High Internal Pressure Research Articles

Hydro-mechanical modeling of cohesive crack propagation of concrete lining in high internal pressure tunnels

High pressure tunnels with concrete lining have been extensively utilized in project practice. However, due to the characteristic of concrete being susceptible to cracking under tension, the lining inevitably develops cracks under high internal water pressure, posing a serious threat to the operation of tunnels. This study aims at developing a hydro-mechanical numerical model of cohesive crack propagation of concrete lining in high internal pressure tunnels. In this regard, the determination of cohesive element parameters is elucidated, the contact simulation within the software ABAQUS is improved to accurately characterize the interface between lining and surrounding rock, and the numerical calculation process in ABAQUS is realized using indirect coupled method. The simulation results align well with the physical model test and engineering monitoring data, demonstrating that the proposed method can accurately simulate the hydraulic interactions of high pressure tunnel. Additionally, a comparison with calculation models employing tie constraints to simulate the lining-surrounding rock interface is conducted. Finally, comparison with traditional continuum method reveals that while both methods exhibit consistent overall trends. It is recommended to choose the proposed method when describing the discontinuous propagation process of cracks, which cannot be simulated by the continuum analysis method.

Failure monitoring and classification from acoustic emission tests on impact-damaged hydrogen composite pressure vessels

Composite overwrapped pressure vessels (COPV) for hydrogen will play an important role in emission free mobility and energy storage. The DELFIN project (2018 – 2022) was set up with the goal of developing improved COPVs that are lighter, cheaper and more durable. A key aspect of this project was to conduct full-scale impact tests with different gas pressure levels that were used to evaluate the vessels’ crash performance and to verify numerical impact simulations. These tests were followed by controlled pressure experiments until the burst pressure was reached. The procedure was monitored with acoustic emission testing (AT) and subsequent computer tomography (CT). The residual COPV stability and the AT results are compared to different scenarios regarding the impact energies and impact angles. The event localization from AT shows a clear correlation of the emitted energy with the damaged areas. We classify the recorded signals into groups that can be related to the failure mechanism and compare those to the pressure evolution before failure of the COPV. All tests indicate that large impact energies lead to a significant reduction of the burst pressure of COPVs, whereas a higher internal pressure can have a stabilizing effect that reduces the damaging effect.

Optimized strategies for efficient CO2 trapping using hydrate technology by pressure adjustment

The hydrate-based method enhances oceanic CO2 storage capacity and is deemed beneficial for controlling greenhouse gas emissions. However, the non-uniform CO2 hydrate crystal interface in the sub-seabed storage layer acts as a barrier, slowing down mass transfer kinetics. This work employed in-situ nuclear magnetic resonance (NMR) technology to compare three different pressure adjustment strategies and observe CO2 bubble dispersion after hydrate dissociation, secondary nucleation, and crystal growth mechanism, along with pore water changes. The presence of micro/nano CO2 bubbles with high internal pressure and high specific surface area in the dissociation liquid significantly accelerated secondary micro-structural phase transition rates. The optimal hydrate-based CO2 storage efficiency reached up to 81.7 %. Moreover, the secondary formation of CO2 hydrates distributed more uniformly within the large, medium, and small pores and led to a significantly increased residual water conversion rate (reaching up to 88 %) in medium pores. The post-secondary formation of high-density hydrates resulted in low fluid mobility (T1/T2 mostly distributed in the range of 0 ∼ 10) and exhibited a mixed wettability state between pore fluids. Utilizing the “memory effects” of CO2 hydrate effectively overcame late-stage mass transfer barriers of solid hydrates films. Our findings extend the understanding of CO2 hydrate formation kinetics under pressure adjustment strategies.

Effect of helium bubbles on the mobility of edge dislocations in copper

Abstract Helium bubbles can form in materials upon exposure to irradiation. It is well known that the presence of helium bubbles can cause changes in the mechanical behavior of materials. To improve the lifetime of nuclear components, it is important to understand deformation mechanisms in helium-containing materials. In this work, we investigate the interactions between edge dislocations and helium bubbles in copper using molecular dynamics (MD) simulations. We focus on the effect of helium bubble pressure (equivalently, the helium-to-vacancy ratio) on the obstacle strength of helium bubbles and their interaction with dislocations. Our simulations predict significant differences in the interaction mechanisms as a function of helium bubble pressure. Specifically, bubbles with high internal pressure are found to exhibit weaker obstacle strength as compared to low-pressure bubbles of the same size due to the formation of super-jogs in the dislocation. Activation energies and rate constants extracted from the MD data confirm this transition in mechanism and enable upscaling of these phenomena to higher length-scale models.

