低温液化气体汽化保护控制装置的研究

低温容器在使用过程中,当液化气体汽化不充分时会使液态介质流入常温管道,从而导致材料的冲击韧性大幅降低。针对这种现状,分析了低温液化气体对人体和设备的危害,以水为介质进行了低温液化气体汽化保护控制试验,研究了介质在0~4℃温度区间内,温度变化和调节阀开度、液体泵转速的关系,得出一种新型的低温汽化保护控制装置。试验结果表明：该装置精密度高,数据准确稳定,对低温液化气体的使用安全起到保障作用。     

Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars

Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.

     

Cryogenic implementation of charging diamond anvil cells with H2 and D2

A cryogenic loading system for introducing H(2) and D(2) into the diamond anvil cell has been designed and constructed. The integration of pressure loading mechanism, ruby fluorescence spectrometer, and microscope camera allows for in situ tuning and calibrating the pressure. The performance of the system has been demonstrated by successful synthesis of hydride and deuteride of transition metal and rare earth metal. Our cryogenic methodology features facile start-over of loading and in situ electrical resistance measurement of as-synthesized sample.     

黑色金属的超低温金刚石超精密切削

黑色金属的超精密切削问题一直是超精加工领域中未能解决的难题。本文提出了在超低温状态下用天然金刚石单晶车刀超精密切削黑色金属的新工艺,为解决这个难题开辟了新的途径。实验结果表明,在超低温状态下,金刚石车刀切钢时的急剧磨损可以有效地被抑制,刀具寿命增加,从而使黑色金属的金刚石超精密切削成为可能。     

Coriolis mass flow measurement at cryogenic temperatures

With the growing interest in liquefied natural gas (LNG) in the energy market, Coriolis mass flowmeters have been applied to many applications in the distribution of LNG. Since Coriolis flowmeters are normally calibrated at around room temperatures, measurements for LNG at cryogenic temperatures present a challenging condition. Firstly, a theoretical analysis for Coriolis mass flow sensors is provided considering the major changes of material properties (Young’s modulus and thermal expansion) at cryogenic temperatures. Then, a practical approach which can be used to correct the flow calibration factor obtained at a reference condition is presented. Finally, flow test results obtained from NIST’s cryogenic calibration facility are provided. Based on the results, it can be concluded that if a Coriolis flowmeter is calibrated at a reference condition and the flow calibration factor is corrected considering the non-linearity of Young’s modulus and thermal expansion change with temperature, it can still provide very accurate mass flow measurement even at cryogenic temperatures.     

液氢温区冷氦增压试验系统的设计

针对液体火箭冷氦增压系统试验研究的不足,设计并建设了液氢温区冷氦增压试验系统,采用深低温制冷机组配合高压低温换热贮罐来实现液氢温区高压冷氦气源;使用管壳式加热器真实模拟箭上换热器的换热性能与流阻;提出以排气方式模拟贮箱推进剂消耗过程中压力的变化情况。该试验系统安全可靠,更加真实地模拟了液体火箭冷氦增压系统的工作过程。     

奥氏体不锈钢深冷容器室温应变强化技术

随着低温液化气体的日益广泛应用,深冷容器的需求量不断增加。在安全的前提下,实现深冷容器的轻量化,对于节能降耗具有重要意义。采用室温应变强化技术可以提高奥氏体不锈钢的屈服强度,显著减薄奥氏体不锈钢制深冷容器的壁厚,减轻重量。中国、美国、德国、澳大利亚等已将该技术用于制造奥氏体不锈钢深冷容器。在简要介绍室温应变强化技术发展历史、标准和优点的基础上,着重分析讨论了该技术推广应用中遇到的常见问题。     

钎焊气氛对金刚石磨耗特性的影响

采用NiCr合金钎料,通过Ar气保护和真空钎焊的方法制备了钎焊金刚石耐磨性试件,并研究了钎焊气氛对金刚石磨耗特性的影响。结果表明：在试验条件完全相同的情况下,不同的钎焊气氛导致金刚石磨耗特性不同,即经真空钎焊金刚石的磨耗特性表现为破碎方式,而经Ar气保护炉中钎焊金刚石的磨耗特性初始表现为磨耗平台方式,其后随着磨耗平台面积的增大,金刚石出现破碎。最后采用Ar气保护和真空钎焊方式制作了金刚石套料钻并进行了钻削试验,由于磨耗特性的不同,Ar气保护炉中钎焊套料钻较真空钎焊套料钻具有更长的使用寿命。     

Cold plasma brush generated at atmospheric pressure

A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 degrees C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.     

