罗茨泵径向间隙泄漏量的研究与建模

分析罗茨泵的工作过程，根据平行平板间衡薄气体的流动理论建立泄漏模型，用模型来描述转子回转和不同流态下的压力差引起的径向泄漏，求解数学模型可以改进泵的性能提供理论依据。     

Newly developed standard conductance element for in situ calibration of high vacuum gauges

A new leak element, which is named as “standard conductance element (SCE)”, has been developed for in situ calibration of ionization gauges (IGs) and quadrupole mass spectrometers (QMSs). The SCE is made of a stainless-steel sintered filter with the pore size of less than 1 μm. Since the gas flow through the SCE satisfies the molecular flow condition even at the pressure up to 10⁴ Pa, some useful characteristics of molecular flow are available. The SCE is supplied to users with a calibration certificate described its molecular conductance. Users can introduce optional test gases with the known flow rate to their vacuum chamber through the SCE in their laboratories. The overview of the SCE, the calibration method and recommended practices are introduced.     

Stability tests of standard leaks for the calibration by a comparison method

At the calibration of standard leaks by a comparison method with reference standard leaks, important factors to evaluate the flow rates are the degrees of stability of a mass spectrometer leak detector (MSLD) and standard leaks. Stability of two leak element type standard leaks, a glass and a plastic, are tested. The test indicates that the warming up time is mainly influenced by the temperature of the mass spectrometer and 2 h is required to obtain a stabilized reading for the tested MSLD. In case of the glass type leak, 1 h pumping is required to obtain the stabilized flow rate after the exposure to the ambient air. In case of the plastic type leak, 1 min pumping is enough for the exposure time below 1 h but 6 h pumping is required after the 7 days exposure. After the valve closed duration within 3 h, the flow rates from both type of leaks recovered within a minute to 100% ± 0.5% of the averaged reading before the valve closed.     

硅片真空夹紧装置设计

设计了一套硅片专用真空夹紧装置，包括夹紧装置和微型无油真空抽气泵。为减少硅片在夹紧过程中变形，夹紧装置采用了多吸口、回旋槽的平面型结构；根据所需夹紧力大小，设计了抽速为0．3L／s的微型真空泵，泵内无油避免了对硅片的污染；对间隙返流进行了计算并分析了对泵性能的影响。     

A comparative study of flow rate characteristics of an averaging Pitot tube type flow meter according to H parameters based on two kinds of differential pressure measured at the flow meter with varying air temperature

A new averaging Pitot tube flow meter that has a shape similar to an Annubar® type flow meter was designed and its flow rate characteristic was evaluated. The air temperature supplied to the developed flow meter was maintained at a constant by controlling electric power supply to an electric heater during the calibration. Two kinds of differential pressure measured at the flow meter were used in calculating the H parameters, which represent characteristics of the developed flow meter. One H parameter (H_ΔP1) which was newly proposed in this research was calculated based on the difference between upstream pressure (stagnation pressure) at the flow meter and static pressure of the measured flow. The differential pressure is equivalent to the dynamic pressure of the flow. The other H parameter (H_ΔP2) which is used in a typical Annubar® type flow meter was calculated based on the difference between upstream and downstream pressure at the developed flow meters. Relationship curves between the two H parameters and the mass flow rate at the developed flow meter were obtained. The curves based on the H_ΔP2 parameter, which uses the difference between up and down stream pressure, show different gradients for varying the controlled air temperature. However, the other curve, based on the other H_ΔP1 parameter, which uses the dynamic pressure, can be represented by one linear curve even with varying air temperature.     