Design and Calculation of Products from Composite Materials Using Software

This article analyzes six types of composite pipes that are good replacements for corrosive steel and metal pipes for oil, gas, and water. The analysis of the six samples of composite pipes was done using the software program Hoffman Engineering, which is intended for the design and calculation of various types of products made of composite materials. For the analysis of the six composite pipes, the same diameter and the same length were taken, and variable parameters are: the type of material from which the composite pipes are made (carbon/epoxy, carbon-glass/epoxy and glass/epoxy), and the angle of winding of the fibers (10º and 90º degrees). Using the Hoffman Engineering software package, an analysis of the durability of the six differently designed composite pipes at high internal pressure was performed. The same conclusion was obtained from all analyses: the high internal pressure resistance of composite pipes is highly dependent on the fiber winding angle and the type of fibers used. Composite pipes obtained with a fiber winding angle of 90º have twice the internal pressure resistance compared to composite pipes obtained with a fiber winding angle of 10º. Composite pipes based on carbon fibers have the highest resistance to internal pressure, then composite pipes based on hybrid materials (glass and carbon fibers) and finally composite pipes based on glass fibers. Finally, a comparison was made with the obtained laboratory results for the same composite pipes. The same conclusion was obtained from all analyses: the high internal pressure resistance of composite pipes is highly dependent on the fiber winding angle and the type of fibers used. The composite pipes obtained by this process are durable and resistant to very high pressures.

Investigation of a novel hydraulic tunnel composite lining with polyurea coating interlayer

PurposeMultilayer composite liner structures are the primary structural form of hydraulic tunnels. However, the bearing mechanism of multilayer composite liners has not been investigated thoroughly. Many existing design schemes do not properly achieve a balance between structural safety, anti-seepage capacity, and cost effectiveness. Thus, a new composite liner structure type and its theoretical model was proposed.Design/methodology/approachA novel hydraulic tunnel composite liner structure with a polyurea spray coating interlayer was proposed in this study. A theoretical model based on the state-space method was developed and verified using FEM models and existing theoretical models. Parametric analysis was conducted based on the theoretical model to investigate the influence of various variables, including interfacial shear stiffness, inner liner thickness, and outer liner elastic modulus.FindingsIt was concluded that the proposed theoretical model can be used successfully to calculate multilayer composite liner structures with high calculation efficiency. The overall deformation stiffness of the composite liner system increased with the interfacial shear stiffness. The sprayed coating interlayer significantly affects the residual force distribution between the outer and inner liners, which can also be affected by the adjustment of the thickness of the outer and inner liners. Thus, attention should be paid to these factors in the rational design of the proposed composite liner system.Originality/valueWith the development of China’s water conservancy projects, complex geological conditions, high surrounding rock stress, high internal and external water pressures, and other unique application scenarios have gradually increased. This places higher requirements on the bearing performance and impermeability of hydraulic tunnel lining structures. On the other hand, conventional hydraulic tunnel lining structures can hardly achieve a satisfactory balance between economy, structural safety, and impermeability. Thus, the proposed structure has the potential to be used in a wide range of applications.

Lining Structure of Water Conveyance Tunnel under Earthquake Action Research on Damage Law

