The corrosive environment in long-distance natural gas pipeline was simulated by the online high shear stress flow test platform. The interaction between flow fields and local corrosion in different local corrosion stages was studied by machining different depths rectangular defect pit (RDP) on X80 pipe steel specimens. The electrochemical signals of each specimen under high shear stress flow were measured online using an integrated three-electrode and electrochemical system. Raman spectroscopy confirmed that the corrosion scale of X80 pipeline steel in CO 2 -saturated National Association of Corrosion Engineers solution was composed of FeCO 3 . The scanning electron microscope images displayed variations in microstructure of the corrosion scale at different RDP depths and different areas. The flow field fluctuations induced by RDP were analyzed by computational fluid dynamics simulations and the development of local corrosion pits was discussed in terms of integrity of corrosion scale, convective mass transfer, and diffusion mass transfer.

Under weakly alkaline conditions, polydopamine (PDA) has strong adhesion to the surface of metal materials and chelate adsorption to nanoparticles. According to this characteristic, polydopamine (PDA) was formed by spontaneous polymerization of dopamine (DA), and then modified with octadecylamine (ODA) and 1H,1H,2H, 2H-perfluoro-decyl mercaptan (PFDT) to form a dense and uniform superhydrophobic film on the surface of zinc material. SEM, XPS, FTIR, SVET, electrochemical measurement (polarization curve and impedance spectroscopy) and other methods were used to characterize the surface morphology and chemical structures of samples before and after modification. The water contact angle (WCA) were further used to analyze the wettability of the superhydrophobic film. The experimental results show that the zinc surface with superhydrophobic PDA film exhibits higher corrosion resistance and lower corrosion current density than control groups, and the modification effect of PFDT is better. Moreover, the corrosion resistance of pure zinc can be significantly improved by the modification treatment, which is the effect of "micro nano structure air valley " formed by the super hydrophobic film layer and the enhancement of adhesion.

The electrochemical corrosion behavior and the development mechanism of the local corrosion of X65 steel under different defect depths were studied by using macroscopic electrochemical measurements and characterization techniques. A CO2-saturated NACE solution was used to study electrochemical corrosion characteristics in the single-phase flow-accelerated corrosion test loop system. Changes in the flow characteristic around the defects at different depths were characterized by COMSOL. The results indicated that samples with lower depth defects tend to deepen towards the radial direction both in the deep defects and shallow defects. Moreover, the upper and trailing edge of the defect has a tendency to deepen and expand the region of the defect under the influence of higher turbulent kinetic energy (TKE) and the shearing rate.

天然气管道内表面局部腐蚀缺陷会诱发局部流场突变影响局部腐蚀进程,利用高剪切力的冲刷腐蚀实验装置进行流动状态下的电化学腐蚀在线测试,研究了局部腐蚀深坑对局部腐蚀进程的影响.试样在冲刷腐蚀过程中的界面腐蚀电化学信号通过电化学阻抗谱进行分析,腐蚀产物膜的成分及特征通过扫描电子显微镜(SEM)、能量衍射谱图(EDS)以及X射线衍射(XRD)表征,并结合计算流体力学(CFD)分析了流场参数对腐蚀传质过程的影响.结果表明,表面缺陷会诱导局部位置流场发生变化,增强局部位置的传质作用,缺陷表面腐蚀产物也因此随着流速的变化而呈现不同的微观形态.在较高强度流场下,局部增强的壁面剪切力会剥离部分致密腐蚀产物膜,导致测试表面形成大阴极小阳极的电化学分布,促进局部位置的腐蚀进程,从而加速局部腐蚀发生.

In this work, the corrosion electrochemical information under different thicknesses of liquid film was tested. The local corrosion development process of X80 steel under different thicknesses of liquid film was studied by combining the detection and analysis of scale and the matrix corrosion morphology. The corrosion was studied by EIS. The composition and microstructures of corrosion scale at different locations were detected by EDS and SEM, and the metal matrix was detected by 3D topography technology to analyze the local corrosion. The results show that a liquid film with a thickness greater than or equal to 1 mm has no effect on the mechanism of the corrosion process, but has a control effect on the corrosion rate and the time of each stage in corrosion. The corrosion process can be divided into two stages: in the early stage, the concentration of ions inside and outside ADP is the same, so the corrosion is uniform; in the later stage, due to the influence of CO2 dissolution and mass transfer distance, the cathodic reaction is mainly outside ADP and the anodic reaction is mainly inside ADP. In addition, corrosion acidification occurs in ADP, which enhances the corrosion process in ADP.

