[Objective]Traditional rapid evaluation methods for small-hole leakage on the sidewall of cylindrical tanks often assume a constant discharge coefficient.This leads to significant deviations under small-aperture and low-Reynolds-number conditions.To improve the evaluation accuracy of leakage flow rate,drainage duration and liquid level state,this study develops an evaluation method for leakage parameters to support emergency rapid assessment during the initial stage of accidents.[Methods]An experimental apparatus was set up to simulate small-hole leakage on the sidewall of atmospheric cylindrical tanks.Using tap water as the test medium,variable liquid-level leakage experiments were systematically conducted across eight different aperture sizes.Key data—including leakage flow rate,drainage duration,and jet range—were acquired,with the experimental Reynolds number ranging from 4.0 × 103 to 2.5 × 104.On this basis,the dynamic variations of the discharge coefficient with respect to aperture size and Reynolds number were analyzed,and a discharge coefficient correction model was established and integrated into the drainage process calculations.Finally,a Multilayer Perceptron(MLP)-based jet range prediction model and a liquid level inversion model were constructed using aperture size,liquid level,and effective head as input variables.Cross-validation was adopted to verify the generalization ability of the models,enabling rapid inversion of the internal tank state based on external leakage characteristics.[Results]Within the 3-10 mm aperture range,the discharge coefficient was not constant but was jointly influenced by orifice geometric features and the Reynolds number.For small apertures(3-4 mm),the mean discharge coefficient was approximately 0.885,which was 36％-45％higher than the mean value(0.61-0.65)of the classic sharp-edged orifice theory.After adopting the corrected discharge coefficient,the prediction error for drainage duration within the effective inversion interval(liquid level:200-500 mm)for small apertures(3-4 mm)decreased from roughly 33％-37％to less than 2％.Throughout the entire drainage process,drainage duration decreased following a power-law trend as aperture size increased,yielding a fitting exponent of-1.954 and a coefficient of determination R2 of 0.999 8.The R2 of the jet range prediction model reached 0.983.In the small-aperture sensitive region,the Mean Absolute Percentage Error(MAPE)was reduced from the traditional theoretical range of 11％-18％to 1.5％-3.5％.The overall MAPE of the liquid level inversion model was 1.91％.[Conclusion]This study develops a rapid evaluation framework for small-hole leakage on the sidewall of cylindrical tanks,comprising three modules:discharge coefficient correction,jet range prediction,and liquid level inversion.The framework collaboratively outputs key parameters including leakage flow rate,residual liquid level,drainage duration,and impact distance.Applicable to low-viscosity,single-phase liquid leakage under atmospheric pressure,this method provides a technical reference for rapid emergency decision-making and digital safety assessments during the initial stage of leakage accidents.(17 Figures,3 Tables,44 References)
[Objective]The formation of hydrogen atoms on the surface of hydrogen pipeline steel serves as the critical link between the external hydrogen environment and internal hydrogen-induced damage.While existing research predominantly concentrate on hydrogen diffusion,hydrogen trapping,and macroscopic mechanical property degradation,systematic reviews regarding the dissociative adsorption of hydrogen on pipeline steel surfaces remain insufficient,which fails to supply direct theoretical basis for safety assessment of operational hydrogen pipelines.[Methods]Centering on of the dissociative adsorption of hydrogen,recent research regarding gaseous hydrogen embrittlement and hydrogen behavior in pipeline steel was summarized across three dimensions:theoretical foundations,experimental testing,and numerical simulations.The application scopes of multiple methodologies were systematically compared,including surface characterization,hydrogen permeation testing,densityfunctional theory,ab initio molecular dynamics,and the finite element method.Furthermore,influencing factors such as surface states,corrosion product films and passive films,impurity gases,alloying elements,temperature,and stress were integrated into a unified analytical framework.