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1.
采用ANSYS FLUENT软件建立了基于欧拉壁面液膜模型的光滑管内蒸汽冷凝流动过程的三维数学模型。模拟管长为500 mm,内径为38 mm。模拟工况为入口蒸汽饱和温度分别为70℃,总传热温差为5℃和7℃,入口蒸汽速度为1420 m/s。模拟结果表明,液膜厚度在管道底部随着流动距离的增加而增加,液膜厚度在管顶部先增大后趋于稳定,更大的蒸汽入口速度产生更高的液膜厚度。液膜流动速度在管道底部随着流动距离的增加而增加,液膜流动速度在管顶部先增大后缓慢降低,更大的蒸汽入口速度产生更高的液膜流动速度。  相似文献   

2.
水平螺旋槽管壁面升膜形成机理的研究   总被引:3,自引:1,他引:2  
李艳  梅宁 《工程热物理学报》2005,26(Z1):149-151
对驱动升膜形成的润湿力进行分析,建立单组分流体的数学模型,得出壁面液膜蒸发时的速度和厚度分布。基于此得到蒸发过程中水平螺旋槽管管外壁升膜的形成机理和流动特性,并给出液膜润湿整个管壁面的临界条件。  相似文献   

3.
液膜在外加电场和电泳电压下会发生转动,并且液膜旋转的方向和速度可通过外加电场和电泳电压来控制.这种可控的电致流动现象可成为微型离心机、马达等新型器件的物理基础.本文用简单的材料制作了液膜电动机的模型,观察得到了良好的旋转现象,并定性研究了液膜成分、面积及不同电泳电压、电场对液膜旋转的影响.  相似文献   

4.
1前言对气液、气固、液固两相或多相流体混合流动的研究在许多领域都显得十分重要,相对气固流动的研究来说,人们对气液两相流动的研究更为薄弱.而工程实际的需要(例如海底石油天然气混输问题)又要求我们对这种复杂流动有进一步的认识.在数值求解不可压单相或多相流动的方法中,应用较广的是压力-速度校正法。时间推进法是解可压问题的主要方法。如果能将它应用到不可压问题中去,在编程、计算兼容性方面都有较大优势。针对时间推进法在解不可压问题时遇到的困难,文献出提出一种所谓的人工可压缩性方法。本文用这种方法尝试计算了叶…  相似文献   

5.
弯管内气液固三相流中液膜区流场的PIV测量   总被引:2,自引:0,他引:2  
为了深入认识螺旋管内多相流相分离现象,应用粒子图象测速仪(PIV),对组合弯管内气水砂三相流底部水平段和上升段中液膜区的流场进行了测量。研究表明:底部水平段流动主流速度分布比较均匀,颗粒跟随流体运动;二次流十分微弱,颗粒在离心力作用下由内弯侧向外弯侧运动;速度脉动强烈,不利于相分离。上升段中流动受到重力的阻碍,同底部平段相比主流速度降低,离心力作用减弱,颗粒径向时均速度较低;流动的间歇性更强,两相速度脉动更剧烈。  相似文献   

6.
为了了解旋转对邱克拉斯基(Czochralski)晶体生长结构液池内熔体流动的影响,利用有限差分法进行了三维非稳态数值模拟,坩埚外半径为50 mm,晶体半径为15 mm,液池深度为50 mm。结果表明,当旋转速度较低时,流动为稳态轴对称流动,随着转速的提高,流动会转化为三维非稳态振荡流动;晶体与坩埚同向旋转时,流动转化的临界转速较高,反向旋转时,临界转速较低;晶体单独旋转时,速度波周向速度远小于晶体旋转速度,坩埚单独旋转时,速度波周向速度与坩埚旋转速度保持一致;坩埚转速越快,速度波动幅度和波数越小。  相似文献   

7.
液滴冲击液膜过程实验研究   总被引:7,自引:0,他引:7       下载免费PDF全文
郭加宏  戴世强  代钦 《物理学报》2010,59(4):2601-2609
实验显示了液滴撞击物体表面液膜后产生水花、发生飞溅,特别是产生“钟形”水花等的流动现象.根据实验结果,探讨了液滴冲击速度、液体黏性、表面张力、液滴直径和液膜厚度等对液滴冲击后产生的流动现象,以及液膜形状演化的影响,分析了观测到的鲜有文献报道的液滴撞击液膜后产生“钟形”水花的现象. 关键词: 液滴 液膜 冲击 流动显示  相似文献   