Based on the concrete damage plasticity constitutive model (CDP model) of ABAQUS software, the dynamic response of high pressure internal water conveyance tunnel during earthquake is simulated, and the dynamic response and dynamic damage law of high internal water pressure water conveyance tunnel structure under surrounding rock grade, buried depth and seismic wave intensity are analyzed. The research shows that the surrounding rock grade is closely related to the dynamic response and damage characteristics of the lining structure of the water conveyance tunnel. The dynamic damage of the tunnel under grade Ⅲ surrounding rock is only 0.08, which is far less than 0.83 under grade Ⅳ surrounding rock. It can be considered that it will not cause great damage to grade Ⅲ surrounding rock under earthquake. The surrounding rock grade is better, which can provide more stable support and reduce the stress and vibration of the structure. If the tunnel is in the seismic zone, the buried depth can be used as one of the design control indexes in the tunnel design. The lining damage is mainly distributed at the top and upper arch waist of the tunnel. With the increase of the buried depth of the tunnel, the dynamic damage amount increases from 0.021 to 0.081, then to 0.085. the damage of the lining structure also increases. This may be because the deep buried tunnel is more constrained by the underground rock and soil layer, thereby reducing the transmission of seismic load. The change of seismic wave intensity can directly affect the damage characteristics of tunnel lining structure. The dynamic damage mainly occurs at the vault and arch waist, and the damage area expands from the vault and arch waist to the side wall and corner. The increase of seismic wave intensity will lead to dramatic changes in the stress of the structure, which will lead to more complex and serious damage.

Stiffness analysis and structural optimization design of an air spring for ships

An air spring (AS) for ships must have the structural strength of its bellows enhanced considerably to ensure its reliability under high internal pressure and strong impact. In this case, the stiffness of the bellows gradually dominates the overall stiffness of the AS. Nevertheless, the parameterization calculation of stiffness for an AS mainly focuses on its pneumatic stiffness. The bellows stiffness is normally analyzed by virtue of equivalent simplification or numeric simulation. There is not an effective parameterization calculation model for the stiffness of the bellows, making it difficult to achieve the structural optimization design of the bellows. In this paper, the shell theory was borrowed to build a mechanical model for the bellows. Subsequently, the state vector of the bellows was solved by precision integration and boundary condition. Iteration was conducted to identify the complex coupling relationship between the vector of the bellows and other parameters. On this basis, the parameterization calculation method was introduced for the stiffness of the bellows to obtain the vertical and horizontal stiffness of the AS. After that, a dual-membrane low-stiffness structure was designed to analyze the dominating factors affecting the strength and stiffness of the AS, which highlighted the way to the low-stiffness optimization design of high-strength ASs. In the end, three prototypes and one optimized prototype were tested to verify the correctness of the parameterization design model for stiffness as well as the effectiveness of the structural optimization design.

Use of Nanobubbles to Improve Mass Transfer in Bioprocesses

Nanobubble technology has emerged as a transformative approach in bioprocessing, significantly enhancing mass-transfer efficiency for effective microbial activity. Characterized by their nanometric size and high internal pressure, nanobubbles possess distinct properties such as prolonged stability and minimal rise velocities, allowing them to remain suspended in liquid media for extended periods. These features are particularly beneficial in bioprocesses involving aerobic strains, where they help overcome common obstacles, such as increased culture viscosity and diffusion limitations, that traditionally impede efficient mass transfer. For instance, in an experimental setup, nanobubble aeration achieved 10% higher soluble chemical oxygen demand (sCOD) removal compared to traditional aeration methods. Additionally, nanobubble-aerated systems demonstrated a 55.03% increase in caproic acid concentration when supplemented with air nanobubble water, reaching up to 15.10 g/L. These results underscore the potential of nanobubble technology for optimizing bioprocess efficiency and sustainability. This review delineates the important role of the mass-transfer coefficient (kL) in evaluating these interactions and underscores the significance of nanobubbles in improving bioprocess efficiency. The integration of nanobubble technology in bioprocessing not only improves gas exchange and substrate utilization but also bolsters microbial growth and metabolic performance. The potential of nanobubble technology to improve the mass-transfer efficiency in biotechnological applications is supported by emerging research. However, to fully leverage these benefits, it is essential to conduct further empirical studies to specifically assess their impacts on bioprocess efficacy and scalability. Such research will provide the necessary data to validate the practical applications of nanobubbles and identify any limitations that need to be addressed in industrial settings.