核反应堆堆芯冷却剂流量测量用涡轮流量计的研制及应用

为适应核反应堆堆芯冷却剂流量测量的需要,开发研制了新型低速涡轮流量变送器,按流量信号输出不同,分别为磁感应模拟信号输出和数字开关量输出低速涡轮流量变送器。实际标定和应用表明,低速涡轮流量变送器的精度和重复性是好的,相对误差的均方根为1．0％,使用寿命长,阻力小,线性范围宽。     

机械密封用螺旋式泵效环泵送性能研究

为了研究机械密封用螺旋式泵效环的泵送性能,利用CFD软件Fluent对泵效环的内部流场进行数值模拟计算,得到泵效环内部流场的压力分布,并计算出泵效环的泵送扬程,获得了流量-扬程性能曲线,分析了泵效环的转速和螺纹头数对其泵送能力的影响。结果表明：螺旋式泵效环具有较强的泵送能力,且泵效环的转速和螺纹头数对其泵送性能都有相应的影响。随着转速的增加,泵效环扬程增大,但扬程随流量的变化幅度并不大。随着螺纹头数的增加,泵效环扬程先增加再减小,且扬程随流量的变化趋于平缓。     

Mathematical model applied to the experimental calibration results of a capillary standard leak

Gas leaks supplied through metal capillaries are nowadays largely used in industry to calibrate “in situ” leak detectors (necessary in tightness tests, versus both vacuum and atmospheric pressure) or in whatever applications in which well-known (and very low) gas flows are necessary. If the capillaries are calibrated with a primary device or a reference one, the traceability of flow measurements to the national primary standards is guaranteed. At IMGC-CNR, standard leaks are calibrated by means of two primary flowmeters, operating respectively with reference to vacuum and to atmospheric pressure. In this paper, with the aim of developing a general calculus model for a unique calibration curve in both fields of use of a capillary leak, results relative to the calibration of a particular type of an all metal, crimped-capillary leak are presented and discussed. This capillary has been calibrated for helium, sulfur hexafluoride and nitrogen with reference both to vacuum and to atmospheric pressure and for molar flows ranging from about 1×10⁻¹¹ mol/s to 5×10⁻⁷ mol/s.     

基于CFD技术管道气体流场计算与分析

基于CFD技术,运用CFD软件结合气体运动基本理论,以电子束焊接真空系统中管道设计为例,对中真空条件下气体在管道内的流动状态、速度、压力分布进行2D有限元数值模拟仿真和可视化研究,为真空系统管道参数确定和结构优化设计提供了有参考价值的数据。提出在真空系统设计选择前级泵时,为保证获得较大的抽速,达到高效与经济的效果,优先考虑主泵排气口直径与前级泵相匹配,再校核前级泵最大反压力和最大排气量,可以极大提高设计效率。     

The smart-orifice meter: a mini head meter for volume flow measurement

Differential pressure based flow meters generally consist of a flow restriction element which generates a differential pressure and a pressure transducer, externally piped to the restriction, which measures the flow related differential pressure. The smart-orifice mini head meter presented takes advantage of silicon technology by incorporating a differential pressure microsensor. In contrast to conventional head meters, it represents a single compact and economic device for general flow meter applications, in particular where small size is of concern. Computational fluid dynamics analyses were applied to develop a non-standard orifice design and prototypes of the smart-orifice were fabricated. The performance of the mini head meter in water flow measurement was determined in a computer supported test bench facility. It was compared to the results predicted by the simulation, as well as to a conventional head meter arrangement with externally mounted pressure transducer, including measurements with water at elevated temperature and different absolute line pressures. The results are very promising and verify the competitiveness of the smart-orifice as a mini head meter.     

同步辐射X射线光刻光束线真空系统设计

本文介绍了BEPC工程(北京正负电子对撞机)同步辐射X射线光刻光束线真空系统设计.对反射镜箱的气载、系统的有效抽速及极限气压进行了分析和计算,并简要论述了有关的一些超高真空工艺问题.     

