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Natural-gas pipelines converted to carry hydrogen could have reduced mechanical properties due to hydrogen embrittlement. The tensile properties of the X65 D pipeline steel from the Dampier-Bunbury Natural Gas Pipeline were assessed in air and in hydrogen. The microstructure consisted of ferrite and pearlite elongated in the transverse and longitudinal directions by the hot and cold rolling during pipe production. Tensile tests were conducted using the linearly increasing stress test with cathodic hydrogen charging. Specimens were from the base metal, weld metal and heat-affected zone, from varying depths in the pipeline wall and for longitudinal and transverse orientations. There was no influence of hydrogen on steel strength, and no sub-critical crack growth. Hydrogen produced a similar reduction in the ductility for the base metal, weld metal, heat-affected zone, and at different depths in the pipe wall. The ductility reduction in the transverse direction was greater than in the longitudinal direction which correlated with more brittle quasi-cleavage facets, and which was attributed to the more pronounced pearlite banding in the transverse direction. The reduction of ductility by hydrogen was attributed to hydrogen causing a change in fracture mode from ductile micro-void coalescence in air to the altered micro-void coalescence fracture mechanism in hydrogen and to the introduction of quasi-cleavage in the presence of hydrogen which might have been by the HELP + HEDE mechanism. • Hydrogen charging reduced ductility similarly for the weld and base metal of X65. • Hydrogen embrittlement was more severe in transverse direction than longitudinal. • SEM showed hydrogen introduced surface cracks from which fracture propagated. • Reduction in ductility due to hydrogen was attributed to HELP + HEDE. • Hydrogen charging had no effect on strength. [ABSTRACT FROM AUTHOR]

A suspension bridge for a natural gas pipeline crossing has a small width-span ratio and is characterized by low damping and low stiffness. To improve the structure's resistance to wind loads, it is necessary to establish a cable system. Given the steep and rugged terrain of the project site, a wind-resistant system incorporating both parallel wind cables and conjugate cables was designed, with the angle between the wind cables and the horizontal plane reduced to 1.2°. Additionally, an effective calculation method was developed to accurately determine the spatial configuration of the wind-resistant cable system. The wind resistance and safety of the connection structure were validated through a 1∶25 scaled aeroelastic model test. The results from tests in both uniform and turbulent flow fields show that under wind attack angles of 0° and 3°, the flutter stability requirements were met, and no discernible vortex-induced vibration was detected within the tested range. The maximum vertical displacement response occurred at the quarter-span position, while the maximum lateral and torsional displacement response were observed at the midspan. Finally, based on the test results, the impact of aerodynamic admittance functions on the frequency-domain buffeting response of the bridge was analyzed. Overall, the test and analysis results indicate that the bridge structure meets the operational requirements of the natural gas pipeline. [ABSTRACT FROM AUTHOR]

The transport of hydrogen-blended natural gas serves as an efficient method for the long-distance conveyance of hydrogen via established natural gas pipelines. Nevertheless, the addition of hydrogen significantly alters the physical properties of the gas mixture and affects the operational characteristics of the pipeline, which directly impacts transportation efficiency and safety. Existing research lacks a systematic analysis of pipeline leakage and pressure variations under different hydrogen blending ratios. In this study, a simulation model for hydrogen-blended natural gas pipelines was established to analyze in-depth the impact of hydrogen injection on pipeline operations. Additionally, a method for evaluating shut-off valves in hydrogen-blended natural gas pipelines, based on leakage pressure drop data, was proposed. The results show that under small crack leakage conditions, the pipeline flow increases by 1.8%, 4.8%, and 9.1% at hydrogen blending ratios of 10%, 20%, and 30%, respectively, compared to pure natural gas. At the same pressure, the leakage mass flow increases with higher operating temperatures. Under catastrophic rupture conditions, the pressure drop decreases more significantly with increasing hydrogen blending ratio. Notably, as the crack opening increases proportionally, the pressure drop variation becomes more gradual with higher hydrogen blending ratios. When the blending ratio reaches a certain threshold, the pressure reduction in the pipeline shows a linear relationship with the crack opening. This novel finding provides new insights and methods for pressure prediction in pipeline leakage scenarios. The results of this study provide a theoretical basis for the further development of hydrogen-natural gas blending technologies. • Hydrogen blending ratio impacts pipeline leakage flow rate more than pressure. • Higher leakage temperature and hydrogen ratio lower the leakage mass flow rates. • At a certain H 2 ratio, leaking pressure positively correlates with opening size. • Design an method to assess valve closure in hydrogen-blended natural gas pipelines. [ABSTRACT FROM AUTHOR]

Hydrogen mixing technology in natural gas pipelines facilitates the large-scale application of hydrogen energy, thereby promoting energy savings and emission reductions. The performance of gas equipment is significantly influenced by the mixing uniformity of hydrogen mixing devices within the natural gas. This study involves the design and optimization of a static mixer structure for hydrogen mixing in natural gas, employing a combination of numerical simulations and experimental approaches. The effects of mixing pressure, mixing ratio, and mixing flow rate on the mixing uniformity are analyzed. Results indicate that the mixing effect can be improved by adding an expanding pipe, adding solid boards, and introducing hydrogen into the natural gas pipeline via swirl and sidewall annular gap entry methods. Increasing the diameter of the natural gas pipe or adding an expanding pipe effectively reduces pressure loss. The influence of mixing pressure on mixing uniformity is minimal. As the mixing ratio or mixing flow rate increases, the uniformity initially improves and then declines, peaking at a mixing ratio of 10 % and a mixing flow rate of 10 m³/h, respectively. [Display omitted] • A new static mixer for mixing hydrogen into natural gas pipeline is designed. • The experiment of static mixer for natural gas mixing with hydrogen is supplemented. • Static mixers for blending hydrogen with natural gas are designed and optimized. • The influence of static mixer structure on the mixing effect is studied. • The influence of operating conditions like mixing ratio on uniformity is studied. [ABSTRACT FROM AUTHOR]

This paper examines the crucial elements of pipeline-based hydrogen transportation, highlighting the particular difficulties and technical developments required to guarantee the sustainable, effective, and safe supply of hydrogen. This study lists the essential phases of hydrogen pipeline management, from design to repair, as the relevance of hydrogen infrastructure in the worldwide energy transition continues to rise. It discusses the upkeep, monitoring, operation, and rehabilitation procedures for aged pipelines with an emphasis on the cutting-edge techniques and technology used to mitigate the dangers related to hydrogen's unique features, such as leakage and embrittlement. Together with highlighting the legislative and regulatory frameworks that enable the infrastructure, this paper also discusses the material, economic, and environmental difficulties related to hydrogen pipelines. Lastly, it emphasizes how crucial it is to fund research, create cutting-edge materials, and implement sophisticated monitoring systems to guarantee the long-term dependability and safety of hydrogen pipelines. These initiatives will be crucial in allowing hydrogen's contribution to the future of renewable energy, together with international collaboration on regulatory standards. [ABSTRACT FROM AUTHOR]

