This study evaluates the fatigue life of Ω-shaped bellows expansion joints subjected to axial cyclic displacement, in accordance with relevant standards. Using fracture mechanics theory, numerical simulations were conducted to analyze fatigue crack propagation in joints with initial small cracks, and their fatigue life was calculated. The proposed small semi-elliptical surface crack model reveals that stress intensity factors at crack tips escalate sharply with cyclic loading cycles. However, the crack propagates significantly faster in the span direction than in the depth direction, leading to gradual flattening of the crack morphology. For the analyzed Ω-shaped bellows expansion joints and applied loads, the fatigue life of defect-free joints calculated according to standards exceeds the fracture mechanics-predicted fatigue life of joints with initial cracks by approximately 94

Abstract To solve the temperature rise issue of disk-type permanent magnet magnetic couplers (PMMCs) under high-load operation, this paper conducts a systematic three-dimensional multi-physics field coupling simulation integrating electromagnetic, thermal, and fluid dynamics analyses. A finite-element model of the single-disk PMMC was first established in ANSYS Maxwell to determine steady-state torque and eddy-current losses at the rated slip of 44.55 rpm. The computed losses were then mapped as a volumetric heat source into ANSYS Fluent for a fully coupled Maxwell–Fluent analysis that accounts for forced convection induced by the rotating heat sinks. Results show that the coupler delivers a stable torque of 1120 Nm with eddy-current losses of 5.29 kW. Within the examined slip range, the torque–slip relationship exhibits near-linear behavior. Thermal analysis reveals that the copper-disk temperature reaches 93.2 °C without heat sinks, whereas the addition of the heat sinks reduces it to 42.2 °C, reduced by 54%, implying the important role of the heat sinks in keeping the safety operation of couplers.

Concentrating solar power (CSP) is a promising renewable energy technology, and molten-salt storage tanks are core equipment for ensuring its stable operation, where the foundation plays a decisive role in the structural design and safe service of the tanks. To address the lack of systematic stress and deformation analysis for large high-temperature molten-salt storage tank foundations, this study aims to investigate the mechanical and thermal behaviors of the foundation under actual operating conditions. A numerical simulation method was adopted to perform stress and deformation analysis on the foundation of a large high-temperature molten-salt storage tank. The results show that the maximum von Mises stress of 229.26 MPa is concentrated on the steel plate of the foundation. The radial deformation of the foundation was calculated, and the maximum radial deformation reaches 36.64 mm, which provides an important reference for the design of both the foundation and the entire molten-salt storage tank. Under the given internal pressure and operating temperature, the height of the molten salt has a significant impact on the radial deformation of the foundation. Additionally, ambient temperature variations from −28.7 °C to 20 °C exert little influence on the temperature distribution of the foundation, indicating that the thermal insulation performance of the tank is excellent. The findings of this study can provide theoretical support for optimizing the design and operation strategies of molten-salt storage tanks, particularly their foundations.

The Sun (6000 K) and outer space (3 K) are huge reservoirs of heat and cold sources that are sustainable and clean. How to fully utilise these two types of energy throughout the year to address the energy crisis and climate change remains a challenge. In this study, a dual-function system integrating solar heating (SH) and radiative cooling (RC) technologies is proposed, which has four operating modes: heat storage, heating air supply, cold storage and cooling air supply. In the SH and heat storage modes, Graphene and Ag-based nanofluid is adopted as the medium, its heat is transferred to the air through a heat exchanger. In the cold storage and cooling air supply modes, an optimised multi-layer film structure with high emissivity in the atmospheric window is employed, and water and air are employed as the mediums. Through the mutual adjustment of four modes, the system can achieve year-round operation. The system with a panel area of 100 m2 has a monthly average equivalent electrical energy of 16,590 kW center dot h in SH mode and over 8200 kW center dot h in RC mode, demonstrating enormous potential application. The temperature of mediums can be easily adjusted by changing their mass flow rate, and the required temperature of supplying air is convenient to adjust by only changing its mass flow rate. This study is of great significance for deepening the understanding of SH and RC technologies and dealing with energy and environmental issues.