采用电化学试验,静态腐蚀浸泡试验,扫描电镜观察等研究了B44660超级铁素体不锈钢和316L不锈钢材料在模拟中国中部地区地热水环境中的腐蚀和结垢行为.结果 表明:在此类地热水环境中,两种不锈钢的腐蚀速率均随温度的升高而增加;且两种不锈钢在低温地热水环境中均存在结垢现象,垢层的主要成分均为CaCO和MgCO3;316L不锈钢的耐腐蚀与阻垢性均优于B44660不锈钢的,更适合应用于地热环境中.

Inspired by mussel adhesive protein, the uniform, compact, and superhydrophobic film was constructed on the 316L stainless steel (316L SS) using self-polymerization of dopamine (DA) and further functionalization of the resulting polydopamine film with 1H,1H,2H,2H -perfluorodecanethiol (PFDT) to form a thin fluorinated polydopamine ( f PDA) coating. Electrochemical analysis revealed that the superhydrophobic f PDA coating has an outstanding potential, lower corrosion current density, and higher coating resistance to protect 316L SS against corrosion in a 3 wt pct NaCl environment. Characterization of the corrosion attack by scanning vibrating electrode technology (SVET) reveals the cooperative effects of superhydrophobicity and strong adhesive ability of the f PDA coating on the highly anticorrosion capability of 316L SS in a 3 wt pct NaCl aqueous solution.

The occurrence and development mechanism of internal local corrosion has always been a controversial topic, and especially under flow conditions. In this paper, an improved high shear force loop was experimentally used, and local flow field is induced by simulating corrosion defects on the surface of X80 pipeline steel specimens. The characteristics of corrosion products deposited on the surface of specimens in CO2-saturated NACE solution were investigated by means of electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, X-ray diffraction（XRD）, and energy dispersive spectrometry（EDS）. The 3 D micromorphology of the corrosion test surface after remove the corrosion scale used to measure the size of localized corrosion pit. Under the influence of local defects, the wall shear stress（WSS） and turbulent kinetic energy of local flow fields enhanced significantly, and pressure fluctuations in local flow field were induced. The results showed that the characteristics of surface corrosion products varied with flow velocity. The corrosion scales formed in various regions of specimens with defects exhibited different surface micro-morphologies and chemical compositions. Overall, these data offer new perspectives for better understanding the mechanisms behind local corrosion.

针对离心压缩机叶轮出现的复合断裂问题,设计了Ⅰ-Ⅱ复合型断裂夹具和改进的紧凑拉伸试样,开展了叶轮典型材料FV520B不锈钢的试验研究.结果表明:FV520B钢Ⅰ-Ⅱ复合型断裂均属微孔聚集型韧性机制,只是在较大加载角度下,断口上的韧窝沿裂纹扩展方向被轻微拉长、深度变浅,主要由剪切分量占比增加所致;随加载角增加,材料总的断裂韧度增大,加载角为22.5°和45°时较纯Ⅰ型的分别增加了1.8倍和4.4倍,断裂韧度的Ⅰ型和Ⅱ型分量、及启裂角亦随之增大,采用复合型J积分断裂准则可以对试验结果进行较好地预测.本研究可为离心压缩机叶轮的复合断裂分析提供技术支撑.

实验研究了不同操作参数、结构参数对除雾器阻力特性、除雾效率及除雾器出口粒径分布的影响规律.同时通过高速摄影流动显示技术对折流板除雾器基本分离规律进行分析.实验结果表明:折流板除雾器基本分离规律可归结3种情况:①液滴跟随气流直接逃逸;②液滴撞击在折流板叶片迎风面直接被捕捉;③液滴撞击到折流板叶片后产生破碎,部分液滴被折流板叶片捕集,部分液滴随气体逃逸出分离器;折线形折流板受截面气速影响最小,临界气速可达到5.3 m/s,但出口液滴粒径偏大;夹角越小分离效率越高,但分离效率对截面气速的敏感性越高,同时在合适气速下,出口液滴粒径较小.