Due to the unobservable nature of underground construction and the destructive nature of horizontal directional drilling rigs with high power, this type of construction has become one of the most important causes of failure of long-distance natural gas pipelines. In recent years, horizontal directional drilling construction has caused pipeline accidents frequently. Once the accident occurs, the normal operation of natural gas pipelines cannot be ensured. Therefore, studying the damage mechanism of buried natural gas pipelines under horizontal directional drilling loads is important for the safe operation of pipelines. This paper combines the construction characteristics of horizontal directional drilling and the actual situation of natural gas pipelines to explore the relationship between horizontal directional drilling and pipelines. The force situation of pipelines after contacting directional drilling bits is analyzed by the drill bit-soil-pipe finite element model created in the ABAQUS software. The Johnson–Cook ductile damage model was utilized to determine the pipe's damage condition. The sensitivity analysis results show that he order of the impact of key parameters on the dynamic response of the pipe is bit thrust > wall thickness > bit diameter > pipe diameter > bit speed > number of bit teeth > pipe operating pressure. Therefore, priority should be given to controlling the size of the drilling thrust and the speed of the drill bit to reduce the damage to pipelines by horizontal directional drilling construction. In addition, appropriately reducing the pipeline operating pressure can also reduce the risk of the pipeline being damaged by horizontal directional drilling construction. [ABSTRACT FROM AUTHOR]

In this study, the fatigue crack growth behavior of X65 welded joints in a natural gas mixed hydrogen environment with a total pressure of 10 MPa and hydrogen volume fractions of 0%, 5%, 10%, 15%, and 20% was examined. The addition of hydrogen increased the fatigue crack growth rate (FCGR) of X65 welded joints by more than 10 times that of nitrogen. With an increase in the hydrogen volume fraction, the fatigue crack acceleration rate gradually increased, and was proportional to the square root of the hydrogen partial pressure. The fatigue crack propagation performance and hydrogen embrittlement sensitivity of the heat affected zone (HAZ) were the worst, which is related to the distribution of lath bainite (LB) with a high dislocation density and hard, brittle martensite/austenite (M/A) constituents in the HAZ. The mechanism of hydrogen-promoting fatigue crack propagation is that hydrogen promotes dislocation movement and enhances plasticity in the base metal (BM) and weld metal (WM) specimens, whereas it inhibits dislocation mobility and reduces plasticity in the HAZ specimens. Thus, the findings of this study can be expected to support the application of hydrogen transportation in natural gas pipelines. • The effect of hydrogen mixing ratios on FCGR of X65 welded joints was evaluated. • The HAZ exhibited the highest hydrogen embrittlement susceptibility. • The hydrogen embrittlement mechanism of X65 welded joints was analyzed. [ABSTRACT FROM AUTHOR]

We examine the effects of self-generated magnetic fields in a Kr gas pipe x-ray source platform. X-ray emission from Kr plasma is dependent on the plasma conditions, as the ionization state is largely a function of temperature. Magnetic fields are known to limit heat conduction, which increases temperature. We show that the emission in simulations of the gas pipe x-ray source is dependent on how self-generated magnetic fields are modeled. The inclusion of self-generated magnetic fields in simulations more accurately captures the emission of lower energy x-ray emission (L-shell), bringing results closer to experiments. The modeled x-ray emission and self-generated magnetic fields are shown to be particularly sensitive to the inclusion of the Nernst effect in simulations. Severely limiting the Nernst effect leads to a hotter Kr plasma, which can account for the discrepancy seen in earlier studies. By modifying the Nernst effect multiplier, we can achieve better experimental agreement in x-ray emission from gas pipes; the value of the multiplier that leads to the best agreement is dependent on the laser power of the drive. Currently, the suppression factor of the Nernst effect needed for high power drives ( P L > 200 TW) is more restrictive than what is currently put forward by non-local models. [ABSTRACT FROM AUTHOR]

Detection of underground natural gas pipeline micro-leakage based on unmanned aerial vehicle (UAV) hyperspectral remote sensing and GIS. Hyperspectral images can indirectly detect underground natural gas pipeline micro-leakage through spectral and spatial variation characteristics of surface vegetation. However, most of existing studies were based on ground-mounted platforms, which could only perform small-range single-point detection and might occur misidentifications. UAV hyperspectral remote sensing can allow wide-range detection of surface vegetation. Moreover, underground pipeline distribution GIS data can provide prior knowledge about leakage points to exclude misidentifications. Therefore, a natural gas pipeline micro-leakage experiment was set up. UAV hyperspectral images of grasslands and pipeline distribution vector data were obtained, which led to a proposed new wide-range multi-points detection methodology of underground natural gas micro-leakage. Firstly, the vegetation identification index (WVI) $\left({{R_{470}} + {R_{674}}} \right)/\left({{R_{555}} + {R_{750}}} \right)$ R 470 + R 674 / R 555 + R 750 was designed based on WOA–VMD (whale optimization algorithm – variational modal decomposition) to segment and extract the vegetation stress zones. Then, UAV- and GIS-based natural gas micro-leakage vegetation stress identification model was constructed to obtain the leak points of natural gas micro-leakage. Finally, the recognition ability was evaluated by comparing with three stress vegetation identification indices proposed in previous studies. The result showed that there was no missing or false detection in identification results; the identification and positioning effect was better than other indices, which could meet the practical application requirements. [ABSTRACT FROM AUTHOR]

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This study investigates the impact of natural gas pipeline leakage on the soil temperature field through numerical simulations. Physical and mathematical models were developed to analyze the temperature and flow field changes resulting from pipeline leaks. The study explores the influence of various leakage factors on the temperature distribution in the surrounding soil. Key findings include the identification of the buried pipeline temperature as a critical factor influencing the soil temperature gradient when surface temperatures are similar to the subsurface constant temperature. Upon leakage, the pressure distribution around the leak is symmetrical, with a higher pressure at the leak point, and the Joule–Thomson effect causes a rapid decrease in gas temperature, forming a permafrost zone. The study also reveals that increased transport pressure expands the permafrost area, with pressure playing a significant role in the temperature field distribution. Additionally, an increase in the leak orifice diameter accelerates the expansion of the permafrost area and reduces the time for temperature stabilization at monitoring points. Conversely, changes in the leak direction mainly affect the spatial distribution of the permafrost zone without significantly altering its size. The findings provide valuable insights for monitoring natural gas pipeline leaks through temperature field variations. [ABSTRACT FROM AUTHOR]

