旋涡压力喷嘴的雾化特性

利用FAM激光粒度测量仪,以水为工质对不同结构旋涡压力喷嘴在不同压力条件下的雾化特性进行了实验研究。建立了描述喷嘴结构、操作压力及喷出速度与液体雾滴平均直径之间关系的数学模型,为进一步优化设计旋涡压力喷嘴提供了依据。     

NaCl水溶液喷射闪蒸-掺混蒸发的实验研究

喷射闪蒸与热空气掺混蒸发(FME)结合是实现含盐废水深度脱盐的有效方法之一。本文搭建了喷射闪蒸-横流掺混蒸发实验系统,结合PIV和Malvern激光粒度仪对FME流场中液滴群的运动、蒸发特性开展了实验研究。实验中掺混风温为104.7～145.3℃、风速为10～17 m·s^-1;液侧液滴初始盐质量分数为0～0.15,温度为20.0～132.0℃,喷射压力为0.5～1.2 MPa。FME中喷射闪蒸主要影响雾化破碎区,而掺混蒸发主要影响蒸发区。液滴群初始粒径随喷射压力或质量分数的提高趋于均匀,而随液滴温度的升高先趋于均匀而后均匀性变差。气液间的动量和能量交换主要发生在蒸发区内的水平方向;定义液滴沿水平方向截面平均速度为FME特征速度,该特征速度随掺混距离的增大先陡增后缓增,而在相同掺混距离处,该特征速度随掺混风温、风速或喷射压力的增大而增大;液滴群的Sauter平均直径沿掺混方向不断减小;增加掺混风温、提高掺混风速、增大喷射压力是强化FME蒸发的有效手段。根据实验结果计算了液滴群表面平均传热系数,并给出了该传热系数的实验关联式。在本文研究范围内,其计算值与实验值的主体误...     

基于图像法的环雾状流液滴参数测量与分析

环雾状流广泛存在于石油化工领域,其内部流场测量具有重要意义。本文结合光学图像法和高速摄影技术对撞针式喷嘴的雾化特性进行了测量分析,以此为基础对基于雾化混合的环雾状流中夹带液滴特性开展了实验研究。利用高速摄影技术对喷雾进行可视化,采用单帧单曝光法对液滴尺寸和速度信息进行提取。研究发现,液滴速度随轴向距离增大呈衰减趋势,且相同轴向距离（约在径向位置10mm处）条件下,速度达到峰值;液滴索泰尔平均直径（SMD）随喷嘴孔径d₀的增大而增大,并与液相质量流量m_l和喷嘴上下游压差?p均呈负相关;另外,在环雾状流环境中,相同气压条件下液滴SMD随气相体积流量Q_g增大而减小,而相同气相体积流量条件下SMD随气压p_g增大而增大。基于实验测量结果,以气相韦伯数We_g和液相雷诺数Re_l为主影响参数,引入相间滑移和压力系数建立了基于量纲分析的环雾状流液滴SMD预测模型,平均绝对百分比误差MAPE为11.4672%。     

湿法脱硫雾化喷嘴特性实验研究

利用FAM激光颗粒测量仪,以水为工质对撞击流燃煤烟气湿法脱硫装置中采用的旋涡压力喷嘴的雾化特性进行了实验研究,测量了不同压力下液体雾化粒子的平均粒径和粒径分布,讨论了压力对雾化特性的影响,得出了压力和喷片结构尺寸对雾化特性的影响规律。     

地沟油生物柴油在旋流喷嘴中的雾化实验及模拟

对地沟油生物柴油在旋流雾化喷嘴中的内部流场及外部流场进行数值模拟,考察了喷嘴孔径、旋流芯螺距、螺柱槽道横截面积和槽道形状等结构参数对出口雾化速度及索特平均直径的影响,通过实验对模型进行了验证。结果表明,0.7 mm孔径的喷嘴的韦伯数最大,索特平均直径与雾化锥角最优。螺距4 mm的喷嘴雾化特性最优,旋流芯螺距越小,流体在喷嘴内旋流次数越多,阻力损失越大,流体在切向分量上速度越大。梯形槽道的雾化效果最好,相同横截面积下槽道的水力直径越大,雾化效果越好;截面积1 mm2槽道的喷嘴最优,槽道横截面积越小,流体在槽道中的湍流程度越大,流体内部剪切应力越大,液体表面不稳定波急剧增大。     

