Optimization of girth welded joint in a high-pressure hydrogen storage tank based on residual stress considerations

The cylinder sections in a high-pressure hydrogen storage tank are usually connected by girth welded joints. However, due to the ultra-thick wall of the cylinder, the weld geometry has a significant influence on the residual stress distributions, which are very difficult to be fully determined by experimental methods. Therefore, in this paper, four sequential coupling two-dimensional (2D) axisymmetric finite element (FE) models with different weld geometries have been developed to study the effects of weld groove shape on the residual stresses. In addition, the effects of working pressure (75 MPa) on the welding residual stress distributions have been investigated. The results demonstrate that different weld groove shapes bring different residual stress distributions, leading to different influences on structural integrity. Among the four types of welded joints, V and U types have similar residual stress distributions, and X and d-U types have similar distributions, but the latter two types have large tensile residual stresses at their inner surfaces, which have a greater risk of generating hydrogen induced cracking (HIC). After introducing a working pressure of 75 MPa, the welding residual stresses are redistributed, and the weld regions of the four types of welded joints are all fully yielded and plasticized. Based on the residual stress considerations, using V-shape groove can obtain the best residual stress distributions in an ultra-thick girth welded joint, which provides a reference for the welding and fabrication of a high-pressure hydrogen storage tank.     

Study on hazards from high-pressure on-board type III hydrogen tank in fire scenario: Consequences and response behaviours

Exploration of thermal performances of composite high-pressure hydrogen storage tank under fire exposure were critical issues to reduce the risk of tank rupture. Three bonfire tests of type III tanks of 210 L-35 MPa with full compressed hydrogen were exposed to a pool fire to study the response behaviours in fire scenarios. Detailed data on the tank wall temperature and inner pressure were presented in this work. Prototype bonfire tests for the type III tank indicated the failure pressure limits amounted to 41.1–41.8 MPa (average 41.4 MPa). Two consequences (rupture and hydrogen blowdown) will be caused when the inner pressure beyond this limits in fire scenario. The loading-bearing capacity of the tank reduced nearly 3 times under the prescribed fire condition when compared to its average burst pressure of 123.5 MPa conducted from the hydraulic burst test. Results also shown that fire resistance rating (FRR, time to rupture) of the three tanks were 784, 666, and 596, respectively. The FRR got shorter when the tank was exposed in the engulfing fire in advance at hydrogen blowdown case.     

Technical assessment of compressed hydrogen storage tank systems for automotive applications

The performance and cost of compressed hydrogen storage tank systems has been assessed and compared to the U.S. Department of Energy (DOE) 2010, 2015, and ultimate targets for automotive applications. The on-board performance and high-volume manufacturing cost were determined for compressed hydrogen tanks with design pressures of 350 bar (∼5000 psi) and 700 bar (∼10,000 psi) capable of storing 5.6 kg of usable hydrogen. The off-board performance and cost of delivering compressed hydrogen was determined for hydrogen produced by central steam methane reforming (SMR). The main conclusions of the assessment are that the 350-bar compressed storage system has the potential to meet the 2010 and 2015 targets for system gravimetric capacity but will not likely meet any of the system targets for volumetric capacity or cost, given our base case assumptions. The 700-bar compressed storage system has the potential to meet only the 2010 target for system gravimetric capacity and is not likely to meet any of the system targets for volumetric capacity or cost, despite the fact that its volumetric capacity is much higher than that of the 350-bar system. Both the 350-bar and 700-bar systems come close to meeting the Well-to-Tank (WTT) efficiency target, but fall short by about 5%.     

Study on inserted curved surface coupling phased array ultrasonic inspection of multi-layered steel vessel for high-pressure hydrogen storage

Multi-layered steel vessel (MLSV) for high-pressure hydrogen storage is an important equipment in hydrogen refueling station and periodic inspection is necessary to be carried out on it. Welded joint between the head and thick-walled nozzle of the vessel is the key point of the inspection. In this study, based on structural characteristics of MLSV, a method of inserted curved surface coupling phased array ultrasonic inspection (PAUI) was proposed. In order to achieve effective inspection on the welded joint, acoustic field calculation model of the welded joint by PAUI was established. Influences of various inspection parameters on the acoustic field were analyzed by considering difficulties of far detection distance, wide detection area and large material attenuation systematically to obtain optimized parameters and scanning method. Corresponding probe was subsequently made according to the analysis, and experiment was carried out on test block to prove effectiveness of the method in this study.     