凸轮转子泵抽送不同浓度非牛顿流体的流场分析及对性能影响

为了探讨摆线型凸轮转子泵抽送粪污介质的性能变化和针对非牛顿流体类抽送的优化设计,以三叶摆线型凸轮转子泵作为研究对象,选取清水和浓度为6.87%,9.20%,12.15%的猪粪作为抽送介质,对凸轮转子泵进行三维非定常数值模拟,分析内部流场瞬态特性,预测其外特性。分析结果表明:在抽送清水和不同浓度的猪粪时,从泵腔的进口区域到出口区域的压力逐渐升高,随猪粪浓度增大,独立工作腔室的压力增大;抽送非牛顿流体时,间隙处因挤压而产生的速度激增,转子泵腔内的速度分布更加均匀;出口的压力脉动主频均出现在2倍叶频处,压力脉动幅值随猪粪浓度增大而减小;随猪粪浓度增大,出口流量、容积效率及水力效率增大,流量脉动系数减小,其性能优于抽送清水介质。研究为凸轮转子泵输送非牛顿流体时的优化设计奠定了基础。     

Development and evaluation of the calibration facility for high-pressure hydrogen gas flow meters

The calibration facility with the multi-nozzle calibrator was developed for the calibration of flow meters to be used with high-pressure, high-flow-rate hydrogen gas. The critical nozzles installed in the multi-nozzle calibrator were calibrated with traceability to the national standard. The relative standard uncertainty of the mass flow rates produced from the calibration facility is 0.09% when the flow rate is between 150 g/min and 550 g/min. In this study, the Coriolis flow meter was calibrated for a pressure range of 15–35 MPa. The relative standard uncertainty of the flow rates obtained from the Coriolis flow meter was 0.44% for the case of the worst fluctuations in the output of the flow meter; based on the calibration curve, this is 0.91%. The present result shows that there is a maximum 3% difference between the output of the Coriolis flow meter and the mass flow rates of the multi-nozzle calibrator, even though the Coriolis flow meter was calibrated using water. Therefore, for the development of a calibration facility that can calibrate a flow meter under the same conditions as those encountered in actual use, it will be important to develop a new flow meter.     

Analysis of flow field around a ribbed helix lip seal

In this study, a direct numerical simulation model has been developed to elucidate the pumping mechanism of a radial lip seal with helical ribs. The flow field around the contact region between the seal lip and the shaft surface in the environment of a pumping-rate test rig, where both air and oil sides are filled with oil initially, was simulated. The streamline pattern and pressure field around the seal lip were examined. Complicate three-dimensional streamline topology was depicted. On the air side, high pressures built up on the windward faces of ribbed helices next to the lip helping to pump oil back to the sump. The vortex generated next to the lip on the oil side rotates such to create an inward pumping effect too. The pumping rates were calculated at shaft speeds, ranging from 2000 to 6000 rpm, and compared to the measured values from the test rig. Good agreement was observed. Both calculated and measured pumping rates increase as the shaft speed increases. The current results demonstrate the promising application of CFD in the design of radial lip seals.     

Measurements and analysis of time constant of the KRISS dynamic flow control system

Time constant is an important property of the continuous flow systems that can be used to estimate the dynamic equilibrium time for the reaction vacuum chamber of such systems. This work is concerned with measurements and analysis of time constant of a dynamic flow control system assembled at the KRISS vacuum laboratory. Being a new system, it was important to know some basic characteristics of the system, including the time constant as well, in the pressure range of 0.1–133 Pa during continuous gas flow. Three types of gases were used for this purpose and the results were compared. It was observed that time constant was dependent on pressure across the conductance-reducer (CR) that was installed in the by-pass pumping line of the system. At low upstream pressures, the time constant was large and vice versa.     

