Pressure jump relaxation setup with IR detection and millisecond time resolution

An instrument is described that allows the use of Fourier transform infrared (FTIR) spectroscopy as a detection system for kinetic processes after a pressure jump of up to 100 bars. The pressure is generated using a high performance liquid chromatography (HPLC) pump and water as a pressure transducing medium. A flexible membrane separates the liquid sample in the IR cell from the pressure transducing medium. Two electromagnetic switching valves in the setup enable pressure jumps with a decay time of 4 ms. The FTIR spectrometer is configured to measure time resolved spectra in the millisecond time regime using the rapid scan mode. All components are computer controlled. For a demonstration of the capability of the method first results on the kinetics of a phase transition between two lamellar phases of an aqueous phospholipid dispersion are presented. This combination of FTIR spectroscopy with the pressure jump relaxation technique can also be used for other systems which display cooperative transitions with concomitant volume changes.     

An Improved Apparatus for Pressure-Jump Relaxation Measurements

The pressure-jump relaxation technique was reviewed recently. It has proven to be a valuable tool in elucidating the mechanism of chemical reactions. In this paper it will be shown that the time range of applicability can be increased and relaxation times as short as 30 μsec can be measured with this technique. This was mainly achieved by reducing mechanical disturbances following the actual pressure jump. Construction and operation of the apparatus has been simplified as well, so that relaxation measurements can be repeated at a rate of 5/min. This allows sampling of the measurements to increase the accuracy of the results. Electronic data recording and processing has been developed by another team.     

Studying the thermodynamic processes in excilamps by the pressure jump method (Review)

A review of studies of thermodynamic processes in KrBr (207 nm), KrCl (222 nm), and XeBr (282 nm) barrier-discharge excilamps and XeBr (282 nm) and XeCl (222 nm) microwave-discharge excilamps is presented. Using various pressure gauges, it was experimentally shown that a pressure jump that occurs upon excilamp switching-on (-off) contains a fast (with a characteristic time of ??100 ms) and a slow (??100 s) component. The fast pressure-jump component is associated with gas heating during the discharge and allows evaluation of the fraction of the discharge power that is thermalized in the gas. From the analysis of the pressure decay after the jump, it follows that the gas is heated as a result of two processes: direct gas heating during the discharge (??100 ms) and the energy dissipation of acoustic waves in the gas (??10 ms). The slow component of the pressure jump is caused by the general heating of the excilamp and can be used to determine the fraction of the discharge power that is converted to thermal energy and to study various excilamp cooling modes.     

Volume ratio and pressure drop on hydraulic dynamic pressure calibration system

The calibration of a pressure transducer that works in dynamic conditions is an unavoidable challenge. To address this challenge, an experimental setup has been designed and developed to simultaneously generate and calibrate the dynamic pressure. The system mainly comprises a pressure chamber that accommodates a step pressure generator and test chamber with a quick open valve and pressure sensor under calibration. Accordingly, an aperiodic type of step pressure generator with a quick open valve is particularly designed. This instrument can generate a positive step pressure with a rise time of up to 11 ms and a negative step pressure with a fall time of up to 12 ms within a working pressure range from the atmospheric pressure to 200 MPa. The volume ratio of the test chamber to the pressure chamber and its effect on pressure drop is critical in such systems. The effect of volume ratio on the dynamic performance parameters, namely, rise/fall time, is explored and inferences for optimizing these parameters are derived. A mathematical model for pressure drop in the test chamber has been developed and validated to precisely determine the magnitude of the step pressure input. Lastly, the experimental study of the effect of volume ratio on pressure drop has been conducted to diminish the pressure drop, thereby minimizing the uncertainty.     