[Results]Statistical analysis indicated that in the field of gaseous hydrogen embrittlement,studies on macroscopic mechanical properties and hydrogen embrittlement mechanisms accounted for approximately 72％,those on hydrogen diffusion in steel accounted for roughly 15％,and only around 8％directly addressed surface dissociative adsorption—revealing insufficient research on this initial process.Comparative analysis of typical numerical simulation methods revealed that density functional theory was applicable to analyzing stable adsorption sites,adsorption energy,and dissociation energy barriers at a scale of 0.1-10.0 nm.Ab initio molecular dynamics described dynamic interfacial processes at finite temperatures for scales of 0.1-20.0 nm,though it was limited by system size and time scale.The finite element method could reach micrometer scales and even component scales,but it relied on atomic-scale input parameters.Experimental results further demonstrated that surface roughness,grain boundaries,dislocation emergences,and inclusion interfaces increased local active site density.The integrity and compactness of corrosion product films/passive films significantly affect hydrogen ingress,and compact films generally show a hydrogen-barrier effect,gas impurities introduced distinct chemical behaviors:O2 and CO primarily induced competitive adsorption and surface poisoning,CO2 exhibited environment-dependent characteristics,and H2S tended to facilitate the ingress of atomic hydrogen into the steel matrix.[Conclusion]The dissociative adsorption of hydrogen on pipeline steel surfaces should not be regarded as an isolated surface reaction,but rather as the starting point of the entire degradation sequence:surface hydrogen generation-interfacial hydrogen ingress-bulk hydrogen diffusion-hydrogen trapping and enrichment-damage evolution.Future research should focus on in-situ characterization under high-pressure gas phases,standardized gaseous hydrogen permeation testing,and multi-scale coupling models to provide quantitative benchmarks for material selection,gas quality management,and the safety evaluation of in-service hydrogen pipelines.(3 Figures,4 Tables,68 References)
[Objective]Driven by the accelerating global transition toward a diversified,low-carbon energy structure,the need for intensive pipeline utilization continues to rise.Pipeline engineering is consequently shifting from traditional oil and gas transportation to a new paradigm involving various media,including carbon-and hydrogen-based energy,chemicals,pastes,slurries,and capsules(collectively termed"novel media").These systems operate under complex conditions spanning onshore areas,deep-sea and extraterrestrial environments.In turn,the unique physicochemical properties of novel media,paired with harsh operating environments,pose major challenges to pipeline design,material selection,operational control,and safety assurance.[Methods]This paper systematically reviews the development status of key pipeline transportation technologies under complex operating conditions in China from both internal conditions(e.g.,temperature and pressure)and external service environments.The review aligns with national strategies of building"a country with strong transportation network"and ensuring national energy security.Representative technical routes and engineering practices are summarized across multiple domains.These include thermal insulation for extreme-temperature pipelines,material development and fracture control for supercritical/dense-phase CO2 pipelines,material compatibility for high-pressure hydrogen pipelines,and corrosion protection and integrity management for deep-sea and deep underground pipelines.They also cover the pipeline transportation of pastes,slurries,hydrogen-based energy,and capsules.[Results]Deficiencies are identified in existing studies regarding the modeling of multi-physics coupling mechanisms,the evolution of material degradation and failure,and the adaptability of current standard systems.[Conclusion]Going foward,it is essential to establish a comprehensive standard system covering the entire lifecycle of pipelines(planning,design,operation,and maintenance),to develop pipeline operation and control technologies based on multi-physics coupling modeling,and to refine pipeline integrity management frameworks tailored to complex operating conditions.Simultaneously,the research,development and application of novel materials and equipment should be accelerated.These efforts aim to construct an intelligent operational management system characterized by coordinated substance-energy transmission,extreme-environment accessibility,security resilience,and multi-network integration.This system will support the safe,efficient,and large-scale development of pipelines for novel media,safeguard national energy and strategic material transportation,facilitate the establishment of a modern energy system,and advance national maritime and aerospace strategies.(2 Figures,1 Table,59 References)
[Objective]Permanent ground displacement from strike-slip faults poses a serious threat to buried oil and gas pipelines.It can induce local plastic deformation that leads to tensile fracture or buckling failure,thereby compromising pipeline structural integrity.Accurate prediction of pipeline deformation under strike-slip fault displacement is therefore essential.Existing analytical methods struggle to capture the nonlinear interaction between pipelines and surrounding soil and the elastic-plastic behavior of the pipes.Finite element modeling(FEM)is complex and often fails to strike an effective balance between computational accuracy and efficiency.