Cryogenic Valve Research Articles

Sub-Cooled Liquid Nitrogen Test System for Cooling HTS Synchronous Motor

A 400 kW radial-axial flux type experimental HTS synchronous motor is designed. There are twelve armature coils using HTS wires in the motor. They are accommodated in the cooling vessels made of FRP material, and twelve cooling vessels are enclosed in the vacuum vessel. In order to cool the HTS coils of the motor, a sub-cooled liquid nitrogen cryogenic system is presented. The operation temperature is below 70 K. This system consists of vacuum system, liquid nitrogen dewar, data acquisition system and a cold box with liquid nitrogen pump, G-M cryorefrigerator, cryogenic valve and a heater inside. The heater can present the heat of the HTS coils. In this paper, the design and the composition of this test cooling system are presented. When liquid nitrogen is injected into the vessel and the cryorefrigerator is operating, the cool down curve of the test system is obtained. After adding heat to the system, the capacity curve of the system is presented in this paper. The results proved that this sub-cooled liquid nitrogen system can be used for cooling the actual armature windings in the HTS motor.

Cryogenic Engineering Design of the ITER Superconducting Magnet Feeders

The ITER magnet system is to be operated at about 4.5 K. It has 31 feeders for high-current power supply, helium distribution and instrumentation cable routing. The feeders (except the smaller ones which are for instrumentation only) are 25 to 30 m long for about 40 tons. They have 3 main components: coil terminal box-cum-S-bend box (CTB-SBB), Cryostat feedthrough (CFT) and in-cryostat feeder (ICF). The CTB is the feeder component placed farthest from the coil (about 25 m away from the magnet center) and outside the bio-shield (the nuclear radiation restriction wall) so that it can be easily accessible in case the critical elements placed within it need maintenance: high-temperature superconducting current leads (HTSCL), large number of cryogenic control valves and pressure-release valves for quench protection. This paper explains the cryogenic design that considers these factors and main components.

Experimental approach to suppress two-phase flow in cryogenic liquid transfer process with the inverted U-bend pipe

LNG (Liquefied Natural Gas) offloading process from LNG cargo to storage tank includes substantial vertical upward fluid transportation. During this LNG transportation process, local boiling may occur at elevated position of the transport pipe due to the decrease of hydrostatic pressure and obstruct liquid flow, concluding long transport time or insufficient transport to a tank. Small scale LN2 (Liquid Nitrogen) transfer system has been fabricated to simulate this LNG transportation process and flow characteristics. Subcooled LN2 is transferred to 5m upward, 1m horizontally, and 5m downward through vacuum insulated stainless steel pipe. Glass pipes are installed at the middle part of transportation pipes to visualize the two-phase flow pattern during fluid transfer. Cryogenic valve is installed at the outlet of transfer pipe to regulate the system pressure inside the transfer tube. Pressurization by manipulating the cryogenic valve at the outlet, has effectively suppressed two-phase flow, which results in transportation advantages, such as low pressure drop and smooth flow. This paper presents the detailed experimental data of the whole procedure of the tested LN2 transfer system.

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.

Growth of deuterium clusters in a gas jet and ion energy spectrum of clusters in ultra-short laser field

Large deuterium clusters are generated using a cryogenic pulse valve with a cone nozzle (21 mm long, 4° open angle). Rayleigh scattering experiment is carried out to obtain the scaling relation between scattering signal SR and backing pressure P0. A method using the Coulomb explosion model is proposed to verify that the clusters continue to grow after their leaving the nozzle. Our experiments suggest a tentatively optimized position for laser cluster interaction.

자켓의 압력 및 두께 변화에 의한 진공 자켓 밸브의 유입 열량 변화에 관한 연구

Abstract: Recently, continuous research on cryogenic valves is being carried out with the rapid development of the cryogenic valve-related industry, and especially, high performance of cryogenic valves is being promoted due to the br eakthrough development and demand of users, etc., of the mechanical, shipbuilding, sem iconductor and display industry and the aerospace industry field, but it is the realit y that technical development and research on cryogenic application equipment on vacuum insulation are insufficient. The present research focused on interception of heat exchange with the outside by keeping low pressure after installing a jacket pipe outside a stem and also considered heat transfer properties on changes in pressure of a vacuum par t and radius of a jacket which can reduce heat exchange for effective heat transmission control by studying it in a three-dimensional numerical analysis method. Key words: Vacuum-jacket valve, Heat flow in, BOG (boil-off gas) †교신저자(동아대학교 기계공학과, E-mail:spkim@dau.ac.kr, Tel: 051-200-7646)1 동아대학교 기계공학과 2 동아대학교 기계공학과 대학원

