尼龙在50-110/12型膨胀机上的应用

我们车间50-110/12型膨胀机的阀杆填料,过去,漏泄问题长期得不到解决,曾先后用过耐油橡胶、石棉绳、棉纱线。从使用情况来看,棉纱线虽较前两种为优,但寿命较短。针对这个问题,1973年元月,车间三结合小组用与聚四氟乙烯有某些相似的MC铸型尼龙材料,改装了膨胀机阀杆填料函。经实际运行,证明尼龙作为50-110/12型膨胀机阀杆填料是     

低温阀门冷态试验的动态传热过程模拟与分析

在确定不锈钢在液氮中沸腾换热系数的基础上，结合其在低温下的物性参数，利用有限元分析软件ANSYS对一低温阀门在正常运行和冷态试验状态下的温度场进行模拟与分析。针对冷态试验情况下填料函处出现冻结的问题，提出在阀杆处添加绝热层的方案，继而通过进一步的模拟计算预测了其改进效果。     

截止阀的有限元模态分析

通过截止阀的三维建模型并进行模态分析,研究不同边界条件设置对模态分析结果的影响,并通过截止阀自由模态试验、工作模态试验对理论分析结果进行验证。结果显示阀杆和阀盘系统的固有频率较低,低噪声截止阀设计时不宜采用刚性壁假设;阀杆的边界条件设置将会极大的影响截止阀的计算结果。     

液氢低温截止阀传热及应力的模拟研究

应用ANSYS有限元分析软件对通径为DN25的液氢低温截止阀在超低温下的传热和应力进行分析.研究了阀体、长颈管、阀杆管等部件的温度和应力在低温下的分布情况.研究结果表明长颈管和阀杆管存在较大的温度梯度,显示了长颈管和阀体应力集中的部位.     

SHPB入射波相似律与整形技术的试验与数值研究

利用量纲分析理论研究了使用整形器的分离式霍普金森压杆(SHPB)试验入射波形是否满足几何相似律的问题。通过试验和数值仿真对其结果进行验证;基于直径为14.5 mm的SHPB装置,分析了整形器和撞击杆参数对入射波形的两个重要拐点的影响规律,得到入射波T₁和T₂拐点的无量纲表达式。结果表明：当撞击杆的速度保持不变,整形器直径与杆的直径同比放大或缩小时,考虑整形器的SHPB装置满足严格的几何相似律;入射波T₁拐点主要与整形器的直径和厚度以及撞击杆的速度有关,而入射波T₂拐点主要受整形器的厚度和撞击杆的速度影响,撞击杆长度只是影响入射波的持续时间,对入射波形上升沿阶段没有影响。     

超临界汽轮机中压调速汽阀2Cr12NiMo1W1V钢阀杆断裂原因分析

通过宏观形貌分析、化学成分分析、力学性能测试、光学显微镜以及扫描电镜分析等方法对某超临界汽轮机中压调速汽阀2Cr12NiMo1W1V钢阀杆断裂原因进行了分析。结果表明:阀杆断裂的主要原因是其表面的渗氮层脆性超标,运行中当阀杆和与其紧密配合的阀碟发生挤压摩擦时,便会在应力集中的排汽孔处的渗氮层形成裂纹源,并在载荷作用下穿透渗氮层扩展至基体进而引发阀杆断裂;阀杆材料长期在超过其许用温度的环境下使用,造成蠕变老化,同时材料硬度偏高、塑性和韧性储备不足,都在一定程度上加速了裂纹的扩展,缩短了阀杆的使用寿命。     

给水三通阀阀杆断裂失效分析

通过对发生断裂失效的给水三通阀阀杆进行宏观检查、化学成分分析、拉伸试验、冲击试验、金相检验和硬度试验,分析了其断裂原因。结果表明:阀杆断裂为疲劳断裂,阀杆断裂的主要原因是表面渗氮处理增加了阀杆与阀芯表面相交处的脆性,加上阀杆与阀芯表面相交的位置结构突变造成应力集中,在流体的长期挤压和剪切力作用下,便会在应力集中部位的渗氮层中形成裂纹源,并在阀杆服役时的交变应力的作用下,裂纹从渗氮层逐步扩展到阀杆基体,最终导致阀杆断裂失效。     

