喷水减温阀离心喷嘴雾化性能的优化研究

为了探索喷水减温阀喷嘴结构参数变化对其雾化效果的影响,优化喷嘴结构参数,根据Fluent软件VOF模块对喷水减温调节阀的离心喷嘴进行气-液两相仿真分析。以喷嘴出口直径、旋流槽倾斜角、旋流室收缩角作为优化因素,以雾化锥角、流量系数作为雾化性能的评价指标,进行正交实验设计。基于响应面法建立雾化锥角和流量系数的代理模型,再运用粒子群优化算法对代理模型进行寻优,得到一个最优结构参数。结果表明:当出口直径为2.55 mm,旋流槽角度为40°,旋流室角度为110°时,雾化性能得到最优,雾化锥角比原模型增大17.7％,流量系数增大32.53％,为喷嘴的设计提供了一个新的方案。     

基于CFD的圆柱形喷嘴设计

喷嘴是流体最后通道,起到最后加减速,控制雾化度、出口速度、喷射射程的关键部件.用三维数值分析软件对影响喷嘴喷射性能的各个参数进行定量的模拟分析,通过计算得出喷嘴出口速度,最后比较各个不同结构的喷嘴出口流速来确定最佳的喷嘴结构形式.得出喷嘴在收缩角度为12°～14°,喷嘴出口端与入口端直径比在0.5～0.6,出口整流段长...     

清洗用扇形喷嘴结构参数对其内部射流的影响

采用标准k-ε湍流模型,利用计算流体软件对扇形喷嘴的内部流场进行了数值模拟;研究了当扇形喷嘴出口投影面积一定时,入口结构、出口几何参数对喷嘴内部流场和出口射流速度的影响.研究表明:锥形入口结构最有利于射流在喷嘴内的加速,可使射流在喷嘴中始终处于加速运动状态.出口段的直径影响出口段内射流的速度,出口射流速度随出口圆柱段直径的增加而增加,但存在影响其变化趋势的一个阙值直径.出口盲端的长径比和V形切槽的夹角对喷嘴内射流流态无明显影响,对出口射流速度也无明显影响.     

基于计算流体力学模拟的蒸汽喷射器结构优化

蒸汽喷射器的设计分析通常采用气体动力学或一维理论方法,但这些方法常常得不到最佳的几何结构。本文应用计算流体力学方法对用于余热回收的蒸汽喷射器的内部流场进行数值模拟,并分析了喷嘴喉部直径、混合室入口直径、等截面段直径、喷嘴出口到混合室入口的距离和等截面段长度对喷射系数的影响,然后采用5水平5因素的正交分析法对喷射器进行了多结构参数的变化分析。结果表明,通过正交分析法得到的喷射器结构参数组合能够实现较优的性能。     

接触网绝缘子带电水冲洗的关键参数研究

为了研究接触网绝缘子带电水冲洗过程中喷嘴入口压力、喷嘴出口直径、风速等关键参数的影响,采用CFD软件Fluent进行气液两相流仿真,对比分析不同参数对水冲洗效果及安全性的影响。结果表明：入口压力是影响水射流速度的关键参数,出口直径是影响水射流水气比的关键参数;入口压力、出口直径、风速等参数都会影响水射流的直线性能及冲洗效果,尽量在风速低于2.5m/s或无风环境下进行冲洗作业,且尽量增加喷嘴入口压力以及选择直径较大的喷嘴;得到了喷嘴直径、射流距离与水气比的关系,为不同水冲洗情况下的喷嘴直径选择提供了参考。     

压力旋流喷嘴内流场特性模拟研究

针对通过试验研究压力旋流喷嘴获取其雾化特性成本较高、耗时长、理论计算难以实现的问题,对压力旋流喷嘴内部流动机理及雾化特性进行了Fluent数字模拟研究。采用了一种基于有限容积VOF方法对压力旋流喷嘴内部流场进行了数值模拟;捕捉了压力旋流喷嘴出口处气-液两相界面,描述了压力旋流喷嘴出口的液膜厚度,阐述了压力旋流喷嘴各截面压力场、密度场和速度场等变化规律,预测了压力旋流喷嘴雾化锥角。模拟研究结果表明:压力旋流喷嘴中心会产生空气芯,压力旋流喷嘴雾化锥角及液膜厚度等雾化特征可通过剖析压力旋流喷嘴出口处空气芯直径和出口处速度获得;将模拟计算的喷嘴雾化锥角与试验值进行了对比,两者基本吻合,说明Fluent数值模拟可作为喷嘴设计工具。     