In this study, for a bellows expansion joint only subjected to axial cyclic displacement, the fatigue life is evaluated in accordance with the relevant standards for bellows expansion joints, and a numerical simulation of crack propagation for the fatigue life in case of a small crack existed on the bellows expansion joint is conducted based on fracture mechanics. Results indicate that based on the semi-elliptical surface crack model proposed herein, both the stress intensity factor at the crack front and the depth of crack propagation exhibit a rapid increase with an increasing number of cycles. Furthermore, it is observed that the propagation of the crack in the span direction exceeds that in the depth direction, leading the crack become more and more flat. For the bellows expansion joint and loads studied here, the fatigue life of the un-cracked corrugated expansion joint based on the standard is larger than that predicted by fracture mechanics for the corrugated expansion joint with a small crack by approximately 46

Due to the complex structure, complicated operation process and extreme working environment, how to ensure the safe and efficient operation of the large-scale special equipment is always a big problem to be concerned. In this study, taking the large LNG storage tank as a research object, the methods and problems of the current risk analysis models of large-scale special equipment were investigated based on the proven numerical analysis technology combining with the big data model technology, Internet of things (IoT) and data sensing system. The method of creating the digital twin of a large LNG storage tank with process optimization, real-time monitoring and forecasting functions was analyzed. The framework of the digital twin was established according to its working process, and the key technologies were analyzed. It can provide references for the direction and method of establishing a relative perfect digital twin system of efficient optimization and risk analysis model for large special equipment.

Pressure vessels having the structure of a cylindrical shell with a tangential nozzle are often used in engineering for some process requirements. But there are no accurate methods in engineering codes for the strength design of this special structure. In this paper, the limit–load analysis was performed to evaluate the weakening effects of the tangential nozzles on the strength of the cylindrical shells under internal pressure. A so-called strength–weakening coefficient was defined to reflect the weakening degree of the load-bearing capacity of the cylindrical shells by the tangential nozzles or specifically by the three dimensionless structural parameters, namely diameter ratio (do/Di), diameter-thickness ratio (Di/T) and thickness ratio (t/T). Results show that when increasing do/Di and Di/T or decreasing t/T, the strength–weakening coefficient increases, which means that the strength–weakening effect of the tangential nozzle on the cylindrical shell increases. With sufficient simulation results, regression equations for the strength–weakening coefficient were obtained which provides a reference for the strength design of cylindrical shells with tangential nozzles under internal pressure.

The pre-cooling of a large LNG storage tank involves complex phenomena such as heat transfer, low-temperature flow, gas displacement, and vaporization. The whole pre-cooling process could take up to 50 h. For large-scale, full-capacity storage tanks, it is particularly important to accurately control the pre-cooling temperature. Digital twin technology can characterize and predict the full life cycle parameters from the beginning of pre-cooling development to the end and even the appearance of damage in real time. The construction of a digital twin platform requires a large number of data samples in order to predict the operating state of the device. Therefore, a simulation method with high computational efficiency for the pre-cooling process of LNG tanks is of great importance. In this paper, the mixture model and discrete phase model (DPM) are applied to simulate the pre-cooling process of a large LNG full-capacity tank. Following Euler–Lagrange, the DPM greatly simplifies the solution process. Compared with the experimental results, the maximum error of the DPM simulation results is less than 11%. Such a highly efficient simulation method for the large LNG full-capacity storage tank can make it possible to build the digital twin platform that needs hundreds of data model samples.

Abstract In this paper, a quick analysis system for the pre-cooling process of large LNG tank was developed, based on ANSYS-Python. The system has the functions of establishing geometric model automatically, dividing grid automatically and solving automatically. Operation of the system is simple with high efficiency. Comparison with the field data results found that the quick analysis system is accurate to meet the requirements of engineering application. The quick analysis system is helpful to optimize the pre-cooling process and the structure of large LNG full-capacity tanks

Cracks in engineered pipelines often appear in the form of multiple cracks or crack clusters with interactions between them. It is important to study the interaction between cracks if the pipeline crack cluster is to be evaluated in terms of equivalence and safety assessment. In this paper, based on FRANC3D crack analysis software, the interaction between circumferential parallel double cracks on the inner surface of pipelines was investigated, the factors affecting the interaction were examined, and the empirical equations for calculating the stress intensity factor (SIF) of double cracks was proposed. The results show that if there is no bias between the double cracks, the crack leading edge is shielded, but if there is offset between the double cracks, the crack leading edge is subjected to different interactions at different locations. The distal end of the cracks is generally strengthened, while the proximal end of the cracks is probably more shielded. The interaction effects between cracks are dependent on their relative positions rather than the pipe size or concerned crack size. According to the numerical simulation, boundaries for shielding or enhancing interactions were obtained, and the stress intensity factor calculation equations were fitted.

