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To alleviate the metal corrosion problem caused by incomplete acid discharge during pickling or acidification, a corrosion inhibitor, long chain fatty hydrazides (LCFH), with a significant corrosion inhibition effect was synthesized from natural grease. The corrosion inhibition and adsorption properties of LCFH on carbon steel in 1 M HCl solution were studied by static sample weight loss test, electrochemical impedance spectroscopy, and potentiodynamic polarization curve. The results showed that LCFH exhibits excellent corrosion inhibition performance in HCl solution. The inhibition efficiency increases with the increase of inhibitor concentration. When the concentration of LCFH is 40 mg/L, the inhibition efficiency can reach 97.9%. The potentiodynamic polarization curve shows that LCFH is a corrosion inhibitor that mainly inhibits the cathodic reaction. The corrosion inhibitor is spontaneously adsorbed on the surface of low-carbon steel in physical form, which conforms to the Langmuir isothermal adsorption model.

In the application of foams in the industrial field, there are often high requirements for foaming ability and stability, but this brings greater pressure for defoaming. This paper discusses the evolution kinetics of aqueous foams stabilized by the anionic surfactant sodium dodecyl sulfate (SDS) under the influence of MgCl2. It is found that MgCl2has a dual effect on the performance of SDS foam, which is shown by the enhanced foaming ability and significantly improved stability but rapid defoaming when drained to a certain film thickness. This phenomenon not only increases efficiency in industrial applications but also facilitates recycling and defoaming. To clarify the mechanism behind this interesting phenomenon, we discuss the influence of MgCl2on bubbles, adsorption, film strength, disjoining pressure, surface tension, and rheological properties. The results show that the addition of MgCl2can significantly reduce the surface tension and interfacial formation energy and increase the adsorption of surfactant, film strength, and bulk phase viscosity. The size of the generated foam becomes smaller and more uniform. These factors together led to the enhancement of the stability of foam with the thicker liquid film. However, the addition of MgCl2can also have some detrimental effects on stability. For example, faster adsorption kinetics and higher surface strength lead to a weakening of the membrane repair capacity. Most importantly, when the liquid film is very thin, the surface adsorbed by SDS has a strong specific adsorption for Mg2+, which causes interfacial adhesion directly, leading to the instability of the thin liquid film. This paper provides theoretical guidance on the use of magnesium salts as additives, offering new ideas for combining high foam application performance and low defoaming difficulty.

Rapid corrosion of steel bars in marine and complex saline environments has become a serious concern, and corrosion inhibitor for steel bar has proved to be one of the main protective measures to prevent the corrosion. In this paper, a new organic composite anti-corrosion agent (HTCI) was synthesised by hydrazine hydrate and tartaric acid for the preventing reinforced concrete from corrosion in marine engineering. The inhibition behaviors of HTCI for Q235 steel in saturated Ca(OH)2solution with 3.0 wt.% NaCl were studied by weight loss, electrochemical measurement and surface analysis. All these techniques revealed that inhibition efficiency increased with increasing HTCI concentration and the inhibitor showed 84.37% inhibition efficiency at a concentration of 500 mg·L–1. Potentiodynamic polarization studies indicated the HTCI with mixed-type inhibitor properties. Scan analysis demonstrated that the depth of the pitting crater decreased with increasing HTCI concentration. Kinetically and thermodynamically simulated that the adsorption of HTCI on mild steel obeys Langmuir adsorption isotherm, and the mechanisms of this corrosion inhibitor were based on physical and chemical adsorption.

Sand particle erosion is always a challenge in natural gas production. In particular, the erosion in gas–liquid–solid annular flow is more complicated. In this study, a three-phase flow numerical model that couples the volume of fluid multiphase flow model and the discrete phase model was developed for prediction of erosion in annular flow. The ability of the numerical model to simulate the gas–liquid annular flow is validated through comparison with the experimental data. On the basis of the above numerical model, the phase distribution in the pipe was analyzed. The liquid entrainment behavior was reasonably simulated through the numerical model, which guaranteed the accuracy of predicting the particle erosion. Additionally, four erosion prediction models were used for the erosion calculation, among them, the Zhang et al. erosion model predicted the realistic results. Through the analysis of the particle trajectory and the particle impact behavior on the elbow, the cushion effect of the liquid film on the particles and the erosion morphology generation at the elbow were revealed.