自激振荡式天然气管道增输器设计及数值计算

基于低压大流量自激振荡射流形成及自激振荡脉冲气体的运动规律,提出了固-脉冲波峰点接触的"滚动摩擦"自激振荡脉冲式天然气管道输送运动形式。分析了下游喷嘴直径、腔室直径、腔室长度和腔室碰撞壁倾角等结构参数对天然气管道减阻增输特性的影响,并确定了较优的自激振荡脉冲腔室无量纲参数。研究结果表明:腔室下喷嘴直径反映自激振荡脉冲射流的过流特性,腔室直径影响自激振荡脉冲射流涡旋配对效果,腔室长度与自激振荡脉冲射流振荡频率及脉动幅值有关,碰撞壁倾斜角直接决定腔室涡漩中心的位置,进而产生周期性高压脉冲射流团的特殊聚能效应。计算后获得的自激振荡脉冲腔室较优无量纲参数为:腔室下游喷嘴与上喷嘴直径比为1.3,腔室长度与上喷嘴直径比为2.4,腔室直径与上喷嘴直径比为6,腔室碰撞壁倾斜角度为120°。     

一种新型燃油炉的喷嘴设计及雾化效果分析

根据预期技术指标,确定燃油炉喷嘴类型为简单离心式喷嘴。使用经验公式法,选取经验系数,对喷嘴的几何参数进行计算与校核,根据几何参数分析雾化效果。结果表明：喷嘴直径,稳定段长度,旋流室直径,喷嘴内锥角,切向槽数目为个、宽度、深度,能够符合喷嘴流量、喷雾锥角及雾化效果的需求,适用于该燃油炉。     

旋流片对喷嘴流场特性影响的数值研究

以水为流体介质,建立了旋流喷嘴的计算流体动力学模型.通过调整旋流喷嘴旋流片的螺旋升角和通流面积等结构参数,对喷嘴雾化的压力、速度场进行计算,推导了喷嘴的雾化角,从而研究旋流片对喷嘴流场特性的影响.将数值模拟的结果与试验结果进行对比,两者基本吻合.验证了数值计算方法的正确性,对旋流喷嘴的设计具有指导意义.     

结构参数对大气喷射器性能影响的数值模拟研究

针对旅客列车真空集便系统中的核心部件之一——大气喷射器,借助CFD软件Fluent,研究了大气喷射器在使用过程中,喷嘴入口长度及锥角、喷嘴喉部长、喷嘴出口长度及直径、扩张管出入口长度及直径、扩张管喉长度对大气喷射器工作性能的影响,为此类大气喷射器结构参数的设计及优化提供了理论依据和指导方向。     

Experimental investigation of mixing-enhanced swirl flows

The experimental objective was to compare disintegration characteristics from the internal mixing pneumatic nozzles under the different operating conditions in terms of swirl angles. For this investigation, supplied air pressures and nozzle configuration ratios were fixed. This experimental comparison is of fundamental importance to the understanding and modeling of turbulent atomization because the axisymmetric swirling flows involve relatively complex interactions. For the measurement, four internal swirl mixing nozzles with axisymmetric holes at swirl angles of 15°, 30°, 45°, and 60° to the central axis were employed, which is responsible for the enhancement of mixing in pneumatic jets. To illustrate the swirl phenomena quantitatively, the distributions of mean velocities, turbulence intensities, and SMD (Sauter mean diameter, or D₃₂) variations with different configuration ratio were comparatively analyzed. It indicated that the atomization characteristics are performed well in the case of 30° of swirl angle, and that turbulence intensities are gradually degenerated with the increase of radial distances, showing a slight increment of SMD at downstream region. In particular, measurements showed that nozzle configuration is one of the significant geometrical parameters affecting the spray trajectories. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park     

Atomization characteristics of emulsified fuel oil by instant emulsification

The breakup and spray formation of swirl liquid jets with respect to the instant emulsification of heavy fuel oil and water were experimentally investigated. The effects of the degree of emulsion and flashing on the macro- and microscopic spray parameters were measured optically in terms of the rotor speed, mixture ratio, and nozzle exit temperature. Enhanced emulsification and flashing improved the spray characteristics. The effect of flashing on the Sauter mean diameter of the spray decreased as the degree of emulsion increased. However, when flashing occurred, the effect of instant emulsification was small because of the blades in the emulsion chamber and filter prior to the nozzle inlet, which served as a static mixer.     

低压燃油雾化喷嘴流动能量损失特性数值研究

建立了描述燃油在有渐扩切向槽的低压燃油喷嘴内的三维流动数学模型,采用SIMPLE算法进行计算,探讨低压下这种喷嘴的流动阻力特性,并采用试验方法研究了低压下油的雾化特性,以确定优化的燃油雾化喷嘴的结构特性。结果表明：在θ= 6o左右时,燃油雾化喷嘴出口流体的回流卷吸作用消失;在低压下(p0=0.8 Mpa),当燃油雾化喷嘴的结构特征为n=3～4,L≤2.5,θ=5o~6o,a/b=1.2和Rx/rb≥2.5时,能量损失达到最小,喷嘴压降达到最低;结构优化的燃油雾化喷嘴在低压下可保持良好的雾化质量。研究得到的燃油雾化喷嘴可用于火电厂、化工及建材等燃烧动力装置的燃烧点火及助燃等。     