Full-scale experiment on the bearing and deformation characteristics for prestressed double-layered shield tunnel linings under high internal pressure

To investigate the bearing mechanism for two types of circular anchorage prestressed double-layered shield tunnel lining under high internal pressure, a set of loading systems and measuring schemes were dedicatedly designed for the standing full-scale lining model. The results show that when the internal pressure reaches 1.10 MPa, the proportion of internal pressure transferred to the outer lining begins to increase with the expansion of the inner lining. When the internal pressure reaches 1.30 MPa, the local cracking of the inner lining will cause structural stiffness variation and stress redistribution, leading to a further increase in the proportion of internal pressure transferred to the outer lining. In addition, the detached bearing structure makes better use of prestress and has a higher bearing capacity, but lower engineering material economy than the combined bearing structure. For the combined bearing structure, there is an initial gap between the inner and outer lining at the left and right arch due to the prestress tensioning and concrete shrinkage. Moreover, it can give full play to the bearing performance of the segment and surrounding rock, thus optimizing the diameter of the prestressed steel strands. However, the initial gap has a certain influence on load-transferring, and it is necessary to control the concrete shrinkage and adopt the backfill grouting.

Thermo-Fluid–Structural Coupled Analysis of a Mechanical Seal in Extended Loss of AC Power of a Reactor Coolant Pump

We proposed a numerical method to investigate the thermo-fluid–structural coupled characteristics of a mechanical seal of a reactor coolant pump (RCP), especially during extended loss of AC power (ELAP) operation. We developed a finite element program for the general Reynolds equation, including the turbulence effect to calculate the pressure, opening force, and leakage rate of fluid lubricant and the two-dimensional energy equation to calculate the temperature distribution of the fluid lubricant. We verified the accuracy of the developed program by comparing the simulated temperature distribution and leakage rate of this study with those of previous research. Heat conduction and elastic deformation due to pressure and temperature changes at the seal structure were analyzed using an ANSYS program. The results showed that temperature more significantly affected the elastic deformation of the seal structure near clearance than pressure both under normal and ELAP operating conditions. High temperature and pressure of the coolant under ELAP operating conditions deform the seal structure, resulting in a much smaller clearance of the fluid film than normal operating condition. However, even with a small clearance under ELAP operation, the leakage rate slightly increases due to the high internal pressure of the coolant. This research will contribute to the development of robust mechanical seals for RCPs by accurately predicting the characteristics of mechanical seals, especially when the RCP is operating under ELAP.

High-energy computed tomography for inspection and monitoring of flexible riser

Flexible risers have been widely used in the offshore oil and gas industry and have many applications, such as production, gas lifting, or gas and water injection. The structure comprises several metal and polymer layers, which allow it to withstand a sizeable bending curve and high internal pressure. Therefore, guaranteeing the integrity of flexible risers throughout their useful life is extremely important. It requires developing and applying effective inspection and monitoring techniques, particularly emphasizing the tensile armor layers. This work evaluated the ability of the High-Energy Computed Tomography (CT) Technique to detect internal defects such as cracks, breaks, and fissures in the riser layers. A flexible riser sample of approximately 2 m in length and 281 mm in external diameter was scanned using a tomography system consisting of a 6 MeV Betatron and a set of 14-bit A-Si digital detectors. The images were acquired in 360° with angular steps of 2°. After acquisition, the images were reconstructed, and 3D models were built for qualitative and quantitative evaluation. Through the segmentation process, the metal layers of the flexible riser could be analyzed individually. Defects were found in the tensile armor layers, indicating ruptures and cracks and the onset of pitting. The results strongly suggest that computed tomography can be used as a non-destructive technique for inspecting flexible risers, with good efficiency in detecting defects, and that its application can be extended to field tests.

Plastic zone and surrounding strain analysis in a lined cavern for compressed air energy storage subjected to cyclic high internal gas pressure and temperature

In the context of compressed air energy storage (CAES) technology, the strategic excavation of hard rock caverns is pivotal for overcoming geological challenges and advancing CAES deployment. This study adopts a circular profile for the cavern and investigates the impact of variables such as cavern diameter and depth. Considering the influence of cyclic internal gas pressure, temperature fluctuations, and potential leakage on the cavern, a thermo-hydro-mechanical coupled numerical model is developed using Comsol software. This model, grounded in classic elastoplastic constitutive relations, aligns with the conditions of a proposed project. It facilitates the computation of the plastic zone and surrounding strain for both the cavern lining and adjacent rock, post-excavation and throughout a typical ‘charging-storage-discharging-storage’ operational cycle. Through detailed analysis, the study delineates the variations and characteristics of the plastic zone and surrounding strain, thereby providing a solid foundation for a comprehensive examination of cavern stability, and the design of linings and sealing mechanisms.