压力雾化喷嘴在受限空间气流中喷雾特性的实验研究

对出口直径为0.21、0.28、0.38、0.46mm的4种压力雾化喷嘴及其组合在150mm×150mm×1 000mm的矩形通道中的喷雾流场进行了实验研究,矩形通道中的空气流速为10m/s。研究了喷嘴布置和组合方式对雾化流场的影响。实验结果表明:喷雾不碰壁距离随入射角的增大而增大;顺流喷雾比无气流时液滴的平均D32减小10%,粒径范围略有扩大;逆流喷雾比无气流时液滴的平均D32增大约70μm,粒径范围扩大了3⁴倍;出口直径小的喷嘴可通过逆流布置和顺流布置的组合,获得液滴粒径分布范围更宽的气液两相流场。双喷嘴在有限空间内的雾化效果与流场中气液流量比有关。所得研究结论对天然气加湿技术的开发有一定参考价值。     

旋涡式压力喷嘴雾化性能的研究

本文研究了旋涡式压力喷嘴雾化所得的液滴大小及其分布与压力的关系,流量及雾化角与压力的关系,以及喷雾速度和空气芯的形成和对料雾的影响。     

空气雾化喷嘴的液滴雾化性能实验研究

采用LSA-Ⅲ型激光粒度仪对一种常用的小流量空气雾化喷嘴的液滴雾化性能进行实验研究。实验主要测定了不同气液比、气相压力和液相压力情况下沿喷雾轴向不同位置处的液滴粒径分布。测定结果表明气液比和气相压力对雾化液滴粒径影响均较大,其中气相压力影响最大,气液比其次,液相压力影响最小。在本实验测定条件下,经过喷嘴雾化后在轴向100、200、300、400和500 mm位置处液滴的表面积平均直径（SMD）和体积平均直径（D43）出现波动性变化。通过对实验测得液滴粒径分布数据的分析,可以得到Rosin-Rammler分布函数中的特征参数和n,为定量计算液滴粒径提供理论基础。     

基于CFD的旋流喷嘴内部流场模拟研究

采用计算流体力学CFD软件对喷淋式脱硫塔中旋流喷嘴的内流场的流体行为进行模拟分析。分析了喷嘴的整体速度与出口的雾化效果,对比了不同入口个数下喷嘴内部流场各截面上的速度矢量,以及有无喉颈段喷嘴的雾化效果。模拟结果显示,在相同条件下,无喉颈段的四入口旋流喷嘴内部流体速度分布均匀,且相对较大,喷射后雾化锥角大雾化,效果。     

空气助力改善气化炉激冷室喷嘴特性的实验研究

设计了4种不同结构的用于气化炉激冷室内喷雾激冷的压力雾化喷嘴,采用马尔文激光粒度分析仪和数码单反照相机分别测量了不同压差、不同水流量等工况参数下的液滴粒径(SMD)D32分布和雾化角变化规律,并对4种喷嘴进行了优化选型。研究结果表明:雾滴粒径随压力的增加而减小,随水流量的减小而减小,空气助力可以明显改善液滴的雾化质量;雾化角随压差的增大先增大后趋于平缓;当压差增大到0.4 MPa时,雾滴粒径、雾化角等参数的变化渐趋平缓。通过比较气化炉激冷室中4种压力式雾化喷嘴的测量结果,1-2号内混式空气雾化喷嘴在4组喷嘴中具有最好的雾化效果,当气压为0.8 MPa,水流量为20 L/h时,SMD极小值为16,因此优选出喷嘴1-2作为气化炉激冷室冷模实验的定型喷嘴。     