Abstract For traditional heat exchangers, segmental baffles form a “dead zone” on the leeward side of the baffle, reducing heat transfer efficiency and causing significant pressure loss in the shell side. In response to these issues, this paper proposed a new type of baffle—the cinquefoil orifice mixed-flow baffle which introduces cinquefoil orifices on the segmental baffle. This design retains some cross-flow while also inducing longitudinal jet-flow as the fluid passes through the cinquefoil orifice. Numerical results found that the cinquefoil orifice baffle not only reduces the adverse effects of the “dead zone” but also enhances turbulence in the shell-side fluid flow due to the jet-induced entrainment effect, thereby improving heat transfer efficiency. With identical boundary conditions, the cinquefoil orifice mixed-flow baffle heat exchanger demonstrated superior shell-side heat transfer effectiveness compared to the traditional segmental baffle configuration. For the heat exchanger studied here, when the cinquefoil orifice is positioned closer to the baffle cut, the shell-side Nusselt number can increase by up to 18.8%, concurrently leading to a reduction of 4.62% in shell-side pressure drop. But it is also found that with increasing the number of cinquefoil orifices, the shell-side heat transfer efficiency did not increase monotonically, implying that in addition of the locations of the cinquefoil orifices, the proportion of the longitudinal jet-flow to the cross-flow could be optimized to get a best heat transfer efficiency.

Abstract Cracking is one of the key factors jeopardizing the safe operation of pipelines, and Stress Intensity Factor (SIF) is an important parameter for evaluating the degree of crack danger. Cracks on engineering pipelines often appear in irregular patterns. In this paper, with FRANC3D crack analysis software, SIFs of the circumferential tilt cracks and axial tile cracks on the inner wall surface of a pipe under internal pressure were studied with concentration on the effects of the crack tilt angles. Mode I stress intensity factor weakening effect KI/K0 was defined and influences of the crack tilt angle, pipe and crack size on KI/K0 were investigated. With enough simulation results, empirical formulas for calculating the Mode I SIF for the circumferential or axial tilt crack were obtained by modifying the formulas for calculating the SIF of the crack in AMSE FFS-1.

As the stress of the frame, especially the bottom side rail supports and bottom inclined supports, of a traditional LNG tank container could be significantly greater than its allowable stress, and the container cannot meet the strength requirement of the specification when it is impacted by a transport vehicle during railway transportation, three improved frame structures were suggested, which removed or changed the side rails or bottom inclined supports; the stress and deformation of these improved frames and the tank container were analyzed using the finite element method under the impact test. The results show that all three improved frames can meet the strength requirement, i.e., the maximum Mises stress is less than the allowable stress and the deformation requirement of the diagonal length difference is less than the allowable value, meaning that the tank containers with improved frames can pass the impact test. Moreover, for the FRP support rings and impact side heads, although the maximum values are different, they are still less than the respective allowable stresses. In addition, the maximum value of the middle cross section of the outer vessel in the direction of gravity does not increase with the change in the frame, and the deformation of the outer vessel remains within the elastic range. Therefore, the improvements of the frames have little effect on the stress and deformation of the other components of the tank container, in particular, the inner vessel and outer vessel. Compared to the frame of the traditional tank container, removing the side rails partially or completely can reduce the weight of the frame by 17.99% and 38.34%, respectively, greatly reducing manufacturing and transportation costs. It can also reduce the maximum Mises stress by 38.89% and 39.24% and the maximum diagonal difference by 57.95% and 61.16%.

针对压缩机入口管道振动问题,通过对管道进行模态分析和谐响应分析,研究管道管卡的支撑位置和数量对管道振动的影响,提出管卡数量和位置的设置应以最大程度提高管道固有频率和降低振动位移为原则.随后以某压缩机入口管为研究对象,按上述原则逐个确定了3个管卡的位置,结果表明管道在两横向上的振动位移比原三管卡管道的振动位移分别降低了88.12％和54.8％,减振效果明显.