减振器节流阀片对阀门水击力的影响研究

针对车用减振器受地面瞬态冲击阀门容易失效的特点,提出了研究阻尼阀水击压强的重要性.建立了带有环形节流阀片的阻尼阀物理模型.通过有限元软件对节流阀片受瞬态冲击的变形时间进行了研究,得出了节流阀片受冲击的最大变形时间只与结构参数和材料特性相关,并随阀片厚度增加而减小的结论.与水击理论相结合,推导了阻尼阀水击的初始和边界条件,创建了阻尼阀水击数学模型.运用节流阀片等效厚度法则,编程分析了叠加节流阀片对水击力的影响规律,得出了在等效厚度相同的情况下,随着叠加阀片物理厚度的增加水击压强增大的结论,可以作为阻尼阀的设计参考.     

核电厂核级手动截止阀阀杆断裂原因

某核电厂核级手动截止阀阀杆在运行期间发生断裂。采用宏观观察、化学成分分析、力学性能测试、金相检验、扫描电镜及能谱分析、填料分析等方法，研究了该阀杆断裂的原因。结果表明：该阀杆的热处理工艺控制不当，造成阀杆的耐腐蚀性能变差；在运行过程中，该阀杆接触的填料腐蚀性元素含量较高，在长期承受较高拉应力的环境下，阀杆发生了应力腐蚀断裂。     

电动闸阀阀杆断裂失效分析

某电厂锅炉主给水管道上的电动闸阀阀杆在服役过程中发生断裂,阀杆材料为38CrMoAlA钢。采用化学成分分析、力学性能试验、金相检验、断口分析以及能谱分析等方法,对阀杆断裂原因进行了分析。结果表明:阀杆断裂主要是由于阀杆材料热处理不当,导致材料硬度偏高、冲击韧度严重偏低,从而使阀杆在开启过程中于应力集中的退刀槽处发生脆性断裂。     

低温地面支持设备系统CGSE中阀箱的方案和强度设计

低温地面支持设备系统CGSE是用于冷却第二代阿尔法磁谱AMS02的磁体组件并将超流氦注入AMS02磁体杜瓦的低温设备系统。介绍用于CGSE系统中气氦管路阀箱和液氦管路阀箱,介绍了阀箱的技术要求、方案设计、结构特征,并进行了强度校核计算,两个阀箱的筒体和下封头的壁厚为4mm,上封头的壁厚为5mm,能满足两个阀箱承受0．1MPa外压的强度要求。     

Design of a hybrid glass composite anchor for LNG cargo containment systems

Large cryogenic container for liquefied natural gas (LNG) should be joined to the inner hull of a ship. The minimum heat inflow, due to the large temperature difference between the LNG cargo container and inner hull, can induce considerable heat flux through the joined area.In this work, a hybrid composite anchor composed of two stainless steel caps and a glass fiber composite body was developed and optimized for strength, thermal stress and heat loss of the anchor. The stainless steel caps were adhesively bonded to the top and bottom areas of the glass composite body. The top stainless cap was then welded to the two stainless steel membranes, and the flange of the bottom stainless steel cap was bolt-fastened to the inner hull of a ship.The static adhesive strength and impact characteristics between the stainless steel caps and glass composite body of the hybrid glass composite anchor at the cryogenic temperature were investigated with respect to adhesive thickness. Finally, the optimal design for the hybrid glass composite anchor for the cryogenic containment systems of a LNG ship was suggested.     