Corrosion poses a great risk to the integrity of oil and gas pipelines, leading to substantial investments in corrosion control and management. Several studies have been conducted on accurately estimating the maximum pitting depth in oil and gas pipelines using available field data. Some of the frequently employed machine learning techniques include artificial neural networks, random forests, fuzzy logic, Bayesian belief networks, and support vector machines. Despite the ability of machine learning methods to address a variety of problems, traditional machine learning methods have evident limitations, such as overfitting, which can diminish the model's generalization capabilities. Additionally, traditional machine learning models that provide point estimations are incapable of addressing uncertainties. In the current study, a Bayesian neural network is proposed to include uncertainty in estimating the corrosion defect of a pipeline exposed to external pitting corrosion. The results are then incorporated into a Bayesian belief network for evaluating the probability of failure and its corresponding consequences in terms of social impact, thus forming a comprehensive risk assessment framework. The results of the Bayesian neural network are validated using field data and achieved a testing accuracy of 90%. The framework of the study offers a powerful decision‐making tool for the integrity management of pipelines against external corrosion. [ABSTRACT FROM AUTHOR]

Pipeline leaks are known to frequently occur in chemical processing and urban gas pipes, which can lead to equipment damage, explosions, and potentially serious injuries. A design of a piezoelectric acoustic sensor for fluid leak detection is proposed in this work. The low-frequency acoustic leak signals that travel through the fluid in a pipeline can be detected using a piezoelectric acoustic sensor. The design and simulation of sensor is done using COMSOL Multiphysics software. The sensor specification is used to guide the choice of materials and optimization of geometry. The simulated results show the characteristics of transient response using a nondestructive detection approach at various leakage rates. The recommended detection method's ability to detect leak signals with tolerable accuracy is shown through simulated results. The designed sensor can be used for both long-term leak monitoring and short-term safety evaluations. The simulated sensitivity of 191 µV/m at 27.46 kHz resonance frequency is achieved by optimizing device design. The maximum deflection at the center is 2.37 nm. The total electric energy generated at 1 N of force and 5 Hz frequency is 8 nJ. [ABSTRACT FROM AUTHOR]

Using the software ANSYS-19.2/Explicit Dynamics, this study performed finite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack, strengthened by steel wire wrapping. The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied. The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force, which was 6.4% more effective than that at its maximum value. The analysis of the influence of the winding diameters showed that the equivalent stresses increased by 32% from the beginning of the crack growth until the wire broke. The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%. The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6% reduction in the length of the straight crack and a 7.9% reduction in the maximum stresses on the strengthened pipeline cross-section. The analysis of the temperature effect on the pipeline material, within a range from −40°C to +50°C, resulted in a crack length change of up to 5.8%. As the temperature dropped, the crack length decreased. Within such a temperature range, the maximum stresses were observed along the central area of the crack, which were equal to 413 MPa at +50°C and 440 MPa at −40°C. The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times, depending on the temperature effect and design parameters of prestressing. This work integrated the existing methods for crack localization along steel gas pipelines. [ABSTRACT FROM AUTHOR]

In this paper, we studied the diffusion characteristics and distribution patterns of gas leakage in soil from buried natural gas pipelines. The three-dimensional simulation model of buried natural gas pipeline leakage was established using Fluent software. Monitoring points of gas leakage mole fraction were set up at different locations, and the influence of buried depth and pressure factors on the mole fraction and diffusion of leaked gas was analyzed. Additionally, a leakage pressure drop test of the buried natural gas pipeline was carried out. The results show that the CH4 gas mole fraction curve at 0.03 m and 0.05 m below the leakage point fluctuates sharply during the second to third second of leakage, with the CH4 gas mole fraction fluctuating by about 7%. The buried depth has the greatest influence on CH4 in the leakage point range of 0.05 m, with the CH4 gas mole fraction above and below the leakage hole differing by nearly 10 times in numerical value. As the buried pipeline depth increases, the pressure drop of the monitoring points at 0.1 m, 0.2 m, 0.3 m, 0.4 m, and 0.5 m is 27.64%, 24.02%, 21.52%, 17.65%, and 17.11%, respectively. In the x-axis direction, CH4 gas presents a U-shaped diffusion in the soil, and after leaking for 200 s, CH4 gas diffused to the top of the pipeline. The errors of the finite element numerical solution and the experimental values of the leakage pressure drop curve of the buried natural gas pipeline under four working conditions are 5.9%, 5.5%, 5.2%, and 5.0%, which are all within the allowable range. The accuracy of the finite element calculation results and the reliability of the test are verified. [ABSTRACT FROM AUTHOR]

Methane is a significant contributor to anthropogenic greenhouse gas emissions. Blending hydrogen with natural gas in existing networks presents a promising strategy to reduce these emissions and support the transition to a carbon-neutral energy system. However, hydrogen's potential for atmospheric release raises safety and environmental concerns, necessitating an assessment of its impact on methane emissions and leakage behavior. This study introduces a methodology for estimating how fugitive emissions change when a natural gas network is shifted to a 10% hydrogen blend by combining analytical flowrate models with data from sampled leaks across a natural gas network. The methodology involves developing conversion factors based on existing methane emission rates to predict corresponding hydrogen emissions across different sections of the network, including mainlines, service lines, and facilities. Our findings reveal that while the overall volumetric emission rates increase by 5.67% on the mainlines and 3.04% on the service lines, primarily due to hydrogen's lower density, methane emissions decrease by 5.95% on the mainlines and 8.28% on the service lines. However, when considering the impact of a 10% hydrogen blend on the Global Warming Potential, the net reduction in greenhouse gas emissions is 5.37% for the mainlines and 7.72% for the service lines. This work bridges the gap between research on hydrogen leakage and network readiness, which traditionally focuses on safety, and environmental sustainability studies on methane emission. [ABSTRACT FROM AUTHOR]

In recent years, with the increasing construction mileage of oil and gas pipelines (OGPs), the aging problem of OGPs has become increasingly prominent, so, ensuring the safety of OGPs is of great significance. In addition, the safety of OGP transportation is also an important component of pipeline integrity. Therefore, to ensure the safety of OGP transportation, regular OGP inspections should be carried out. During this process, defects in the OGP and measured wall thickness information should be recorded to provide a basis for subsequent pipeline repair or replacement. This study analyzes the literature on pipeline testing and reviews approximately eighty articles. Based on these articles, we summarize the types of common OGP defects and review the basic principles of various non-destructive testing methods for pipelines, including electromagnetic acoustic transducer inspection, magnetic flux leakage testing, ultrasonic testing, and eddy current testing. We also provide a detailed introduction to the applications and innovative testing methods based on the above OGP inspection methods. Finally, an analysis and outlook on the future research focus of OGP inspection technology are presented. This research suggests that different detection methods should be used for different types of defects, such as using the magnetic leakage method for the internal detection of natural gas pipelines. [ABSTRACT FROM AUTHOR]

