Thermodynamic analysis of the emptying process of compressed hydrogen tanks

During the driving of fuel cell vehicles, the fast depressurization of compressed hydrogen tanks plus the high storage pressure and the low thermal conductivity of carbon fiber reinforced plastic (CFRP) can lead to significant cooling of the tank. This can result in a temperature below −40 °C inside the compressed hydrogen tanks and cause safety problems. In this paper, a thermodynamic model that incorporates the nature of external natural convection was developed to describe the emptying process of compressed hydrogen tanks and was validated by experiments. Thermodynamic analyses of the emptying process were performed to study the global heat transfer characteristics and the effects of ambient temperature, defueling rate, defueling pattern, initial and final density of hydrogen gas, liner and CFRP thickness and the crosswind velocity on the final temperature decreases of hydrogen gas, the inner wall and the outer wall.     

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.     

雅克拉污水处理站污水管线腐蚀分析及治理建议

雅克拉污水处理站设计处理污水量为500m3/d,来水主要包括雅克拉站污水、YK12井单井流程污水和大涝坝站污水,处理后出水达到A3标准。污水站自2008年投运至今,污水处理管线及储罐本体累计穿孔40次,主要集中在提升泵进口管线、接收罐进口管线和弯头,频繁更换金属管线和管件,腐蚀治理费用已达27.2万元。影响腐蚀的因素包括污水pH值、矿化度、溶解氧浓度、流体间歇性高流速冲刷、管线材质和加注药剂等。对腐蚀因素进行分析后,建议将污水站低压金属管线更换为非金属管线,玻璃钢管线连接、玻璃钢管线与阀门连接采用承插式连接;将接收罐进口弯头更换为抗冲刷的改型弯头;增设除氧剂加注流程,降低溶解氧浓度;对加注药剂进行改性处理,减缓其对污水管线的腐蚀;在沉降罐开罐检查、处理时,将沉降罐中心筒更换为耐腐蚀材质或有涂层处理的中心筒。     

火灾场景下碳纤维复合高压储氢装置热损伤特征研究

通过火烧试验、水压爆破试验和热分析等手段,研究典型火烧工况下储氢装置的热响应行为、损伤形态及碳纤维复合材料微细观损伤特征。结果表明,在规定火烧条件下储氢装置平均失效压力为41.5 MPa,比常温环境下（35 MPa-166 L水爆压力125.5 MPa）降低约67%;环氧树脂热分解发生在100~600 ℃,并表现出4个明显的阶段性反应特征;碳纤维热分解主要发生在600~950 ℃,在849 ℃时失重速率最快为0.87%/℃;火灾场景下高压储氢装置可能出现火烧损伤、爆炸损伤和热辐射损伤3种典型热损伤模式,其中爆炸场景下碳纤维残余物丝体呈多处层状脆性破碎,具有明显的力学损伤特征。     

Review on studies of the emptying process of compressed hydrogen tanks

Compressed hydrogen tanks are now widely used for onboard hydrogen storage in fuel cell vehicles (FCVs). However, because of the high storage pressure and the low thermal conductivity of carbon fibre reinforced polymer (CFRP), the emptying of such tanks during driving or emergency release can cause a significant temperature decrease and result in an in-tank gas temperature below the low safety temperature limit of ?40 °C even in warm weather. Once the gas temperature within the tank is lower than ?40 °C, the sealing elements at the boss of the tank may fail, and glass transition of the polymer liner of the type IV tank may occur; both can cause hydrogen leakage and severe safety problems. In this paper, the heat transfer correlations, thermodynamic analyses, computational fluid dynamics (CFD) simulations, experimental studies, and thermal management methods associated with the emptying process of compressed hydrogen tanks are comprehensively reviewed. Future research directions on this topic are suggested.     