单喷雾射流在受限空间内的错流混合(英文)

In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are designed by using the orthogonal design method. The Eulerian-Lagrangian formulation is employed for modeling the droplets-crossflow two-phase flow while the realizable k-ε turbulence model is used to describe the turbulence. A new index, mixedness quality, is proposed to assess the overall mixing of the droplets in the crossflow. The simulation results demonstrate that the counter-rotating vortex pair (CVP) imposes a more significant impact on the spatial distribution than on the size distribution of the droplets. Pairs of CVP with smaller scales are preferable for achieving a better mixing. The influencing factors are listed in the following order in terms of the degree of their impact from the greatest to the least: the Sauter diameter of the initial droplets, the mixing tube diameter, the spray angle, the velocity of the inlet crossflow, and the vertical velocity of the initial droplets. A moderate droplet diameter, a smaller tube diameter, a moderate spray angle, a greater crossflow velocity and a moderate vertical velocity of the droplet are favorable for achieving a higher mixedness quality of the jet spray in a confined crossflow.     

新型湿法除尘系统内气液两相流动的数值模拟

结合湿法除尘及挡板绕流技术,本文设计开发了一种带有挡板结构的新型湿法除尘系统。为探究该系统内挡板结构诱导产生的涡旋流动特性及其内部离散相运动规律,基于计算流体力学（CFD）方法,文章选用重整规划群（RNG）k-ε湍流模型数值对比了不同挡板参数下的涡旋结构、速度分布及压降情况等气相流场特性。同时利用离散相模型（DPM）分析了不同工况下喷淋液滴的运动轨迹、逃逸率及驻留时间表现。结果表明,集尘区内弓形挡板的设置可诱导产生涡旋流动,不仅能够抑制低速“流动死区”,同时还可不同程度改善喷淋液滴逃逸情况、有效延长其在装置内的驻留时间。综合考虑气相入口速度v、挡板安放角θ及喷淋液滴粒径D_p的影响,文章推导获得了液滴逃逸率的计算公式,可较为准确地预测喷淋液滴的运动情况。     

三维混合层中大涡结构与扩散颗粒的相互作用

In order to understand the interaction between large-scale vortex structure and particles, a two-way coupling temporal mixing layer laden with particles at a Stokes number of 5 with different mass loading planted initially in the upper half region is numerically studied. The pseudospectral method is used for the flow fluid and the Lagrangian approach is employed to trace particles. The momentum coupling effect introduced by a particle is approximated to a point force. The simulation results show that the coherent structures are still dominant in the mixing layer, but the large-scale vortex structure and particle dispersion are modulated. The length of large-scale vortex structure is shortened and the pairing is delayed. At the same time, the particles are distributed more evenly in the whole flow field as the mass loading is increased, but the particle dispersion along the transverse direction differs from that along the spanwise direction, which indicates that the effect by the addition of particle on the suanwise large-scale vortex structure is different from the streamwise counterpart.     

基于结构曳力的吸收塔内部气液流动模拟

湿法脱硫系统中的吸收塔为多尺度结构构成的复杂系统,其中介观结构对液滴和烟气在塔内流动有重要影响。而液滴和烟气的流动状况直接关系着脱硫系统的脱硫效率及运行阻力。本文基于吸收塔内部结构,建立基于介观结构的曳力模型,并将该模型耦合到多相流模型中,结合商业软件Fluent对吸收塔内部烟气和液滴流动状况进行模拟预测。在模拟结果中,通过对吸收塔二维、三维的压降、速度和液滴分布的模拟计算结果分析和对比,表明模拟结果准确预测了烟气和液滴在吸收塔内流动结构,充分说明了基于介观结构的曳力模型可以很好反映液滴和烟气之间的作用力。     