BLDC 모터로 구동되는 액체 추진제 로켓엔진용 극저온 추력제어밸브 개발

본 논문에서는 KSLV-II의 로켓엔진에 사용될 BLDC 모터로 구동되는 극저온 추력제어 밸브의 개발 과정 및 결과를 소개하였다. 개발된 추력제어밸브는 90K의 극저온, 113.2bar의 고압 환경에서 액체산소의 유량을 BLDC 모터로 작동되는 밸브 구동기를 통해 조절할 수 있다. 추력제어밸브는 모든 개발 인증시험을 통과하였으므로 향후 일부 하드웨어 수정 후, 엔진 연소시험에 적용이 가능하다. This paper summarizes the activities performed for the development of a BLDC(Brushless Direct Current) motor driven cryogenic thrust control valve with application to KSLV-II rocket engine. The developed thrust control valve can modulate the flow rate of liquid oxygen under cryogenic temperature of 90K and high pressure of 113.2 bar with the help of electro-mechanical actuator driven by a BLDC motor. This valve can be applied to an engine combustion test after minor change because all development certification test have been performed successfully.

Construction and Commissioning of the KSTAR Helium Distribution System

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The KSTAR components requiring cryogenic helium coolant for superconducting magnet operations are connected to the helium refrigeration system (HRS) through the helium distribution system (HDS), the final helium distribution station. Twenty eight cryogenic valves including 4 quench protecting valves, many sensors such as temperature sensors, pressure transmitters, and flowmeters are mounted on the system. The HDS has to control the 4.5 K supercritical helium (600 g/s) for 30 superconducting coils and their superconducting bus-lines, 55 K helium (270 g/s) pressurized to 18 bars for the thermal shields and the gravity supports, and a maximum 17.5 g/s of liquid helium for 18 current leads, provided from the HRS which has a 4.5 K equivalent cooling power of 9 kW. The helium distribution system consists of a helium distribution box (DB), 5 helium transfer lines, a PLC based helium control system (HCS), etc. The helium control system is connected to the KSTAR supervisory control &amp; interlock system. The detailed status regarding the construction, commissioning during first cool-down, and the instrumentation &amp; control (I&amp;C) system are included in this paper. </para>

극저온 버터플라이 밸브의 유속에 따른 캐비테이션 발생 예측

The butterfly valve is widely used in the industrial field as an on-off or a flow control valve. When the butterfly valve is used as a flow control valve, cavitation sometimes occurs in the range of high flow rate because of the small valve opening. Therefore, the pressure loss and the cavitation characteristics are investigated by use of a commercial CFD code. The results show that the possibility of cavitation occurrence in the cryogenic butterfly valve is very high in the case of valve opening angle below 10 degree and incident velocity over 6m/s. By increasing the inlet velocity at 10 degree of valve opening angle, the value of loss coefficient increased. However, by increasing the inlet velocity at 50 degree of valve opening angle, the value of loss coefficient decreased.

LNG선용 버터플라이밸브의 유동특성에 관한 연구 (제1부 : CFD해석과 실험결과의 비교)

Butterfly valves are widely used as control valves for industrial process. For the definition of optimum configuration of the valve, wide range of related studies has been actively conducted in the case of working fluids of water or air under the normal temperature. Recently, internal flow and performance characteristics of cryogenic butterfly valve for LNG carrier take a growing interest in the field of research and development. Therefore, present study is aimed to investigate the internal flow and performance characteristics of the cryogenic butterfly valve because the study result for the valve can be hardly found at present. Part 1 of this paper describes the study result of a butterfly valve model under the condition of the normal temperature. Succeeding Part 2 of this paper will describe the internal flow characteristics of a cryogenic butterfly valve for LNG carrier. The results of Part 1 show that pressure loss coefficients and flow rate coefficients obtained by the present experiment and CFD analysis agree well each other. Moreover, internal flow visualization for the valve by CFD analysis and PIV measurement have revealed complicated flow patterns of the internal flow field in detail.