A V-Cone meter measurement correlation in low pressure wet gas based on Chisholm model

To gain a deeper understanding of the performance of V-Cone meter in low pressure wet gas measurement, the over-reading of the V-Cone meter was experimentally investigated in the present study. The equivalent diameter ratio of the V-Cone meter is 0.55. The experimental fluids were air and tap water. The operating pressure and the gas volume fraction ranged from 0.1 MPa to 0.4 MPa and 97.52%–100%, respectively. The results showed that the existing V-Cone wet gas correlation, which was developed for the medium and high pressure wet gas cannot be well extended to the low pressure conditions. The Chisholm exponent monotonically decreased with the ratio of liquid-to-gas mass flow rate increasing, and was almost not affected by the gas to liquid density ratio and the gas densiometric Froude number in the present test ranges. A measurement correlation dedicated for the low pressure wet gas was developed. In the present cases, the relative deviation of the gas mass flow rate predicted by the new correlation was within ±4.0% and ±3.0% under the 95% and 90% confidence level, respectively; the average relative deviation was 0.046%. Our results provide insights into the measurement performance of V-Cone meter in low pressure wet gas and may help to develop a more comprehensive wet gas correlation.     

混凝土泵送中管壁磨损过程的离散元模拟研究

建立了混凝土离散元模型,并通过L箱流动实验校核了该模型,得到了计算参数。采用该模型及得到的参数对混凝土泵送过程进行数值模拟,其中,以颗粒对管壁的冲击力和平均力表征壁面磨损程度,对泵送过程中管壁磨损过程进行研究。分析了泵送速度、弯管角度等因素对管壁磨损分布的影响,预测了最易磨损位置。结果表明：弯管管壁磨损随着泵送速度的增大而增大,随着弯管角度的增大而增大,模拟结果与实际泵送过程中观测到的最易磨损位置吻合较好。     

Development of a new dynamic gas flow-control system in the pressure range of 1 Pa-133 Pa

A new flow-control system (FCS-705) has been developed at Korea Research Institute of Standards and Science. The system is intended for calibration of vacuum gauges in the pressure range of 1 Pa-133 Pa by comparison method. This paper describes some basic characteristics of the system including; (1) the design and construction of the system, (2) the generation of stable pressures in the chamber, (3) achieving high upstream pressure limit by installing a short duct in the by-pass pumping line, and (4) investigation of the gas flow regimes within the short duct.     

Study on wet gas online flow rate measurement based on dual slotted orifice plate

According to the current technical problems existing in gas and liquid flow measurement for wet gas production, the slotted orifice-couple flow meter was developed and the basic measurement principles for gas and liquid flow was presented. A new wet gas flow meter was developed based on the dual slotted orifice transducer. The flow characteristics of liquid flow through dual slotted orifice plate, the relationship of differential pressure between the dual slotted orifice plate, pressure, temperature, and flow rate of gas/liquid of different aperture ratio were studied. A mathematical measurement model was established to be applied in the flow meter measurement system with dual slotted orifice plate. The model was tested and calibrated by on-site field experiments in the China National Center of Metrology at Daqing Oil field. The results showed that the maximum measurement error of the gas and liquid flow was less than 10% and 15% respectively, when the Gas Volume Fraction (GVF) was greater than 90 vol%. The measurement accuracy of this industrial prototype can meet the requirements of well fluids.     

On the Dynamic Behavior of Two Gas-Lubricated Two-Lobe Journal Bearing Configurations

A Finite Element model for the noncontacting gas face seal is developed based on the modified Reynolds Equation developed by Fukui and Kaneko (4), (5) that considers the slip flow effects. Numerical studies of a representative spiral groove seal at the slow speed (≤, 500 rpm) and the low pressure (≤ .303 MPa) conditions showed that slip flow can significantly affect the seal performances such as the lift-off speed, leakage rate, load carrying capacities. Without the consideration of the slip flow effect, the lift-off speed and the corresponding leakage rate would be greatly underestimated, especially at near ambient pressure condition. By examining the F-h characteristic curves, it was found that under the parameters presented in the present study the slip flow could be significant for Knudsen number, Kn as small as .05, and the slip flow in effect reduces the viscous pumping resulting in a loss of load carrying capacities.