关键结构参数对高压除鳞喷嘴性能影响的研究

高压除鳞喷嘴广泛地应用在热轧除鳞工艺中,喷嘴结构参数的变化会对射流性能产生影响。通过数值模拟和实验测试相结合,研究了锥孔深度变化对外部射流的影响。研究表明:锥孔深度增加,射流水喷射角增加、射流速度沿轴向方向衰减变慢,射流距离增加。在相同射流距离下,锥孔深度的增加可以使打击力的大小增大、有效的射流宽度增大。     

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。     

应用于油气钻采的磨料水射流喷嘴优化设计与试验研究

为了优化总长度和出口直径被限制的喷嘴的内部结构,进行喷嘴内外流场数值模拟、喷嘴流量系数测试以及喷嘴对砂岩冲蚀深度的试验。对试验结果进行分析表明,各喷嘴射流轴心线上的速度在喷嘴的内部达到最大后开始减小;数值模拟结果和流量系数测试结果相吻合,即喷嘴外部射流速度最大的喷嘴流量系数也最大,该喷嘴的工作性能最好;在设计试验的喷嘴范围内,进口收缩角为30°,出口圆柱段长度为11mm的喷嘴性能最好,其对砂岩的冲蚀深度高出其他喷嘴的200mm~300mm。     

基于FLUENT的压电式无针注射器喷嘴射流分析

为研究压电式无针注射器的喷嘴结构对其射流形态、平均喷射速度和平均湍流强度的影响,首先,基于粘性不可压缩流体纳维-斯托克斯方程,利用计算流体动力学软件Fluent的Realizable k-ε湍流模型和流场体积函数多相流模型,对四种结构的喷嘴高压自由射流进行数值模拟,结果显示,锥柱形结构的喷嘴能得到可控性较好的对称射流;其次,利用正交试验法对锥柱形结构喷嘴的锥形收缩角和中部圆柱长度进行设计仿真分析,以得到上述结构参数及其交互作用对喷嘴的平均喷射速度和平均湍流强度的影响;最后,利用SPSS软件对仿真结果进行分析。结果表明,中部圆柱长度对喷嘴的平均喷射速度和平均湍流强度具有显著影响,锥形收缩角对前者无显著影响,而对后者具有显著影响,中部圆柱长度和锥形收缩角的交互作用对前者和后者均无显著影响。综合考虑,当锥形收缩角为30°、中部圆柱长度为0.2mm时,锥柱形喷嘴可得到最佳射流特性,此时出口平均速度可达6.56m/s,湍流强度均值为1.04%。该研究可为压电式无针注射器的喷嘴设计提供参考。     

喷嘴结构对水射流性能影响的分析

介绍了水射流理论及其计算流体力学的数学模型,运用FLUENT软件对不同结构喷嘴的水射流流场进行仿真分析。通过仿真结果比较得出:锥直形喷嘴整流段长度对喷射速度具有一定影响,且有利于喷嘴出口流量的增加;当喷嘴收缩角为14°时,水射流性能最佳。     

三维旋转喷射枪喷嘴结构的优化

基于工业油罐清洗对水射流射程远、打击力大和清洗面积大的三大要求,采用计算流体力学数值分析的方法,进行三维旋转喷射枪喷嘴结构的优化。结果表明：收缩角在20°~30°区间段内、长径比在20~3.0区间段内,喷嘴具有最佳的喷射性能。     

圆锥形喷嘴结构参数设计研究

为了获取圆锥形喷嘴结构参数与其工作性能的作用规律,建立了喷嘴内部流场的数值仿真模型.通过仿真研究获取了喷嘴结构参数与喷嘴内部射流特性的作用规律.仿真结果表明:喷嘴的收缩角α和长径比cp决定了喷嘴射流的最大出口速度和喷嘴出口射流速度在径向的变化幅值.随着α的增加,喷嘴射流的最大出口速度先增大后减小.当α较小时,喷嘴出口射流速度在径向基本保持不变.当α较大时,喷嘴出口射流速度在径向变化明显.随着cp的增加,喷嘴射流的最大出口速度先增大后减小.当cp较小时,喷嘴出口射流速度在径向变化明显.当cp较大时,喷嘴出口射流速度在径向基本保持不变.圆锥形喷嘴的最优结构参数为α=40°,cp=3.对不同α的喷嘴性能进行了实验测试,实验结果表明:当α =40°时,喷嘴产生的射流出口速度最大.     

