超音速虹吸式空气雾化喷嘴雾化影响因素实验研究*

为掌握超音速虹吸式空气雾化喷嘴雾化机理及特性,采用流体力学线性不稳定理论分析雾化机理,通过喷雾实验研究不同因素对雾化性能的影响及对比不同类型喷嘴的雾化效果。研究结果表明:随着距喷嘴出口距离增加,超音速虹吸式空气雾化喷嘴在雾滴破碎后碰撞聚合作用由强到弱,300 mm内雾滴粒径增长速率明显,300 mm外雾滴粒径增长速率较缓。随着供气压力增加,超音速虹吸式空气雾化喷嘴雾滴粒径逐渐减小,在实测距离内SMD（平均粒径）最小为17.5 μm。不同供气压力下,超音速虹吸式空气雾化喷嘴随距离增加,雾滴粒径增长趋势基本一致。有效射程内供气压力为0.1~0.5 MPa时,SMD仅为17.5~31.16 μm。对比实验中,超音速虹吸式空气雾化喷嘴SMD比内混式空气雾化喷嘴和X旋流型压力喷嘴小53.5%~74.0%。     

煤矿用喷嘴的优选方法研究与应用

喷嘴作为煤矿喷雾降尘技术的最重要元件之一,其优选问题一直没有统一的方法,在一定程度上影响了喷雾降尘技术的最佳效果。为此,在尘雾耦合沉降实验基础上,找出了雾滴沉降粉尘规律,确定了粉尘与雾滴粒径的关系:D尘≈0.1 D雾;结合喷嘴性能实验,建立一种以喷嘴雾滴粒径与各工序粉尘粒径关系为主、常规性能参数为辅的优选方法,力求进一步改善井下喷雾系统,并在高庄煤矿综放面进行了应用。通过现场实测,降尘效果有所提高。     

压力旋流喷嘴雾化特性数值模拟

为了改善生产作业环境,针对喷雾降尘作业运用最为广泛的1.5 mm孔径压力旋流喷嘴进行模拟仿真以研究雾化压力对雾化效果的影响。研究表明:在压力旋流喷嘴的雾化场中,沿喷嘴轴线方向,随着轴向距离的增大雾滴粒径不断增大、雾滴速度逐渐减小;在距喷嘴一定距离的横截面上,雾滴径向速度由中心向边缘先增大后减小,雾滴粒径随着径向距离的增大而增大,但增幅较小;同一孔径的喷嘴,随着喷雾压力的增加,雾滴轴向速度、径向速度均不断增加,速度衰减速率也增大;雾滴粒径随着喷雾压力的增大而减小,当喷雾压力达到一定数值时,继续增大喷雾压力,雾滴粒径减小幅度较小。     

气水喷雾降尘系统在采煤机上的应用研究

针对综采工作面传统的喷雾降尘措施存在的易堵塞、雾化效果差、覆盖范围小等不足,提出了一套防堵塞,易安装的气水喷雾降尘系统。分析了气水喷嘴的雾化原理,通过实验确定了单个喷嘴最佳雾化效果的气水压力比,根据现场实际情况设计了气水喷雾模块及过滤系统,并在综采面采煤机安装应用,取得了良好的降尘效果。     

密闭空间硫化氢泄漏喷淋捕消实验研究

搭建密闭箱实验装置,使用30°超声波喷嘴,在纯硫化氢释放速率为60 L/min条件下,待密闭空间硫化氢体积分数达到0.1%和0.3%时,分别采用质量分数为3%的碳酸钠单一溶液和质量分数为3%的碳酸钠+体积分数为0.6%的过氧化氢混合溶液,进行泄漏硫化氢的喷淋捕消实验,捕消效率达到91.3%及90.7%时的用时分别为6 min 58 s和8 min 31 s。实验结果表明,喷雾雾化均匀、雾滴粒径小,混合溶液捕消效果优于单一溶液。     