Physical model of onboard hydrogen storage tank thermal behaviour during fuelling

A physical model to simulate thermal behaviour of an onboard storage tank and parameters of hydrogen inside the tank during fuelling is described. The energy conservation equation, Abel-Noble real gas equation of state, and the entrainment theory are applied to calculate the dynamics of hydrogen temperature inside the tank and distribution of temperature through the wall to satisfy requirements of the regulation. Convective heat transfer between hydrogen, tank wall and the atmosphere are modelled using Nusselt number correlations. An original methodology, based on the entrainment theory, is developed to calculate changing velocity of the gas inside the tank during the fuelling. Conductive heat transfer through the tank wall, composed of a load-bearing carbon fibre reinforced polymer and a liner, is modelled by employing one-dimensional unsteady heat transfer equation. The model is validated against experiments on fuelling of Type III and Type IV tanks for hydrogen onboard storage. Hydrogen temperature dynamics inside a tank is simulated by the model within the experimental non-uniformity of 5 °C. The calculation procedure is time efficient and can be used for the development of automated hydrogen fuelling protocols and systems.     

Refueling-station costs for metal hydride storage tanks on board hydrogen fuel cell vehicles

Refueling costs account for much of the fuel cost for light-duty hydrogen fuel-cell electric vehicles. We estimate cost savings for hydrogen dispensing if metal hydride (MH) storage tanks are used on board instead of 700-bar tanks. We consider a low-temperature, low-enthalpy scenario and a high-temperature, high-enthalpy scenario to bracket the design space. The refueling costs are insensitive to most uncertainties. Uncertainties associated with the cooling duty, coolant pump pressure, heat exchanger (HX) fan, and HX operating time have little effect on cost. The largest sensitivities are to tank pressure and station labor. The cost of a full-service attendant, if the refueling interconnect were to prevent self-service, is the single largest cost uncertainty. MH scenarios achieve $0.71–$0.75/kg-H₂ savings by reducing compressor costs without incurring the cryogenics costs associated with cold-storage alternatives. Practical refueling station considerations are likely to affect the choice of the MH and tank design.     

Autofrettage of thick cylinders

Based on the third and the fourth strength theory, this paper presents an analytic equation for the optimum radius of an elastic–plastic juncture, r_jopt, in autofrettage technology; the influence of autofrettage on the stress distribution and load-bearing capacity of a cylinder is studied and optimum pressure in autofrettage technology is presented.     

Fatigue life prediction and verification of high-pressure hydrogen storage vessel

A fatigue life prediction method is developed for the high-pressure hydrogen storage vessel based on theoretical research and experimental verification. Firstly, the finite element model of vessel was built considering wound angle of head, thickness and number of the composite layer, then simulation was performed. The optimum range of autofrettage pressure was obtained by FEA with consideration of the DOT-CFFC and CGH2R standards. The influence of autofrettage pressure, metal liner thickness, and fiber thickness on vessel fatigue life was discussed under internal pressure cyclic load. Finally, the experimental verification was carried out. It was found that fatigue failure first occurred in middle cylinder. The experiment results agree well with theory analysis. Their average error is 6.33%.     

Hydrogen gas filling into an actual tank at high pressure and optimization of its thermal characteristics

Gas with high pressure is widely used at present as fuel storage mode for different hydrogen vehicles. Different types of materials are used for constructing these hydrogen pressure vessels. An aluminum lined vessel and typically carbon fiber reinforced plastic (CFRP) materials are commercially used in hydrogen vessels. An aluminum lined vessel is easy to construct and posses high thermal conductivity compared to other commercially available vessels. However, compared to CFRP lined vessel, it has low strength capacity and safety factors. Therefore, nowadays, CFRP lined vessels are becoming more popular in hydrogen vehicles. Moreover, CFRP lined vessel has an advantage of light weight. CFRP, although, has many desirable properties in reducing the weight and in increasing the strength, it is also necessary to keep the material temperature below 85 °C for maintaining stringent safety requirements. While filling process occurs, the temperature can be exceeded due to the compression works of the gas flow. Therefore, it is very important to optimize the hydrogen filling system to avoid the crossing of the critical limit of the temperature rise. Computer-aided simulation has been conducted to characterize the hydrogen filling to optimize the technique. Three types of hydrogen vessels with different volumes have been analyzed for optimizing the charging characteristics of hydrogen to test vessels. Gas temperatures are measured inside representative vessels in the supply reservoirs (H2 storages) and at the inlet to the test tank during filling.     