A New Shaft Sealing Solution for Small Cryogenic Pumps

Commonly scaled cryogenic fluids include liquefied gases such as nitrogen, argon and oxygen, pumped both on site and from road tankers at temperatures approaching — 200°C (392°F). Traditionally, cryogenic sealing has employed conventional contact sealing technology, the seal typically being of a metal bellows design.

However, because most liquefied gases are pumped at temperatures close to their boiling points, vaporization at the sealing interface is a major problem. Dry running causes accelerated face and seat wear and short seal life.

A new type of seal has been developed which combines two critical seal, technologies. It comprises a profiled noncontacting seal face and seal as the primary seal, and a welded metal bellows as the secondary seal, and spring.

The paper will outline the technology employed in solving this cryogenic sealing application. It will describe the equipment and environments that are typically employed, focusing on those issues that are relevant, to the shaft seal. Some examples of operating installation will be given, together with measurements taken from them.     

Hole drilling with abrasive fluidjets

Small-hole drilling in several materials using abrasive fluidjets—abrasive-waterjets and abrasive cryogenic jets with liquefied nitrogen as the working fluid—were investigated through laboratory tests, numerical simulation, and phenomenological analysis. Drilling is accomplished by an abrasive slurry for abrasive-waterjets and primarily by a stream of dry abrasives for abrasive cryogenic jets as the liquefied nitrogen changes phase after exiting the mixing tube. Scaling factors were successfully derived through analysis of profiles digitized from hole images to collapse the data. For abrasive-waterjets, water is nearly incompressible; a high stagnation pressure inside the blind hole was developed causing delamination in laminates and cracking in the thermal barrier coating. The return abrasive slurry also possesses considerable residue erosion power that could cause damage to the hole entrance due to secondary wear. Neither delamination in laminates nor cracking in the thermal barrier coating is however observed when abrasive cryogenic jets were used.     

低温氮气射流对钛合金高速铣削加工性能的影响

在钛合金的高速切削过程中，切削区温度很高，加速了刀具的磨损，限制了切削速度的进一步提高。为降低切削区温度、防止刀具的氧化磨损，提出在低温氮气射流条件下进行钛合金的高速铣削加工。在干铣削、浇注切削液、常温氮气油雾、低温氮气射流和低温氮气射流结合微量润滑等冷却润滑条件下进行了钛合金的高速铣削对比试验。试验结果表明，低温氮气射流结合微量润滑能够最有效地降低铣削力，抑制刀具磨损。借助扫描电镜的检测手段，研究了不同冷却润滑条件下刀具的失效形式。指出在低温氮气射流条件下高速铣削钛合金时，只要热裂纹的形成与扩展未引起刀具的崩刃及刀面的剥落，进一步降低低温氮气的温度将提高刀具的使用寿命。     

基于应变强化技术的低温储罐轻量化设计

随着低温液化气体的日益广泛应用,深冷容器的需求量不断增加。在保证安全的前提下,实现深冷容器的轻量化,对于降低制造成本具有重要意义。采用室温应变强化技术可以提高奥氏体不锈钢的屈服强度,显著减薄奥氏体不锈钢制深冷容器的壁厚,减轻重量。试验测定了304不锈钢应变强化效应,并采用常规设计、分析设计和极限分析三种不同的方法,对相同设计参数的304不锈钢制低温储罐内筒进行强度设计,发现应变强化后材料的屈服强度显著提高。若考虑应变强化,按常规设计内筒柱壳厚度可降低50％,按分析设计可降低45％,而按极限分析,承载能力可提高139％。     

Construction of phase diagram up to 2 GPa and 200°C for thermo‐reversible gel lubricants by diamond anvil cell

The objective of this research was to make the phase diagram up to 2.0 GPa and 200°C of thermo‐reversible gel lubricants (TR Gel‐Lube) using diamond anvil cell (DAC). TR Gel‐Lube consisted of base fluid and gelling agent. The most important characteristic of TR Gel‐Lube is the reversible change of its physical state. The DAC is able to concerning visual observation of the sol/gel and liquid/viscoelastic–solid transition at high pressure and high temperature. DAC enables the visual observation of the photoelastic effect in order to generate local principal stress difference under the compression field for liquid/viscoelastic‐solid transition of base oil poly‐α‐olefin. The direct observation for sol/gel transition of TR Gel‐Lube at high pressure was also made possible. The phase diagram corresponding to transition from liquid to viscoelastic solid for base oil poly‐α‐olefin and sol to gel for TR Gel‐Lube was made by using DAC. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of the mechanical behavior of a flexible solid metal seal for a cryogenic butterfly valve

