方形管道内壁面微结构对湍流减阻效果的影响

利用循环管路系统,对方形管道内壁面微结构对湍流减阻效果的影响进行了试验研究,研究了循环管路系统不同壁面微结构下流动的范宁系数和减阻率。试验采用的肋条结构尺寸为:肋条宽度均为1.0mm,肋高分别是h=0.3mm、0.5mm、0.7mm。试验介质为普通自来水,水温控制在25℃±0.5℃,水平管道内流体流速范围为0.03~1.80m/s。试验研究结果表明:在量纲为1的肋深h+处于4~15范围内,肋条壁面的范宁系数小于光滑壁面的范宁系数,肋条壁面具有减阻效果;肋高h=0.5mm肋条的减阻效果最好,最大减阻率为11.91%;粒子成像测速仪研究了不同壁面微结构下流体流动的平均速度、雷诺切应力和近壁区的涡量。实验结果表明:肋条的存在使得湍流边界层增厚,雷诺切应力减小,近壁区的涡量降低,从而达到减阻的效果。     

改性橡胶混凝土在复合盐冻融循环-风沙冲蚀作用下损伤研究

使用15％(质量分数)NaOH溶液对橡胶颗粒浸泡改性处理,研究普通混凝土、未改性橡胶混凝土和改性橡胶混凝土力学性能变化,采用模拟风沙环境侵蚀实验系统对复合盐冻融循环后的混凝土试件进行冲蚀试验,探究改性橡胶混凝土在复合盐冻融循环-风沙冲蚀作用下的损伤机理.结果表明:15％(质量分数)NaOH溶液改性橡胶混凝土较未改性橡胶混凝土强度提高,弹性模量进一步降低,韧性有所提高;改性橡胶混凝土在抗风沙冲蚀性能方面仍表现出脆性材料特性;80目(0.18 mm)橡胶混凝土抗复合盐冻融循环性能最优,10目(2.00 mm)橡胶混凝土抗风沙冲蚀性能最佳,NaOH溶液对不同粒径橡胶混凝土不同性能的改性作用也不同;改性橡胶混凝土对抗复合盐冻融循环性能和抗冲蚀性能均有一定的改善作用,通过微观形貌分析其主要原因为改性橡胶颗粒与混凝土基体粘结作用更强,弹性变形更大.     

矿热炉烟道气固两相流冲蚀机理研究

研究了镍铁冶炼矿热炉烟道中气固两相流动特性,建立了气固两相流的传质模型,揭示了气固两相流的传质机理。本研究采用了DPM离散模型和DNV冲蚀模型,结合用户自定义函数（UDF）的宏（DEFINE＿DPM＿BC）对Grant和Tabakoff颗粒壁面反弹模型进行编译,分析了颗粒的运动轨迹对烟道壁的冲蚀影响,研究了烟气黏度和密度对颗粒冲蚀行为的影响。结果表明：烟气黏度增大,颗粒受到烟气的影响增大,颗粒对壁面影响减小,冲蚀区域发散;烟气密度增大,颗粒受到的曳力减小,从而减弱了颗粒对壁面的冲蚀影响。     

高压管汇弯头仿生结构冲蚀规律

非常规油田开采需要高压管汇对压裂液进行输送,输送过程中,固相颗粒对管道的内壁造成冲蚀磨损,降低管道的寿命。为探究管道减磨、抗磨的方法,本文以90°弯头为对象,建立了耦合仿生模型。采用数值模拟、理论分析的手段,对设计的圆形、三角形、六边形三种耦合仿生抗冲蚀内表面模型分析,结果表明四种模型均随着质量流量增加和速度提高呈现冲蚀率上升趋势,但同种工况下圆形壁面最大冲蚀率最低,光滑壁面最大。圆形壁面可降低冲蚀速率91%。该研究对油气输送管道的理论设计和实际应用提供指导意义。     

高铝浇注料常温冲蚀磨损性能及机理

通过改变基质成分以及骨料临界粒径大小制备六种高铝浇注料预制件,选用粒度在1 ～3 mm之间的棕刚玉颗粒为磨料,用自由落体式冲蚀磨损试验机在预制件原砖面和内部切面上进行固体颗粒冲蚀试验.研究了高铝浇注料预制件在不同冲蚀角度、磨料速度、冲蚀时间下耐磨性能的变化情况.实验结果表明:在相同冲蚀试验条件下,高铝浇注料预制件原砖面的耐磨性能低于内切面,内部颗粒紧密相嵌,原砖面颗粒堆积松散从而基质占比偏多;骨料临界粒径大的浇注料抗冲蚀磨损性能较好,表面层中基质占比更大,进入稳态冲蚀所需的时间更长.     