The internal erosion of pipelines in oil and gas storage and transportation engineering is highly risky. High gas velocity of annular flow entrained sand will cause damage to the pipelines, and may further result in thinning of the wall. If this damage lasts for a long time, it may cause pipeline leakage and cause huge economic losses and environmental problems. In this research, an experimental device for studying multiphase flow erosion is designed, including an erosion loop and an experimental elbow that can test the erosion rate. The annular flow state and pipe wall erosion morphology can also be tested by the device. The computational fluid dynamics (CFD) method is combined with the experiment to further study the annular flow erosion mechanism in the pipeline. The relationship between gas-liquid-solid distribution and erosion profile was studied. The results show that the most eroded region occurs between 22.5° and 45° in the axial angle direction and between 90° and 135° in the circumferential angle direction of the elbow. The pits and deep scratches form on the surface of the sample after the sand collision.

To improve the accuracy of erosion prediction, the effect of subsequent particles impacting the same area while the first single particle rebounds from the substrate must be considered. This issue has rarely been considered in studies pertaining to erosion damage. In the present study, the ABAQUS software is used to investigate the erosion crater morphology and stress distribution on a target material subjected to overlapping impacts of spherical particles. Subsequently, the validated model is applied to investigate the effect of the overlapping impacts of particles on the target. Accordingly, the correlation between erosion severity and the impact locations of the two incident particles is quantified. The results show that the horizontal distance between two solid particle impact locations can significantly affect the erosion magnitude and pattern. The interactions of the resulting craters diminish when the horizontal distance exceeds 0.6 times the particle diameter. When the horizontal distance is approximately 0.06 times the particle diameter, the energy loss originating from collisions reaches the maximum, which modifies the crater morphology. The present study is expected to provide in-depth insights into erosion mechanisms and erosion modeling.

The extensive usage of fossil fuels has caused significant environmental pollution, climate change and energy crises. The significant advantages of hydrogen, such as cleanliness, high efficiency, and a wide range of sources, make it quite promising. Hydrogen is prone to material damage, which may lead to leakage. High-pressure leaking hydrogen is highly susceptible to spontaneous combustion due to its combustion characteristics, which may cause jet fire or explosion accidents, resulting in serious casualties and property damage. This paper presents a detailed review of the research progress on hydrogen leak diffusion characteristics, leak spontaneous combustion mechanisms and material hydrogen damage mechanisms from the perspectives of theoretical analysis, experiments and numerical simulations. This review points out that although a large number of research results have been obtained on the safety characteristics of hydrogen, there are still some deficiencies and limitations. Further research topics are clarified, such as further optimizing the kinetic mechanism of the high-pressure hydrogen leakage reaction and turbulence model, exploring the expansion and dilution law of hydrogen clouds after liquid hydrogen flooding, further studying the spontaneous combustion mechanism of leaked hydrogen and the interaction between mechanisms, and investigating the synergistic damage effect of hydrogen and other components on materials. The leakage spontaneous combustion process in open space, the development process of the bidirectional effect of hydrogen jet fuel and crack growth under the impact of high-pressure hydrogen jet fuel on the material may need to be explored next.

In order to further understand the effect of solid impurities on pipeline wall during erosion, the particle impact process without fluid was extracted for specific study. The effect of multi-impact particles on the wall of pipeline was studied experimentally and simulated. In this experiment, an improved ejection apparatus was implemented to carry out multi-impacts non-overlapping impingement by rhombic particles made of high speed steel(W18Cr4V) on the AA6061 aluminum alloy plate through changing particle angle, incident angle, orientation angle and impact velocity. As a result, each particle's penetration depth was investigated and particles' rebound trajectory can be described through this experiment as well as surface morphology of the target material after impingement. The ductile damage criterion, shear damage criterion and MSFLD damage criterion were jointly implemented in ABAQUS/CAE software to simulate the whole process of collision which proved to be effective by getting consistent result compared with experimental data. It is found that under the condition of continuous non-overlapping impact, the target material produces a small work hardening effect in the impact area by converting kinetic energy of moving particles into internal energy of plate so as to reduce the penetration depth of each impact particle.

