4种脱硫喷嘴雾化特性对比试验

对目前湿法烟气脱硫系统中常用的4种机械式雾化喷嘴进行了雾化试验,采用高速数码摄影法对4种喷嘴在不同压力下的喷雾状况进行测试,并用ImageJ软件处理,得到各喷嘴在不同工况下的粒径、粒径分布和雾化角等特性。研究结果表明:4种喷嘴雾化粒径随液压的增大呈减小趋势,其中螺旋喷嘴雾化粒径最小,扇形喷嘴雾化粒径最大;螺旋喷嘴、空心锥喷嘴和扇形喷嘴的雾化角随液压增大变化不大,较为稳定,实心锥喷嘴雾化角随液压增大而增大,螺旋喷嘴与扇形喷嘴的雾化角较大,空心锥喷嘴的雾化角最小;各喷嘴在小于0.2MPa的液压下粒径分布不均匀,当达到0.2MPa后粒径分布较为均匀。综合结构特点和雾化特性,螺旋喷嘴较适用于火电厂湿法烟气脱硫系统。     

基于Ｆｌｕｅｎｔ的雾化器雾滴粒径的研究

对雾化器的喷嘴结构进行研究，通过分析实验结果，得出影响液滴粒径的因素。以不同尺寸的液相通道为实验对象，通过改变轴向中心截面距、气液比、液相压力和气相压力的大小，分析以上实验参数对雾化发生器雾化后液滴颗粒大小的影响。由实验结果可知:在气液比、液相压力和气相压力的逐渐增加的过程中，液滴粒径呈现变小的趋向；在轴向中心截面距逐渐增加的过程中，液滴粒径呈现增大趋向。     

压力对直射式喷嘴雾化影响的机理研究

为了揭示压力对直射式喷嘴雾化影响的雾化机理,针对D=0. 2 mm、D=0. 3 mm的直射式喷嘴采用实验和数值模拟研究。主要获得以下结论:压力是影响直射式喷嘴雾化的重要因素。压力越大,燃油液滴粒径SMD越小、喷雾锥角越大。直射式喷嘴的压力增大,雾化效果增强趋势逐渐降低;压力增大对一次雾化影响较大,对二次雾化影响较小。使用TAB模型的数值模拟结果能很好的预测出与实验一致的直射式喷嘴雾化特性,可应用于工程设计。     

压力条件对旋流槽数不同的离心式喷嘴液膜破碎及雾化的影响研究

利用粒子动态分析仪和高速摄影系统,研究不同注压下的锥形液膜流动、破碎及雾化特性,分析不同注压下液膜流动速度对液膜破碎的作用以及喷雾质量参数的变化规律,并结合相应试验数据求解了锥形液膜的色散方程,验证了注压对液膜破碎的影响.结果表明,随着注入压力增大,喷嘴流量增大,喷嘴液膜破碎长度下降,喷雾锥角先增加后趋于稳定,雾场SMD(索特尔平均直径)减小,雾滴流动速度增大,液膜切向速度对锥形液膜的作用效果显著;旋流槽数的增加使液膜速度增加,喷雾锥角减小,雾滴流速增大,雾场浓度增加且均匀性更好;通过求解色散方程得到了液膜表面波增长率,从理论的角度说明旋流槽数的增加使液膜表面波增长率增加,导致锥形液膜破碎长度减小.     

不同喷口扩张比下离心喷嘴雾化特性研究

为研究喷口扩张比对航空发动机离心喷嘴雾化特性的影响,对多种结构离心喷嘴开展试验研究。用工业相机捕捉油雾场形态;用多普勒激光粒度仪测量喷嘴出口液膜速度、雾化粒径;结合数值模拟得到的液膜流动情况,对雾化性能进行详细分析。研究结果表明：随着喷口扩张比的增加,雾化锥角增大,雾化粒径减小,液膜轴向速度减小;当扩张比一定时,不同压差下雾化锥角基本一致;喷嘴下游存在三个流动区域,分别为燃油射流区、射流内侧空气区及射流外侧空气区,射流内侧形成对称的空气涡;在扩张段处液膜与壁面之间会形成分离区,当扩张比较大时,液膜可绕过分离区重新靠近壁面,且扩张比越大,液膜与壁面贴合程度越高。     