LNG선용 버터플라이밸브의 유동특성에 관한 연구 (제2부 : 극저온에서의 밸브 유동특성)

Recently, butterfly valves are used as control valves for industrial process. However, there are not so many reports on cryogenic butterfly valves in spite of broad application in LNG storage station and LNG carriers. Present study is focused on the investigation of the detailed hydrodynamic and aerodynamic characteristics of cryogenic butterfly valves to contribute to the operation during the handling on LNG transportation system, and to the practical utilization in design of butterfly valves and actuators. The results show that large recirculation vortices in the region downstream of the valve are founded and the cavitation flows are intensively generated on the surface of valve disc at the relatively small opening angle. The aerodynamic characteristics, lift, drag and torque, acting on the valve disc are calculated. The pressure distribution and the pressure loss coefficient of the cryogenic butterfly valve show almost similar pattern with those of the butterfly valve which is used on the normal temperature.

ANALYSIS AND DESIGN OF CRYOGENIC BALL VALVE

Natural gas is being hailed as alternative energy sources for a petroleum, because it is almost no emissions of pollutants in the environment. Use of equipment for liquefied natural gas, along with increased demand for natural gas is also growing. Cryogenic ball valve is used to control the liquified natural gas which temperature is -196 , supplied pressure �� is 168kg/cm 2 . To acquire the safety along with durability of cryogenic ball valve, we should consider the structural mechanics such as stress, deformation and dynamic vibration characteristics and identify those important aspects in the stage of preliminary design engineering. For the cryogenic ball valve, the assurance of structural integrity and operability are essential to meet not only normal, abnormal loading conditions but also functionality during a seismic event. In this study, analytical approach and results using finite element analysis and computational method are herein presented to evaluate the aspects of structural integrity along with operability of cryogenic ball valve. Moreover, we have done the optimal design through special processing and heat treatment and so on. Finally, we designed the high pressure cryogenic ball valve that accomplishes zero leakage.

Bubble counter based on photoelectric technique for leakage detection of cryogenic valves

In order to overcome the inconvenience of manual bubble counting, a bubble counter based on photoelectric technique aiming for automatically detecting and measuring minute gas leakage of cryogenic valves is proposed. Experiments have been conducted on a self-built apparatus, testing the performance with different gas inlet strategies (bottom gas-inlet strategy and side gas-inlet strategy) and the influence of gas pipe length (0, 1, 2, 4, 6, 8, 10 m) and leakage rate (around 10, 20, 30, 40 bubbles/min) on first bubble time and bubble rate. A buffer of 110 cm3 is inserted between leakage source and gas pipe to simulate the downstream cavum adjacent to the valve clack. Based on analyzing the experimental data, experiential parameters have also been summarized to guide leakage detection and measurement for engineering applications. A practical system has already been successfully applied in a cryogenic testing apparatus for cryogenic valves.

유한요소법을 이용한 극저온 미니어쳐 글로브 밸브의 구조설계에 관한 연구

This cryogenic miniature globe valve is used to transfer the liquified natural gas which temperature is -169℃, supplied pressure is 30bar(3.0㎫). In the present work the temperature distribution and thermal deformation is calculated numerical the FE method is useful to predict the thermal matter of cryogenic miniature globe valve. For this reason, to optimum design of the cryogenic miniature globe valve, the analysis of the parameter about bonnet has been studied. It‘s used 3-D modeling to analyze cryogenic globe valve, which is 1/2

スラッシュ水素の極低温バルブ内流動特性に関する研究

Slush hydrogen is a mixture of solid hydrogen particles and liquid hydrogen. The flow characteristics of slush hydrogen in two types of cryogenic valves (i.e., vertical- and horizontal-moving piston valves) were investigated by visualization of its flow and measurement of pressure loss. In a preliminary ice/water flow test, circulation flow was observed in a vertical-moving piston valve, and this caused the accumulation of ice particles in the flow path. Based on the preliminary test results about particle behavior in the valve, a horizontal-moving piston valve was improved, and it was observed that slush hydrogen flows smoothly and the pressure loss of slush hydrogen is only slightly larger compared to liquid hydrogen flow. These test results show that a horizontal-moving piston valve is more suitable for slush hydrogen compared to the vertical-moving piston valve, and that an appropriate flow path design leads a smooth flow of slush hydrogen at the same level as liquid hydrogen.