淹没环境下高压水射流喷嘴的结构优化

为提高高压水射流在辅助大型沉井沉降施工中的效率,对水射流关键元件喷嘴进行选型和结构优化,要求射流具备高能量、低衰减特性。从4类回转形喷嘴中优选速度衰减小的喷嘴,确定合理的速度衰减研究指标,再结合尺寸参数设计正交实验,利用回归分析建立预测模型,可以确定各个尺寸参数对速度指标的影响程度。由高压泵站输入压力和流量确定喷嘴的最大直径,再由预测模型确定最佳喷嘴是出口直径2.8 mm、入口直径5.26 mm、收缩角为12.3°的锥形喷嘴。     

带气环旋喷射流流场特征及喷嘴结构正交优化研究

为提高二/三重管法旋喷射流切割土体效率,采用Mixture多相流模型和RNG κ-ε湍流模型,开展了淹没环境下带气环旋喷射流流动模拟研究,获得了射流速度、气液两相体积分布、靶体作用压力等流场特征,并基于L₁₆(4⁵)正交试验设计及误差分析方法,获得了旋喷射流喷嘴关键结构参数对射流速度及其作用靶体压力的影响敏感程度与影响规律。结果表明：带气环旋喷射流能量衰减慢且集中在轴心区域,射流等速核心段长,冲击破坏土体性能好;喷嘴结构参数对射流冲击性能的影响敏感次序为：射流喷嘴出口直径>收敛角>气体喷嘴直径>气液喷嘴间距>射流喷嘴长径比;射流轴心速度及其作用靶体压力随出口直径和气体喷嘴直径的增大呈先快速增加后缓慢增加趋势,随收敛角、长径比、气液喷嘴间距的增大呈先增加后降低趋势。基于此,考虑旋喷射流设备性能,给出了最优结构参数为：射流喷嘴出口直径2.0 mm,收敛角12°或18°,长径比1,气体喷嘴直径0.9 mm,气液喷嘴间距5 mm。     

深孔机床DF系统射流间隙的结构与参数分析

为提高深孔机床的排屑性能,以现有深孔机床DF(Double Feeder)系统为基础,应用Fluent软件对DF系统射流间隙的结构进行仿真研究。将射流间隙由直线型改为锥线型,并且设置合适的喷嘴收缩角、过渡段长度与出口直径比后,可以使射流间隙造成的能量损失最小。所做研究可以为提高深孔机床DF系统的负压抽吸效果与结构参数优化提供理论参考。     

阶梯孔数控电解镗孔加工的阴极设计及试验研究

NC electrochemical boring method was adopted to solve the processing problems of stepped inner holes with small inlet,large inner cavity,and large deep diameter ratio.According to the structural characteristics of stepped holes,cathodes with different spiral outlets,different rotating angles,and different taper of shunt blocks were designed.The flow fields were analyzed by FLUENT,and the results show that the cathodes with 24° conical angle,360° rotating angle,and double spiral outlets meet the design requirements.Orthogonal tests were carried out to study the influences of processing parameters on removal amount and processing clearance.Main size of the cathode is determined by the testing results,and the problems of uneven wall thickness of the stepped hole are solved by correcting the tapers of the cathodes.By the proposed method,errors of the stepped hole are small,and quality of processing surfaces is good,which meet the production requirements.     

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。     

Atomization characteristics of intermittent multi-hole diesel spray using time-resolved PDPA data

The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally. Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (d_n=0.42 mm) to 5 (d_n=0.32mm). The time-resolved droplet diameters of the spray including the SMD (Sauter mean diameter) and the AMD (arithmetic mean diameter), injected intermittently from the multi-hole nozzles into still ambient air, were measured by using a 2-D PDPA (phase Doppler particle analyzer). The 5-hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions with the radial distance, the spray structure can be classified into the three regions : (a) the inner region showing the high SMD distribution; (b) the mixing flow region where the shear flow structure would be constructed; and (c) the outer region formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the nozzle tip. The SMD remains the constant value near the Z/d_n=166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle spray proceed more rapidly than that of the 3-hole nozzle spray.     

