共查询到19条相似文献,搜索用时 187 毫秒
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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。 相似文献
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基于流体体积(Volume of Fluid,VOF)方法和realizable k-ε湍流模型,对航空发动机双油路离心式喷嘴的主油路进行数值模拟,通过仿真与实验结果相结合对关键件的尺寸公差和配合尺寸进行了调整。通过实验加工出了不同尺寸公差的配合试件,并在不同工况条件下进行测试,对比主油路的雾化性能,验证燃油喷嘴关键件的配合精度对主油路雾化性能的影响,找到了导致燃油喷嘴出现油膜过厚、喷雾锥角偏大和流量偏小等性能不达标的影响因素,为优化航空发动机燃油喷嘴雾化性能和提高整套喷嘴性能一致性提供了参考。 相似文献
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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。 相似文献
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在定容弹上利用高速摄影进行不同背压下3种喷油器的甲醇低压喷射射流特性试验。测量3种喷油器不同背压下单次喷射的甲醇质量。使用Matlab软件对数字图像进行后处理,测取射流贯穿距离和射流锥角。结果表明,甲醇射流的贯穿距离、射流锥角和单次喷射的甲醇质量随背压的增加而减小。当背压增加到0.15 MPa以上时,射流贯穿距离快速减小。在喷射初期,射流的锥角较大,随着射流的发展,锥角以波动形式向减小方向变化,最后趋于3.8°。3种喷油器的质量流量随背压的变化符合伯努利方程的变化趋势。2孔和4孔喷油器的质量流量比伯努利方程的理论计算数值大。当背压达到与喷射压力相同的0.3 MPa时,3种喷油器喷射的甲醇质量随喷射时间的增加趋于定值。 相似文献
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核主泵2号密封在事故工况下,需要承受一回路高压,由于缺乏2号密封在承受高压条件下的密封机理研究,严重制约2号密封承受高压时的可靠性分析和评价。依托CPR1000核电机组100型核主泵2号密封,提出一种流固耦合分析数值模型并通过台架试验验证,系统阐述了核主泵2号密封承受高压时由摩擦面密封向流体静压型密封的转变机理,并研究了动环锥角、泄漏量随压差增加的变化规律。通过数值研究,发现2号密封锥角和泄漏量在5 MPa压差左右出现拐点,动环锥角最大约为0.05°,随着压差进一步增加,动环锥角基本保持不变,泄漏量则随压差呈现近似线性上升。 相似文献
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基于FLUENT软件的动网格技术,将湍流模型与多相流技术相结合,通过计算与分析球阀阀组的结构参数对转子泵出口球阀的运动特性及球阀内部流场特性的影响规律,给出了阀球运动参数的变化曲线和球阀内部流场的分布云图。阀座半锥角小于45°时,阀球速度、升程变化较大,阀隙最大流速较小且变化较快,大于45°时,阀球速度、升程、阀隙最大流速变化较接近。阀球上下表面压差随阀座半锥角的增大而增大,且阀座半锥角大于45°时,阀球上下表面压差随介质气液比的增大明显减小。阀座入口直径增大,阀球速度、升程及阀隙最大流速变小。阀球速度随时间函数呈现先增大后减小趋势;但当介质气液比增加到0.8、0.9时,阀球速度则呈现先减小后增大趋势;随介质气液比的增大,阀球速度、升程变化梯度和阀隙开度减小,阀隙最大流速增大。气液比小于0.5时,流量系数缓慢变化,超过0.5时,流量系数发生突变,甚至于在超过0.65以后,流量系数急剧变化超过1.0。 相似文献
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Effects of injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure, and injection
pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal
flow inside nozzle on the external spray, flow details inside model nozzle and real nozzle were also investigated both experimentally
and numerically. For the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure
of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle
and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening
pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure.