内混式喷嘴雾化特性的试验与仿真研究

利用马尔文测雾仪对内混式喷嘴在不同工况下的雾化特性进行试验研究。根据试验结果,分析气压、水压以及气液比等因素对液滴粒径及均匀性的影响。利用Fluent软件对内混式喷嘴进行数值模拟,研究喷嘴混合段以及外流场的粒径变化。结果表明:随着气压、气液比的增加,喷嘴的雾化粒径减小,且气压为主要影响因素;内混式喷嘴内部粒径先增大后减小,在喷嘴出口处锐减,外流场中粒径沿轴向方向逐渐增大;将喷嘴出口处模拟粒径与实验结果对比,粒径大小及其变化趋势吻合较好。     

SCR系统尿素喷嘴雾化特性与结晶风险研究

为研究发动机SCR系统尿素喷嘴雾化特性和结晶风险,探究了不同喷嘴雾化性能以及不同雾化性能对尿素结晶影响,结果表明SCR系统尿素喷嘴主要通过改变雾化方式和提高喷射压力来提高喷雾的雾化效果,即通过降低喷雾液滴的索特平均直径(SMD)来提高喷雾的雾化效果,达到降低尿素结晶的目的。在同等喷射压力下,气助式尿素喷嘴产生的喷雾的SMD比非气助式喷嘴产生的喷雾的SMD更小,雾化效果更好,相同工况下结晶量更少;而同样类型的喷嘴,其喷雾SMD随着喷射压力的提高逐渐减小,喷雾SMD越小,雾化效果越好,相同工况下结晶量越少。     

关键结构参数对离心式雾化喷嘴雾化效果的影响研究

为提高某离心式喷嘴的雾化质量,对其内部结构进行改进优化,并采用数值模拟和试验相结合的方法详细探讨切向槽位置和倾斜角度对雾化效果的影响。结果表明:数值仿真可以较好地模拟喷嘴的雾化特性,其结果与试验吻合良好;位置和倾角的改变会影响雾化颗粒粒径和雾化锥角,其中雾化锥角受倾角的影响较为显著,随倾角的增大而减小;随着压力增大,雾化颗粒粒径会逐渐减小,雾化锥角逐渐增大并趋于稳定;9组不同工况下喷嘴雾化效果对比表明,在旋流室圆锥半径1/2或3/4处设置20°倾角的切向槽,雾化效果最佳。     

喷孔结构对双旋流气泡雾化喷嘴喷雾特性的影响

研究了喷孔形状对双旋流气泡雾化喷嘴雾化特性的影响规律,分析了圆形孔、椭圆形孔和正方形孔喷嘴对流量特性、索特尔平均直径、粒径分布和粒子速度的影响。结果表明,不同喷孔结构的喷嘴流量特性曲线呈现相同的趋势,随着气液质量流量比的增大,喷嘴出口单位面积下的喷雾流量逐渐减小;相同气液质量流量比下,正方形孔喷嘴流量最大。相同工况条件下,椭圆形孔和正方形孔对比圆形孔的喷嘴具有更加优良的雾化效果,其D32降幅分别为28.2%,35.8%,而正方形孔喷嘴的雾化粒径最小。正方形孔喷嘴的微分分布曲线向左移动,累积分布曲线变陡,说明大颗粒液滴减少,小颗粒液滴所占比例增大,液滴的雾化质量得到改善,正方形孔喷嘴小尺度粒径更多,粒径分布更集中。异形喷嘴的速度大于圆形孔喷嘴的速度;椭圆形孔喷嘴和正方形孔喷嘴的粒子速度分别增加了14.8%和24.4%。     

喷油嘴喷孔结构参数对甲醇燃料喷射流场影响的数值模拟

针对甲醇燃料不同于汽油的物化特性以及甲醇发动机冷启动困难等问题,以甲醇发动机喷油嘴喷孔为研究对象,采用Fluent软件的气液两相VOF湍流模型对喷嘴进行了数值模拟。研究发现了喷嘴入口处曲率半径变化以及喷嘴倒锥角度变化对喷嘴流量和雾化效果有一定的影响。结果表明:在压力不变的条件下,随着入口处曲率半径增大负压层的厚度逐渐变薄,喷孔内部气相体积分数减小,质量流量增大,雾化性能变差,但是喷孔的流速随着曲率半径的增大而增加;增大喷孔的倒锥角,喷嘴出口处的流速及质量流量均减小,但是负压层变厚有利于甲醇燃料的雾化。     

