高温线管式静电除尘器内颗粒捕集的解析方法

通过分析荷电颗粒在气相流场耦合电场中的受力情况,计算出颗粒在有效除尘空间内的运动轨迹,并推导出颗粒的捕集效率表达式。结果表明:在温度为350~700℃、端口电压高于15 900V的条件下,计算与实验结果符合较好,最大相对误差小于9%;当气流平均速度大于0.2m/s时,应考虑阴极线的边界作用;相同直径的颗粒在电场中的初始位置不同时,驱进速度差异很大;提高端口电压可减小除尘器需求高度,以620℃、10μm的颗粒为例,除尘效率达到100%,端口电压为15 925V时,需要的有效除尘器高度约为0.86m,而端口电压为19 200V时,需要的有效除尘器高度约为0.42 m;在进入电场时,颗粒的初始位置在阴极线或阳极管附近时,更易被捕集。     

烟气流速对湍流涡旋以及颗粒凝并影响的研究

采用欧拉-拉格朗日法结合O'Rouekr碰撞模型,模拟了电厂满负荷下静电除尘器前的烟道流速区间内颗粒物的碰撞和凝并.结果表明:凝并器入口烟气流速越大,凝并区的湍流强度和涡量越大,有利于减少细颗粒物的数量,但减少的幅度较小;凝并器入口烟气流速越大,颗粒物在凝并区的停留时间越短,碰撞凝并形成的颗粒物粒径也越小,不利于形成粒径较大的颗粒物,所研究的电厂常见烟气流速范围内凝并器入口烟气流速的提高对湍流凝并的负面作用大于正面作用.     

柴油机颗粒捕集器内颗粒沉积结构的实验研究

基于可视化单通道实验系统,采用激光位移测量方法,对柴油机颗粒在陶瓷捕集器内的沉积过程进行了在线测量.研究结果发现,颗粒沉积过程分为4个阶段:深床期、长树期、搭桥期和颗粒层期;颗粒层厚度的增加在长树期迅速增长,而后在颗粒层期呈缓慢增加的趋势.颗粒层过滤期颗粒层的孔隙结构受过滤速度的影响,过滤速度增大,颗粒层的渗透系数和孔隙率减小,形成的颗粒层致密.实验结果证实了当Pe<1时,渗透系数和孔隙率随Pe的增大而减小,且变化显著;当Pe>1时,渗透系数和孔隙率随Pe数的变化趋于平坦.     

电晕极形式对静电旋风除尘器性能影响的实验研究

随着工业生产的迅速发展和生活水平的提高,工业设备的污染物排放（特别是大气污染物排放）日益成为国内外关注的焦点。为了提高旋风除尘器的性能,可利用高压静电技术将旋风除尘器改造成静电旋风除尘器。通过建立实验系统,对静电旋风除尘器中三种不同的电晕极布置方式进行了实验研究,并分析比较了其伏安特性以及电晕极布置方式对除尘器的除尘效率、分级除尘效率和压力损失的影响。实验结果表明,所研究电晕极中的一种不但可显著提高除尘效率,还使除尘器压力损失约降低30％,是一种新型的高效减阻电晕极,具有很大的应用和发展前景。     

省煤器灰斗出口布置拦截网对大颗粒灰捕集效率影响实验研究

为研究省煤器灰斗出口安装拦截网装置对大颗粒灰捕集效率的影响,得到较为合适的拦截网布置方式,搭建冷态实验台,以不同孔型、角度和长度布置方式下的平板型拦截网为研究对象,对1.0~3.35 mm、3.35~6.7 mm以及6.7 mm 3个粒径区间的大颗粒灰,展开单颗粒的捕集实验研究。实验结果表明:拦截网装置能有效提高大颗粒灰的捕集能力,实验条件下就综合捕集效率与系统压降来看,3×12型网孔拦截网的性能要优于6×6型网孔拦截网;30°~45°是较为理想的布置角度,较好的布置长度在竖直方向的投影长度为12.8~13.7cm,约占水平管段竖直高度的45.4%~48.6%。     

燃煤烟气中的SO3对微细颗粒物电除尘特性的影响

采用BDL粉尘比电阻测定仪、巴柯粒度分析仪和COULTERTM SA 3100TM比表面积分析仪对某燃用准格尔煤电厂飞灰的比电阻、粒度及比表面积进行了分析,研究了烟气中SO3对微细颗粒物导电性能和团聚性能的影响.结果表明：在锅炉额定工况下当烟气中SO3的质量浓度增加约34.3 mg/m^3时,飞灰比电阻降低约2个数量级,同时飞灰表面张力减小,黏附力增大,使得微细颗粒团聚为大颗粒,平均粒径增大,比表面积减小,从而使电除尘器效率明显提高.     