T型管道的冲蚀磨损数值模拟分析

三通管道作为石化行业中常见部件。针对天然气三通管道冲蚀破坏问题,采用标准k-epsilon模型,SMPLE算法,对T型三通管道内部流场进行了仿真分析。数值模拟结果表明:T型三通冲蚀部位最易发生在迎流壁面偏向出口处区域;流体速度和砂粒的质量流量对T型三通管道的冲蚀速率有促进作用;管道壁面的最大冲蚀速率在砂粒质量流量大于0.009kg/s之后,增长幅度变大;最大冲蚀速率随着砂粒的圆球度数值的增大而减小,当颗粒中的圆球度在0.1至0.4之间变化时,最大冲蚀速率值减小的幅度相对较大,之后最大冲蚀速率呈缓慢减小的趋势。     

海底管道弯管冲蚀实验

海底管道冲蚀损伤会增加海底管道运行风险,严重威胁海上油气田的高效稳定运行,而弯管冲蚀实验研究对海底管道冲蚀评估有重要意义。文章自行设计搭建管道冲蚀实验系统并研究了弯管不同位置处的冲蚀,发现颗粒经过弯管时,其运动对流体的跟随性较好。弯管外拱入射颗粒受弯管内二次流的影响,在进入弯管后向内拱偏移,并最终撞击在弯管出口内拱附近。弯管外拱中下部的冲蚀微观形貌为颗粒小角度倾斜划擦撞击壁面导致的倾斜向上的重叠划痕,而弯管出口内拱附近的冲蚀微观形貌为颗粒大角度撞击壁面导致的短而深的冲击坑点。研究所得结论对海底管道系统设计和安全评估具有指导作用。     

旋风分离器锥体局部磨损对内流场及性能的影响

为了探究局部磨损对旋风分离器性能的影响,采用Oka磨损方程以及计算流体动力学(CFD)对旋风分离器壁面磨损以及内流场特性进行数值模拟,考察旋风分离器内流场等参数随磨损厚度增大的变化规律。结果表明,旋风分离器壁在锥体底部排尘口附近壁面局部磨损严重,形成螺旋形冲蚀磨损带。磨损引起设备几何结构的改变会导致切向速度降低,颗粒所受离心力降低,锥体内局部涡强度及影响范围增大,涡核旋进(PVC)的影响加大,不利于主流的稳定与固体颗粒的分离。与未磨损时相比,当局部磨损厚度为20 mm时,粒径为4μm的颗粒分离效率由100%降低至93%,分割粒径由1.3增大至1.9μm,设备压降降低了约40%。研究工作对保障旋风分离器的长期安全稳定运行具有重要理论指导意义。     

缓冲板对煤气化闪蒸罐内冲蚀过程的影响研究

针对煤气化闪蒸罐易被黑水中煤粉颗粒冲蚀的问题,考察设置不同结构人字形缓冲板对入口区域流动和气-固冲蚀过程的影响,采用欧拉-拉格朗日方法耦合冲蚀模型进行数值模拟,得到不同结构条件下闪蒸罐和三通接管内的流场分布以及冲蚀样貌。结果表明:闪蒸罐入口区域三通接管的冲蚀速率最高且分布范围广,最大冲蚀速率比闪蒸罐内筒壁高两至三个数量级;设置人字形缓冲板可以有效降低含固气流对闪蒸罐内筒壁的冲蚀速率,且设置圆弧形不开孔人字板时外筒壁处的最大冲蚀速率最小,防冲蚀效果最佳,可以将闪蒸罐内筒壁处的最大冲蚀速率降低至初始结构的1/43,并且从冲蚀失效的角度来看,可以延长外筒壁的使用寿命。     

基于CFD的3点放样弯管冲蚀模拟研究

弯头是管道冲蚀破坏中最脆弱的部分，直接决定管道的寿命。针对这一问题，提出一种3点放样弯管结构，并采用数值模拟技术对其抗冲蚀特性进行研究，详细分析了不同微米级颗粒粒径、流速、颗粒质量流量等对最大冲蚀率的影响。模拟结果表明：弯管冲蚀主要发生在弯管外侧。不同3点放样管均具有一定的抗冲蚀效果，且3点放样管最大直径越大，抗冲蚀效果越明显，这一规律不随流速、颗粒质量流量的变化而变化。虽3点放样弯管最大直径越大抗冲蚀效果越好，但能耗随弯管最大直径的增大线性增加，故需保证在能源消耗范围内尽量减少冲蚀。文中的研究结果为弯管的耐磨设计提供指导作用。     

Numerical Investigation of a New Method for Reducing Bends Erosion from Particles Impacts