Finite element-based simulation of a metal hydride-based hydrogen storage tank

In this paper, a novel 3D flexible tool for simulation of metal hydrides-based (LaNi₅) hydrogen storage tanks is presented. The model is Finite Element-Based and considers coupled heat and mass transfer resistance through a non-uniform pressure and temperature metal hydride reactor. The governing equations were implemented and solved using the COMSOL Multiphysics simulation environment. A cylindrical reactor with different cooling system designs was simulated. The shortest reactor fill time (15 min) was obtained for a cooling design configuration consisting of twelve inner cooling tubes and an external cooling jacket. Additional simulations demonstrated that an increase of the hydride thermal conductivity can further improve the reactor dynamic performance, provided that the absorbent bed is sufficiently permeable to hydrogen.     

A literature review of failure prediction and analysis methods for composite high-pressure hydrogen storage tanks

With the development of hydrogen fuel cell vehicles, the on-board hydrogen storage technology with safety, efficiency and economy has become a fundamental part. Low cost, light weight and good safety performance are required for the on-board hydrogen storage tanks. The composite high-pressure hydrogen storage tank has been recognized as an efficient solution that could address these problems. However, the complex working environment of hydrogen-thermo-mechanism presents challenge to the failure analysis and predictive model establishment of the composite hydrogen storage tanks. The crucial parameters or indicators for tank's failure analysis include burst pressure, damage state and fatigue lifetime, etc. So this paper gives a comprehensive review on the failure behavior analysis methods and prediction models of composite high-pressure hydrogen storage tanks from the literature. First, the failure analysis methods of composite high-pressure hydrogen storage tanks are summarized. Second, the latest literature regarding failure mode predictive methods and models of type III and type IV tanks are reviewed. The different failure criteria are compared and summarized, including some new failure criteria. These criteria enable failure analysis methods to obtain the interaction information on the interaction between the microscopic and macroscopic aspects of the composite. Damage evolution model and constitutive model are summarized. The post-initial failure behavior of the composite laminates structure is simulated by the material property degradation method (MPDM), especially the continuum damage mechanics (CDM) in conjunction with commercial finite element (FE) analysis method. The process of progressive failure analysis of composite tank is summarized as a reference for subsequent failure analysis. The future work of progressive failure analysis should focus on the initial failure of the composite material and microscopic failure mechanisms. The burst, fiber damage and fatigue life are the mainly investigated failure modes for type III composite hydrogen storage tank. For Type IV, the mainly researched failure modes are the collapse and blistering of the liner, burst and damage. The different finite element analysis methods and failure predictive models were classified and summarized. Further improvements were required for the simulation models of full-scale structure of the tank in the working environment or under the complex fiber winding modes. The liner of the type IV cylinder is completely distinct from that of the type III, therefore the behavior of collapse and blistering of the liner needs to be further investigated. The factors that affect collapse and blistering should be explored. The future research need focus on controlling these factors and monitoring the effects of these factors towards structural strength.     

Assessment of detonation hazards in high-pressure hydrogen storage from chemical sensitivity analysis

In this study, a series of detonation sensitivity analyses have been carried out to assess detonation hazards in hydrogen–air mixture. The present investigation in particular concerns with the effect of elevated initial pressure on the detonation sensitivity, which stems from the renewing interest in preventing possible explosion scenario in hydrogen economy when high-pressure hydrogen storage facilities are contaminated with air. From the steady ZND analyses based on a recently updated comprehensive kinetic mechanism of hydrogen combustion by Li et al. [Int J Chem Kinet 2004;36:566–75] and using improved semi-empirical models, various dynamic parameters, i.e., characteristic cell size and direct initiation energy, for hydrogen–air detonations are estimated and assessed against available experimental data. Results for the hydrogen–air detonation sensitivity indicated that from a purely chemical kinetics consideration, the probability of having a detonation of hydrogen–air mixture at elevated initial pressure is not higher than in other hydrocarbon fuels at elevated initial pressure.     