双油路离心喷嘴雾化锥角的试验研究

针对双路离心喷嘴开展雾化锥角的研究，采用高速摄影仪拍摄不同供油压差，仅副油路、主油路和主副油路同时工作时的喷雾形态，进而分析不同工况下雾化锥角的变化规律，同时与传统经验关系式结果进行对比。结果表明，单路压差增加时，平口式的主油路锥角迅速增大，扩口式的副油路锥角逐渐减小，共同喷射时，由于低压核心区的作用双路锥角处于两路单独喷射之间，并随主油路压差增大而增大，随副油路压差增大而减小。最后将传统经验关系式结果和试验结果进行对比，由于特殊的喷口结构产生了径向速度分量，关系式结果均偏高。     

阀芯结构对双流体喷雾粒子特性的影响

为了研究阀芯结构对双流体喷雾粒子特性的影响,提升喷雾效果,运用相位多普勒粒子分析仪（PDPA）对不同阀芯结构的双流体喷雾雾滴粒径、轴向速度以及雾滴数目进行了测试,并对测量结果进行了分析和讨论。结果表明：随着轴向距离的增大,雾滴索特平均直径(SMD)、算术平均直径(AMD)呈先增大后趋于平缓的趋势,轴向速度以及湍流脉动速度均呈减小趋势,雾滴数目呈先增大后减小的趋势;随着气液压力比的增大,SMD呈先增大后减小的趋势,而AMD、轴向速度以及雾滴数目均呈减小趋势;阀芯的喉口直径、出口直径的减小均有利于喷雾效果的提升,但同时导致速度稳定性变差;当喉口直径为1.5mm、出口直径为2.5mm时,与原始阀芯结构相比,雾滴数目和雾滴轴向速度分别增大了82.43%和22.31%,SMD和AMD分别减小了52.18%和21.47%,综合喷雾效果得到了大幅提升。     

The effect of swirling flow in the mixing chamber of atomizer and the length/diameter ratio of atomizer exit on the distribution of coal particles in CWM spray

This research is aimed to investigate how the swirling phenomena in an atomizer and the ratio of length/diameter of the atomizer exit affect the size distribution of coal particle in spray. CWM slurries are injected by a swirling twin-fluid atomizer. Five different caps and a swirler are designed and fabricated into an existing twin fluid atomizer. The droplets are sampled by test tubes and microscope slides coated with magnesium oxide. The data analysis are done by photo technique and Malvern particle sizer. The experimental results reveal that there are many droplets which do not have any coal particles. Those are simply water droplets. The population ratio of droplets without coal particles to total sampled CWM droplets is increased as the sampling position moves outward in the radial direction from the axis of spray. The length/ diameter ratio of an atomizer exit and the swirling phenomena in an atomizer affect a lot the spray pattern and the spray angle but they make no noticeable effects on the size distribution of coal particles in droplets and spray.     

Effect of nozzle geometry for swirl type twin-fluid water mist nozzle on the spray characteristic

Experimental investigations on the atomization characteristics of twin-fluid water mist nozzle were conducted using particle image velocimetry (PIV) system and particle motion analysis system (PMAS). The twin-fluid water mist nozzles with swirlers designed two types of swirl angles such as 0°, 90° and three different size nozzle hole diameters such as 0.5mm, 1mm, 1.5mm were employed. The experiments were carried out by the injection pressure of water and air divided into 1bar, 2bar respectively. The droplet size of the spray was measured using PMAS. The velocity and turbulence intensity were measured using PIV. The velocity, turbulence intensity and SMD distributions of the sprays were measured along the centerline and radial direction. As the experimental results, swirl angle controlled to droplet sizes. It was found that SMD distribution decreases with the increase of swirl angle. The developed twin-fluid water mist nozzle was satisfied to the criteria of NFPA 750, Class 1. It was proven that the developed nozzle under low pressures could be applied to fire protection system.     

乙醇圆柱射流雾化破碎过程的PIV试验研究

在喷雾容弹上利用PIV激光测试系统,研究了容弹背压、容弹温度和喷射脉宽对乙醇圆柱射流破碎雾化的影响。试验结果表明：容弹背压升高,乙醇圆柱射流贯穿距离减小,射流锥角变大;温度由20℃变为60℃时,乙醇运动黏度变小,射流贯穿距离增大,射流锥角略有增加;喷射脉宽的改变对乙醇圆柱射流贯穿距离和射流锥角影响很小,然而大脉宽的乙醇射流雾化困难。     