The present paper intends to introduce a new method for reducing bends erosion from particles impacts: the ribbed bend erosion protection method. Ribs are evenly fixed in the range of 20°-80° on the inner-wall of inside 90?bend and the bend (including ribs) is made of medium carbon steel. Three-dimensional numerical work is performed and the result shows satisfactory agreement with the experimental measurement. Numerical simulation studies the characteristics of axial gas flow along the bend and secondary flow at cross section. Detailed analyses involving the impact velocity and incidence angle of particle-metal (either particle-rib or particle-duct) impact unveil the mechanism of the anti-erosion effect. As a result, predications achieve that the average erosion rate of the ribbed bends is only a third of the bare bend under test conditions and rectangle ribs possess higher anti-erosion effect than square ribs, while the wear distribution pattern remains unchanged after adding ribs onto the bend. All     

局部磨损对α型旋风分离器内流场及分离性能的影响

以α型旋风分离器为研究对象,基于欧拉-拉格朗日方法,采用雷诺应力模型（RSM）、颗粒离散相模型（DPM）、E/CRC磨损方程对分离器内流场与磨损特性进行数值模拟。通过分析速度矢量、切向速度、颗粒运动轨迹等参数的分布规律,研究了局部磨损对设备内流场及分离性能的影响。结果表明,α型旋风分离器入口正对壁面磨损最为严重,最大磨损率约为1.4×10^-5kg/(m²·s)。磨损引起壁面几何结构的改变,导致气流方向发生偏转,不利于主流的稳定与固体颗粒的分离。随局部磨损的加剧,排气管下口短路流急剧增大,从而导致排气管下口以下区域流体流量减少,外涡切向速度降低;细颗粒的逃逸现象更加明显,粗颗粒运动轨迹趋于重合,更易形成高浓度灰环加剧壁面磨损。与未磨损时相比,局部磨损厚度50mm时,3μm粒径颗粒的分离效率由74.38%降低至54.97%,分割粒径d₅₀由0.73μm增大至2.36μm;设备压降降低了约15.41%。     

垂直上升内螺纹管内流动沸腾传热特性

在压力9～22 MPa,质量流速450～2000 kg·m^-2·s^-1,内壁热负荷200～700 kW·m^-2的参数范围内,试验研究了用于1000 MW超超临界锅炉φ28.6 mm×5.8 mm垂直上升内螺纹水冷壁管内汽水流动沸腾传热。研究表明：内螺纹管内壁螺纹的漩流作用可抑制偏离核态沸腾（DNB）传热恶化,内螺纹管在高干度区发生蒸干型（DO）传热恶化。增大质量流速可推迟壁温飞升,壁温飞升幅度随质量流速增大而降低。热负荷越大管壁温越高,随热负荷增大管壁壁温飞升提前,且传热恶化后壁温飞升值增大。随着压力增加,壁温飞升发生干度值减小。内螺纹管汽水流动沸腾传热系数呈π形分布,传热系数峰值出现在汽水沸腾区。文中还给出了亚临界压力区内螺纹管单相区和汽水沸腾区的传热系数试验关联式。     

模拟分析小颗粒对T型管的冲蚀

T型管道在天然气输送中较为常见的管件,气体在管道内流动时流向会发生改变导致气体直接冲击管壁,此时气体内夹带的微小颗粒也会冲击管壁,形成冲蚀降低管道输送的安全性。为了充分了解颗粒对管壁冲蚀影响,以两端为入口,一端为出口的T型管为研究对象,利用FLUENT模拟不同流速下产生的冲蚀情况。在T型管的一个入口端注入小颗粒并且保持入口条件不变,另外一个入口端不加颗粒而改变气体的速度来观察产生冲蚀的情况。结果显示改变无颗粒进气端的速度会对冲蚀的位置产生影响,同时冲蚀的程度也会产生一些变化。对比分析在不同气体流速下管道内压力云图、速度云图和流线图,来揭示颗粒的运动规律进而说明气体流速对于颗粒对于管壁冲蚀的影响。为实际生产中确定管道危险位置提供依据。     

水泥改良黄土抗冲刷性能影响因素研究

为了分析水泥改良黄土抗冲刷性能及影响因素,试验研究了成型方法、水泥剂量、压实系数和冲刷作用次数对水泥改良黄土抗冲刷性能的影响规律,并进一步研究了冲刷作用对水泥改良黄土强度劣化的影响。结果表明:与静压法相比,振动法成型试件的抗冲刷性能更优,其相对冲刷量至少可降低10%;水泥剂量提高1%(质量分数),抗冲刷性能平均提高16%,压实系数提高0.01,抗冲刷性能至少提高6.2%;冲刷作用次数对水泥改良黄土的冲刷质量损失影响较为显著,改良黄土累积冲刷量随冲刷作用次数增加呈线性增长;冲刷作用使改良黄土的抗压强度显著下降,振动法成型试件劣化度平均值为79.5%,静压法成型试件劣化度平均值为73.7%。     

Air plasma ablation/erosion test for 4D C/C composites used in the throat of solid rocket motor