The research on the gas axial flow regulating valve is one of the key tasks for the localization of critical valves in natural gas pipelines. With the main purpose of improving the design of the sleeve of the gas axial flow regulating valve, numerical simulation calculations are conducted on the internal flow passage of the gas axial flow control valve by using fluid simulation software. According to the existing design of the valve sleeve, the design scheme of the valve sleeve is improved by changing the diameter of the throttle hole of the valve sleeve. After improving the valve sleeve, eight simulations have been performed at different openings to analyze the velocity field, pressure distribution, and variations in aerodynamic noise within the flow passage at two design schemes. A comparison is also made between two valves for their respective flow fields and noise characteristics which use two different sleeve designs. The simulation results indicate that appropriately increasing the throttle aperture can improve the flow performance of a gas axial flow regulating valve, reducing noise levels to below 100 dB at medium and small openings. [ABSTRACT FROM AUTHOR]

In the article, the solution of the issues of transportation of the produced product in the oil and gas extraction department occupies one of the main places. Pipelines belong to technological systems that represent fire-explosion dangerous objects with a complex structure capable of hydrate formation, erosion, ignition, explosion and environmental pollution. By reducing technological risks that may occur in underwater pipelines, it is possible to ensure technological and environmental safety at sea and protect marine bioresources. Risk analysis using statistical data can reveal the negative consequences of natural hazards and other external influences on the pipeline system. [ABSTRACT FROM AUTHOR]

While green hydrogen production technologies like electrolysis have reached commercial scale, the primary challenge centers on efficient, and economically viable transportation of hydrogen. This study proposes an integrated geospatial techno-economic modeling approach to optimize hydrogen transportation through blending in existing pipelines. The simulations strategically locate green hydrogen production and blending points. The paper evaluates blending ratios, flow dynamics, and operating parameters to optimize hydrogen blending in natural gas pipelines. A techno-economic analysis quantifies costs and revenues across the supply chain, identifying the most economically viable hydrogen blending locations. The approach is validated through a case study in Wyoming, providing insights for industry stakeholders considering hydrogen-natural gas blending as a transition strategy. This integrated method offers a robust decision support tool for leveraging existing infrastructure to realize hydrogen's potential as a sustainable energy vector contributing to the broader goal of cleaner energy alternatives. [Display omitted] • Map energy infrastructure to optimize hydrogen production and injection points. • Simulate blending ratios, flow dynamics, and parameters for system optimization. • Perform a cost-benefit analysis to identify optimal hydrogen blending locations. • Validate the model with a Wyoming case study for industry stakeholder insights. [ABSTRACT FROM AUTHOR]

The increasing demand for energy and the urgent need to reduce carbon emissions have positioned hydrogen as a promising alternative. This review paper explores the potential of hydrogen blending in natural gas pipelines, focusing on the compatibility of pipeline materials and the associated safety challenges. Hydrogen blending can significantly reduce carbon emissions from homes and industries, as demonstrated by various projects in Canada and globally. However, the introduction of hydrogen into natural gas pipelines poses risks such as hydrogen-assisted materials degradation, which can compromise the integrity of pipeline materials. This study reviews the effects of hydrogen on the mechanical properties of both vintage and modern pipeline steels, cast iron, copper, aluminum, stainless steel, as well as plastics, elastomers, and odorants that compose an active natural gas pipeline network. The review highlights the need for updated codes and standards to ensure safe operation and discusses the implications of hydrogen on material selection, design, and safety considerations. Overall, this manuscript aims to provide a comprehensive resource on the current state of pipeline materials in the context of hydrogen blending, emphasizing the importance of further research to address the gaps in current knowledge and to develop robust guidelines for the integration of hydrogen into existing natural gas infrastructure. • Hydrogen blending in natural gas pipelines can significantly reduce carbon emissions. • Hydrogen embrittlement poses safety risks for pipeline materials in NG infrastructure. • Testing shows minimal yield strength changes after hydrogen exposure in various steels. • Fracture toughness of pipeline steels decreases notably with increasing hydrogen pressure. • Advanced testing and materials development are needed for safe hydrogen integration. [ABSTRACT FROM AUTHOR]

It is likely that blending hydrogen into natural gas grids could contribute to economy-wide decarbonization while retaining some of the benefits that natural gas networks offer energy systems. Hydrogen injection into existing natural gas infrastructure is recognised as a key solution for energy storage during periods of low electricity demand or high variable renewable energy penetration. In this scenario, natural gas networks provide an energy vector parallel to the electricity grid, offering additional energy transmission capacity and inherent storage capabilities. By incorporating green hydrogen into the NG network, it becomes feasible to (i) address the current energy crisis, (ii) reduce the carbon intensity of the gas grid, and (iii) promote sector coupling through the utilisation of various renewable energy sources. This study gives an overview of various interchangeability indicators and investigates the permissible ratios for hydrogen blending with two types of natural gas distributed in Tunisia (ANG and MNG). Additionally, it examines the impact of hydrogen injection on energy content variation and various combustion parameters. It is confirmed by the data that ANG and MNG can withstand a maximum hydrogen blend of up to 20%. The article's conclusion emphasises the significance of evaluating infrastructure and safety standards related to Tunisia's natural gas network and suggests more experimental testing of the findings. This research marks a critical step towards unlocking the potential of green hydrogen in Tunisia. [ABSTRACT FROM AUTHOR]

Objective The aim is to study the corrosion burst problem that may occur during the transportation of overhead largescale pure hydrogen/hydrogen-doped natural gas pipelines to prevent safety accidents caused by leakage and combustion due to this issue. Methods Based on the theory of gas combustion dynamics and computational fluid dynamics (CFD), a three-dimensional pipeline small hole leakage model under different conditions was established, and CFD Fluent software was used to simulate the combustion characteristic of pure hydrogen/hydrogen-doped natural gas jet diffusion flame under different conditions. Results The relative error between the height of simulated jet flame and the experimental jet flame is 1.48%; as the delivery pressure and leakage aperture increase, the height of the jet flame increases significantly, and the peak position of the flame temperature is further away, making it more harmful; as the hydrogen doping ratio increases from 10% to 90%, the jet flame height decreases by 13.7%. Conclusion The research results are consistent with the experiment, which can provide data support and practical reference for optimizing the design parameters of pure hydrogen/hydrogen-doped natural gas pipeline network transmission and fire safety accident disposal. [ABSTRACT FROM AUTHOR]

Objective Doping hydrogen into natural gas pipelines is an effective way to transport hydrogen on a large scale and long distances. However, during the venting process, high-pressure hydrogen-doped natural gas poses a risk of spontaneous combustion due to various factors such as pressure, temperature, chemical reactions, and electrostatic friction. Therefore, the conditions leading to spontaneous combustion during the venting process of hydrogen-doped natural gas were analyzed. Methods Based on fluid mechanics, chemical reactions, and electric field theory, a coupled model of the flow field, temperature field, chemical reaction field, and electric field for venting hydrogen-doped natural gas was established, and the model decoupling solution algorithm was studied. Then, taking the venting system of a valve chamber in the West-East Gas Pipeline as an example, this study analyzed the effects of hydrogen doping ratio, inner diameter of vent pipe, height of vent riser, and vent pressure on spontaneous combustion. Results The increase in hydrogen doping ratio, inner diameter of the vent pipe, height of the vent riser, and vent pressure not only leads to the rising of maximum temperature but also promotes the increase of OH− mass fraction, while the length of the horizontal pipe has no significant effect on gas temperature and OH− mass fraction. In addition, even under the most prone conditions to spontaneous combustion, the gas temperature and OH− mass fraction have not reached the spontaneous combustion criterion. Conclusion Under the existing design and operation conditions of the valve chamber venting system mentioned above, hydrogen-doped natural gas venting does not have the conditions for spontaneous combustion to form stable combustion flames. [ABSTRACT FROM AUTHOR]