In this paper, the impact process of a large LNG tank container for trains was studied by performing experiments and numerical simulations. Impact force with induced stress and deformation on the container especially on the frame was investigated and LNG sloshing inside the container was simulated. Experimental results show that for the initial velocity of 6.1 km/h, the maximum compressive stress is −366.3 MPa occurring on the longitudinal beam near the impact side corner fittings. The impact force produced by the transport vehicle is influenced by both the initial clearance and initial velocity, i.e., its maximum value increases with the clearance or velocity, which in turn directly affects the LNG impact force on the head, the tank container axial acceleration at the mass center and the frame deformation and stress distribution. The largest average pressure brought on by the LNG impact force is 8.83% of the design pressure, the inner vessel should be designed with a thickness allowance. When the initial velocity is 8 km/h, the ratio of the maximum LNG impact force to the static inertia force at each clearance is less than 0.23, which means that the calculation method of LNG static inertia force is conservative. In addition, the maximum axial acceleration of the tank container can reach 63 m/s2, greater than 4g inertial acceleration specified in the container design standard, meaning if assessed by the impact, the specifications of the standard are not conservative.

本文以氯气液化器为例,根据固定双管板立式换热器的结构特点,从部件加工、管束组装、换热管与管板的胀接与焊接以及检验等介绍了制造过程的特殊性.目前氯气液化器运行良好,说明其制造过程是有效的,具有工程参考价值.

裂纹是引起管道开裂失效的主要原因,裂纹尖端应力强度因子是表征裂纹应力场强度的主要物理量,也是对管道进行安全评估时的主要依据之一,但管道不同于平板,有曲率影响,因此基于平板推导出来的裂纹尖端应力强度因子公式必须进行修正.为了准确计算管道上斜裂纹应力强度因子,建立了不同管道直径、不同裂纹倾角以及不同裂纹长度下的管道穿透斜裂纹有限元模型,并计算了裂纹尖端应力强度因子,在无限大板中心斜裂纹应力强度因子计算公式基础上,修正得到了管道穿透斜裂纹应力强度因子计算公式,这对于含裂纹管道安全评定有重要参考价值.

In ideal manufacture of multilayer wrapped high pressure vessels， pre-stresses would be induced at the cylinders. But if the manufacture is not so accurate， interlayer clearances would exist and the pre-stresses cannot be guaranteed. In this paper， expressions for the stresses in multilayer wrapped high pressure vessels under pressure loading with or without pre-stresses were derived. Numerical simulations were conducted for verification. It is found that the analytic results are in good agreement with the numerical simulations and both indicate that application of pre-stresses can effectively improve the elastic stress distribution at the cylinder and increase the pressure-bearing capacity of the cylinder in the elastic stage. In the whole yielding stage， however， the limit-pressure of the cylinder only depends the thickness and materials of the inner cylinder and layers and is not affected by the pre-stresses. In addition， both analytic and numerical results also found the limit-pressure of the cylinder is not affected by the interlayer clearances.

对方形车载氧舱的加强筋合理设计问题进行研究,提出了基于极限分析的等强度设计方法,即根据极限载荷分析确定强度薄弱区域并设置加强筋,不断重复直至结构满足强度要求.结果表明,和根据工程经验设计的原氧舱加强筋相比,按此方法设置的加强筋重量减少27.64％时,车载氧舱极限载荷值大于工作压力对应的许用极限载荷值,满足了氧舱结构承载要求.研究也表明:在薄壁结构上依据等强度原则逐渐设置和优化加强筋的方法既可以满足强度要求,又能较大程度地减轻加强筋重量,在工程上是可行且合理的.

急冷锅炉的管板结构特殊,是由并排焊接的扁圆管组成.在扁圆管板的布管区承受换热管与夹套管间的热变形差的影响,容易产生较高的热应力.非布管区在内压作用下也易产生较大应力导致强度失效.本文应用数值模拟方法,对急冷锅炉的扁圆管板进行应力分析,并根据JB 4732-1995进行强度评定.结果发现,对于本文研究的扁圆管板,只有对换热管进行预拉伸,布管区的应力才能通过强度评定,但预拉伸不能有效降低非布管区的应力.为此,本文设计了环形加强筋,使得扁圆管板可以满足强度要求.