气液传质液滴界面的Marangoni对流

通过氮气吹扫双组分液滴,用激光投影法定性观察由于轻组分向气相扩散导致的Marangoni对流结构,结果表明Marangoni对流以小尺度涡流结构和大尺度对称循环流动的形式出现,其中乙醇-水体系首先出现小尺度涡流结构,涡流不断长大合并;丙酮-水体系则以大尺度对称循环对流结构为主,随后在近界面处形成小尺度涡流结构。采用氮气吹扫乙醇-水及丙酮-水静止悬垂单液滴的方法,通过比较实验测量传质系数与理论预测值,表明液滴近界面处Marangoni对流小尺度涡结构对传质促进作用较小,而液滴内大尺度循环对流结构对传质促进作用大。     

方管横向射流流动特性的DPIV实验研究

引　言横向射流现象广泛存在于各种工程领域 ,如自然河道中工业生活废水排放口处污染物扩散过程 ,燃气轮机叶片及燃烧室气膜冷却过程等 .早期的实验研究以Ｋａｍｏｔａｎｉ等[1] 为代表 ,主要致力于射流轨迹及影响范围等宏观特性的研究 .自 2 0世纪 80年代以来 ,不少研究者利用     

Flow visualization and solute transport in evaporating droplets

We have investigated the velocity field and associated particle transport in an evaporating water droplet using the tool of particle image velocimetry. Experiments were performed where single droplets containing polystyrene particles were exposed to evaporation. Our method applicable to droplets confined between two parallel surfaces differs from the conventional PIV techniques on the 3D droplets and removes many of the limitations associated with mapping of velocity field. To avoid refraction of light at the droplet surface we have studied the motion in a disc‐shaped droplet which was prepared by confining the drop between two nonwetting surfaces and its base is pinned to a wetting surface. Experiments were carried out under the conditions where Marangoni flow creates convection cells and finally leading to deposition of particles toward the pinned edge. The contact angle, height of the droplet, velocity field, and the particle concentration inside the evaporating droplet was measured and its time evolution was recorded. © 2009 American Institute of Chemical Engineers AIChE J, 56: 1674–1683, 2010     

Dispersion of spray from swirl nozzles

Atomization and dispersion of a liquid in the form of a spray from an atomizing nozzle is associated firstly with the disintegration of a high speed thin liquid sheet into droplets and then with the dynamics of those droplets in the surrounding atmosphere. In the present work a theoretical model has been set up to evaluate the droplet trajectories of an atomized spray from a swirl nozzle as a function of the liquid properties, injection conditions and geometrical dimensions of the nozzle. The theoretical model is based on the analytical solution of the internal hydrodynamics of the nozzle followed by the dynamics of droplets in a stagnant atmosphere. Experiments have been conducted to determine the drop size distributions and the spatial mass flow distribution of the spray. The pertinent governing parameters regarding the spray dispersion are the liquid velocity, viscosity and surface tension of the liquid, the density of the ambient atmosphere and the geometrical dimensions of the nozzle. The theoretical and ex     

Validation of the Lagrangian Approach for Predicting Turbulent Dispersion and Evaporation of Droplets within a Spray

The accuracy of the Lagrangian approach for predicting droplet trajectories and evaporation rates within a simple spray has been addressed. The turbulent dispersion and overall evaporation rates of droplets are modeled reasonably well, although the downstream velocity decay of the larger droplets is underpredicted, which is attributed to a poor estimate of the radial fluctuating velocity of these droplets at the inlet boundary. Qualitative agreement is found between the predicted and experimental evolution of the droplet size distribution downstream of the nozzle. These results show that smaller droplets evaporate preferentially to larger droplets, because they disperse more quickly toward the edge of the jet, where the entrainment of fresh air from the surroundings produces a significant evaporative driving force. Droplet dispersion and evaporation rates are highly influenced by the rate of turbulence generation within the shear layer. This work demonstrates the potential of the Lagrangian approach for analyzing particle trajectories and drying within the more complex spray dryer system.