90°弯管冲蚀磨损的数值模拟研究

利用FLUENT软件中的DPM模型,对含少量固体的90°液体管道内的冲蚀磨损情况进行了数值计算,得到了90°弯管中冲蚀磨损最严重的部位,并且流体对弯管的冲蚀磨损速率随着弯管中流体速度的增大而呈线性增加,随着弯管中颗粒含量的增加而呈线性增加,且弯管的最佳弯曲半径为R=1.5D或R=2D。     

基于Fluent的90°弯管冲蚀磨损的结构改善

本文采用数值计算的方法,研究了90°弯管内的冲蚀磨损情况,针对弯管外侧受到流体冲蚀磨损较严重的结果,对90°弯管处的结构以设置导流片的方式进行了改善。研究过程中发现,在弯头处设置导流片,管道的冲蚀磨损速率会降低,最优情况是在弯头处设置一片导流片,且导流片距弯管内侧壁面约为0.36D,此时管道的冲蚀磨损速率明显降低。对弯管结构的改善可以大大延长在役管道的使用寿命。     

基于灰色预测模型的水煤浆输送管道冲蚀磨损寿命预测

固液两相流广泛出现在煤化工生产过程中，管道输送系统受固液两相流介质冲蚀磨损尤为严重，系统突发性失效风险极高，已成为煤化工装置安全生产与稳定运行的重大隐患。降低生产安全风险，保障管道系统安全可靠运行，开展冲蚀磨损寿命预测研究是煤化工设备完整性研究的关键一环。本文以新疆某煤化工企业水煤浆汽化炉进料管为研究对象，应用ANSYS 2021R1软件进行数值模拟分析，确定弯管冲蚀磨损主要位置与短期内冲蚀磨损减薄量，为预测模型建立提供原始序列，通过灰色预测理论分别建立GM(1,1)模型、无偏GM(1,1)模型以及灰色马尔科夫模型完成对弯管冲蚀速率的预测，并结合SY/T 6151—2009《钢质管道管体腐蚀损伤评价方法》得出该管道服役寿命与检修周期。结果表明：冲蚀磨损减薄主要集中在弯管轴向70°左右，且在工艺条件相同的情况下冲蚀磨损减薄的最大位置不随时间变化发生移动。无偏GM(1,1)模型与灰色马尔科夫模型在中长期预测中优势显著，且灰色马尔科夫模型更适宜长期预测工作。所涉及的水煤浆汽化炉进料输送弯管服役寿命为570天左右，在弯管投入使用450天后冲蚀减薄量增长显著，需要定期开展该弯管重点部位的监测与预...     

油浆管道冲蚀风险预测的数值模拟研究

采用RSM雷诺应力模型,对以油浆为流体的弯管三通和组合管道进行了数值模拟研究,根据壁面剪切应力的大小来表征管道冲蚀磨损的风险大小。模拟结果表明,弯管在内弯曲侧壁面最容易发生冲蚀磨损,三通支管靠近水平出口侧一个直径长度范围内的区域最容易发生冲蚀磨损。     

基于正交设计的90°弯管冲蚀率多元非线性回归分析

研究90。弯管冲蚀率影响因素,应用Ansys Fluent软件数值模拟,得出入口流速、颗粒质量流量、颗粒粒径、弯径比、管径与弯管冲蚀率最佳曲线拟合方程;通过正交试验得出:入口流速对弯管冲蚀率影响程度最大;运用SPSS软件建立多因素共同作用影响90°弯管的多元非线性回归方程,回归方程相关系数高,能较好的表征各因素对冲蚀率的影响规律。     

三通管内冲蚀磨损的数值计算与试验研究

以三通管为研究对象,采用试验和数值计算相结合的方法,确定了数值计算模型。湍流模型选择RNG k-ε模型,多相流模型选择DPM模型,并分析了三通管内的流场和冲蚀磨损严重部位。结果表明,三通管中冲蚀磨损最严重的位置在入口直管和出口支管相贯处。     