Seat tightness at the fully shut position should be a consideration in the development of a butterfly valve for use in a liquefied natural gas (LNG) vessel. A flexible solid metal seal offers sufficient tightness of the butterfly valve and meets the specifications for cryogenic temperature. In the present study, characteristics for a cryogenic butterfly valve, such as the flow coefficient and the pressure loss coefficient, were estimated by numerical fluid analysis carried out to simulate 3-D flow and to study performance as it was affected by the opening angles of the valve disc. A design criterion to ensure the seat tightness of the butterfly valve at the fully shut position was proposed, in which the contact pressure between the metal seal and the valve disc would be compared with the fluid pressure. Numerical structural analysis showed that the contact pressure can be calculated by simulation of the frictional contact behavior on the surface of the metal seal and the valve disc. As a result, an adequate flexibility of the metal seal and the valve disc was required in order to accomplish a contact pressure that would be high enough to satisfy the seat tightness requirement. Under cryogenic temperature, thermal shrinkage caused the metal seal to adhere closely to the valve disc periphery at both sides and raised the contact pressure to a relatively high value, though there was no contact across a small area at the center position, which is susceptible to leakage. An additional displacement of the metal seal and the valve disc appeared at an operating fluid pressure of 6.9 bar and produced sufficient contact pressure at the no-contact area. This was verified by experimental leakage tests performed at room and cryogenic temperatures.     

小型精密CVD金刚石热沉片的制备研究

CVD金刚石具有优异的导热性能,在微电子热沉应用方面有着广阔的应用前景。利用ICP工艺制造了硅模具,利用有限元对CVD系统中硅模具的温度场和流场进行了研究,在硅模具内制备了小型精密CVD金刚石热沉片。试验结果表明模具法能够获得表面品质好、形状和尺寸精度很高的小型金刚石热沉片。     

A test setup for the bead cryogenic neutron moderator of the IBR-2 reactor

The design and main characteristics of a test setup for studying the serviceability of the bead cryogenic neutron moderator and determining its optimal operating conditions on the fast pulsed IBR-2 reactor are presented. Using the test setup, the possibility has been demonstrated of filling the moderator chamber with the working medium—beads of a mixture of aromatic hydrocarbons, delivered to the chamber by a cold (T < 85 K) helium gas flow over an intricately shaped cryogenic pipeline system.     

A gas microflowmeter with a specified sensitivity value

A method for specifying the output signal and constant (in a 0- to 50-mg/s flow rate range) sensitivity of a microflowmeter independently of the sort of the monitored gas is described. Results of an experimental study of quantitative and qualitative characteristics of a thermoanemometric thermal flowmeter based on indirect-heating thermistors are given. In a 0- to 25-mg/s nitrogen and argon flow rate range, the output signal varies from 70 to 100 V and the sensitivity is 2 V/(mg s^?1). The measurement accuracy is 0.13–0.28%, depending on the specified tempeature difference. The temperature self-regulation of the flowmeter is ensured by heat-carrier thermal stabilization at temperature levels specified by a special thermostabilization system. The active behavior of the heat-carrier thermostabilzation system assumes that it can be used in the vacuum chamber of the test stand.     

Development of variable temperature instrument for sensor calibration

An experiment to calibrate temperature sensors at cryogenic temperature has been performed. The main objective of this study was to develop a precise instrument for calibrating the temperature sensors over a temperature range of 4 K to approximately room temperature without liquid helium. The instrument consists of radiation shields, a sensor block, an electric heater, a cryocooler and a vacuum chamber. In a vacuum chamber, the cold head of the cryocooler is thermally anchored to the sensor block to bring the apparatus to a desired temperature. An electric heater is placed at the second stage of the cryocooler to control the temperature of the sensor block. The entire apparatus is covered by radiation shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. The dimensions of components including instrumental wires are optimized to reduce total heat invasion from room temperature into cryogenic temperature. The vacuum chamber is pumped down and cooled to cryogenic temperature by a cryocooler. The resistance of each temperature sensor is measured at steady state as well as cooling down and warming up cycles, and the performance of calibration is discussed with respect to the sensitivity and resolution.     

基于数字汽车衡多路自动装车的设计

液化石油气出厂的装车安全与准确称重非常重要。文章基于数字汽车衡称重技术,通过可编程控制器、数据采集卡、电脑软件系统等与装车设备配套,实现对八路液化石油气槽罐车自动装车、称重和安全监控,具有一定的参考应用价值。