Inspired by the layered structure of dental enamel in the human body, a superhydrophobic coating with an elastic gradient was developed and placed on the inner wall of a gas transmission pipeline to reduce erosion and corrosion. The coating comprises a hard bionic superhydrophobic top coating and a hydrogel layer underneath for buffering and self-repair. To improve the impact resistance of the top coating, layered structures with different viscoelasticities were constructed by controlling the content of TiO2@lauric acid (LA) particles and carbon nanotubes (CNTs). The amylose hydrogel underlayer not only acts as a shock absorber but also restores potential damage in the top layer, bringing an additional benefit to the corrosion resistance of the coating. Thanks to these three cooperative approaches, the coating exhibits excellent mechanical durability (800 cycles with 600-mesh sandpaper under a 49 kPa load) and corrosion resistance (with a corrosion potential of −0.21 V). Moreover, it maintains its superhydrophobicity after sanding, bending, soaking, and scratching, demonstrating its potential for application to protect transmission pipelines from erosion and corrosion.

Atmospheric transport drives the widespread distribution of microplastic (MP) in various ecosystems, posing a growing potential threat to environmental safety and human health. Understanding the source and fate of atmospheric MPs is thus crucial to constrain MP’s widespread exposure. However, the source–sink dynamics of atmospheric MPs, especially in remote areas, are uncertain, and their transport routes have yet to be identified. Here, we conducted a 13-month monitoring of the atmospheric MPs in the uninhabited area of Mount Taibai, estimated the potential risk of MP exposure to the environment, and modeled the MP trajectory to analyze their transportation. We first found that as many as 15 polymer types of MPs, whose shapes mainly include fiber, fragments, films, and granules, maintained abundance (0.7 and 0.3 particle/m3for PM10and PM2.5, respectively) in the mountain atmosphere at respirable sizes. It is worth noting that the risk assessment results that comprehensively consider the influences of abundance and morphological characteristics suggest that the exposure level of MPs exhibits a risk even in this remote mountainous area that is not disturbed by frequent human activities. Backward trajectories revealed the likely source of MPs in the sparsely populated Liupan Mountains and Qinling Mountains of short-range transport. Further, polymer characteristics of MPs and airflow-based source analysis indicated the emission source of MPs in southern Xianyang in a longer-range transport. MPs were directionally transported to Mount Taibai through atmospheric transport under the premise of stable climate and geographical conditions. These suggest that MPs inevitably occur in remote mountainous areas driven by atmospheric transport, and the mountainous areas are persistently bearing the environmental impact of MP exposure. This study reveals the risk impacts of MP exposure and the transport dynamics of atmospheric MPs in a mountain ecosystem.

This paper introduced supersonic expansion liquefaction technology into the field of hydrogen liquefaction. The mathematical model for supersonic condensation of hydrogen gas in a Laval nozzle model was established. The supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions were investigated. The simulation results show that the droplet number rises rapidly from 0 at the nozzle throat as the inlet temperature increases, and the maximum droplet number generated is 1.339 × 1018 kg−1at inlet temperature of 36.0 K. When hydrogen nucleation occurs, the droplet radius increases significantly and shows a positive correlation with the increase in the inlet temperature, and the maximum droplet radii are 6.667 × 10−8 m, 1.043 × 10−7 m, and 1.099 × 10−7 m when the inlet temperature is 36.0 K, 36.5 K, and 37.0 K, respectively. The maximum nucleation rate decreases with increasing inlet temperature, and the nucleation region of the Laval nozzle becomes wider. The liquefaction efficiency can be effectively improved by lowering the inlet temperature. This is because a lower inlet temperature provides more subcooling, which allows the hydrogen to reach the thermodynamic conditions required for large-scale condensation more quickly.