结霜工况下空温式翅片管气化器传热试验研究

为深入掌握低温液体在空温式翅片管汽化器内的气化情况以及其与翅片管表面霜层生长的相互影响规律,以液氮为介质进行了低温液体在空温式翅片管气化器内的气化试验。通过热电偶和刻度带分别对翅片管上不同位置的温度和霜层厚度进行了测量,并分析了翅片管表面霜层的生长规律及翅片管内低温液体的流动特性。结果表明:气化器表面结霜过程受冷表面温度影响较大,冷表面温度越低,结霜速率越大,霜层越厚。结霜工况下的气化器工作状态分预冷和稳态两种工作状态。预冷工作状态低温液体进入气化器后迅速气化,其过程包含气液两相和单气相两个换热段。稳态工作状态低温液体在气化器内气化经历单液相、气液两相、单气相三个换热段,单液相段翅片管表面结霜最为严重,单气相段翅片管表面无霜晶形成。因此认为,可通过分状态分段设计空温式翅片管气化器从而减弱结霜对翅片管传热的影响,提高气化器换热效率。     

Gas gap thermal switches using neon or hydrogen and sorption pump

The very low pressure obtained thanks to adsorption phenomenon at low temperature can be used to build cryogenic heat switches, which offer the possibility to make or break thermal contact between two parts of a cryogenic system. The ON (conducting) and OFF (insulating) states of the switch are obtained by varying the gas pressure between two copper blocks separated by a gap of 100 μm. This pressure is controlled by acting upon the temperature of a small sorption pump (activated charcoal) connected to the gap space. For a “high” sorption pump temperature, the gas previously adsorbed in the sorption pump is released to the gap between the two blocks, allowing a good thermal conduction through the gas (ON state). On the opposite, cooling the sorption pump allows a very good vacuum between the copper blocks, which efficiently break the thermal contact (OFF state). Experimental thermal characteristics (Conductance in the ON and OFF state, ON-OFF switching temperature) of such a “Gas Gap Heat Switch” are described using hydrogen or neon as exchange gas and are compared with theoretical calculations.     

B型LNG模拟舱内低温流体两相流动与相变传热数值研究

本文以内容积为40 m3，绝热层厚度为400 mm的新型独立B型液化天然气船模拟舱为研究对象，对模拟舱内低温流体的两相流动及相变传热问题进行了非稳态三维CFD模拟。采用流体体积函数（VOF）模型追踪气液相界面，利用Lee模型作为相变模型，在相变模型中考虑了静压的影响，对模拟舱的温度分布及静态BOG生成速率进行了计算。研究了在不同液位以及绝热层存在破损的情况下模拟舱的温度分布及静态BOG生成速率的变化，同时研究了当模拟舱密闭时的增压特性。对比模拟结果与实验结果，偏差在10%以内，模型对模拟舱内的低温液体的蒸发过程模拟较好，可为新型独立B型液化天然气实船的设计和改进提供参考。     

跨临界二氧化碳压缩机热力性能仿真与分析

针对跨临界二氧化碳半封闭式往复式活塞压缩机建立了一个通用数学模型,既包括热力学模块,也包括机械模块。热力学模块主要描述气缸内部的气体压缩过程。机械模块包括运动学模型和曲轴连杆机构模型,考虑了轴承上的功耗损失。采用一台压缩机样机对模型进行了不同运行工况下的实验验证,结果显示压缩机流量和耗功的最大误差分别不超过5%和8%。通过仿真分析了变结构和变工况条件下的压缩机性能,结果表明:在不同的运行工况下,存在最佳缸径行程比;容积效率和等熵效率都随着转速的增加而下降;吸排气阀门内径存在最佳值;对于容积效率的影响,吸气阀间隙比排气阀间隙更大,活塞与汽缸间隙比活塞环与汽缸间隙更大。     