Supercritical cryo-compressed hydrogen storage for fuel cell electric buses

Liquid hydrogen (LH₂) truck delivery and storage at dispensing sites is likely to play an important role in an emerging H₂ infrastructure. We analyzed the performance of single phase, supercritical, on-board cryo-compressed hydrogen storage (CcH₂) with commercially-available LH₂ pump enabled single-flow refueling for application to fuel cell electric buses (FCEB). We conducted finite-element stress analyses of Type 3 CcH₂ tanks using ABAQUS for carbon fiber requirement and Fe-Safe for fatigue life. The results from these analyses indicate that, from the standpoint of weight, volume and cost, 2-mm 316 stainless steel liner is preferred to aluminium 6061 alloy in meeting the required 15,000 charge-discharge cycles for 350–700 bar storage pressures. Compared to the Type 3, 350 bar, ambient-temperature H₂ storage systems in current demonstration FCEBs, 500-bar CcH₂ storage system is projected to achieve 91% improvement in gravimetric capacity, 175% improvement in volumetric capacity, 46% reduction in carbon fiber composite mass, and 21% lower system cost, while exceeding >7 day loss-free dormancy with initially 85%-full H₂ tank.     

宽温域中碳纤维导热特性研究

碳纤维作为一种被广泛应用的微纳米材料,对其导热性能的测量研究一直被作为对碳纤维性能研究的重要内容。在利用氦气的气体液化基础上搭建的超低温实验环境中,基于瞬态电热法对处于290到10 K温度内的碳纤维样品的导热性能进行研究。实验发现,当实验温度低于某一特定温度后,材料的热扩散率表现出与声子散射分析相反的实验结果。通过引入热扩散系数倒数这一理论研究声子热阻在低温下的变化,分析得出,当实验环境温度低于某一特定温度后,低温会造成碳纤维材料内的石墨微晶体结构发生变化,从而造成材料热扩散率下降。     

Effect of gas injection mass flow rates on the thermal behavior in a cryogenic fuel storage tank

Large scale using of liquid hydrogen and liquid oxygen on energy engineering, chemical engineering and petrochemical industries, bring a series of non-equilibrium thermal behaviors within fuel storage tanks. Accurate simulation on the thermal behavior in cryogenic fuel storage tanks is therefore a critical issue to improve the operation safety. In the present study, a 2-dimensional numerical model is developed to predict the active pressurization process and fluid thermal stratification in an aerospace fuel storage tank. Both external heat penetration and heat exchange occurring at the interface are accounted for in detail. The volume of fluid method is adopted to predict the thermal physical process with high-temperature gas injected into the tank. The effect of the gas injection mass flow rate on the tank pressure, the interface phase change, and the fluid temperature distribution are investigated respectively. Finally, some valuable conclusions are obtained. The present study may supply some technique references for the design of the pressurization system.     

碳纤维全缠绕铝内胆气瓶预紧压力的优化

以2L的碳纤维全缠绕铝内胆气瓶为例，利用ANSYS完成其在各个压力过程下的有限元应力分析。在内胆结构尺寸和缠绕层一定的情况下，研究了预紧压力的变化对该气瓶应力影响的结果。根据分析得出的结果．依据DOT CFFC标准的要求确定出了该气瓶的最佳预紧压力值，实现了对该气瓶预紧压力的优化。     

Three dimensional numerical computations on the fast filling of a hydrogen tank under different conditions

Hydrogen-fueled vehicles offer a clean and efficient alternative for transportation. Compressed gas in high pressure tanks is a popular storage mode for hydrogen fuel. Time required for filling a hydrogen tank for vehicular applications should be short. But quick filling of hydrogen tanks at high pressures can result in high gas temperatures which can damage the tank and lead to its rupture. Hence the real time monitoring of gas temperature is essential during filling. This paper reports the findings of numerical simulation of filling process of hydrogen tanks. Real gas effects are considered. Local temperature distribution in the tank is obtained at different durations of the fill. Effect of changes in ambient temperature and initial and inlet gas temperatures is studied. Results of the study can aid in optimizing the filling time and in identifying the most suitable locations for the feedback devices within on-board hydrogen tanks.     