基于相似理论的REAC出口弯管冲蚀瞬态特性

针对加氢REAC系统的频繁失效问题,研究流动与腐蚀耦合作用下REAC出口弯管的冲蚀破坏机理;在确定相似准则的基础上,结合具体的工艺特性运行数据,设计模型弯管,确定实验常数,并运用环道式多相流冲蚀实验装置,进行冲蚀瞬态特性测试,结合实验过程的CFD数值模拟获取模型弯管冲蚀瞬态特性参数。实验和仿真结果表明,模型弯管出现冲蚀瞬态特性时速度为7.93 m·s^-1,最大剪切应力为2.21 Pa;运用量纲分析法建立原型与模型冲蚀临界特性之间的数理方程,实现相似理论的求解,修正实验结果形成实际弯管的冲蚀瞬态特性参数,冲蚀剪切应力为1.79 Pa,结合工程测厚验证冲蚀瞬态特性测试实验和相似理论修正结果的可靠性和准确性;研究成果可为压力管道的多相流冲蚀预测提供科学的理论依据和实验方法。     

基于DDPM模型的气力输送弯管冲蚀模拟

通过稠密离散相模型(Dense Discrete Phase Model, DDPM)和标准k-ε湍流模型探究了气力输送弯管的冲蚀情况和颗粒运动情况。数值模拟结果表明,颗粒流经弯管时,会撞击弯管外侧壁面的中部,导致此处弯管的冲蚀速率最大,冲蚀形貌呈现“V”型。在流体曳力和颗粒惯性力的共同作用下,弯管的冲蚀速率随气体速度的增加而增加,随管道压力的增加而减小,随弯管半径的增大而减小,由冲蚀角度考虑应尽量选择方位为竖直管道A的气力输送弯管,其冲蚀速率相对竖直管道B减小8.5%。     

基于Ansys Fluent及正交试验的90°弯管冲蚀影响因素分析

管道系统在物料运输过程中,受固体颗粒的冲蚀,常导致管道弯头失效。应用Ansys Fluent软件进行90°弯管冲蚀模拟,得出入口流速、颗粒质量流量、颗粒粒径、管道直径、弯径比均会影响90°弯管冲蚀率。采用正交试验方法分析得到冲蚀影响因素主次顺序为:入口流速颗粒质量流量弯径比管道直径颗粒粒径;通过方差分析得出,入口流速、颗粒质量流量对弯管冲蚀率的影响高度显著,入口流速、颗粒质量流量、颗粒粒径间交互作用不显著。     

通风管路90°弯管壁面颗粒磨损的数值模拟

基于离散颗粒模型(DPM)对通风除尘管路90°弯管进行气-固两相流动数值模拟,计算了无烟煤颗粒对90°弯管的磨损率,分析了弯管弯径比(弯管曲率半径R与管道直径D之比)、气流入口速度、颗粒粒径及管壁材料等对弯管磨损的影响,并将模拟结果与文献实验值及经验公式计算值进行比较.结果表明,模拟结果和经验公式计算值及实验数据吻合较好,表明模拟结果基本可信;入口风速和颗粒粒径一定时,弯管的磨损率随弯径比增加先减小后增大,当R/D=3～4时,弯管磨损较小;R/D一定时,90°弯管的磨损率E与速度V的关系式为E=KV1.08～1.32,且V=0～5 m/s时,磨损率随速度变化较小,当V5 m/s时,磨损率随风速变化较大;弯管磨损率与颗粒粒径dp的关系式为E=Kdp2.38～3.01,且R/D越小,磨损率随颗粒粒径变化越明显.而d_p5μm时,弯管磨损率几乎为0;管壁材料特性(如布氏硬度)也会影响磨损率,布氏硬度大的材料磨损率较小,而布氏硬度小的材料磨损率较大.     

Scratch behavior of glass fiber reinforced polyester matrix composite after solid particle erosion

In current study, the tested material is a glass fiber reinforced polyester matrix composite with one stacking sequence namely [0/90]_s. First of all, the solid particle erosion behavior of composite samples was investigated under various impingement angles (15°, 30°, 45°, 60°, 75°, and 90°, respectively). Eroded composite samples were examined by non‐contact optical profilometer and 3D surface roughness maps were obtained. From optical profilometer results, it was clearly shown that values of erosion crater hole volumes were well suited with erosion rate values versus impingement angles. Maximum and minimum erosion crater hole volumes observed at 60° and 15° impingement angles due to semi‐ductile characteristic of the target material, respectively. After erosion tests, the scratch behavior of composite samples was examined. The results showed that the coefficient of friction was decreased by the increase in impingement angles of 45° and 60°. The maximum scratch hardness value was determined at 60° impingement angle. Scratch damage morphologies were determined by using optical microscope and scanning electron microscope. It was observed that low (15° and 30°) and high (75° and 90°) impingement angles result in remarkably severe surface deformation on the samples. POLYM. COMPOS., 36:1958–1966, 2015. © 2014 Society of Plastics Engineer     