高压细水雾灭火喷嘴的雾化特性研究

高压细水雾灭火系统是采用纯水液压技术的新型灭火装置,具有无环境污染、灭火迅速、用水量少和水渍损失极小等优点,是目前国际上推祟的哈龙替代系统。运用轴对称射流边界层动量积分法,对系统关键执行元件—直射式雾化喷嘴的内部流动进行分析,对边界层厚度δ和加速因子K这两个内部流动参数进行考查;同时对一些与灭火效果有关的外部雾化特性参数如出口速度和雾滴平均粒径SMD等进行分析,得出压力是影响外部雾化特性参数的最关键因素。认为8~9 Mpa是所设计喷嘴的最低稳定雾化工作压力区域。同时,喷嘴结构参数收缩角α、收缩段长度l/d对内部流动参数、外部雾化特性参数均有影响,但不明显。试验验证了上述分析结果,优选出了适合的喷嘴内部结构。     

An investigation on effect of geometrical parameters on spray cone angle and droplet size distribution of a two-fluid atomizer

A visual study is conducted to determine the effect of geometrical parameters of a two-fluid atomizer on its spray cone angle. The liquid (water) jets exit from six peripheral inclined orifices and are introduced to a high speed gas (air) stream in the gravitational direction. Using a high speed imaging system, the spray cone angle has been determined in constant operational conditions, i.e., Reynolds and Weber numbers for different nozzle geometries. Also, the droplet sizes (Sauter mean diameter) and their distributions have been determined using Malvern Master Sizer x. The investigated geometrical parameters are the liquid jet diameter, liquid port angle and the length of the gas-liquid mixing chamber. The results show that among these parameters, the liquid jet diameter has a significant effect on spray cone angle. In addition, an empirical correlation has been obtained to predict the spray cone angle of the present two-fluid atomizer in terms of nozzle geometries.     

超高压高低温条件下节流阀Y形圈的影响因素分析

为研究天然气设备中节流阀的Y形密封圈在超高压、高低温工况下的影响因素,选择PTFE及其4种改性材料作为密封材料,研究唇口过盈量、唇前角、唇后角对Y形密封圈静密封性能的影响。结果表明：Y形密封圈最大von Mises应力随唇口过盈量增加而减小,随唇前角和唇后角的增大先增加后减小;内唇最大接触应力随唇口过盈量、唇后角的增加而增大,随唇前角的增加先增大后减小。选取密封圈宽度、基体高度、唇尖高度、唇前角、唇后角5个参数,采用ISIGHT软件对各参数进行灵敏度分析。结果表明：密封圈宽度及基体高度对Y形密封圈最大Mises应力及内唇接触应力影响最大。通过多岛遗传算法获得密封圈的优化尺寸,通过试验验证理论设计结果。     

Microscopic spray characteristics in the effervescent atomizer with two aerator tubes

An experimental study is performed on atomization characteristics and stable operating conditions for the injection of high viscous waste vegetable oil using an effervescent atomizer with 2 aerator tubes. Consideration is given to the effects of ALR and liquid viscosity on the velocity and mean diameter of the injected droplet. It is found that (i) as ALR increases, the axial velocity of the droplet is increased, while half-velocity width and SMD are decreased regardless of the change in liquid viscosities, (ii) the rate of fine drop distribution occupied in the total spray field is increased with an increase in ALR, and (iii) the effect of viscosity on the atomization characteristics is minor. Consequently, it is expected that the effervescent atomizer will exhibit an excellent atomization performance at the high ALR condition, regardless of liquid viscosities.     

Comparison of experimental and predicted atomization characteristics of high-pressure diesel spray under various fuel and ambient temperature

The aim of this study is to investigate the effects of the fuel temperature and the ambient gas temperature on the overall spray characteristics. Also, based on the experimental results, a numerical study is performed at more detailed and critical conditions in a high pressure diesel spray using a computational fluid dynamics (CFD) code (AVL, FIRE ver. 2008). Spray tip penetration and spray cone angle are experimentally measured from spray images obtained using a spray visualization system composed of a high speed camera and fuel supply system. To calculate and predict the high pressure diesel spray behavior and atomization characteristics, a hybrid breakup model combining KH (Kelvin-Helmholtz) and RT (Rayleigh-Taylor) breakup theories is used. It was found that an increase in fuel temperature induces a decrease in spray tip penetration due to a reduction in the spray momentum. The increase of the ambient gas temperature causes the increase of the spray tip penetration, and the reduction of the spray cone angle. In calculation, when the ambient gas temperature increases above the boiling point, the overall SMD shows the increasing trend. Above the boiling temperature, the diesel droplets rapidly evaporate immediately after the injection from calculation results. From results and discussions, the KH-RT hybrid breakup model well describes the effects of the fuel temperature and ambient gas temperature on the overall spray characteristics, although there is a partial difference between the experimental and the calculation results of the spray tip penetration by the secondary breakup model.