沥青喷嘴结构型式对喷洒性能的影响

为分析喷嘴自身结构对喷洒性能的影响,有效提高其喷洒性能,针对目前普遍采用的沥青喷嘴典型结构,改变其开口型式和导流面等结构参数,运用Fluent软件进行仿真.研究了沥青喷嘴槽口宽高比、槽口类型、导流面以及喷嘴收缩段与槽口重合处的接合形式,研究了它们对喷嘴有效喷洒距离、喷洒角、喷洒均匀性和单位面积喷洒量的影响.结果表明：喷嘴喷洒角与槽口宽高比成反比,双槽型喷嘴喷洒性能优于单槽型喷嘴.分析结果可为合理设计与应用提供参考.     

Determination of diesel sprays characteristics in real engine in-cylinder air density and pressure conditions

The present paper centers on the establishment of a quantified relationship between the macroscopic visual parameters of a Diesel spray and its most influential factors. The factors considered are the ambient gas density, as an external condition relative to the injection system, and nozzle hole diameter and injection pressure as internal ones. The main purpose of this work is to validate and extend the different correlations available in the literature to the present state of the Diesel engine, i.e. high injection pressure, small nozzle holes, severe cavitating conditions, etc. Five mono-orifice, axi-symmetrical nozzles with different diameters have been studied in two different test rigs from which one can reproduce solely the real engine in-cylinder air density, and the other, both the density and the pressure. A parametric study was carried out and it enabled the spray tip penetration to be expressed as a function of nozzle hole diameter, injection pressure and environment gas density. The temporal synchronization of the penetration and injection rate data revealed a possible explanation for the discontinuity observed as well by other authors in the spray’s penetration law. The experimental results obtained from both test rigs have shown good agreement with the theoretical analysis. There have been observed small but consistent differences between the two test rigs regarding the spray penetration and cone angle, and thus an analysis of the possible causes for these differences has also been included.     

柴油机燃烧室匹配参数对撞壁喷雾特性的影响

利用高速纹影摄像技术,研究了喷油器喷孔角度、喷孔与活塞顶面间的撞壁距离、燃烧室缩口半径和凸台夹角对柴油撞击燃烧室壁面后喷雾特性的影响。研究结果表明,试验条件下适宜的喷孔角度为75°,增大喷孔角度可以促进喷雾撞壁后的油气混合,但是喷孔角度过大会增加油束撞击气缸盖和气缸套的风险;适宜的撞壁距离为4.2mm,即压缩上止点前15°CA（CA指曲轴转角）,较小的撞壁距离会促进喷雾液滴在凹坑区域的碰撞与黏结,而较大的撞壁距离不利于燃烧室中心区域的空气利用;此外,适当增大缩口半径可以促进燃油与空气的混合,减小燃烧室壁面的燃油湿壁面积;改变凸台夹角可以控制撞壁后喷雾在燃烧室中心区域的扩散速度。     

Hole number effect on internal and discharged flow characteristics of diesel injector during transient operation

Selecting the proper number of nozzle holes is a critical matter to achieving optimal combustion in diesel engines. In recent years, short transient injections with ultra-high injection pressure have been adopted in diesel engines to achieve cleaner combustion but the effect of hole number on this transient diesel injection has not been thoroughly investigated. The current study performs an experimental observation of discharged flows from diesel injectors during transient operation using the X-ray phase-contrast imaging technique for six multi-hole injectors (three-, five-, six-, eight-, nine- and ten-hole). The observation results showed that discharged flows varied without any distinctive trends among the injectors. The largest spray dispersion angle and fastest velocity deceleration were observed in the 3-hole injector which showed an almost 3 times larger dispersion angle and 10% faster deceleration than the 10-hole injector. To understand possible factors governing such flow characteristics, three-dimensional internal flow simulations were conducted for the injectors. Unlike the results trend of discharged flows, the pressure and vorticity magnitude in the nozzle sac showed a linear change by altering the hole number. However, the hole-to-hole interaction of vortex flows varied in a complex way depending on the nozzle hole number. The nozzles with small and odd hole numbers, in general, showed a stronger hole-to-hole vortex interaction that can be the primary factor governing the discharged flow characteristics during the transient operation.     

A study of the relation between nozzle geometry,internal flow and sprays characteristics in diesel fuel injection systems

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed : one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.