Cavern spacing of CAES cavern group in hard rock based on plastic zone and deformation analysis

Existing research on layout parameters of compressed air energy storage (CAES) cavern groups in hard rock has indicated that the key influential factors for group stability include buried depth, diameter, and cavern spacing. Among these, in contrasting to other factors, the research on cavern spacing is limited. This paper focuses on the issue of safe spacing and proposes a numerical method to determine it. By establishing a series of finite element models, the stress state of surrounding rock, changes in shape, equivalent plastic strain of plastic zone, and cavern wall deformation under different spacing have been studied. When a group of air storage caverns in rows is subjected to high internal pressure, for a small spacing, the plastic zone of the surrounding rock between two caverns is connected. Here, the size of the plastic zone, equivalent plastic strain value, and deformation of the cavern wall are relatively large, making the surrounding rock highly susceptible to damage. As the spacing increases, the horizontal width of the plastic zone, the maximum equivalent plastic strain value, the displacement changes of the cavern wall remain stable. This spacing is virtually the same as that when the plastic zone of the surrounding rock is no longer connected and can be selected as a safe spacing. This study explores the design of cavern safe spacing of underground CAES cavern groups and discusses several influencing factors, which can provide references for follow-up energy storage engineering and research.

Extracorporeal membrane oxygenation (ECMO) assisted huge mediastinal tumor resection combined with superior vena cava replacement: A case report and literature review.

As to huge solid mediastinal tumor which direct compression or invasion of the superior/inferior vena cava (SVC/IVC), surgical resection remains the main lifesaving treatment. However, it would present formidable anesthetic challenges due to the extremely high risks of cardiorespiratory compromise, drastic hemodynamic fluctuations and death at all perioperative stages. Here, we report a case of huge anterior mediastinal tumor resection combined with SVC replacement under the assistance of venoarterial extracorporeal membrane oxygenation (VA ECMO), and stable hemodynamics were maintained as well as high internal jugular vein pressure being avoided during the operation procedure. He was weaned off ECMO successfully just after surgery and eventually discharged. No signs of postoperatively neurological complications occurred. Therefore, the use of ECMO assistance in huge mediastinal tumor resection combined with SVC replacement is feasible and safe, which may provide the possibility of surgical treatment for such patients and improve outcomes.

A study on the integrity and behavior of nuclear fuel in temporary storage

Due to the saturation of spent fuel pools of nuclear power plant in Korea, spent fuel will be stored in dry casks for a considerable period. Since spent fuel must withstand continuous decay heat, radiation, and high internal pressure of the fuel rod in the cask, behavior of spent nuclear fuel is needed to be reviewed.It is very important to evaluate the behavior of nuclear fuel with realistic modeling. In this study, the behavior of spent nuclear fuel after being burned in a reactor for three cycles and subsequently cooled in a spent fuel pool was analyzed by FALCON-1.5.0 which is a computational code for mechanical and thermal analysis of nuclear fuel. For code analysis, three burnup levels of 42,000 MWD/MTU, 50,000 MWD/MTU, and 58,000 MWD/MTU were considered. The hoop stress, strain, and other parameters were analyzed for each burnup level. Furthermore, the cooling periods in the spent fuel pool are set to 5, 10, 15, and 30 years, allowing for an evaluation of nuclear fuel behavior consistent with the burnup levels. Additionally, nuclear fuel behavior with normal and high thickness of oxidation is reviewed as well.The behavior of various nuclear fuels during the temporary storage period is studied with FALCON and the factors affecting the integrity of nuclear fuel are analyzed for up to 50 years of the temporary storage. This evaluation will contribute to demonstrating the safe storage of nuclear fuel in dry storage.