The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the
increased injection pressure produced a higher percentage of droplet that are likely to breakup. 相似文献
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Sejun Lee Soojin Jeong Ocktaeck Lim 《Journal of Mechanical Science and Technology》2012,26(10):3323-3330
We investigated the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system were used since DME has compressibility and vaporization at atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed for spray shape, penetration length, and spray angle at the six nozzle holes. There are two types of injectors: 0.166 mm diameter and 0.250 mm diameter. The ambient pressure, which was based on gage pressure, was 0, 2.5, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 to 70 MPa. By comparing with the common injector, using the converted injector it was shown that the DME injection quantity was increased 127% but it didn??t have the same low heating value. Both the common and converted injectors had symmetric spray shapes. In case of converted injector, there were asymmetrical spray shapes until 1.2 ms, but after 1.2 ms the spray shapes were symmetric. Also, the converted injector had shorter penetration length and wider spray angle than the common injector. 相似文献
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作为喷射系统的终端,喷油器内部的空穴流动对燃油雾化具有重要影响。采用比例放大透明喷嘴,研究不同燃油温度对喷嘴内空穴流动及其对近场喷雾的影响。引入无单位参数空穴数表征喷油器内燃油空化程度,研究发现燃油温度升高,其空穴初生时的压力减小,同一空穴数下,空穴程度更强烈。同时,试验观察到喷嘴内空穴区域的不对称性,喷孔管壁下壁面的空穴分布远大于上壁面的空穴分布;发生超空穴之后,随着空穴数的增加,试验结果中喷嘴内部的空穴流动变化不太明显,但仿真结果中看出喷孔出口流速减小。相同燃油温度下,随着空穴数增加,体积流量增加,流量系数减小,空穴相对面积增加,近场喷雾锥角增大;相同空穴数下,燃油温度增加使体积流量和流量系数都增加,空穴相对面积逐渐增大,近场雾化效果更好。 相似文献
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为确定喷嘴进口压力对喷嘴出口扩散角的影响,采用SolidWorks建模,利用Fluent对不同进口压力的同一喷嘴模型进行仿真,经分析得知喷嘴喷出硼砂的角度随进口压力的增大而增大,喷出的硼砂速度流线图也随压力的增大而变得密集。 相似文献
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Performance of diesel engines are influenced by fuel spray distribution, fuel-air mixture formation and combustion, which are also influenced by hole-to-hole fuel injection rate from multi-hole injectors. In this study, a customized spray momentum flux experimental test rig was used to measure the transient injection rates from a two-layered 8-hole diesel injector. The results indicated that the fuel injection rate and the cycle fuel injection quantities of the lower-layered nozzle holes were 3–15% higher than the fuel injection rates and the cycle fuel injection quantities of the upper-layered nozzle holes. A three-dimensional (3D) computational fluid dynamics (CFD) model of the two-layered 8-hole diesel injection nozzle was developed and validated by analyzing the relative error between the numerical results obtained from the model and the experimental results measured with the test injector. The simulation results showed that the relative average deviation of hole-to-hole cycle injection quantities were less than ±1%, which is the result of 5% increment in the cross-sectional area of the upper-layered holes. 相似文献
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Ainul Ghurri Jae-Duk Kim Hyung Gon Kim Jae-Youn Jung Kyu-Keun Song 《Journal of Mechanical Science and Technology》2012,26(9):2941-2947
An experimental study was conducted to examine the effect of injection pressure and fuel type on the spray tip penetration length and the angle of spray injected into atmospheric chamber. The objective of the present study is to formulate empirical correlations of the spray tip penetration and the spray angle for non-evaporative condition. The experiment was performed by a common rail type high-pressure injector for the diesel engine at the injection pressure 40??100 MPa and four different fuels (D100, BD25, BD45, and BD65). The results showed that the biodiesel content increased the spray tip penetration and decreased the spray angle. The correlation of spray tip penetration is expressed for each region before and after spray break-up time in terms of injection pressure, fuel viscosity and time after start of injection. The correlation is also obtained for spray angle equation terms of injection pressure and fuel viscosity. 相似文献
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Raul Payri F. J. Salvador J. Gimeno V. Soare 《Journal of Mechanical Science and Technology》2005,19(11):2040-2052
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. 相似文献
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Comparison of experimental and predicted atomization characteristics of high-pressure diesel spray under various fuel and ambient temperature 总被引:1,自引:0,他引:1
Su Han Park Hyung Jun Kim Chang Sik Lee 《Journal of Mechanical Science and Technology》2010,24(7):1491-1499
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. 相似文献