DMU(Digital Mockup) 기법을 적용한 LNG 선박용 극저온 버터플라이 밸브 설계의 우수성 검증

Recently, cryogenic butterfly valves for LNG carriers are actively developed by ship equipment companies. The dual core structure unlike usual butterfly valve has both translation and gyration motions of the disk of the valve assembly. Especially, the ship equipment companies can not have overcome 2D design method; in addition, even though 2 years of development has passed, the drawing cannot be secured. In this research, for the cryogenic butterfly valves and the product design, 3D design method was introduced and DMU(Digital Mockup) was applied to complement the problems in 2D design and investigate application possibility of 3D design method.

The influence of temperature and strain rate on the constitutive and damage responses of polychlorotrifluoroethylene (PCTFE, Kel-F 81)

Polychlorotrifluoroethylene (PCTFE), also known as Kel-F 81, is a semi-crystalline fluoropolymer. Although it has been employed in a wide range of cryogenic components, valve seats, seals, and microelectronics packaging, its mechanical behavior has received limited coverage in the literature. In this work, we present the tensile and compressive constitutive response of PCTFE for a range of temperatures (−85 to 150 °C) and strain rates (1 × 10 −4–2.9 × 10 3 s −1). Both large-strain experiments based on flow stress and small-strain dynamic mechanical analysis (DMA) using the elastic modulus exhibit a strong increase in the glass transition temperature, T g, with increasing strain rate. The quasistatic fracture behavior of PCTFE is presented using J-integral fracture experiments. Finally, a discussion of the implication of the constitutive and damage responses of PCTFE on impact failure modes observed in Taylor impact experiments is presented.

Cryogenic valve pneumatically actuated by use of vapour pressure

A new concept of a cold actuator chamber is realized to avoid using cumbersome high-pressure helium gas cylinders in space for the cold valves in AMS-2 project [Cryogenic system for a large superconducting magnet in space, Part IV, alloy]. A good repeatability was shown in the first experiment with the cold valve opened and closed.

Multi-Element Unstructured Analyses of Complex Valve Systems

The safe and reliable operation of high-pressure test stands for rocket engine and component testing places an increased emphasis on the performance of control valves and flow metering devices. In this paper, we will present a series of high-fidelity computational analyses of systems ranging from cryogenic control valves and pressure regulator systems to cavitating venturis that are used to support rocket engine and component testing at NASA Stennis Space Center. A generalized multi-element framework with submodels for grid adaption, grid movement, and multi-phase flow dynamics has been used to carry out the simulations. Such a framework provides the flexibility of resolving the structural and functional complexities that are typically associated with valve-based high-pressure feed systems and have been difficult to deal with using traditional computational fluid dynamics methods. Our simulations revealed a rich variety of flow phenomena such as secondary flow patterns, hydrodynamic instabilities, fluctuating vapor pockets, etc. In the paper, we will discuss performance losses related to cryogenic control valves and provide insight into the physics of the dominant multi-phase fluid transport phenomena that are responsible for the “choking-like” behavior in cryogenic control elements. Additionally, we will provide detailed analyses of the modal instability that is observed in the operation of a pressure regulator valve. Such instabilities are usually not localized and manifest themselves as a system-wide phenomena leading to an undesirable chatter at high flow conditions.

Numerical analysis of cooldown and warmup for the Large Hadron Collider

As the basis of studies, the paper presents the inventory of components and materials for LHC magnets, especially for main dipoles and quadrupoles firstly. Then a mathematical model and analytical method for LHC transient modes, such as cooldown and warmup of a magnet, a standard cell and the eight LHC sectors, has been developed on the basis of the up-to-date layout of the LHC machine, and validated by experimental data. The model and method do not only consider the momentum and continuity equations as well as the energy equations for helium and materials, but also take into account the pressure evolution in the different headers of the cryogenic distribution line and the effect of the pressure drop across the cryogenic valves. Based on the simulation results, the heat transfer in the magnets has been studied and the transient modes optimized.