振弦栅与高压喷雾协同作用下除尘特性研究

为防治矿井排风口的粉尘对矿区周边大气环境的污染问题,基于流体动力学、气液耦合和喷雾降尘及振弦栅除尘理论,运用计算流体动力学(CFD)三维数值模拟方法,优化振弦栅与高压喷雾协同作用下除尘特性参数,研究不同雾化压力对雾滴粒径分布及质量浓度分布的影响,分析振弦栅直径及间距对雾滴拦截效果、风速对双层振弦栅水膜作用特征。结果表明:随着雾化压力增大,雾滴粒径逐渐变小且分布集中化,雾化压力超过8 MPa后雾滴粒径分布变化不明显;不同间距的振弦栅均对流场有截流作用并伴有严重回流现象,而间距为5 mm的振弦栅对粒径较小的雾滴拦截效果更好;当进口风速为3 m/s时振弦栅表面形成水膜效果最佳,更利于粉尘捕集;模拟数据与试验结果变化趋势基本一致。     

改善热轧降尘效率的雾化参数分析*

为提高热轧工作区的雾化降尘效率,研究尘雾颗粒碰撞相关理论,以热轧产生的氧化铁皮粉尘为研究对象,建立基于雾滴粒径、雾滴速度和液体流量多个雾化参数的降尘效率计算模型;分析单一雾化参数对降尘效率的影响;通过实验,测得不同气液压力组合下的雾化参数,运用响应曲面法,分析多个雾化参数耦合对降尘效率的影响。结果表明:降尘效率随着雾滴粒径的减小、液体流量增大而提高,雾滴速度对其影响不明显;多因素耦合时,通过调节气液压力组合来控制降尘效率,结合高温环境对雾滴存活时间的影响分析,当气压0.3 MPa、液压0.5 MPa时,粒径为21～27 μm的粉尘沉降效果最佳,降尘效率达到90%以上,可有效解决热轧车间粉尘污染问题。     

X形旋流压力喷嘴质量中值直径预测模型

X形旋流压力喷嘴是喷雾降尘常用的一类喷嘴,喷嘴雾滴粒径是重要参数.为了更好地指导喷雾降尘过程中喷嘴的选型,对工业现场常用的6种X形旋流压力喷嘴展开了雾化参数试验研究.通过试验获得了喷嘴水流量、雾化角和喷嘴MMD实测数据,结果表明,X形旋流压力喷嘴MMD随供水压力增大而减小,随喷嘴出口直径增大而增大.在此基础上,根据已有的压力喷嘴MMD经验公式,采用多元非线性回归的方法,建立了 X形旋流压力喷嘴MMD预测模型.经试验验证,模型预测值与试验值变化规律一致且平均相对误差仅约7％.所建立的预测模型可用于该类喷嘴MMD的理论预测,指导喷雾降尘工程应用中喷嘴的选型.     

多层螺旋雾幕技术的喷雾模拟及降尘试验研究

为了解决掘进工作面传统喷雾除尘无法有效抑制粉尘扩散的问题,提出了一种将气动喷嘴呈螺旋状布置的多层螺旋雾幕除尘方法。采用k-ω湍流模型与K-H液滴破碎模型,通过Comsol多物理场耦合数值模拟,得出了多层螺旋雾幕速度场分布和粒子轨迹的变化规律,结合模拟结果搭建试验平台,并将多层螺旋雾幕与传统喷雾的除尘效果进行对比分析。以2层雾幕为例的模拟结果显示,喷雾2 s时就会形成明显的2层螺旋状雾幕,10 s后旋转水雾充满整个模拟区域,并且雾滴粒径较传统喷雾更小。试验表明多层螺旋雾幕的除尘效果明显强于自然降尘与传统喷雾,3 min后可将浓度470 mg/m3左右的粉尘降到4 mg/m3以下。     