1 000 MW机组静电除尘器对粉尘颗粒脱除的数值研究

基于计算流体动力学软件FLUENT,对某电厂1 000 MW机组的电除尘器(ESP)流场、电晕电场和颗粒运动场进行三维数值模拟,其中流场的模拟采用k-ε双方程,电晕电场采用有限体积法,颗粒相运动采用拉格朗日方法,数值计算采用SIMPLE算法,在验证该数值模拟结果合理的前提下,模拟了出口压力、烟气流速、粉尘浓度及粉尘粒径对电除尘器除尘效率的影响。结果表明:粉尘脱除效率随出口压力绝对值的减小而增大,且当出口压力维持在-3 000 Pa～3 500 Pa时,电除尘器运行稳定;在较高的烟气流速下飞灰颗粒所受惯性力增大,克服电场力逃逸收尘板捕获的能力增强,使得电除尘器收尘效率降低;当烟气粉尘浓度维持在30 g/m~3时,电除尘效率最高;粉尘粒径越大,电除尘器收尘效率越高,但增长速率减缓。     

切向燃烧锅炉中屏结构对烟气偏差影响的试验研究

在冷模拟试验台上利用热线风速仪对屏区中气流流动情况进行了详细的测量,分析了分隔屏和后屏在烟气偏差形成中所起的作用,还提出了3个屏结构改进措施并进行了相应的试验,使水平烟道中烟气偏差状况得到了较大改善。图6表2参2     

HIAC-8011型液体自动颗粒计数器流速对固体污染度的影响

液体自动颗粒计数器在液压润滑系统的污染控制中获得广泛应用,但是,用户在使用这些仪器测试各种油样固体污染度的过程中,对于仪器流速的控制还存在误区。文章以目前国内广泛使用的HIAC一8011型液体自动颗粒计数器为例,详细探讨了在使用过程中其流速的控制对于得到准确固体污染度数据的重要性。     

Particle Image Velocimetry study on the formation of gas bubbles and electrolyte velocity due to electrochemical reactions for different distances between the electrodes of Flooded Lead_ Acid batteries

During the charging processes in Flooded Lead_ Acid batteries (FLA), the production of gas bubbles occurs and it effects on the FLA performance. In this experimental investigation, the effect of distance between electrodes at different charge-discharge rates on the electrolyte flow velocity and bubbles behavior is investigated based on the Particle Image Velocimetry method. The reduction in the distance decreases the FLA capacity linearly at the same processes. It leads to an increase in the void fraction of bubbles and a decline in the diameter and rising velocity of the bubbles. The maximum diameter of the bubbles during the charging processes is very small compared to the distances between the electrodes. The effect of electrolyte velocity compared to the effect of the average rising velocity of bubbles on the FLA performance is negligible. The results show that the increase in the void fraction of the bubbles and the formation of bubble layers in the vicinity of the electrodes is the most critical factor at the increase of the ohmic resistance.     

Effect of capillary pressure on liquid water removal in the cathode gas diffusion layer of a polymer electrolyte fuel cell

In order to investigate the effect of capillary pressure on the transport of liquid water in the cathode gas diffusion layer (GDL) of a polymer electrolyte fuel cell, a one-dimensional steady-state mathematical model was developed, including the effect of temperature on the capillary pressure. Numerical results indicate that the liquid water saturation significantly increases with increases in the operating temperature of the fuel cell. An elevated operating temperature has an undesirable influence on the removal of liquid water inside the GDL. A reported peculiar phenomenon in which the flooding of the fuel cell under a high operating temperature and an over-saturated environment is more serious in a GDL combined with a micro-porous layer (MPL) than in a GDL without an MPL [Lim and Wang, Electrochim. Acta 49 (2004), 4149–4156] is explained based on the present analysis.     

Effect of wettability heterogeneity and compression on liquid water transport in gas diffusion layer coated with microporous layer of PEMFC

This study applied the pseudo-potential Lattice Boltzmann method (LBM) for investigating liquid water transport in the microporous layer (MPL) and gas diffusion layer (GDL) of polymer electrolyte fuel cell. The MPL and GDL reconstruction is performed by using a stochastic method. Unlike previous studies that examined the GDL as two distinct layers of hydrophilic and hydrophobic, this study considered the wettability heterogeneity. In the present study, some of the carbon fibers in the GDL are randomly considered hydrophilic. Moreover, liquid water transport in the compressed and uncompressed GDL with different hydrophilic fibers percentage are compared. The effect of hydrophilic fibers percentage and the compression ratio of the GDL on the liquid water saturation level, the steady-state time, and the formation and growth of droplets in the gas channel (GC) are investigated. The results indicated that more than 10% of hydrophilicity of the fibers lead to the formation of discontinuous water clusters. This phenomenon increased the steady-state time and water saturation level significantly. The simulation showed that compression increased the number of discontinuous water clusters in the GDL. The obtained results demonstrated that the hydrophilic fibers may have positive or negative effects on water transport in the GDL due to their location. In addition, this study indicated that for 10% of hydrophilic fibers with 10% compression, water saturation level and time required to reach steady-state decreased by 5.2% and 22% respectively compared to purely hydrophobic GDL.