A small-scale plasma ablation facility was employed to test the four-directional carbon/carbon (4D C/C) composites under high enthalpy multi-phase jet condition for ablation/erosion performance evaluation with the ablation flow field studied via computational fluid dynamics (CFD). The various ablation rates, ablation behavior and microstructure of the C/C specimens were investigated. The overall mass ablation rate was 0.05715 g·s^?1 with 0.05550 mm·s^?1and 0.01794 mm·s^?1 axial linear ablation rate of inner and outer walls. In the radial direction, the linear ablation rates were 0.07794 and 0.00517 mm·s^?1 for the inner and external diameter respectively. Ablation changes the inner wall of the annular specimen into an inverted horn shape, while the edge near the jet becomes rounded corners after the plasma procedure. The interface between the axial carbon rod and the matrix has visible ring fractures. Alumina particles are lodged in cracks and holes as a result of multiphase flow scouring. The regression rate of the composites can be considerably accelerated by particle erosion and the existence of inherent defects. The specimen ablation of top surface and inner wall is attributed to the coupling of the heterogeneous reaction and multiphase erosion. On the back wall of specimen, the regression is mainly caused by thermochemical ablation.     

Improvement of anti-erosion performance of TiN coatings through using a filtration cathode vacuum arc deposition method

Sand erosion is a major factor that shortens the service life of aircraft in desert regions. The anti-erosion performance of titanium alloys may be improved using TiN coatings. However, few studies have employed Ti sputtering on Ti transition layers to improve the erosion resistance of the coatings. Herein, TiN coatings with a sputtering layer between the Ti transition layer and the TiN layer were deposited on a Ti–6Al–4V alloy by filtered cathodic vacuum arc deposition. For comparison, another group of TiN coatings without a Ti sputtering layer but processed using the same deposition parameters were prepared. The effects of the nanoscale sputtering layer on the microstructure, mechanical properties, and anti-erosion performance of the coatings were investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nanoindentation. The results show that the introduction of a Ti sputtering layer promoted the growth of TiN grains, leading to the formation of finer and denser TiN columnar grains. The preferred orientation of the coatings with the sputtering layer is (111) plane, whereas that of the coatings without the sputtering layer is (200) plane. The TiN coatings containing a sputtering layer exhibit higher hardness, elastic modulus, and H³/E² ratio, which enhances the anti-erosion performance of the coatings. The coatings with a sputtering layer exhibited better erosion resistance (erosion rate reduced by 75%) than the coatings without a sputtering layer. The underlying mechanism to understand the effect of the sputtering layer on the erosion resistance was discussed based on variations in the microstructure and mechanical properties of the coatings with and without the Ti sputtering layer. Ti sputtering layer was finally proved to be an effective method to improve the erosion resistance of TiN coatings.     

溢流管结构对天然气水合物用旋流器分离性能的影响

建立了主直径100 mm的旋流器模型,采用计算流体力学(CFD)方法研究了溢流管内径、插入深度及壁厚对旋流器分离天然气水合物性能的影响规律。结果表明,入口流速为9 m/s时,随溢流管内径增大,水合物分离效率增大,砂的分离效率降低,旋流器的压力降逐渐减小;随溢流管壁厚增大,水合物和砂的分离效率稍有增大,旋流器的压力降先增大后减小;随溢流管插入深度增大,水合物分离效率先减小后增大,砂的分离效率先增大后减小,旋流器的压力降波动较小。溢流管内径对旋流器分离天然气水合物性能的影响最大,插入深度次之,壁厚的影响最小。     

Turbulent flow in helically ribbed pipes

Velocity profiles, turbulence intensities and Reynolds stresses were determined in pipes containing three helical ribs equally spaced on the pipe wall. Pitch to diameter ratios of 8 and 11 were used. The fluid considered was air and measurements were made with X wire probes calibrated for pitch and yaw effects. The ribs appeared to affect the axial flow via the tangential component which reached a maximum below the ribs in most cases. Evidence of increases in mixing length near the wall and decreases in the central core was obtained. These are in agreement with recent theoretical predictions of other workers. Turbulence intensities were not significantly altered when normalized with the usual friction velocity.     

Turbulent flow in helically ribbed pipes

Velocity profiles, turbulence intensities and Reynolds stresses were determined in pipes containing three helical ribs equally spaced on the pipe wall. Pitch to diameter ratios of 8 and 11 were used. The fluid considered was air and measurements were made with X wire probes calibrated for pitch and yaw effects. The ribs appeared to affect the axial flow via the tangential component which reached a maximum below the ribs in most cases. Evidence of increases in mixing length near the wall and decreases in the central core was obtained. These are in agreement with recent theoretical predictions of other workers. Turbulence intensities were not significantly altered when normalized with the usual friction velocity.