In this paper, local corrosion pits were stimulated by arc defect pits (ADP) of different sizes. The corrosion of specimens was tested in high-speed flow CO2-saturated NACE solution. Electrochemical corrosion characteristics were monitored online. The characteristics of corrosion scale were then investigated by SEM and Raman spectroscopy. The results showed deepening and expansion of corrosion pits will occur at the same time under flow conditions for shallow pits. The development of corrosion pits at certain depth led to formation of complete corrosion scale, which inhibited further corrosion. As corrosion pits deepened, expansion process decreased and deepening rates accelerated. In-depth analysis suggested that corrosion rates were mainly affected by mass transfer rate and integrity of formed corrosion scale.

A new fast separator with internal flow guide was proposed compared with traditional riser structure in an FCC unit for Jingbo Petrochemical.The gas flow profile, particle movement and separation efficiency were simulated using Fluent for both optimized and traditional riser structure.For the optimized structure, simulation results suggest that the tangential velocity exhibits hump type distribution, and axial velocity is saddle-shape distribution.The pressure distribution is axial symmetry.The pressure does not change along the axial direction, but decreases with radius.Compared with traditional structure, both of tangential velocity and axial velocity in the optimized structure are higher, which is in favor of gas and solid separation.In addition, for the optimized structural design, pressure drop is much lower, which indicates higher cyclone separation efficiency.It can be observed that the separation efficiency for 5-20μm particles can be greatly improved.As inlet velocity increases, separation efficiency will improve, but this will lead to a higher pressure drop.Therefore, the determination of inlet gas velocity in operation should consider the above two factors.

Through experimental study on distribution of oil concentration and oil droplet size,as well as vertical distribution of heat transfer temperature in open drain sump caisson,This paper studied the mechanisms of oil droplet collision coalescence and shear breakage as well as the vertical temperature distribution inside the open drain sump caisson,in combination with the oil/water two-phase flow and oil droplet force conditions between ramps.Study results indicate that ramps could form a static area and capture the oil droplets in sewage.However,the spoiler effect of ramps will further break up oil droplets while enhancing oil droplets collision coalescence.Hence,it is considered to install rectifier components at the ramp baffle place to reduce the breakage of oil droplets;once the coalescence effect of oil droplets is higher than the breakage effect,the macroscopic improvement on separating performance will be observed,but conversely,the emulsified backmixing will be observed and the separation mainly occurs at the ramps static area.Therefore,it is recommended to increase the area and quantity of static spaces during open drain sump caisson design.Due to influence of ramp spoiler,heat transfer on the ramp will be intensified by the strong turbulent flow field,and the temperature gradient here is higher than that of straight pipe section.Accordingly,heat preservation measures shall be taken to enhance corrosion control.The study results of this paper can be used to provide references for the internal structure optimization of open drain sump caisson and offer optimal operation parameters for the actual production and water treatment process.Meanwhile,temperature field measuring and analyzing can also do benefit to alleviate the corrosion resulted by the temperature differential under severe ocean conditions.

A liquid–liquid cyclone reactor (LLCR) was designed to enhance mixing and accelerate separation between reaction products and catalysts during isobutane alkylation catalyzed by ionic liquid. The LLCR was designed on the basis of the axial-flow hydrocyclone. The effect of total inlet flow (Qt), feed ratio (rf), overflow ratio (ro) and overflow outlet diameter (Do) on the performance of LLCR (pressure drop, ΔP, and recovery, R) was investigated. The LLCR's performance indices underflow pressure drop (ΔPu), overflow pressure drop, (ΔPo), glycerin water solution recovery (Rg), kerosene recovery (Rk), reduced efficiency were determined. The results were used to establish an empirical models predicting LLCR efficiencies from total inlet flow, feed ratio, overflow ratio and overflow outlet diameter. Besides, an optimal overflow ratio, ror, was proposed to realize the optimization of two-phase recovery, which is linear with the expression of feed ratio. The results show that the range of the empirical coefficients (k) in the expression of ror is 1.02–1.14.

烟气轮机是催化裂化装置能量回收系统中的关键设备,但内部烟气介质含有催化剂颗粒,易在内壁面沉积、结垢且对叶片造成冲蚀、磨损,影响机组正常运行.为研究烟气轮机内部复杂的两相运动规律,以实际烟气轮机为基准设计了模型烟气轮机,利用高速摄像机拍摄模型烟气轮机动叶流道内的颗粒运动形态,捕捉颗粒与壁面的作用过程.结果表明,动叶前缘是颗粒碰撞的高频区,且颗粒碰撞后速度方向变化量较大.颗粒与动叶压力面发生多次碰撞的位置集中在压力面后缘,小粒径颗粒较易紧贴动叶压力面运动.实验结果为进一步探索催化剂颗粒在烟气轮机内部的沉积结垢机理提供了重要依据.