[Methods]Taking into account shortcomings of previous research,a method for solving pipeline deformation under strike-slip fault displacement based on a Physics-Informed Neural Network(PINN)is proposed.A Deep Neural Network(DNN)is constructed to map axial and lateral pipeline displacements within the axial spatial coordinates of pipelines.Using the principle of virtual work and the Green-Lagrange strain measure,a nonlinear soilspring model simulates axial and lateral nonlinear interactions between pipelines and the surrounding soil,while a linear-hardening constitutive model characterizes the pipe's nonlinear material behavior.A physics-informed loss function is formulated to express pipeline deformation under strike-slip fault displacement.A boundary condition loss function is established,further integrating mechanical characteristics of pipelines under fault displacement and enforcing Dirichlet boundary conditions.The combined formulation enables high-precision prediction of pipeline deformation under strike-slip fault displacement.[Results]In a case study based on a 1,016 mm pipeline section crossing a strike-slip fault zone,the PINN calculation results for crossing angles of 30°,45°,60°,75°,and 90° under a fault displacement of 2.5 m were compared with the reference values from FEM calculations and found to be closely aligned.Subsequent quantitative error analysis yielded the following ranges of mean squared errors(MSE)for the PINN calculations:3.82 × 10-7-1.85× 10-6 for axial displacement and 1.73 × 10-6-6.18× 10-6 for lateral displacement.For strain metrics derived from the PINN results,the axial tensile-strain MSE ranged from 1.20× 10-10-6.06× 10-9,and axial bending-strain MSE ranged from 8.01 × 10-10-2.73 × 10-8.To broaden the comparison conditions,comparisons were also made with international representative methods for solving peak pipeline strain under strike-slip fault displacement.Results showed that the PINN results remained consistent with the FEM results under different load conditions,with an average relative error of 2.88％,demonstrating its significant superiority to other methods for solving peak strain.[Conclusion]The proposed PINN method exhibits significant advantages in computational efficiency and accuracy,providing a new approach to maintaining pipeline structural integrity under fault displacement.(13 Figures,2 Tables,26 References)
[Objective]Against the backdrop of the"dual carbon"goals,methanol holds significant potential as a clean liquid fuel and hydrogen carrierfor large-scale pipeline transport.Given the high investment costs and long construction cycles of dedicated pipelines,batch transportation of methanol via existing product oil pipelines offers a practical alternative.Nevertheless,methanol differs substantially from gasoline and diesel in physical properties and miscibility,and its mixing dynamics during batch transportation remain unclear,necessitating systematic research under engineering-scale conditions.[Methods]With reference to mixing dynamics in conventional gasoline and diesel batch transportation,this research was conducted through miscibility tests and pilot-scale flow experiments.The miscibility characteristics between methanol and gasoline/diesel,alongside their effects on product oil quality,were analyzed.A self-built pilot-scale test loop was adopted to carry out batch transportation tests for methanol-gasoline and methanol-diesel under turbulent flow.Tests were performed across different flow velocities,transportation sequences,and transportation distances.Combined with visual observations through transparent pipeline segments and data from online densimeters,the mixed oil concentration distribution and axial development of mixed oil length were quantitatively characterized.[Results]The test results indicated that methanol and gasoline exhibited good miscibility.During batch transportation,the mixed oil section maintained high transparency,and the concentration changed continuously along the pipeline axis,showing marked similarities with traditional gasoline-diesel mixing dynamics.Within the investigated operating conditions,the mixed oil length of the methanol-gasoline system decreased with increasing flow velocity,whereas the transportation sequence exerted only a minor influence.In contrast,methanol and diesel exhibited poor miscibility and distinct physical properties.Longer mixed oil sections and pronounced tailing characteristics were observed during their batch transportation,making the mixed oil length more sensitive to the transportation sequence.Although increasing the flow velocity suppressed the mixed oil growth rate,it failed to completely eliminate the mixed oil expansion caused by poor miscibility and viscosity differences.[Conclusion]The mixing dynamics of methanol-gasoline batch transportation can draw on the operational experience of traditional gasoline-diesel systems,rendering this mode technically feasible for engineering applications under properly controlled flow velocities.Conversely,the batch transportation of methanol and diesel involves a more complex mixing process.Consequently,process design should prioritize the selection of the transportation sequence,optimization of operating parameters,and formulation of mixed oil cutting strategies.These research findings provide a valuable reference for engineering tests and operational optimization of methanol batch transportation in existing product oil pipelines.(10 Figures,2 Tables,32 References)