热压含碳球团高温冶金性能的实验研究

热压含碳球团是一种利用煤热塑性提高强度的新型炼铁原料。在实验室条件下，对碱度1．2和FC／O比1．0的未热处理和热处理热压含碳球团，分别检验其低温还原粉化、还原膨胀、还原冷却后强度等高温特性，并与其他炼铁原料进行合理对比。实验结果表明，热压含碳球团的高温冶金性能优于普通球团矿或烧结矿，适用于炼铁生产。     

Acoustic emission characteristics of used 70 MPa type IV hydrogen storage tanks during hydrostatic burst tests

Currently, the periodic inspection of composite tanks is typically achieved via hydrostatic test combined with internal and external visual inspections. Acoustic emission (AE) technology demonstrates a promising nondestructive testing method for damage mode identification and damage assessment. This study focuses on AE signals characteristics and evolution behaviors for used 70 MPa Type IV hydrogen storage tanks during hydrostatic burst tests. AE-based tensile tests for epoxy resin specimen and carbon fiber tow were implemented to obtain characteristics of matrix cracking and fiber breakage. Then, broad-band AE sensors were used to capture AE signals during multi-step loading tests and hydrostatic burst tests. K-means ++ algorithm and wavelet packet transform are performed to cluster AE signals and verify the validity. Combining with tensile tests, three clusters are manifested via matrix cracking, fiber/matrix debonding and fiber breakage according to amplitude, duration, counts and absolute energy. The number of three clustering signals increases with the increase of pressure, showing accumulated and aggravated damage. The sudden appearance of a large number of fiber breakage signals during hydrostatic burst tests suggests that the composite tank structure is becoming mechanically unstable, namely the impending burst failure of the tank.     

Effect of Thermal Cycling on Hardness and Impact Properties of Polymer Composites Reinforced by Basalt and Carbon Fibers

The polymer-matrix composites may be significantly affected by cyclic temperature changes. This study investigates the effects of thermal cycles on hardness and impact resistance of three types of phenolic-matrix composites, that is, phenolic resin reinforced with (1) woven basalt fibers, (2) woven carbon fibers and (3) hybrid of basalt and carbon fibers. The effect of thermal cycling on hardness and impact resistance was material-dependent. While the thermal cycling rapidly decreased the hardness of composites reinforced by carbon fibers, it gradually decreased the hardness of composites reinforced by basalt fibers. Yet, the Charpy impact energy of carbon/phenolic (CFP) and basalt/carbon/phenolic (BCFP) composites was not significantly affected by thermal cycles, the Charpy impact energy of basalt/phenolic (BFP) composites shows a sharp decline with increasing thermal cycling, and reaches a plateau after a certain cycles. Based on the results, the BFP composites was significantly harder than CFP and the composites containing carbon fibers in spite of demonstration of low impact resistance at primal cycles, possessed very gradual decline in impact resistance compared to BFP composites after the thermal cycling.     

JRC reference data from experiments of on-board hydrogen tanks fast filling

At the JRC-IET, on-board hydrogen tanks have been subjected to filling–emptying cycles to investigate their long-term mechanical and thermal behaviour and their safety performance. The local temperature history inside the tanks has been measured and compared with the temperatures outside and at the tank metallic bosses, which is the measurement location identified by some standards. The outcome of these activities is a set of experimental data which will be made publicly available as reference for safety studies and validation of computational fluid dynamics.     

大直径高温熔盐储罐罐顶接管的强度及罐体稳定性分析

随着可再生能源技术的大力发展与应用,对太阳能热发电站中持久储热的钢制储罐的安全性能进行研究具有重要意义.以青海省某塔式太阳能热发电站中直径为25 m的高温熔盐储罐(储热罐)为例,利用ANSYS软件的平面实体轴对称单元建立了储罐有限元模型,着重对储罐顶部与熔盐管道接口处进行了强度和稳定性分析,通过对管道连接部位进行局部精...