Xuewen Cao

Microbiologically influenced corrosion (MIC) is a major challenge for extending the service life of X65 pipeline steel, especially in environments with high concentrations of Pseudomonas aeruginosa. This study prepared a Ni-P/PDMS-SiO2 hierarchical composite coating to extend protection by creating a dual-barrier defense system. Systematic electrochemical tests over 45 days showed that both bare X65 steel and the single Ni-P intermediate layer deteriorated rapidly. However, the composite coating maintained a relatively high level of low-frequency impedance modulus (|Z|0.01 Hz), approximately 1010 Ω∙cm2. It was six orders of magnitude greater than that of bare steel and did not show any significant change after being immersed in the P. aeruginosa-containing medium. Based on these results, it could be assumed that a stable Cassie-Baxter air plastron and a dense amorphous Ni-P interlayer have a combined effect of physically blocking bacterial attachment and metabolite infiltration, thereby providing a support structure. This paper offers a feasible approach to designing extended-life anti-MIC coatings in bacterial-laden environments.

To meet the synergistic requirement of both high strength and high toughness in gel materials for product oil pipeline isolation and pigging operations, this study designed and prepared a novel oil-based gel through Al-O-P coordination cross-linking between alkyl phosphate and sodium aluminate. By combining macroscopic rheological tests with all-atom molecular dynamics simulations, a quantitative structure-property relationship was established with the cross-linking ratio as the core tuning parameter. An optimal molar ratio of 0.10:1 (cross-linker to gellant) was identified. Gels at this ratio exhibited outstanding comprehensive performance: a high storage modulus (120.8 Pa), a wide linear viscoelastic region (3.0% strain), and excellent toughness (6.0% yield strain). Multiscale simulations revealed that this optimal ratio drives the formation of a homogeneous and dense three-dimensional cross-linked network. This network possesses the strongest spatial confinement capability (diffusion coefficient as low as 2.75×10-4 cm2 s-1), the lowest dynamic heterogeneity (non-Gaussian parameter approximately 0.045), and the highest thermodynamic stability. This work not only provides a rationally designed gel formulation for specific pipeline engineering applications but also offers a general strategy for the performance-oriented molecular design of soft materials based on coordination interactions.

During offshore gas field exploitation, cuttings and proppant particles entrained in wellhead fluids cause severe erosion wear to the valve bodies of subsea manifolds. Meanwhile, the mechanism of secondary damage induced by particle rebound has yet to be fully clarified. In this study, gas-solid two-phase jet experiments and discrete phase model (DPM) simulations are performed to investigate the erosion damage laws of D2 alloy steel under multiple influencing factors, and an erosion prediction model applicable to D2 alloy steel is modified. The flow field distribution, particle motion behavior and erosion damage characteristics of the ball valve under gas-solid erosion conditions are analyzed via computational fluid dynamics (CFD). The results show that low-angle impact is dominated by ploughing and cutting damage, while high-angle impact is characterized by fatigue damage. Particles inside the valve mainly impinge on the back side of the valve element at 45°–60° and undergo multiple rebounds, which aggravates the damage. Particles have the highest kinetic energy at the first impact, and the kinetic energy of subsequent impacts attenuates successively, with the damage mode shifting from impact-dominated to cutting-dominated. The maximum error between the modified erosion model and experimental results is only 10%, with improved prediction accuracy. The research findings can provide technical support for erosion failure prevention and structural optimization of subsea manifolds.

Against the backdrop of the low-carbon transition in the energy sector, the sequential pipeline transport of methanol and diesel is a key technology for improving pipeline network efficiency; however, the primary obstacle is the “fuel mixing” issue caused by differences in their physical properties. Isolation gels technology offers a highly promising solution for suppressing fuel mixing by forming a flexible barrier that is pumpable, capable of forming a plug, and can be removed in a controlled manner. This paper systematically reviews research progress in this field from a materials science perspective: First, starting from the multiscale mechanisms of fuel mixing, it clarifies the performance requirements for ideal isolation gels and the core thermodynamic contradiction faced by the “methanol-diesel dual resistance” function; it then systematically reviews the research progress and limitations of traditional, composite, and smart gels systems; and details key performance characterization, pipeline evaluation, and computational fluid dynamics simulation methods; Finally, it summarizes current challenges and future directions. This review aims to provide a systematic theoretical reference and technical framework for the rational design and application of high-performance isolation gels.

Although B10 Cu-Ni alloy elbows are widely used in ship seawater piping systems, B10 is prone to premature failure due to the synergistic effect between erosion and corrosion. To accurately predict the erosion-corrosion damage involving the synergistic effect, a series of erosion, corrosion, and erosion-corrosion experiments were conducted under different flow rates. Combined with simulations of erosion and erosion-corrosion, an erosion-corrosion function based on particle impact frequency, impact angle, and impact velocity was ultimately established. Through simulation, the spatiotemporal variation patterns of erosion, synergy, and erosion-corrosion effects in the elbow were revealed. The average relative error between the experimental and simulation results was 15.7%, demonstrating an improvement in the accu-racy of predicting erosion-corrosion in B10 Cu-Ni alloy for engineering applications.

A two-dimensional Computational Fluid Dynamics (CFD) model, grounded in classical nucleation theory, is developed to investigate CO2 frosting and the associated heat transfer under cryogenic conditions. The model integrates gas–solid phase-change kinetics with multiphysics transport equations to capture the coupled phenomena governing frost formation. The Peng–Robinson equation of state is employed to predict CO2 frost points in binary mixtures, with model predictions validated against experimental data, yielding errors in frost thickness and thermal conductivity below 15%. The results demonstrate that decreasing the cryogenic wall temperature from 160 K to 150 K increases the average frost thickness and density by 57% and 78%, respectively, while advancing the peak in thermal resistance by approximately 5 min. A reduction in CO2 mol fraction from 10% to 6% leads to an 82% decrease in average frost density. Although inlet velocity exerts a limited influence on frost density, excessively high velocities increase porosity and inhibit densification. Flow field analysis reveals that progressive frost growth constricts the effective channel area, resulting in a local velocity increase of approximately 23%. Moreover, the spatial distributions of supersaturation and nucleation rate exhibit strong consistency. These findings elucidate the complex coupling between CO2 frosting, fluid flow, and heat transfer in Pressurized Liquefied Natural Gas (PLNG) systems, offering theoretical insights for optimizing low-energy CO2 cryogenic capture and enhancing natural gas liquefaction processes.

Multiphase flow entrainment in natural gas engineering significantly influences the safety and efficiency of oil companies since it affects both the flow and the heat transfer process, but its mechanisms are not fully understood. Additionally, current computational fluid dynamics (CFD) methodologies seldom consider entrainment behavioral changes in pipe elbows. In this article, a verified CFD method is used to study the entrainment behavior, mechanism, and changes in an elbow. The results show that droplet diameter in a developed annular flow follows a negative skewness distribution; as the radial distance (from the wall) increases, the fluctuation in the droplets becomes stronger, and the velocity difference between the gas and the droplets increases linearly. Turbulence bursts and vortices sucking near the wall jointly contribute to droplet entrainment. As the annular flow enters the elbow, the secondary flow promotes the film expansion to the upper and lower parts of the pipe. Droplets re-occur near the elbow exit intrados, and their size is much smaller than those in the upstream pipe. Vortices sucking under low gas velocity play an important role in this process. These findings provide guidelines for safety and flow assurance issues in natural gas production and transportation and bridge the gap between multiphase flow theory and natural gas engineering.