Effects of external corrosion defect growth on wall pipeline under internal pressure and various defect sizes with mechano‐electrochemical interaction

AbstractThe assessment of the impact of corrosion defects on the integrity and safe operation of through‐wall pipelines is critical. In this work, a finite element‐based model was developed to study the mechano‐electrochemical (M‐E) effects of external corrosion defects on 10CrMoAl steel pipelines. The effects of parameters such as defect sizes and internal pressures on pipeline conditions are also studied. The results show that increased corrosion depth leads to stress concentration at the center of the defect. The increase in internal pressure causes local plastic deformation and anodic current density concentration at the inner edge of the defect and in the adjacent areas of the defect. M‐E interaction causes the growth of corrosion defects significantly at higher internal pressures. The corrosion defects increase with time. As the pressure increases, the failure pressure of the pipeline gradually decreases. The influence of defect depth on the corrosion rate at the defect is greater than that of defect width. With increasing in internal pressure and corrosion defect size, it will lead to more severe plastic deformation, resulting in accelerated corrosion.

An analytical solution for elastoplastic responses of a lined rock cavern for compressed air energy storage considering excavation and high internal pressure

An analytical solution for elastoplastic responses of an underground lined rock cavern for compressed air energy storage under initial hydrostatic pressure and high internal air pressure is proposed. In the analytical solution, the stress paths during cavern excavation and operational stages are considered. A numerical simulation is performed by using the finite element software Abaqus to verify the analytical solution. The concept of “high-pressure plastic zone” is proposed and the evolution of “high-pressure plastic zone” is analyzed. Furthermore, taking the occurrence of “high-pressure plastic zone” and failure of the sealing layer as the critical states, the calculation methods for critical internal pressure pcr1 and ultimate internal pressure pu are proposed. Sensitive analyses are conducted to study the key parameters affecting the “high-pressure plastic zone” and the critical internal pressure. The research indicates that the proposed analytical solution can accurately predict the elastoplastic responses of an underground lined rock cavern. The radius of “high-pressure plastic zone” are mainly related to the surrounding rock quality, magnitude of air internal pressure and buried depth of cavern. The critical internal pressure pcr1 and ultimate internal pressure pu are mainly related to the surrounding rock quality, cavern size, buried depth and thickness of concrete layer.

The Influence of CO2 Physical Properties on Casing and Its Prediction Method

In order to reveal the physical properties of CO2 under actual formation conditions, this paper establishes a mathematical model of the temperature field and pressure field in the wellbore under CO2 injection conditions, optimizes the state equation of CO2 physical-property parameters, calculates the change trend of CO2 density, viscosity, and compression factor along the wellbore, and obtains the influence law of CO2 corrosion on the casing and interface. The viscosity showed a downward trend along the well depth; the compression factor showed an upward trend. The surfaces of the three casings were smooth and flat without obvious defects, the cement structure was dense, and there was no obvious pore structure. After corrosion, with the increase of Cr content, the change of interfacial corrosion decreases. The morphology of the Q125 and 3Cr interface is loose after corrosion, while there is no obvious change in the 13Cr interface. With the prolongation of corrosion time, low wellbore internal pressure easily causes casing yield, and high wellbore internal pressure easily causes cement-sheath compression failure. The circumferential stress of the casing increases with the corrosion time extension, and the radial stress of the casing and cement sheath decreases first and then increases with the corrosion time. The compressive strength of the cement sheath does not exceed the compressive strength.

Investigation on toxicity of ammonia releasing from storage tank onboard through CFD simulations

ABSTRACT This study investigates potential risks associated with ammonia releases from a case ship to be constructed in a Korean Shipyard and operated in Korean coastal areas. The focus is on understanding how ammonia disperses from the onboard storage tank’s Vent Master and the associated toxic zones. Numerical simulations using CFD tools were employed to model ammonia gas dispersion scenarios. The study revealed that if the safety valve opens, the high internal pressure of the ammonia tank could release a significant amount of ammonia through the vent mast. Thus, determining the position and height of the vent mast is crucial for safety design. Simulations showed that even if ammonia is released at sea through the vent mast, it poses minimal risk to nearby residential areas. The vent mast, positioned at least 4 m above the ship’s deck, ensured rapid gas dispersion, reducing the chance of human exposure. The findings aim to enhance the safety design and operation of ships, providing valuable reference material for policymakers, regulators, engine manufacturers, and ammonia suppliers, ultimately contributing to the establishment of safe ship design and construction practices in the future.