基于虚拟仪器技术的电磁阀综合特性测控系统

传统的电磁阀综合特性测试劳动强度大,效率和测试精度都较低,为了克服这一不足,介绍了一种基于虚拟仪器技术的电磁阀综合特性测控系统。该系统实现了电磁阀综合特性的各项测试和测试过程中的自动控制,大大提高了电磁阀综合特性测试的测试精度和效率。简要说明了电磁阀综合特性试验的内容;介绍了流体试验台架;设计了采用虚拟仪器技术开发的测试系统软件和硬件部分;给出了实现大范围且高精度压力测量的压力分级测量方法;最后提出了测控系统实现精确压力控制的控制策略并通过具体的测试结果给以验证。     

复合制动系统的电控制动阀设计与仿真研究

针对传统气压制动回路时延较长的问题,提出了一种改进的复合制动回路;对复合制动回路中关键元件--电控制动阀进行功能与性能需求分析,设计了一种基于高速开关电磁阀的电控制动阀,建立了其动态特性响应解析模型,用Simulink对其进行了性能仿真测试。结果显示,所提出的电控制动阀结构满足调压范围、压力响应时间、流量特性、压力特性与稳态误差、制动完全释放时间等性能指标。复合制动回路及电控制动阀的提出可减小制动过程中的压力响应时延,对实现差动制动,促进主动安全技术的发展具有重要意义。     

直驱式力马达阀性能检测系统

直驱式力马达阀（FMV）因响应快、控制精度高、抗污染能力强等特点被广泛应用于轧机自动厚度控制系统。对FMV的各项性能指标进行有效、实时的检测是控制钢材生产成本的一个重要环节。传统的伺服阀测试系统一般通过负载腔之间的流量、压力变化来检测其静态特性,这一原理可有效用于三位四通伺服阀的静态性能检测。而直驱式力马达阀是一种特殊的三通阀,它的性能指标无法像常见的三位四通伺服阀一样通过负载腔之间的流量、压力变化来检测。提出并实现了一种直驱式力马达阀性能测试方法,根据液压阀测试性能指标,设计、搭建了用于检测直驱式力马达阀性能的测试平台,有效检测了FMV的性能指标并绘制了其性能曲线。结果表明,根据伺服阀测试标准所提出的直驱式力马达阀性能测试方法以及所搭建的测试系统可有效用于FMV的静态性能指标的检测。     

往复压缩机流量无级调节系统动态特性研究

基于主动控制吸气阀原理的流量调节系统具备调节范围宽、速度快、稳定可靠等优点,在大型工艺往复压缩机中具有较大优势,调节系统动态特性是衡量调节性能的重要指标。建立了耦合控制系统、液压系统、执行机构等组件的数学模型,分析了排气储罐内气体压力、阀片位移、缸内气体压力、控制角度等特性参数的变化规律。结果表明：调节工况下阀片打开过程早于执行机构,随后共同复位,且复位过程中存在微小碰撞。利用排气储罐内气体压力间接控制压缩机排气量的方法存在调节滞后性,造成罐内压力脉动增大,低流量时更加明显。调节过程中阀片位移与缸内气体压力均具有周期性变化规律,PID参数的欠优化导致调节过程中多次出现最小控制角度,降低了调节系统的稳定性。     

The extended surface forces apparatus. IV. Precision static pressure control

We report on design and performance of an extended surface forces apparatus (eSFA) built into a pressurized system. The aim of this instrument is to provide control over static pressure and temperature to facilitate direct surface force experiments in equilibrium with fluids at different loci of their phase diagram. We built an autoclave that can bear a miniature eSFA. To avoid mechanical or electrical feedtroughs the miniature apparatus uses an external surface coarse approach stage under ambient conditions. The surface separation is thus pre-adjusted to approximately ~3 μm before sliding the apparatus into the autoclave. Inside the autoclave, the surface separation can be further controlled with a magnetic drive at sub-?ngstrom precision over a 14 μm range. The autoclave pressure can then be set and maintained between 20 mbar and 170 bars with few mbar precision. The autoclave is connected to a specially designed pressurization system to precondition the fluids. The temperature can be controlled between -20 and 60 °C with few mK precision. We demonstrate the operation of the instrument in the case of gaseous or liquid carbon dioxide. Thanks to a consequent decoupling of the eSFA mechanical loop from the autoclave structure, the obtained measurement stability and reproducibility, at elevated pressures, is comparable to the one established for the conventional eSFA, operated under ambient conditions.     