钢厂电缆隧道水喷雾灭火系统设计及优化

为实现对某钢企电缆隧道中水喷雾自动喷水灭火系统的参数优化设计,对水喷雾灭火系统中喷头雾化角大小、间距及喷雾流量展开数值模拟,最终确定水喷雾灭火系统的最佳灭火系统参数为：水供给强度13 L/(min·m²),下喷喷头雾化角120°,喷头间距为1 m,侧喷喷头雾化角90°,喷头间距为1.7 m,工作压力0.34 MPa,喷雾流量30 L/min。     

Production of fire extinguishing mixture by solid propellant propulsion

The behavior of fire suppression by water mist spray has been studied by using the experimental setup which employs the double-based solid propellant gas generator for water mist production. The burning products of solid fuel form a supersonic flow injected through the nozzle into the diffuser chamber having input for the water component ejected from the storage. High values of temperature and pressure at stagnation point impart the substantial kinetic energy to the flow, which provides the atomization of water droplets into mist spray. Since the water evaporation occurs already in the diffuser chamber due to the high temperature of input gas flow, the droplet size is gradually decreases to the lower limit value that could ever exist. The presence of vapor phase enlarges the volume of fire extinguishing jet allowing it to operate as a flooding agent (along with the effect of heat consumption due to water evaporation) at the very beginning of fire suppression process, much before the water droplets evaporation by the flame itself. Proposed technique of the water mist production has showed noticeable fire suppression capability through the series of testing application to the gasoline and wood model fire sources.     

磁化荷电水雾最佳降尘参数确定实验研究*

为实现对煤尘的有效防控,进一步提高磁化水降尘性能,提出磁化荷电喷雾降尘技术,通过研究液滴在磁化、荷电情况下的受力,揭示磁化荷电喷雾降尘机理;通过自主搭建的动、静态综合除尘实验平台,研究不同磁化强度、荷电电压下溶液表面张力和雾滴粒径的变化规律,进而确定最佳雾化参数。研究结果表明:磁化荷电后的溶液表面张力和雾滴粒径随磁化强度、荷电电压的增大呈现先下降而后上升,最后趋于平稳。荷电电压为9 kV、磁化强度为350 mT时达到最佳效果,此时,与清水相比全尘降尘效率达到92.79%、提高69.63%,呼尘降尘效率达到78.59%、提高94.01%。磁化荷电的溶液表面张力降低,破碎时所做表面功更小,雾化后液滴粒径更小更均匀,与尘粒接触面积增大,可提高捕尘效率,改善矿井环境。     

超音速气动液滴荷电雾化及降尘性能试验研究*

为探究煤炭生产过程中呼吸性粉尘难以捕捉且对人体造成伤害的问题,提出超音速水雾荷电降尘技术。基于荷电雾化机理,研究电极环直径、电极间距、电压3因素对超音速气动液滴荷电、雾化效果的影响。利用网状目标法测量雾滴群电流并计算荷质比,采用SPSS软件分析3因素与雾滴荷质比之间的相关性,并用激光粒度仪测量雾滴粒径。最后,采用最优荷电雾化参数进行喷雾降尘试验。研究结果表明:各因素对荷电效果的影响次序为:电压>电极间距>电极环直径;雾滴粒径随电压的升高而减小,随电极间距的增大先增大后减小,随电极环直径的增大先减小后增大;当电压12 kV,电极间距2.5 cm,电极环直径6 cm时,超音速荷电水雾降尘效果最佳,与普通水雾降尘相比,全尘降尘效率提高12.4%,呼尘降尘效率提高49.6%。     

隔爆水幕对瓦斯爆炸传播规律影响的试验研究

为研究自制隔爆水幕抑制瓦斯爆炸的有效性,采用大直径瓦斯爆炸试验管道系统,在不同瓦斯浓度和不同水幕流量条件下进行瓦斯爆炸试验,利用数据采集系统测量瓦斯爆炸特性参数并对其变化规律和隔爆效果进行分析。结果表明:瓦斯浓度9.5%时经过隔爆水幕抑制作用,瓦斯爆炸压力峰值由64 kPa下降到39 kPa,衰减了39%;温度峰值由969 K下降到498 K,衰减了49%;速度最大值由136 m/s下降到73 m/s,衰减了15%。虽然隔爆水幕对不同浓度瓦斯产生的爆炸起到良好的抑制效果,但隔爆之后的传播规律依然受到瓦斯浓度影响。隔爆水幕对瓦斯爆炸的抑制效果取决于喷水流量的大小,随着流量的增加,水幕的隔爆效果增强,喷头最佳的工作流量为16.4 L/min。     