PRELUDE: Violence. Dead crabs by the many thousands on the beach. Dead fish too. Ponds full of tires. Bubbles surfacing from broken gas pipes somewhere at the bottom of the river. The wind sweeping through the wreckage of an abandoned steelworks providing an incessant hum that echoes across this coastal 'wasteland' of the Anthropocene. Someone fishing sits huddled on a concrete jetty. A surfer, shivering, hurriedly pulls and tugs on a neoprene wetsuit as they dance on the snow. His mates wait for him. A beachcomber hunts for washed up mining tools to turn into art. Relationships with nature—this post-industrial 'wasteland' is nature too—in this place may make you feel better. They may not, also. This is polluted leisure in the Anthropocene. [ABSTRACT FROM AUTHOR]

Wax deposition in oil and gas pipelines and equipment is a fundamental challenge that can lead to a decrease in the performance and useful life of these systems. To address this issue, various methods have been developed to reduce wax deposition. This article investigates two novel methods, namely microwave and ultrasonic, for wax deposition mitigation. The microwave method utilizes high-frequency electromagnetic waves and short wavelengths to transfer heat to the wax and separate it from the internal surface of the pipelines. In this method, microwave waves provide energy to the wax, increasing its temperature and causing it to melt and move. Due to its speed, efficiency, and applicability in industrial environments, the microwave method has been recognized as a leading approach in wax deposition reduction, requiring minimal modifications to the pipeline structure. The ultrasonic method employs high-frequency sound waves to disrupt and prevent wax deposition. Ultrasonic waves generate alternating pressure waves at the site of wax accumulation, breaking down the wax structure. This nondestructive and reliable method is capable of reducing wax deposition in hard-to-reach areas. Both microwave and ultrasonic methods have gained attention as innovative approaches for wax deposition reduction. However, further research is needed to optimize and enhance these methods, aiming to improve their implementation capabilities, increase efficiency, and reduce costs. The study also addressed conventional and common methods, such as insulators heat-proofing materials, heating techniques to prevent wax deposition, cold flow, wax inhibiting tools, wax removal techniques, chemicals, and bacterial treatment. [ABSTRACT FROM AUTHOR]

This paper primarily investigates the influence of spatial layout on the safety risks associated with urban natural gas pipelines. Drawing from the actual spatial configuration around the pipeline and local climatic characteristics, the study delves into the distribution patterns of natural gas leakage diffusion and explosion accident consequences, considering various factors such as leakage apertures, soil porosity, and spatial layouts. By integrating the outcomes of the consequence analysis, the quantitative risk of urban natural gas pipelines, accounting for the impact of spatial layout, was computed and juxtaposed with the results of traditional two-dimensional risk analysis. The findings underscore that spatial layout exerts a substantial impact on risk distribution, with significantly elevated risk values in more congested spatial layouts. Additionally, the introduction of a barrier along the pipeline leakage path resulted in a 91.4% reduction in risk compared to scenarios without obstruction. It is evident that the spatial layout surrounding the pipeline plays a pivotal role in influencing the distribution of pipeline failure risks, establishing the spatial environment as a critical factor in risk analysis. This study offers valuable insights for urban land planning, safety control line establishment, and related considerations. [ABSTRACT FROM AUTHOR]

By 2025, the total mileage of natural gas pipelines in China is expected to reach 163,000 km, placing urgent demands on the simulation technology for increasingly large-scale and more complicated pipeline networks. This paper describes the development of a new sectionalizing method, which is based on optimization strategy, for simulating large-scale and complicated natural gas pipeline networks. Based on analysis of the topological structures, the entire pipeline networks are decomposed into multiple sub-networks according to the connecting nodes between the adjoined pipelines. The sectionalizing method is then implemented by minimizing the residuals of conservation for continuity and momentum at the connecting nodes in isothermal mode. The hydraulic variables in each sub-network are obtained after the hydraulic variables at connecting nodes are updated. The calculation accuracy and efficiency of this sectionalizing method are demonstrated by comparison with a commercial software through three different test cases. It is shown that the maximum relative deviation of pressure of the method developed is within 2.5% of that calculated using the commercial software. In a 5 x 104 km test case with variable spatial step sizes, the computational efficiency is 2.1 to 3.2 times of that of the commercial software. The results of the three case studies suggest that this sectionalizing method is promising and suitable for application to large-scale complicate natural gas network simulation. [ABSTRACT FROM AUTHOR]

In order to study the flow blending and transporting process of hydrogen that injects into the natural gas pipelines, a three-dimensional T-pipe blending model is established and the flow characteristics are investigated systematically by the large eddy simulation (LES). Firstly, the mathematical formulation of hydrogen-methane blending process is provided and the LES method is introduced and validated by a benchmark gas blending model having experimental data. Subsequently, the T-pipe blending model is presented, and the effects of key parameters, such as the velocity of main pipe, hydrogen blending ratio, diameter of hydrogen injection pipeline, diameter of main pipe and operating pressure on the hydrogen-methane blending process, are studied systematically. The results show that, under certain conditions, the gas mixture will be stratified downstream of the blending point, with hydrogen at the top of the pipeline and methane at the bottom of the pipeline. In the nostratified scenario, the mixing distance increases at lower hydrogen mixing ratio and larger diameter of the hydrogen injection pipe or the main pipe. Finally, based on the numerical results, the underlying physics of the stratification phenomenon during the blending process are explored and an indicator for stratification is proposed using the ratio between the Reynolds numbers of the natural gas and hydrogen. [ABSTRACT FROM AUTHOR]

This paper proposes a method for determining the speed of hollow steel billet casting to produce seamless oil and gas pipes. At the same time, the use of hollow billet excludes, in the technological process of pipe production, the piercing of the billet. The results of industrial production modeling were recalculated into natural quantities according to the Fourier number similarity criterion. The calculations determined that the optimal drawing speed and casting speed of a billet with a diameter of 210 mm are 2.01 m/min and 0.273 t/min, respectively. At the same time, productivity increased by 16%, compared to the one when casting a solid billet. To ensure the homogeneity of structure and mechanical properties over the entire cross-section of the hollow billet, the optimum ratio of coolant flow rates into the inner cavity and outside the billet in the secondary cooling zone was determined, considering the area of the cooled surface, which is equal to 1.46. [ABSTRACT FROM AUTHOR]