8.
离心式喷嘴内气液两相流动的数值模拟   总被引:16,自引:0,他引:16  
求解三维不可压NS方程,并应用VOF方法捕获气液分界面,计算不同压降下离心式喷嘴内的气液两相流动状况,研究了不同压降对喷嘴内流动的影响。计算很好地模拟了喷嘴内的气液两相流动,并得到了出口液膜速度、喷雾锥角以及液膜厚度等参数,数值计算所得结果同试验符合得较好,好于经验公式的结果。  相似文献   

9.
常规钻井返出管线敞口,钻井液在返出管线中流动为非满管流动,小气侵量时,泥浆池液面变化不明显,检测装置无法测量液面变化,钻井液返出流量无法测量或者测量误差较大,无法感知小流量差的变化。本文基于气液两相流理论建立了井筒气液两相流参数与井口溢流速度的关系模型,计算表明气侵速度越大,气泡运移距井口越近,井口溢流速度越大。并以空气和钻井液(非牛顿流体)为介质,基于VOF多相流模型,模拟了钻井液返出流量变化时气液界面变化情况,分析了纯钻井液和不同含气率钻井液在返出管线流动时液面变化特征,得出纯钻井液流动时喇叭口处液面变化最明显,优化液面检测装置安装在喇叭上,更能准确及时地检测液面变化早期发现溢流,进气速度影响返出管线钻井液液面稳定性。  相似文献   

10.
用分子动力学模拟方法研究了电流变液泊肃叶流动中颗粒的运动方式,模拟出的速度剖面分为两个区域,靠近电极区域的颗粒表现为呼吸式的跃迁运动形式,称为跃迁区,而在两个电极中间区域则为平稳运动方式,称为柱塞区.此外模拟出了体积流率与相对压力梯度之间的关系.并分析了临界压力梯度和临界电场强度及阻断流动的影响因素 关键词:  相似文献   

11.
In this paper, model of effects of powder concentration distribution on fabrication of thin-wall parts in coaxial laser cladding was developed. There exists relationship between powder concentration distribution and power density distribution, which affects fabrication of thin-wall parts in coaxial laser cladding. Changes in powder concentration distribution lead to changes in wall thickness and wall growing rate. Fluctuation of powder feed rate deteriorates the growing wall in laser cladding. Deviation of the powder flow stream makes the powder concentration distribution, the thermal flux density and consequently the molten pool not symmetrical against the x-axis, resulting in irregular upper faces of the formed wall. This was verified by the results of experiment.  相似文献   

12.
以铁水脱硫渣作为研究对象,利用铁水脱硫渣作为橡胶填料取代部分炭黑与丁苯橡胶进行复合,制备铁水脱硫渣/丁苯橡胶。利用多种方法测试铁水脱硫渣/丁苯橡胶的性能,采用傅里叶变换红外光谱仪测试硫化过程中不同阶段铁水脱硫渣的结构组成。结果表明:利用铁水脱硫渣部分替代炭黑,可达到补强效果与降低补强剂成本的目的。铁水脱硫渣/丁苯橡胶的正硫化时间(t90)为25.08 min,其焦烧期为0~15 min、热硫化期15~25 min和硫化平坦期25~45 min。在焦烧期铁水脱硫渣可以提供碱环境,利于增加丁苯橡胶流动性;在热硫化期与硫化平坦期,铁水脱硫渣中Ca2SiO4能够持续加速发生水化反应生成C-S-H凝胶,达到对丁苯橡胶补强的效果。另外,铁水脱硫渣可以避免铁水脱硫渣/丁苯橡胶过硫化期的出现。  相似文献   

13.
The oxide layer growth of molten tin was monitored by measuring the specular reflection intensity of laser light. The intensity decreased during the oxidation process and the rate of intensity reduction depended on the temperature of the molten tin. On this basis, a new method for monitoring the temperature of molten metal is proposed.  相似文献   

14.
用高温共焦显微激光Raman光谱仪测定了不同温度下固体和熔融状态的亚硝酸钠的拉曼光谱图,获得了有关固体和熔态NaNO2的结构信息,分析了NaNO2熔化过程中的结构变化。  相似文献   

15.
 新研制的3 GPa熔融盐固体介质高温高压三轴实验系统,改进了高压容器的装样方式以及样品的尺寸,由于装样部件之间摩擦以及克服传压介质本身的强度,视载围压和真实围压具有较大差异,在完成压力容器温度标定的基础上,采用部分熔融法在不同温度和压力条件下进行围压标定实验研究。实验使用LiCl-KCl混合氯化盐样品,分别在300~1 400 MPa视载围压的条件下,对样品进行缓慢加温,成功观测到实验力学数据和温度数据的同时响应,确定了混合氯化盐的初熔温度,通过已知熔融曲线方程计算得出真实围压。通过比较不同的实验条件和观察实验后装样结构,给出了摩擦力的变化规律:在300~500 MPa压力条件下,摩擦力百分比呈现降低趋势,从52%降低到31.2%;在700~1 200 MPa压力条件下,摩擦力约占11.4%;在1 400 MPa压力条件下,摩擦百分比从11.4%上升到15.5%。通过对比国内外同类实验设备摩擦力认为,该设备真实围压的精度达到了国际同类设备的水平。  相似文献   