Effectiveness of Direct Lagrangian Tracking Models for Simulating Nanoparticle Deposition in the Upper Airways

Direct Lagrangian particle tracking may provide an effective method for simulating the deposition of ultrafine aerosols in the upper respiratory airways that can account for finite inertia and slip correction effects. However, use of the Lagrangian approach for simulating ultrafine aerosols has been limited due to computational cost and numerical difficulties. The objective of this study is to evaluate the effectiveness of direct Lagrangian tracking methods for calculating ultrafine aerosol transport and deposition in flow fields consistent with the upper respiratory tract. Representative geometries that have been considered include a straight tubular flow field, a 90° tubular bend, and an idealized replica of the human oral airway. The Lagrangian particle tracking algorithms considered include the Fluent Brownian motion (BM) routine, a user-defined BM model, and a user-defined BM model in conjunction with a near-wall interpolation (NWI) algorithm. Lagrangian deposition results have been compared with a chemical species Eulerian model, which neglects particle inertia, and available experimental data. Results indicate that the Fluent BM routine incorrectly predicts the diffusion-driven deposition of ultrafine aerosols by up to one order of magnitude in all cases considered. For the tubular and 90° bend geometries, Lagrangian model results with a user-defined BM routine agreed well with the Eulerian model, available analytic correlations, and experimental deposition data. Considering the oral airway model, the best match to empirical deposition data over a range of particle sizes from 1 to 120 nm was provided by the Lagrangian model with user-defined BM and NWI routines. Therefore, a direct Lagrangian transport model with appropriate user-defined routines provides an effective approach to accurately predict the deposition of nanoparticles in the respiratory tract.     

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     

Erodent size effect on the erosion of polyphenylene sulfide composite

The effect of erodent particle size on solid particle erosion of randomly oriented short glass fiber and mineral particle reinforced polyphenylene sulfide (PPS) was investigated. To examine the effect of erodent size on the erosion resistance of the PPS composite, aluminum oxide particles at three different sizes, namely, 300–425 μm, 150–212 μm, and 45–75 μm, were used. The erosion tests were performed at six different contact angles of 15°, 30°, 45°, 60°, 75°, and 90°, respectively. The results showed a strong relationship between the erodent particle size and erosion rates of PPS composite. Maximum erosion rate for the erodent particles with sizes of 45–75 μm and 150–212 μm occurred at contact angle of 30°, on the other hand maximum erosion rate for particles having 300–425 μm size occurred between 45° and 60°. The morphologies of eroded surfaces were characterized by the scanning electron microscopy (SEM). Possible erosion mechanisms were discussed. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Evaluation of oxy-acetylene flame angle effect on the erosion resistance of SiC/ZrB2–SiC/ZrB2 multilayer coatings fabricated by the shielding shrouded plasma spray technique

In the present study, the effect of oxy-acetylene flame angle on the erosion resistance of SiC/ZrB₂–SiC/ZrB₂ multilayer coatings with the gradient structure was investigated. To this aim, first, the SiC inner layer was applied by the reactive melt infiltration (RMI) technique; then ZrB₂ and ZrB₂–SiC layers with 10, 20 and 30%wt. SiC were applied on graphite by the plasma spraying technique. To prevent the oxidation of ZrB₂ and SiC particles, the plasma spraying process was performed by a solid protective shield. To evaluate the performance of the coatings in erosive environments, the samples were exposed to oxy-acetylene flame at the angles of 30°, 60° and 90° for 360 s; the destruction mechanism of SiC/ZrB₂–SiC/ZrB₂ multilayer coatings appeared to be controlled mechanically and chemically. The results of the erosion test showed that at the low flame angles of about 30°, due to the shear forces of oxy-acetylene flame, mechanical erosion overcame the chemical one. With increasing the flame angle, due to raising the surface temperature, chemical erosion overcame the mechanical one; so, most chemical destruction occurred at the flame angle of 90°. Also, the results of the erosion test showed that the total chemical and mechanical destruction at the angle of 60° was greater than that in other angles. Also, among the coatings tested, SiC/ZrB₂- 20% wt. SiC/ZrB₂ coatings had the best erosion resistance; so, the weight changes under the oxy-acetylene flame at the angles of 30° and 60°, respectively, were about ?0.038%. and ?0.355%; meanwhile, at the angle of 90°, it was about +4.3%.     