In multiphase flow pipelines, the timely and precise identification of flow pattern characteristics is crucial to guide industrial production, assess pipeline safety, and facilitate early risk warnings. Current research highlights that the combined application of flow imagery and convolutional neural networks (CNNs) can yield high accuracy flow pattern recognition. However, in the industrial sector, conveniently measurable signals such as pressure and flow rate present as one-dimensional signals rather than two-dimensional signals such as images and matrices, which CNNs are equipped to process. Therefore, the selection of a suitable data encapsulation type to convert one-dimensional signals into matrix or image form is vital to the successful application of CNNs in this field and to the precise identification of flow patterns in industrial production. In this research, we propose a Flow–Hilbert–CNN hybrid model, which integrates the one-dimensional liquid holdup signal, the Hilbert curve technique, and CNNs. The experimental data from multiphase flow in an undulating pipeline with low liquid holdup demonstrates that this hybrid model provides excellent classification accuracy, the model effectively identified four flow patterns—slug flow, pseudo-slug flow, wavy-stratified flow, and smooth-stratified flow—with recognition accuracies of 100.0%, 90.38%, 93.07%, and 100.0%, respectively, from a 16,384-length data source. Compared to models that employ standard data encapsulation methods (Space Folding (SF) and Fast Fourier Transform (FFT)) combination with CNNs, this hybrid model exhibits remarkable recognition accuracy and superior adaptability to data source scales. Notably, in the case of small-scale datasets, the accuracy improvement was 43.24% and 35.89% in comparison with SF- and FFT-based models, respectively. Moreover, the recognition accuracy of the hybrid model shows significant improvement when compared to results from traditional machine learning models and deep neural networks combined with the liquid holdup signal. The hybrid model, when used with different CNNs—MobileNetV2, Resnet18, and VGG16—yields recognition accuracies of 95.87%, 97.76%, and 96.64%, respectively, while the accuracies of machine learning models—deep neural network, k-nearest neighbors algorithm, and support vector machine—stand at 91.35%, 74.12%, and 90.57%, respectively. These results convincingly demonstrate the universality of combining the Hilbert curve with CNNs in the hybrid model, as well as the model's reliability and superiority in industrial application. This hybrid model can facilitate online, high-precision monitoring of flow patterns in the industrial sector and aid in preventing risk accidents within the production process.

The mass flow rate of natural gas through the supersonic separator was numerically calculated by various cubic equations of state. The numerical results show that the compressibility factor and specific heat ratio for ideal gas law diverge remarkably from real gas models at a high inlet pressure. Simultaneously, the deviation of mass flow calculated by the ideal and real gas models reaches over 10 %. The difference increases with the lower of the inlet temperature regardless of the inlet pressure. A higher back pressure results in an earlier location of the shock wave. The pressure ratio of 0.72 is the first threshold to get the separator work normally. The second threshold is 0.95, in which case the whole flow is subsonic and cannot reach the choked state. The shock position moves upstream with the real gas model compared to the ideal gas law in the cyclonic separation section.

Nano-biochar (NBC) is an effective material for environmental relevance due to its larger specific surface area and richer functional groups than bulk biochar. However, the interaction between NBC and Cd2+when they coexist with environmental media, in addition to the mechanism of this action, is still unknown. In this study, adsorption experiments and characterization of zeolite and NBC were carried out for revealing the interaction of NBC and Cd2+on zeolite. The results of isothermal adsorption demonstrated that the Sips model best fitted the co-adsorption of NBC and Cd2+on zeolite. The adsorption capacity of NBC increased by 10.2% ± 0.03% as opposed to that of Cd2+decreased by 24.8% ± 0.07% in the co-existence of NBC and Cd2+. It was found that the coexistence of NBC had a dual effect on the environmental behavior of zeolite and contaminant, acting as a double-edged sword. The positive effect was that the adsorption of NBC on zeolite tended to make zeolite more accessible to organic functional groups and inorganic salts. The negative effect was that NBC inhibited contaminant adsorbing on zeolite when NBC coexisted with Cd2+. This study revealed that the coexisting NBC can also enhance the migration risk of Cd2+in the environment by affecting the adsorption behavior of Cd2+on zeolite.

Combination of the hydrogen pre-cooling and liquefied natural gas gasification processes is forward-looking in the hydrogen liquefaction industry. To enhance the cold energy utilization, a hydrogen liquefaction process integrated in conjunction with a liquefied natural gas gasification process assisted by an organic Rankine cycle is designed. Furthermore, a simplified refrigeration system incorporating a dual-pressure Joule-Brayton cycle is developed to provide efficient cryo-cooling for the hydrogen. A binary mixture consisting of ethylene and propane is preferred as the working fluid for the organic Rankine cycle when liquefied natural gas gasification pressure is 30 bar, which results in 2.2% and 15.5% improvement in the liquefied natural gas cold energy utilization compared to the organic Rankine cycle with the pure refrigeration as the working fluid and the hydrogen pre-cooling process without the organic Rankine cycle, respectively. In the proposed cryo-cooling process using two Joule-Brayton cascade cycles, the utilization rate of the input exergy reaches 48.84%. The exergy loss generated in the compressors and coolers accounts for approximately 66.2% of the total exergy loss. Therefore, they are regarded as the priority targets for improving the hydrogen liquefaction system. After the optimization of the proposed process using the genetic algorithm, optimal results are obtained with a specific energy consumption of 6.59 kWh/kgH2and an exergy efficiency of 47.0%.