Enhancement of heat transfer in hydrogen storage tank with hydrogen absorbing alloy (optimum fin layout)

Optimization of the fin layout in a metal hydride (MH) bed has been sought to enhance poor heat transmission in a hydrogen storage tank, and to obtain a maximum hydrogen absorption rate with a smaller volume of fins. Two different fin configurations, radial and circular fins, in a vertical cylindrical reactor vessel were tested with a La‐Ni‐based AB5 type hydrogen storage alloy. A two‐dimensional transient heat conduction analysis, coupled with predicted temperature and concentration of absorbed hydrogen in the bed for the exothermic hydride reaction, was used to evaluate enhancement of the hydrogen absorption time. The estimated temperature and concentration agreed within 6 K and 8.5%, respectively, with our experimental results. The effect of thickness and the spacing and shape of fins on the hydrogen absorption time were analytically evaluated, so that the optimum range of the each fin layout was obtained by the trade off between absorption time and reduction in the MH volume due to the volume occupied by fins. The hydrogen absorption time for the recommended layout of circular fins was reduced to approximately one‐third of that without fins. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(3): 165–183, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20195     

Finite element simulation of welding residual stresses in martensitic steel pipes

Abstract

Finite element (FE) simulations of the welding of two high grade steel pipes are described. The first is a P91 steel pipe welded with a similar P91 weld consumable, and the second is a P92 steel pipe welded with dissimilar nickel–chromium based weld consumables. Both welds are multipass circumferential butt welds, having 73 weld beads in the P91 pipe and 36 beads in the P92 pipe. Since the pipes and welds are symmetric around their axes, the FE simulations are axisymmetric, allowing high FE mesh refinement and residual stress prediction accuracy. The FE simulations of the welding of the P91 and P92 pipes comprise thermal and sequentially coupled structural analyses. The thermal analyses model the heat evolution produced by the welding arc, determining the temperature history throughout the FE models. Structural analyses use the computed temperature history as input data to predict the residual stress fields throughout the models. Post-weld heat treatment (PWHT) of both pipes has also been numerically simulated by assuming that the FE models obey the Norton creep law during the hold time period at 760°C. The residual stresses presented here have all been validated by corresponding experimental measurements. Before PWHT, it has been found that, at certain locations in the weld region and heat affected zone (HAZ) in the pipes, tensile hoop and axial residual stresses approach the tensile strength of the material, presenting a high risk of failure. It has also been found that PWHT substantially reduces the magnitude of residual stresses by varying degrees depending on the material.     

Residual stress and plastic strain analysis in the brazed joint of bonded compliant seal design in planar solid oxide fuel cell

This paper uses finite element method (FEM) to predict the residual stress and plastic strain in the brazed joint of sealing foil-to-window frame in bonded compliant seal (BCS) design in a planar solid oxide fuel cell (PSOFC). The effects of window frame material type, sealing foil thickness, filler metal thickness and window frame thickness on residual stress and plastic strain are discussed. Large residual stress is generated in the joint, and the stress and strain are concentrated around the fillet. It is proved that the BCS design can mitigate and trap some residual stress by plastic deformation within the sealing foil. The residual stress and the ability of trapping stress of sealing foil are affected by window frame material and structure thickness. Based on the comprehensive considerations of the impact of residual stress and plastic strain, Alloy 625 as a window frame material is found to be better than Haynes 214, Hastelloy X and SUS 316L. The optimum thickness of sealing foil and filler metal BNi2 are found to be 150 μm and 75 μm, respectively. The residual stress and plastic strain are increased with the increase of window frame thickness.     