Operational Characteristics of the 200-m Flexible Cryogenic Transfer System

A proper cryogenic environment is essential for the operation of superconducting devices. A test area for the superconducting radio-frequency modules (SRF) has been established in the RF laboratory at National Synchrotron Radiation Research Center in Taiwan; these modules require much liquid helium during conditioning and performance tests; a cooling capacity of 120 W is expected for the acceptance test of the SRF module. The cryogenic environment of the test area is completed on transferring the liquid helium over a remarkable length of 205 m from the two cryogenic plants at Taiwan Light Source, with a valve box located at each end to control and to measure the cryogenic flow. Flexible cryogenic transfer lines of concentric four-tube type are chosen for both the supply of liquid helium and the return of cold helium gas. Functional examination of this long transfer system was first achieved with a 500-L Dewar in the radio-frequency laboratory; an SRF module was then installed in the test area for practical operation. The primary concern about the cryogenic transfer system is the heat loss; a measurement technique based on the principle of thermodynamics is developed and proposed herein. With the available sensors inside the valve boxes and the heaters inside the 500-L Dewar and the test SRF module, this technique has proved promissing from the measured results.     

Design and development of a direct injection system for cryogenic engines

The cryogenic engine has received increasing attention due to its promising potential as a zero-emission engine. In this study, a new robust liquid nitrogen injection system was commissioned and set up to perform high-pressure injections into an open vessel. The system is used for quasi-steady flow tests used for the characterisation of the direct injection process for cryogenic engines. An electro-hydraulic valve actuator provides intricate control of the valve lift, with a minimum cycle time of 3 ms and a frequency of up to 20 Hz. With additional sub-cooling, liquid phase injections from 14 to 94 bar were achieved. Results showed an increase in the injected mass with the increase in pressure, and decrease in temperature. The injected mass was also observed to increases linearly with the valve lift. Better control of the injection process, minimises the number of variables, providing more comparable and repeatable sets of data. Implications of the results on the engine performance were also discussed.     

A study of hypervelocity impact on cryogenic materials

This paper reports a result of hypervelocity impact experiments on cryogenically cooled aluminum alloys and a composite material. Experiments are carried out on a target palate at 122 K. Aluminum spheres at 1.95 km/s in 50 kPa air were impinged against the target plate at cryogenic temperature and the result was compared with room temperature target plates. Hypervelocity impact (HVI) processes were visualized with shadowgraph arrangement and recorded with high-speed video camera and to ensure the temperature dependence we compared HVI tests with metal target plates with AUTODYN 2D and SPH numerical simulations. We found that cryogenic impacts created slight differences of impact damage from room temperature ones, i.e., the shape and averaged diameters of HVI crater holes were less at cryogenic impacts.     

Relating damage evolution of concrete cooled to cryogenic temperatures to permeability

Typically, 9% Ni steel is used for primary containment of liquefied natural gas (LNG). Utilization of concrete in place of 9% Ni steel for primary containment would lead to significant cost savings. Hence, this study investigates changes in the microstructure of concrete due to cryogenic freezing that would affect its relevant engineering properties for containment. The study also evaluates the effect of aggregate type on the damage potential of concrete subjected to cryogenic freezing. The aim is to investigate design methodologies to produce damage-resistant cryogenic concrete. The study employed four concrete mixture designs involving river sand as fine aggregate, and coarse aggregates with different coefficient of thermal expansion (CTE) values. Specifically, the coarse aggregates were limestone, sandstone, trap rock and lightweight aggregate. Concrete cubes were cured under water for at least 28 days and thereafter frozen from ambient (20 °C) to cryogenic temperature (−165 °C). Acoustic emission (AE) sensors were placed on the concrete cubes during freezing. X-ray computed tomography (XRCT) was employed to study the microstructure of concrete cores, before and after cryogenic freezing. The impact of the microstructural evolution thus obtained from AE and XRCT on relevant engineering properties was determined via water and chloride permeability tests. Microcrack propagation determined from AE correlated with changes in permeability. There were no observable cracks in majority of the concrete mixtures after freezing. This implies that microcracks detected via AE and increased permeability was very well distributed and smaller than the XRCT’s resolution. Damage (microcracking) resistance of the concrete with different aggregates was in the order limestone ⩾ trap rock ≫ lightweight aggregate ⩾ sandstone.