湍流度得知表明分离空间的湍流是各向异性的.Reynolds应力值在内旋流区大于外旋流区,而且在排尘口附近、排气管下口附近都有陡增,湍流黏性系数也反映了这个特点.     

Effect of a Stick on the Gas Turbulence Structure in a Cyclone Separator

Laser Doppler Velocimetry (LDV) was used to measure the turbulence structure of the flow field in a cyclone separator. The measurement results showed that a stick inserted in the cyclone changed the distribution of the flow field. A flow wake region downstream the stick decreased the tangential velocity and increased the turbulence intensity. The size and shape of the stick cross-section had a remarkable effect on the distribution of the flow wake and the turbulence structure of the flow field. The changes of the flow field explained how the stick reduced the pressure drop over the cyclone.     

旋风分离器入口结构改进及其对“短路流量”的影响

常规切向进口旋风分离器的气流进入旋风分离器后必定要经过排气芯管外壁和筒体内壁之间,因此不可避免会使得相当一部分气流没有经过分离空间而直接从排气芯管底部排出(短路流量),这也是影响旋风分离器分离效率的重要因素之一。在前人工作的基础上,对旋风分离器的进口结构进行了改进:使得旋风分离器的入口具有一定截面角,并借助数值计算技术,分别对传统的和具有一定入口截面角旋风分离器内的三维流场进行了数值模拟,计算了芯管底部的"短路流量",结果表明:进口具有一定截面角可以明显减小芯管底部的"短路流量",这对改善旋风分离器的分离效率具有重要的实际意义。