Adding a certain percentage of hydrogen into the natural gas pipeline network is regarded as an efficient way to store and transport hydrogen. CH4-H2 binary fuel is also considered to be an important means of hydrogen utilization. In this paper, flame acceleration (FA) in stoichiometric CH4/H2/air mixtures with various hydrogen blend ratios (i.e., Hbr = 0%, 20%, 50%, 80%, and 100%) was studied experimentally and numerically. In the experiments, high-speed photography was used to record the FA process. In the numerical simulations, the two-dimensional, fully-compressible, reactive Navier-Stokes equations were solved using a high-order algorithm on a dynamically adapting mesh. The chemical reaction and diffusive transport of the mixtures were described by a calibrated chemical-diffusive model. The numerical predictions agree reasonably with the experimental measurements. The results show that a larger hydrogen blend ratio leads to a faster FA. The difference in FA due to hydrogen blending mainly depends on the property change of the fuel mixtures, the increase of flame surface area and the interactions between flame and pressure waves, corresponding to three different stages. In addition, the heat loss to the channel walls and obstacle surfaces has an impact on the FA process, especially in the mixtures with low hydrogen blend ratios (i.e., Hbr ≤ 20%). This is related to the weakening of interactions between pressure waves and flame under isothermal boundary condition. [ABSTRACT FROM AUTHOR]

The failure probability of a pipeline is a quantification of the likelihood of an accident occurring in the pipeline, which is an indispensable part of the pipeline risk assessment process. To solve the problems of strong subjectivity, low feasibility, and low accuracy in the existing pipeline failure probability calculation methods, a three-layer Bayesian network topology model of "pipeline failure–failure cause–influencing factor" is proposed, with the pipeline failure as the subnode, the type of pipeline failure as the intermediate node, and the factors affecting the pipeline failure as the parent node of the network. Based on data fitting and fuzzy theory analysis methods, the functional relationship between the impact factor and the failure frequency of various pipelines is quantified. Using the mean value theorems for definite integrals and the analytic hierarchy process, the conditional probability of the directed edge in the network is calculated. The proposed function relationship provides a method to calculate the prior probability according to the parameters of the pipeline and its surroundings and a new idea to train the network model even without sufficient data. [ABSTRACT FROM AUTHOR]

The failure state of the natural gas pipelines in underground space may cause explosions, and an explosion flow field is affected by the structure of the venting duct. Based on FLACS software v9.0, the influence of the explosion vent and venting duct on temperature and pressure fields is studied. The results show that when the area of the explosion vent increases from 0 to 100 cm2, the peak overpressure decreases by half, and the overpressure drops to zero within 0.3 s. For different L-type venting ducts, when the structural coefficient is less than 5, the peak overpressures and pressure variations are similar. When the structural coefficient is equal to 5, the peak overpressure significantly decreases, and the time to reach the peak value is extended by 50%. From the perspective of achieving a safe and efficient venting effect, the optimal structural coefficient is 5 for the L-type venting duct. [ABSTRACT FROM AUTHOR]

Blending hydrogen for transportation in offshore natural gas pipelines is an important way to develop green energy, which is prone to hydrogen embrittlement leading to failure. The mechanical behaviour of defective hydrogen-blended natural gas pipelines with different hydrogen contents, was investigated by experimental and numerical methods. In addition, the failure mechanism analysis, including the effects of defect depth and combined loads, was carried out. According to the results, the evolution laws of pipeline strength and fatigue life under different hydrogen proportions are grasped. For example, under low hydrogen content (25%), its strength significantly decreases. Furthermore, the safety management method of offshore hydrogen-blended natural gas pipelines is given to provide a reference in the application of the project. [ABSTRACT FROM AUTHOR]

The transportation of natural gas through pipelines offers numerous advantages. However, physical explosions in high‐pressure natural gas pipelines can cause casualties and property loss. There is currently no method for accurately predicting the damage range of physical explosions in pipelines, and a safer site selection plan cannot be determined during the pipeline construction design stage. This study proposes a method for determining the range of pipeline physical explosion damage by comprehensively considering two factors: the size range of the physical explosion craters, and the attenuation distance of the shock waves. A high‐pressure natural gas pipeline physical explosion crater model was constructed using HyperMesh software, and the accuracy of the model was verified using the PRCI calculation model. Based on the Sadovsky formula, a program was developed to simulate the spatiotemporal changes in shock wave diffusion, demonstrating the law of shock wave diffusion. The results show that the distance from the overpressure peak attenuation of the physical explosion shock wave in air to 0.02 MPa is calculated to be 33 m, and the maximum damage range of the crater is 9.27 m. Finally, the safe protection distance for personnel and buildings was determined to be 33 m. [ABSTRACT FROM AUTHOR]

In the transition towards a hydrogen-based energy system, the strategic use of pipelines is crucial for efficient hydrogen distribution. Leveraging existing natural gas pipelines to carry a mix of hydrogen and natural gas offers a cost-effective alternative to building new infrastructure. This study explores the development of a leak detection system compatible with existing pipelines, specifically tailored for the blended hydrogen and natural gas mix. Given the scarcity of leak data for blended hydrogen-natural gas pipelines, the study introduces a Real-Time Transient Model (RTTM) for blended gases, simulating leak dynamics to generate necessary data. Additionally, a leak detection system (LDS) is developed using a fusion of Convolutional Neural Network (CNN) and Explainable Artificial Intelligence (XAI) through Adaptive Neuro-Fuzzy Inference Systems (ANFIS). This LDS framework overcomes the "black box" issue common in AI-driven systems, enabling reliable detection. The integration of Explainable and traditional AI techniques holds promising implications for blended hydrogen pipelines by enhancing the safety and efficiency of hydrogen transportation, thereby mitigating economic and environmental impacts, and addressing public concerns. • Development of a Real-Time Transient Model (RTTM) for simulating blended hydrogen and natural gas leak dynamics. • AI-based leak detection system (LDS) that addresses the typical "black box" issue in AI-driven systems. • The LDS combines outputs from Convolutional Neural Networks (CNN) and Adaptive Neuro-Fuzzy Inference Systems (ANFIS). • In simulated tests, the framework demonstrates high predictive accuracy using data from common field instrumentation. [ABSTRACT FROM AUTHOR]