Characterization of a medium velocity deluge nozzle for offshore installations

It is important to study the characteristics of the nozzle of the deluge spray to comply with the standards developed by the petroleum industry for offshore installations in Norway. Due to the stochastic nature of the decomposition processes and geometrical features within the nozzle, the deluge spray has a complex flow field. Since the flow field determines the performance of the spray, the present study performs an experimental characterization of a medium velocity deluge nozzle for validation of computational fluid dynamics (CFD) models. The experiment was conducted for a maximum supply water pressure of 8.0 bar (g), which is identical to the operating pressures of offshore installations. Formerly, characterization studies of deluge or sprinkler spray were mostly targeted on residential usage with lower supply water pressures. I utilized a laser-based shadow imaging system to capture high-speed images, which were later processed in MATLAB. A linear patternator was used to validate the results of the shadow imaging technique. The geometrical features of the deluge nozzle played an important role in determining the characteristics of the spray. In addition, the supply water pressure significantly affected the size and velocity distributions of the droplets, applied density (volume flux), and area coverage. However, the Sauter mean diameter did not vary significantly with the azimuthal or radial position of the droplet within the inner region of the spray. The measurements obtained in this study can be used to estimate the extinguishing efficiency of a deluge system for offshore installations with elevated supply water pressures. Deviations between measurements with shadow imaging and patternator technique are discussed and discrepancies are discussed.     

Performance of water mist system with base injection in extinguishing small container fires

The purpose of the present work is the experimental investigation on the extinguishment of diesel container fires by a water-mist system with base injection through multiple nozzles placed symmetrically at various positions around the rim of the container. Experimental parameters selected are the orifice diameter of the nozzle, the number of nozzles, position of nozzles (angle of orientation, radial and vertical distance of the nozzle from the edge of the container), and injection pressure. Nozzles used in the present work are pressure-swirl nozzles with Z-type swirl-insert with solid-cone spray. Desirable properties of the system such as the non-clogging operation of the nozzle and uniform mass flux density in the spray are tested for the nozzles. The optimized solution is provided considering water consumption and the physical stability of the fuel surface in the container. Displacement of oxygen is observed as a predominant extinction mechanism due to the effective application of spray in the base region of the fire. The present work provides the parametric study of the extinction establishing the feasibility of the water mist system with a base injection for extinguishing tank fires. This may serve as guidelines for the preliminary design of the system with the extension for larger tank fires.     

自进式旋转钻头钻孔修复理论及关键参数研究

瓦斯预抽钻孔在抽放过程中经常出现塌孔、堵孔等现象。针对这一问题,提出采用自进式旋转钻头修复失效钻孔的新方法。其利用自进式旋转钻头后置喷嘴的喷射反冲力作为动力,自行至钻孔堵塞段处,前置喷嘴形成的高压水射流对堵孔煤渣进行破碎,将其与水混合返出孔外,实现清孔排渣、钻孔修复的目的。对自进式旋转钻头钻孔破煤清渣的临界射流压力及流量进行分析,基于摩擦动力学计算钻头自驱的临界射流压力,在此基础上设计钻头结构及优化喷嘴布置,数值分析不同喷嘴组合情况下射流速度分布,得出最优喷嘴布置方式。并应用于鹤煤八矿-655轨道石门揭煤瓦斯预抽,实验结果表明:该方法能够实现失效钻孔的修复,并有效的提高了瓦斯抽采效果,缩短了瓦斯抽放时间。