Effect of boundary layer swirl on supersonic jet instabilities and thrust

This paper reports the effects of nozzle exit boundary layer swirl on the instability modes of underexpanded supersonic jets emerging from plane rectangular nozzles. The effects of boundary layer swirl at the nozzle exit on thrust and mixing of supersonic rectangular jets are also considered. The previous study was performed with a 30° boundary layer swirl (S=0.41) in a plane rectangular nozzle exit. At this study, a 45° boundary layer swirl (S=1.0) is applied in a plane rectangular nozzle exit. A three-dimensional unsteady compressible Reynolds-Averaged Navier-Stokes code with Baldwin-Lomax and Chien’sk-ε two-equation turbulence models was used for numerical simulation. A shock adaptive grid system was applied to enhance shock resolution. The nozzle aspect ratio used in this study was 5.0, and the fully-expanded jet Mach number was 1.526. The “flapping” and “pumping” oscillations were observed in the jet’s small dimension at frequencies of about 3,900Hz and 7,800Hz, respectively. In the jefs large dimension, “spanwise” oscillations at the same frequency as the small dimension’s “flapping“ oscillations were captured. As reported before with a 30° nozzle exit boundary layer swirl, the induction of 45° swirl to the nozzle exit boundary layer also strongly enhances jet mixing with the reduction of thrust by 10%.     

Effects of ALR and configuration ratio on turbulent structures in swirling flows

To assess the significant physics associated with the increase of ALR and configuration ratio of the nozzle tip in pneumatic swirling flows, comprehensive observations using a 3-D PDPA system were experimentally carried out. Profiles of mean velocities, turbulence intensities, SMD variations, and correlations between droplet size and turbulence components were quantitatively acquired. As discussed in a previous literature, axisymmetric swirl angle of 30° is selected for this investigation because of its strong turbulence levels in the flowfield and finer droplet disintegrations. Various ALRs (Air-to-Liquid Mass Ratio) as well as the length-to-diameter ratios of nozzle tip as parameters were chosen. Due to the complex interactions in swirling flows under these variables, this experimental observation will be of fundamental importance to the understanding of turbulence structures. From the observations, it indicated that increasing the ALR causes the spray development to be positively fluctuated on the atomization in both axial and tangential RMS velocities. Also, it can be concluded that the SMD decreases continuously with increase of ALR, substantiating the fact that the fluctuations are inversely proportional to the SMD variation. Meanwhile, the spray behavior is characteristic with a reduction of length-to-diameter ratio; smaller the configuration ratio, the higher the turbulence intensities and smaller SMD variations in the flowfield.     

基于自激振荡脉冲效应的雾化喷嘴出口流道空化特性研究

喷嘴结构及射流运动参数对液体空化流动状态有重要影响。基于空化泡溃灭的雾化机理和自激振荡脉冲喷嘴出口流道空化过程,分析空化效应对自激振荡脉冲射流雾化效果的影响。依据自激振荡脉冲雾化喷嘴结构,分析射流来流速度和脉动压力对喷嘴出口流道空化效应的影响,提出利用来流雷诺数和脉动特征值表征喷嘴出口流道空化程度,并根据自激振荡脉冲喷嘴有限元分析得到喷嘴出口流道较好空化状态的来流雷诺数和喷嘴腔室长径比。研究结果表明:当来流雷诺数在2.14×10~5~3.05×10~5内逐渐增大时,自激振荡脉冲雾化喷嘴出口流道液相体积分数先减小后增大,相应的空化程度先增大后减小。雷诺数在2.44×10~5~2.75×10~5内可以使喷嘴出口流道形成较好空化效应,尤其在2.44×10~5附近时喷嘴出口流道出现最好的空化状态;脉动特征值与喷嘴出口流道处脉动压力幅值差成正比,随着自激振荡脉冲雾化喷嘴腔室长径比增大,脉动压力幅值差值先减小后增大。当喷嘴腔室长径比为0.60~0.70时,喷嘴出口流道空化状态较好。计算结果为自激振荡脉冲射流雾化喷嘴设计提供了理论依据。     

配备下限流导液管的环缝喷嘴雾化能力研究

高品质金属粉末是众多制造领域中的基础材料,微细粉末成型的关键技术在于气雾化制备阶段,而喷嘴及导液管结构和雾化工艺参数对气雾化粉末的质量有重要影响。基于高速射流流体动力学的数值模拟方法研究了雾化压力、雾化气体温度、导液管下口直径与伸出长度对配备下限流导液管环缝喷嘴雾化能力的影响,通过喷盘流场检测验证模型的可靠性。结果表明：环缝喷嘴装配下限流导液管临界入口压力为128.1 kPa,雾化压力2.0 MPa时既能有效增大雾化腔内的气体最大速度和降低最低温度,又能防止过高压力造成返喷而影响气雾化顺行。此外,在极限雾化压力2.0 MPa下,通过增大雾化气体温度、下限流导液管下口直径由5 mm降低至1 mm以及伸出长度由0 mm增大至2 mm均能继续提升气液质量流速比而提升其雾化能力。生产实践也证实了模型的预瞻性,在此优化工艺下生产顺行且粉末粒度D50仅为23.84μm。