Solid Particle Erosion of Lantana Camara Fiber-Reinforced Polymer Matrix Composite

The present investigation reports the solid particle erosion behaviour of randomly oriented short Lantana-Camara fiber-reinforced polymer composites (LCRPCs) using silica sand particles (200 ± 50 µm) as an erodent. The erosion rates of these composites have been evaluated at different impingement angles (15°–90°) and impact velocities (48 m/s–109 m/s) with constant feed rate of erodent (1.467 ± 0.02 gm/min). Highest wear rates were investigated at impingement angles 45°. Erosive wear rates were found to have a close relationship with the impingement angle of the erodent and speed. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms were discussed.     

Performance of the silicon carbide coating under erosion wear by erosion by solid particles

In this article, the phenomenon of erosion by solid particles on the silicon carbide coating (SiC) deposited on AISI 304 stainless steel substrates was analyzed. The specimens used were 25 mm square and 3 mm thick, using 300–450 μm silicon carbide as abrasive particles. Experimental tests were performed on an apparatus developed in accordance with some parameters of the ASTM G76-95 standard. Four angles of impact at 30°, 45°, 60°, and 90° are contemplated with an approximate particle velocity of 25 ± 2 m/s with a maximum exposure time of 10 min per specimen, taking measurements of weight intervals every 2 min to determine the mass loss. The wear mechanisms that were identified to small angles were: plastic deformation, displacement of material, and plow mechanisms. While at higher impact angles, the mechanisms were mainly: cutting, pitting, fractures, and cracks. It was observed that the rate of erosion depends on the angle of incidence of the abrasive particles. The results indicated that a higher damage zone was obtained at 30° of impact angle; on the other hand, at an angle of 90° there was less damage.     

Aerosol Aspiration Efficiency of Blunt and Thin-Walled Samplers at Different Wind Orientations

The measured aerosol aspiration efficiency of a thin-walled probe and 5 blunt (thick-walled) samplers was used to compare the aspiration efficiency calculated using the models developed by Belyaev and Levin (1972, 1974) and by Vincent and his colleague (1987, 1995). At 0° wind direction, the model developed by Belyaev and Levin agrees quite well with the experimental value for both the thin-walled probe and the blunt samplers. In this case, the blunt sampler body diameter ( D b ) was used to replace the inlet diameter ( D i ) for the calculation of the Stokes number (St). At 90° and 180° wind directions, the model developed by Vincent and his colleague agrees fairly well with the experimental value. This study shows that the model developed by Belyaev and Levin, at 0° wind direction, can be modified to calculate the aerosol aspiration efficiency by using personal samplers as area samplers. For the model developed by Vincent and his colleague, in addition to personal sampler application, at 90° and 180° wind directions their model can also be used to estimate the aspiration efficiency of area samplers.     

Numerical simulation of turbulent gas–particle flow in a 90° bend: Eulerian–Eulerian approach

A numerical investigation into the physical characteristics of dilute gas–particle flows over a square-sectioned 90° bend is reported. The modified Eulerian two-fluid model is employed to predict the gas–particle flows. The computational results using both the methods are compared with the LDV results of Kliafas and Holt, wherein particles with corresponding diameter of 50 μm are simulated with a flow Reynolds number of 3.47 × 10⁵. RNG-based κ–? model is used as the turbulent closure, wherein additional transport equations are solved to account for the combined gas–particle interactions and turbulence kinetic energy of the particle phase turbulence. Moreover, using the current turbulence modelling formulation, a better understanding of the particle and the combined gas–particle turbulent interaction has been shown. The Eulerian–Eulerian model used in the current study was found to yield good agreement with the measured values.