This paper uses Fluent software to create a 3D leakage model for hydrogen-blended natural gas pipelines and analyzes how hydrogen blending ratio (HBR), soil type, and leakage hole shape affect gas dispersion. Results show that hydrogen and methane have different concentration distributions in soil: hydrogen forms an 'n' shaped distribution while methane forms an 'M' shaped distribution, with higher hydrogen concentrations observed further from leakage holes. HBR has a minimal effect on diffusion; higher HBR leads to lower concentrations at saturation. Soil type significantly impacts diffusion, with sandy soils showing higher gas concentrations than clay. Slit-type holes result in faster concentration saturation compared to square-type holes. Increasing the number of leakage holes from two to four enhances concentration differences and accelerates diffusion. The optimal axial spacing for fast diffusion is 200 mm. These findings support monitoring and risk assessment for hydrogen-blended natural gas pipelines. [Display omitted] • The effect of hydrogen ratio and leakage hole shape on gas dispersion with a three-dimensional model. • The diffusion behaviors of hydrogen and methane were analyzed with a multi-component diffusion approach. • The influence of the number of leakage holes and their spacing on the diffusion of mixed gases were analyzed. [ABSTRACT FROM AUTHOR]

The management and prevention of hydrates are crucial for the gas industry. This study delves into the intricate challenges associated with gas hydrate formation, with a specific focus on investigating the impact of corrosion by‐products on prevention strategies. Employing a distinctive methodology, the sapphire pressure–volume temperature (PVT) cell was utilized. Experimental tests were conducted using sodium chloride (NaCl) concentrations of 1% and 3% to simulate brine solution levels at the wellhead, incorporating 3% filtrate and unfiltered iron carbonate (FeCO3) as corrosion products associated with the production process. The 1% and 3% salt concentrations were chosen to encompass a broad range of temperature depressions, reflecting common industry standards for simulating realistic environmental conditions. PVT cell test conditions ranged from 80 to 200 bar, with increments of 40 bar. The experiments investigate the effects of common pipeline salts on a monoethylene glycol (MEG)/water mixture in the presence of methane gas at typical industry high‐pressure conditions. The investigation uncovers that the introduction of salts to water, methane, and MEG solutions serves as a hydrate inhibitor, with inhibitory effects directly correlated to salt concentration. While generally hydrate growth inhibition is beneficial in natural gas pipelines, the findings indicate that elevated salt concentrations and lower pressure conditions contribute to the formation of larger hydrates, heightening the risk of surface adhesion and potentially introducing complications in piping equipment, despite the decreased temperature at which these hydrates form due to the inhibitory effects of the salts. In particular, the mixed condition of 3% NaCl and 3% FeCO3 (filtered) has the strongest effect. Examination of hydrate formation temperature and macroscopic observations suggests that the existence of substantial precipitates, as evidenced in the unfiltered FeCO3 sapphire cell experiment, may have the potential to enhance hydrate growth. [ABSTRACT FROM AUTHOR]

In this study, we aim to develop advanced machine learning regression models for the prediction of hydrate temperature based on the chemical composition of sweet gas mixtures. Data were collected in accordance with the BOTAS Gas Network Code specifications, approved by the Turkish Energy Market Regulatory Authority (EMRA), and generated using DNV GasVLe v3.10 software, which predicts the phase behavior and properties of hydrocarbon-based mixtures under various pressure and temperature conditions. We employed linear regression, decision tree regression, random forest regression, generalized additive models, and artificial neural networks to create prediction models for hydrate formation temperature (HFT). The performance of these models was evaluated using the hold-out cross-validation technique to ensure unbiased results. This study demonstrates the efficacy of ensemble learning methods, particularly random forest with an R2 and Adj. R2 of 0.998, for predicting hydrate formation conditions, thereby enhancing the safety and efficiency of gas transport and processing. This research illustrates the potential of machine learning techniques in advancing the predictive accuracy for hydrate formations in natural gas pipelines and suggests avenues for future optimizations through hybrid modeling approaches. [ABSTRACT FROM AUTHOR]

Hydrogen doping using existing natural gas pipelines is a promising solution for hydrogen transportation. A large number of non-metallic seals are currently used in long-distance natural gas pipelines. Compared with metallic seals, non-metallic seals have the advantages of corrosion resistance, light weight, and easy processing, which can improve the safety and economy of pipelines. In order to ensure the long-term safe use of seals in hydrogen-doped natural gas pipelines, this paper selects the non-metallic seals commonly used in long-distance natural gas pipelines and carries out the hydrogen-doped sealing test, hydrogen-doped aging test, and hydrogen-doped anti-explosion test on the non-metallic seals under the conditions of different hydrogen-doped ratios. At the same time, combined with the actual working conditions of a hydrogen-doped natural gas pipeline, the external environment, and other factors, the applicability evaluation index system was established, and the applicability evaluation model based on hydrogen-doped physical and chemical properties, fuzzy comprehensive evaluation, and the structural entropy weight method was developed and applied in the field. The results show that the evaluation result of nitrile rubber in soft seals is 1.7845, and the evaluation result of graphite-polytetrafluoroethylene material in hard seals is 1.5988, and both of them are at a good level. This paper provides technical support and judging strategies for the selection of non-metallic sealing materials for hydrogen-doped natural gas pipelines. [ABSTRACT FROM AUTHOR]

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In order to improve defects detection efficiency in polyethylene (PE) gas pipelines and decrease leakage or other pipelines abnormalities in operation, this research proposed an improved YOLO(You Only Look Once) v5 detection model. First, the collected pipeline defect images were processed in grey scale, which improved the computational efficiency of the computer; then, Gamma transform and double filtering algorithms were applied respectively for image enhancement and noise reduction filtering of defects, which enhanced image quality and reduced image noise. Finally, the improved Sobel algorithm was applied to detect defective image edges and the defects in the image were segmented by adaptive threshold segmentation method to obtain binary images. The obtained binary images were employed to train the improved YOLO v5 detection model. The obtained experimental results showed that, compared with the original algorithm, the improved detection algorithm had better detection efficiency and higher robustness as well as higher recognition for common defects, improved YOLOv5 mAP and recall were 97.18% and 98.03%, respectively, the mAP has increased by 1.33% and the recall has increased by 3.83%, which can achieve the detection and identification of defect types of effects in PE gas pipes. [ABSTRACT FROM AUTHOR]

A new study by DNV analyzes the potential for hydrogen export from Sweden, Finland, and the Baltic states to Germany and Central Europe. The study examines the production potential, costs, and benefits of developing an H2 network in the region. It also compares different pipeline routes for large-scale hydrogen export. The study highlights the importance of establishing stable partnerships for hydrogen import chains to ensure a stable supply in Europe. [Extracted from the article]

Natural gas pipelines are an essential part of the economy. Natural gas pipelines may leak after aging, strong vibration signals may be generated in the pipeline when leakage occurs, and vibration signals may be noisy. Traditional variational mode decomposition (VMD) noise reduction methods need to set parameters in advance, and so may not achieve the best decomposition effect. To solve this problem, this paper proposes a method for pipeline leakage location based on the sparrow search algorithm (SSA) optimization of VMD combined with generalized quadratic cross-correlation. The method first calculates the original signal-to-noise ratio (SNR), and if the SNR is low, wavelet threshold denoising is used to process the signal. Then, SSA optimization is used to refine the two key parameters of VMD (penalty parameter α and mode decomposition number K) based on sample entropy. Subsequently, the signal undergoes decomposition into K intrinsic mode function (IMF) components through VMD according to the obtained analysis parameter combination. Then, the IMF components are screened to obtain the reconstructed signal. Finally, the noise reduction signal is obtained. The signal delay after noise reduction is obtained through a generalized quadratic cross-correlation and the accurate leakage position is obtained using the delay. Experiments showed that the minimum relative error of this method could reach 0.6%, which was more accurate than the traditional VMD method, and effectively improved the accuracy of noisy signals in pipeline leakage locations. [ABSTRACT FROM AUTHOR]