Experimental investigation and theoretical modeling of dehydriding process in high-pressure metal hydride hydrogen storage systems

This study explores the endothermic dehydriding (desorption) reaction that takes place in a high-pressure metal hydride (HPMH) hydrogen storage system when hydrogen gas is released to the fuel cell. The reaction is sustained by circulating warm fluid through a heat exchanger embedded in the HPMH powder. A systematic approach to modeling the dehydriding process is presented, which is validated against experimental data using two drastically different heat exchangers, one using a modular tube-fin design and the other a simpler coiled-tube design. Experiments were performed inside a 101.6-mm (4-in) diameter pressure vessel to investigate the influences of hydrogen release rate, heat exchanger fluid flow rate and fluid temperature on the dehydriding process for the HPMH Ti_1.1CrMn. It is shown the dehydriding reaction rate can be accelerated by increasing the fluid temperature and/or the rate of pressure drop. HPMH particles located in warmer locations close to heat exchanger surfaces both began and finished dehydriding earlier than particles farther away. 2-D and 3-D models were created in Fluent to assess the dehydriding performances of the modular tube-fin heat exchanger and coiled-tube heat exchanger, respectively. The models are shown to be quite accurate at predicting the spatial and temporal variations of metal hydride temperature during the dehydriding reaction.     

Forced convective mixing in a zero boil-off cryogenic storage tank

This paper presents the results of a study of fluid flow and heat transfer of liquid hydrogen in a cryogenic storage tank with a heat pipe and an array of pump-nozzle units. A forced flow is directed onto the evaporator section of the heat pipe to prevent the liquid from boiling off when heat leaks through the tank wall insulation from the surroundings. An axisymmetric computational model was developed for the simulation of convective heat transfer in the system. Steady-state velocity and temperature fields were solved from this model by using the finite element method. Forty five configurations of geometry and velocity were considered. As the nozzle fluid speed increases, the values of the maximum, average, and spatial standard deviation of the temperature field decrease nonlinearly. Parametric analysis indicates that overall thermal performance of the system can be significantly improved by reducing the gap between the nozzle and the heat pipe, while maintaining the same fluid speed exiting the nozzle. It is also indicated that increased inlet tube length of the pump-nozzle unit results in slightly better thermal performance. Increased heat pipe length also improves thermal performance but only for low fluid speed.     

Performances comparison of adsorption hydrogen storage tanks at a wide temperature and pressure zone

Large-scale application of hydrogen requires safe, reliable and efficient storage technologies. Among the existing hydrogen storage technologies, cryo-compressed hydrogen (CcH₂) storage has the advantages of high hydrogen storage density, low energy consumption and no ortho-para hydrogen conversion. But it still needs higher hydrogen storage pressure when reaching higher hydrogen storage density. In order to reduce hydrogen storage pressure and improve storage density, solid adsorption technology is introduced in CcH₂. Activated carbon and metal-organic framework materials (MOFs) are employed as adsorbents in this paper. The gravimetric/volumetric hydrogen storage capacities of different adsorption tanks are studied and compared with the hydrogen storage conditions of 1–55 MPa at 77–298 K. The results show that the hydrogen storage density of CcH₂ combined with adsorption is higher than that of pure adsorption hydrogen storage, and the storage pressure is lower than that of pure CcH₂ under the same hydrogen storage capacity. And the combination of two hydrogen storage technologies can achieve a high hydrogen storage capacity equivalent to that of liquid hydrogen at a lower pressure.     

Effect of the welding heat input on residual stresses in butt-welds of dissimilar pipe joints

This study used finite element techniques to analyse the thermo-mechanical behaviour and residual stresses in dissimilar butt-welded pipes. The residual stresses at the surface of some weld specimens were measured experimentally by using the hole-drilling method. The results of the finite element analysis were compared with experimentally measured data to evaluate the accuracy of the finite element modelling. Based on this study, a modelling procedure with reasonable accuracy was developed. The developed finite element modelling was used to study the effects of welding heat input on magnitude and distribution of welding residual stresses in butt-welded pipes made of ferritic and austenitic steels. The hoop and axial residual stresses in dissimilar pipe joints of 8 mm thick for V-groove shape were studied. It is shown that the welding heat input has a significant effect on magnitude and distribution of residual stresses in the stainless steel side of the studied joints.     