16.
X-ray diffraction patterns have been obtained from molten silicon and germanium near the melting point. In both cases the structure factor was a low first peak maximum with a small hump on its high angle side in contrast with those of simple molten metals such as sodium and aluminum. It was also found that the pair correlation functions for these molten elements are characterized by a low peak maximum which follows the usual first peak maximum corresponding to the nearest neighbour distance. The electrical resistivity and thermoelectric power have been calculated on the Ziman theory using thet-matrix of muffin-tin potential based on the structural data observed in this work. Good agreement was found in most cases.  相似文献   

17.
新型低熔点熔盐黏度的实验研究   总被引:2,自引:0,他引:2  
熔盐因其具有广泛的使用温度范围,低蒸气压,大热容量,低黏度,良好的稳定性,低成本等诸多特性已成为聚光太阳能热发电中颇有潜力的传热蓄热介质。准确的熔盐热物性对于太阳能发电过程中介质的传热蓄热性能有重要影响。其中熔盐黏度作为重要的热物性之一,对于提高传热效率和降低流动阻力具有决定作用。本文利用研制的高温黏度测量仪对水和HITEC盐的黏度温度特性进行了实验研究,实验结果与文献数据具有较好的一致性,证明了该高温熔盐黏度仪的可靠性。为了降低混合熔盐的熔点,改进其热物性能,本文对Solar Salt进行改性研究,得到两种新型低熔点混合熔盐,并测定得到了黏度温度特性曲线。结果表明,改性后的高温熔融盐黏度有所降低,有利于降低太阳能热发电熔盐传热管路系统的阻力和成本。  相似文献   

18.
A pulse laser (Nd:YAG) interaction with an AZ91 magnesium alloy has been experimentally and numerically studied. A two-dimensional (2D) axisymmetric model of a molten pool created by a laser heat source has been developed. The elaborated model solves the coupled equations of a laminar fluid flow and heat transfer to demonstrate the flow behavior in the pool. This model takes into account the coupled effects of buoyancy and Marangoni forces, the thermophysic variation properties with temperature, and the radiation and convection heat losses. Concerning numerical results, the molten temperature distribution, velocity field and molten shape were discussed. It was noted that the Marangoni flow significantly alters the characteristics of the thawing and solidifying processes, and makes the molten pool wider and shallower. On the other hand, the experimental results showed that the material thermal properties have significant effects on the transport phenomena which takes place in the molten pool, and consequently on the formation as well as the shape of the pool. Finally, a comparison between the numerical and experimental results exhibited a good agreement.  相似文献   

19.
Effects of process variables on laser direct formation of thin wall   总被引:2,自引:0,他引:2  
In this paper, effects of process variables on wall thickness, powder primary efficiency and speed of forming a thin metallic wall in single-pass coaxial laser cladding are investigated, and some resolution models are established and testified experimentally. With some assumptions, each of wall thickness, powder primary efficiency and formation speed can be defined as a function of the process variables. Wall thickness is equal to width of the molten pool created in single-pass laser cladding and determined by laser absorptivity, laser power, initial temperature, scanning speed and thermo-physical properties of clad material. Powder primary efficiency and formation speed are both dependent on an exponential function involving the ratio of melt pool width, which is decided by the process variables, to powder flow diameter. In addition, formation speed is influenced by powder feed rate. In present experiment, a 500 W continual-wave (CW) CO2 laser is used to produce thin-wall samples by single-pass coaxial laser cladding. The experimental results agree well with the calculation values despite some errors.  相似文献   

20.
X-ray radiography was applied to observe the segregation process of iron from silicate at high pressure and high temperature in mixtures containing light elements. As the temperature of the hydrogen-containing sample increases, the molten iron becomes coherent. Small droplets of iron sink to the bottom of the chamber, where they merge into a single, large droplet. The small iron droplets exhibit complex motion, moving in random directions. Markedly different behavior is found in the sulfur-containing sample, where no clear motion of the molten iron is observed. Instead, as the sample temperature is increased, the concentration of iron near the wall of the sample chamber gradually increases. These observations demonstrate that the behavior of molten iron changes according to the dissolved elements. This X-ray radiography experiment represents a powerful technique to study the segregation process of molten iron from solid or partially molten silicate, particularly when combined with high-resolution tomography techniques.  相似文献   

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