Incorporating hydrogen into the natural gas pipeline network (NGPN) plays a key role in absorbing large-scale renewable energy and mitigating the supply-demand contradictions between electricity and natural gas. The gas-electricity integrated energy system (GEIES) using hydrogen as an intermediate carrier is an effective approach for efficient utilization and low-carbon development in the energy sector. To analyze the influence of hydrogen blending on the operation optimization of GEIES, and to study the impact of fluctuating hydrogen supply and different user acceptance on the economic operation of hydrogen-blended GEIES, this paper proposes a gas-electric integrated energy double-way coupling model (GIEDCM), composed of gas turbines, coal-fired units, wind turbines, photovoltaic units, electrolytic cells, and hydrogen storage tanks (HST). The objective function is to minimize system operational costs, establishing a mixed integer nonlinear programming problem considering hydrogen blending. The nonlinear equations are handled using a piecewise linearization method, and the algorithm is solved by the branch-and-bound method and using the GUROBI solver to verify the effectiveness of the algorithm. This ultimately addresses the issue of low utilization of renewable energy sources (RES). Taking the Belgian 20-node NGPN and the IEEE-39-node electric grid system as examples, different scenarios of GEIES operational optimization are analyzed. The optimization results show that natural gas hydrogen blending significantly enhances the utilization level of wind and solar resources, substantially reduces the wastage of RES, and promotes the coupling and complementarity between various energy sources, reducing system operational costs. However, fluctuations in hydrogen supply and changes in user acceptance directly affect the hydrogen content in the NGPN, thereby influencing the hydrogen blending process. Therefore, hydrogen fluctuations should be minimized in the hydrogen mixing process, and if fluctuations are unavoidable, hydrogen should be supplied in intermittent wherever possible. Appropriate improvement of user acceptance can better improve the economic benefits of system operation. • Establish a new GIEDCM considering hydrogen blending. • Piecewise linearization was used to address nonlinearity. • Hydrogen-blended GEIES, hydrogen fluctuation supply, user acceptance. • Hydrogen supply should reduce fluctuations, and appropriately improve user acceptance. • The feasibility and advantages of the present method are verified by comparing with the GUROBI solver. [ABSTRACT FROM AUTHOR]

Hydrogen blending has proved to be a promising alternative to reduce CO 2 emissions in current applications such as the industrial sector in which natural gas is the fuel source since it can mitigate GHG emissions and help to reach nation's goal of decarbonization. This study explored the feasibility of different hydrogen blend compositions going from 1% to 30% hydrogen content (by volume) by computational simulations to determine the best performance of the system considering real operating conditions from Central Plant at UC Irvine. This work also performed an economic analysis as part of the implementation plan. It was determined that a blend of 19% H 2 content could be implemented without any major renovation of utility infrastructure based on the operating conditions and change in the properties of the mixture. An addition of 30% H 2 can reduce around 11% of the emissions produced by pure natural gas. This is equivalent to 1422 kg of CO 2 in 1 h. It is evident that the higher the H 2 content, the better the CO 2 benefits that would be produced, but for the actual application of higher hydrogen content, there is a need for a better understanding of the effects of hydrogen in the current natural gas pipeline. Based on the CO 2 savings, it was determined that a 30% blending of hydrogen may save about 22.2% of the economic cost compared to natural gas. • A hydrogen blending model is developed considering a hydrogen content between 1% and 30% by volume. • Real operating conditions such as temperature, pressure, pipeline dimensions, and power output requirements were considered based on UCI power plant for validation. • An economic analysis is considered as part of the implementation plan. • A blend of 19% H 2 content could be implemented without major renovation of infrastructure based on the operating conditions and change in the properties of the mixture. • 30% H 2 can reduce ∼11% of the emissions produced by pure natural gas. [ABSTRACT FROM AUTHOR]

This study presents a physics-based reduced-order model (ROM) to assess the mixing behavior of hydrogen and natural gas in pipelines, facilitating the integration of hydrogen into natural gas networks—a key strategy for reducing carbon emissions. The methodology consists of dimensional analysis to identify crucial dimensionless parameters, CFD simulations for data collection, and statistical analysis for effective data modeling. This approach enables rapid evaluation of injection strategies and operational conditions, reducing the computational demands of traditional CFD simulations. The model correlates reduced-order parameters with key dimensionless numbers like Reynolds number, and diameter and velocity ratios, to develop a predictive tool for assessing mixture quality. Validated through extensive simulations, the model accurately predicts gas mixing, using beta distributions for statistical representation to enhance data interpretability and applicability. • Developed a reduced-order model based on CFD data for hydrogen-natural gas mixing. • Used dimensional analysis to simplify the model and reduce computational demand. • Applied beta distributions to analyze mass fractions and improve mixture prediction. [ABSTRACT FROM AUTHOR]

A novel static mixer is designed specifically to blend hydrogen into natural gas pipelines, and its effectiveness is validated by numerical simulation method. Firstly, the structural model of the proposed static mixer model for hydrogen-methane blending is introduced, and the evaluation indicators are defined. Secondly, the computational fluid dynamic model for the mixing process is established based on the Large Eddy Simulation(LES) method, and the accuracy of the numerical results is validated against the experimental data of a benchmark gas mixing model. Subsequently, using LES, effects structural parameters (angle and height of trapezoidal baffle, number of mixing elements, and spacing and installation distance of mixing elements) and flow parameters (main flow velocity and hydrogen blending ratio) on the mixing homogeneity and pressure drop of the static mixer are investigated systematically to explore the optimal design and operational conditions. The numerical results showed that the static mixer can significantly improve the mixing efficiency of hydrogen and natural gas with acceptable pressure loss. In the range of flow conditions concerned, a best performance of mixing could be obtained by installing the mixer at a distance of 3 D (D is the diameter of the natural gas pipeline) downstream the blending point, setting the spacing between mixing elements as 1 D and employing four mixing elements. Finally, the underlying physics of mass transportation are analyzed based on the vortex structures generated by the mixer. • A novel static mixer is designed to blend hydrogen into natural gas pipelines. • A Large eddy simulation solution procedure is proposed to solve multi-component mixing. • Effects of key parameters of the static mixer and operating conditions are revealed. • The mixing mechanism of static mixer is revealed based on vortex dynamics analysis. [ABSTRACT FROM AUTHOR]