Background: Capacitive micromachined ultrasonic transducers (CMUTs) is a promising component of mechanical-electrical-acoustical conversion, which shows valuable applications in non-distructive testing and obstacle detection fields. In order to study the influence of dimension parameters on the directivity of CMUTs, the three-dimensional multi-physics coupling model is proposed for CMUTs in this paper. Methods: The model combines multiple physical fields through finite element method (FEM), which is more efficient and accurate. The influence of dimension parameters on the transducer is studied from two aspects: the pitch between adjacent cells and cell number, respectively. Results: When increasing the pitch, the directivity becomes better if the pitch is less than half of the wavelength, the grating lobe and side lobe are aroused. However, the bandwidth at -3dB is reduced by up to 71.1% at the same time. When increasing the cell number, the better the direcitvity, while the change of the cell number has little effect on the bandwidth of the array. However, 5.4% frequency shift was caused due to the effective mass change of the transducer. Conclusion: In this study, a 3D model based on FEM is proposed for the influence of dimension parameter on CMUTs. The simulation results indicate that the directivity can be enhanced by changing the dimension. At the same time, it also introduces other performance issues, such as bandwidth decrease and frequency shift through this approach. Therefore, the simulation proposed the guidance of CMUTs performance optimization and patented technology application work in the future.

The supersonic nozzle is a new apparatus which can be used to condense and separate water and heavy hydrocarbons from natural gas. The swirling separation of natural gas in the convergent-divergent nozzle was numerically simulated based on a new design which incorporates a central body. Axial distribution of the main parameters of gas flow was investigated, while the basic parameters of gas flow were obtained as functions of radius at the nozzle exit. The effect of the nozzle geometry on the swirling separation was analyzed. The numerical results show that water and heavy hydrocarbons can be condensed and separated from natural gas under the combined effect of the low temperature (−80 °C) and the centrifugal field (482,400g, gis the acceleration of gravity). The gas dynamic parameters are uniformly distributed correspondingly in the radial central region of the channel, for example the distribution range of the static temperature and the centrifugal acceleration are from −80 to −55 °C and 220,000gto 500,000g, respectively, which would create good conditions for the cyclone separation of the liquids. However, high gradients of gas dynamic parameters near the channel walls may impair the process of separation. The geometry of the nozzle has a great influence on the separation performance. Increasing the nozzle convergent angle can improve the separation efficiency. The swirling natural gas can be well separated when the divergent angle takes values from 4° to 12° in the convergent-divergent nozzle.

Chokes are one of the most important components of downhole flow-control equipment. The particle erosion mathematical model, which considers particle-particle interaction, was established and used to simulate solid particle movement as well as particle erosion characteristics of the solid-liquid two-phase flow in a choke. The corresponding erosion reduction approach by setting ribs on the inner wall of the choke was advanced. This mathematical model includes three parts: the flow field simulation of the continuous carrier fluid by an Eulerian approach, the particle interaction simulation using the discrete particle hard sphere model by a Lagrangian approach and calculation of erosion rate using semiempirical correlations. The results show that particles accumulated in a narrow region from inlet to outlet of the choke and the dominating factor affecting particle motion is the fluid drag force. As a result, the optimization of rib geometrical parameters indicates that good anti-erosion performance can be achieved by four ribs, each of them with a height (H) of 3 mm and a width (B) of 5 mm equaling the interval between ribs (L).

To date, numerous studies using experimental methods or computational fluid dynamics (CFD) simulations to investigate erosion in elbows have been published. However, most of these studies focused on erosion caused by large particles flowing through a single elbow, whereas erosion due to small particles in elbows mounted in series is largely ignored. Studying erosion in elbows mounted in series is essential for improving the design of pipeline systems. In this paper, a CFD model is developed and validated against experimental data in the literature. The effects of both the connecting length (i.e., the distance between two elbows connected in series) and the elbow radius of curvature on erosion behavior were investigated using the verified model. In addition, the Dean number and Stokes number were used to investigate particle motion. The results show that erosion in the second elbow first decreases and then increases, as the connecting length increases, and the maximum erosion zone always occurs in the first elbow. However, when the number of elbows is increased to four, interestingly, the maximum erosion zone is located in the fourth elbow. The findings are valuable and provide guidance for designing novel pipeline systems that can mitigate erosion.