建立了催化剂颗粒在烟气轮机叶片表面沉积粘附模型,将催化剂颗粒与叶片表面的碰撞处理为理想弹塑性球体与刚性平面的碰撞进行数值计算.结果表明,模型预测的催化剂颗粒在烟气轮机叶片表面沉积粘附的部位与实际工况一致,所建模型可有效地预测催化剂颗粒沉积粘附的发生部位.

采用改进的Devanathan双面电解池检测了热镀锌钢材的氢渗透电流,结合慢应变速率拉伸试验和断口形貌分析,研究了受工业海洋大气污染有亚硫酸盐沉积的热镀锌钢材氢吸收行为及其在此环境中的氢脆敏感性.结果表明:随着试样表面亚硫酸盐的增加,其氢渗透电流显著增大;镀层缺陷使试样的氢渗透电流增大,且亚硫酸盐与镀层表面的缺陷协同效应进一步促进热浸镀钢材的氢吸收行为;氢吸收降低了热镀锌钢材的断后延伸率,表明海洋大气中的亚硫酸盐污染物会降低热镀锌钢材的韧性,导致氢损伤.

In order to investigate the drop-interface coalescence mechanism under pulsatile electric fields, micro-experiments were conducted on the effect of electrical parameters (electric field intensities, frequencies and waveforms) and physical parameters (surface tension, conductivity, primary droplet size and SiO2particles) with deionized water as dispersed phase and sunflower oil as continuous phase. The results show that two mechanisms exist, i.e. complete coalescence and partial coalescence, during drop-interface coalescence. The dominant factor is the competition of pumping and necking process. Partial coalescence is enhanced with increasing field strengths, while it is decreased with increasing frequencies. This is resulted from the strength of electrostatic force and the stability of droplets under pulsatile fields. With increasing surfactant concentrations, secondary droplets increase rapidly. When the concentration is higher than that of the critical micelle, secondary droplets decrease slightly. With increasing conductivities and SiO2concentrations, partial coalescence is enhanced first and then decreases. On the other hand, with increasing primary droplet sizes, partial coalescence increases continuously. Among the waveforms utilized in the experiments, constant DC wave has the highest partial coalescence while sawtooth wave has the lowest. The outcome of this work is potentially useful for optimizing the design of compact and efficient oil-water separators.

Flue gas turbine is the core equipment in the energy recovery system of catalytic cracking unit. In order to ensure the safe operation,it is necessary to solve the deposition problem of catalyst particles on the rotating blade surface. The influence of inlet air flow rate,concentration and particle size on the particle deposition on the rotating blade surface was studied. The results showed that the deposition quality decreases with the increase of the air flow rate. The smaller the particle size,the faster the deposition quality decreases. When the concentration is low,the deposition quality increases with the concentration increasing. While the concentration increased to a certain extent(10g/m3 under experimental conditions),the deposition quality did not vary with the concentration. In the same concentration,air flow rate and other conditions,the smaller the size of the inlet particles are,the greater the quality of deposition. Particles with size less than 40μm are more prone to deposition. Particles larger than 40μm are difficult to deposit on the blade surface. The experimental results provide a reliable basis for controlling the particle deposition.

Flue gas turbines are key equipment in energy recovery systems of catalytic cracking units. Catalyst particles within flue gas can easily deposit onto the inner wall of flue gas turbines, which affects the operation performance of the units. Therefore, it is necessary to study gas-solid two-phase flow in flue gas turbines to avoid catalyst deposition. A model flue gas turbine was designed based on actual flue gas turbines, and gas-solid two-phase flow characteristics of top, middle and root blades of the model flue gas turbine were measured by particle image velocity technique under cold status. The flow characteristics of two-phase flow at 1000 and 1400 m3?h-1were studied. The results show that the two-phase flow velocity gradually deflects and the velocity and deflection angle are maximized at the outlet of the stationary blade flow channel. The velocity of the particles is less than that of gas phase under same gas flow rates. In the rotating blade flow channel, the gas velocity gradually decays along the flow direction, and the velocity direction is aligned with the axial direction at the channel exit. The solid phase has a tangential velocity component opposite to the direction of rotation in the vicinity of the blade tip near the channel exit. These results are important for further exploration of deposition mechanism of catalyst particles in flue gas turbines.