Real-time microscopic monitoring of temperature and strain on the surface of magnesium hydrogen storage tank by high temperature resistant flexible integrated microsensor

Magnesium hydrogen storage tanks shrink and expand due to different states of hydrogen absorption and desorption, so it is important to monitor the body expansion, temperature change and stress change on the surface of magnesium hydrogen storage tank in real time. At present, commercially available temperature sensors and strain gauges are bulky, and the two sensors are not easy to be placed on the surface of magnesium hydrogen storage tanks for accurate measurement. Therefore, this study used micro-electromechanical systems (MEMS) technology to innovate and integrate micro-temperature sensor and micro-strain sensor, and make a small volume but high sensitivity high temperature resistant flexible integrated microsensor, which can be placed on the surface of the magnesium hydrogen storage tank to monitor the temperature, expansion and stress changes in real time, thus providing a reference for improving the optimal design of the magnesium hydrogen storage tank.     

Effect of opening area on the suppression of self-ignition of high-pressure hydrogen gas leaking in the air by an extension tube

The most influential factor for self-ignition of high-pressure hydrogen is known to be the strength of the shock. Thus, the self-ignition can be suppressed by weakening the shock strength, which is possible by reducing the area where the hydrogen is ejected in this study. To confirm the possibility of this method, experiments were done by controlling the burst pressure of up to 302 bar and the ratio of the opening area. The experimental results showed that the minimum burst pressure of self-ignition is increased exponentially as the opening area is reduced. This confirmed that reducing the opening area under the same burst pressure conditions has an effect on the suppression of self-ignition. However, it was also found that the minimum shock speed that causes self-ignition gradually decreases as the opening area becomes smaller, which results from an increasing in mixing. The CFD simulation results showed that the volume of the flammable region in the tube was increased and the hydrogen-air mixing efficiency also increased when the opening area became smaller. The results suggest that reduction of the opening area can suppress a self-ignition by weakening the shock strength, but it should be noted that an increase in mixing effect also occurs.     

Numerical study on particle distribution characteristics of slush hydrogen in a cryogenic tank

A numerical model considering phase change and heat transfer was established by the Euler-Euler two-fluid method to investigate the storage characteristics and two-phase flow field of slush hydrogen. Numerous numerical simulations were performed to discuss the effect of particle diameter (d_p = 0.02–0.5 mm), content of solid hydrogen (α_s = 10%–50%), and heat leakage (q = 50–200W·m⁻²) on the flow field. It was found that particle deposition could occur during the storage process, and there exist moving vortices with contrary directions under specific conditions. The sedimentation characteristics and vortex size are influenced by many factors including particle size, solid hydrogen content, and heat leakage. An increase in particle size could lead to the strengthening of precipitation and the expansion of the counterclockwise vortex region on the right side of the tank. And the increase in solid hydrogen content could result in more deposition and more collisions and friction between particles. Moreover, the increase in heat leakage could increase the area of the counterclockwise vortex. Numerical results of the deposition and flow field characteristics in the storage tank could clearly show the physical law of the slush hydrogen so that the uniform distribution of slush hydrogen could be promoted for efficient storage and application.     

Performance of hydrogen storage tank with TPRD in an engulfing fire

The performance of a composite hydrogen storage tank with TPRD in an engulfing fire is studied. The non-adiabatic tank blowdown model, including in fire conditions, using the under-expanded jet theory is described. The model input includes thermal parameters of hydrogen and tank materials, heat flux from a fire to the tank, TPRD diameter and TPRD initiation delay time. The unsteady heat transfer from surroundings through the tank wall and liner to hydrogen accounts for the degradation of the composite overwrap resin and melting of the liner. The model is validated against the blowdown experiment and the destructive fire test with a tank without TPRD. The model accurately reproduces experimentally measured hydrogen pressure and temperature dynamics, blowdown time, and tank's fire-resistance rating, i.e. time to tank rupture in a fire without TPRD. The lower limit for TPRD orifice diameter sufficient to prevent the tank rupture in a fire and, at the same time, to reduce the flame length and mitigate the pressure peaking phenomenon in a garage to exclude its destruction, is assessed for different tanks, e.g. it is 0.75 mm for largest studied 244 L, 70 MPa tank. The phenomenon of Type IV tank liner melting for TPRD with lower diameter is revealed and its influence on hydrogen blowdown is assessed. This phenomenon facilitates the blowdown yet requires further detailed experimental validation.