Design of a rotary valve orifice for a continuous wave mud pulse generator

High-speed downhole transmission technology plays an important role in measurement while drilling (MWD) and logging while drilling (LWD) systems, where the continuous wave mud pulse transmission method is currently the most advantageous method for wireless downhole transmission. To increase the production rate, transmission distance and testing intensity and to decrease the ground detected difficulty of continuous wave mud signals, the valve orifice must be optimized to satisfy the requirements for the continuous sinusoidal pressure output. In this study, an improved arc-fillet-line triangular valve orifice is designed based on a general line triangular valve orifice according to the relationships between the fluid differential pressure of a thin-walled cutting edge and the fluid flow area and between the correlation coefficient of the theoretical pressure difference and standard sinusoidal signal. The improved orifice is designed by calculating the variation between the flow area and relative rotation angle of the rotor to the stator through the established polar coordinate equations. The optimized valve structure is simple and easy to machine, and highly similar sinusoidal pressure wave signals can be achieved during practical operation to meet the requirements of the instrument design.     

氮气式水击泄压阀试验平台设计和试验研究

为实现对氮气式水击泄压阀的功能和关键性能进行充分研制试验,设计并搭建了一种能够满足工作压力高、流量大等试验条件的液流试验平台,并在试验过程中设计了包含设定压力、响应时间和设定压力误差试验在内的四项试验验证方法.根据所设计方法分别对型号为200YXY-100D的氮气式水击泄压阀主阀在氮气腔压力为1,2,3,4,5 MPa...     

离合起步用高速开关阀工作特性与驱动方法研究

在普通脉宽调制(PWM)信号驱动下,高速开关电磁阀的开启和关闭时间较长,反应慢,影响了高速开关电磁阀的控制性能。为了进一步提高高速开关阀的控制性能,在分析高速开关阀工作特性的基础上,提出了多路混合驱动方法,缩短了高速开关阀的开启和关闭时间,减小了压力控制时的压力波动,改善了高速开关阀的控制性能。在汽车离合器起步控制中,使用该方法很好地改善了汽车的起步性能,发动机转速比较平稳,从动盘转速增加趋势的波动较小。     

高压检测系统中低压仪表保护阀设计分析

矿用液压阀与立柱、千斤顶等元部件都需要进行高压与低压密封性能试验。为了提高检测过程自动化水平,减少人为干预试验过程引起的操作失误,设计出可以自动切换低压与高压检测回路的低压仪表保护阀。该阀可以设定保护压力,低压与高压情况下密封可靠,结构紧凑。并对设计过程的分析计算作了解释和说明。     

液压支架大流量安全阀冲击特性试验系统设计与分析

针对液压支架大流量安全阀,设计了以蓄能器组为辅助动力源的冲击特性试验系统。通过FAD500/50型大流量安全阀的冲击试验,得到了安全阀受冲击作用下压力、流量的响应曲线,并研究了蓄能器总容积、充液压力及插装阀组阻尼孔直径等关键参数对试验结果的影响规律。结果表明:所设计的试验系统可在规定时间内达到国家标准要求的阀前冲击压力,且被试安全阀在冲击压力到达前开启;增大蓄能器的总容积或充液压力,均对冲击载荷响应时间影响不大,但增大插装阀组可调阻尼开口量,会显著缩短冲击载荷响应时间,且流量超调、压力波动也明显增大;通过调整试验系统关键参数,可改变冲击载荷的强度,变化压力上升梯度,提供安全阀冲击试验所需的不同流量,进而模拟不同的冲击工况。     

高速机车防滑阀检测系统设计

基于高速数据采集、PWM控制、差压测密封技术,研制了一套防滑阀性能检测系统,实现了对防滑阀的动作响应时间、阶段充排气性能和密封性检测。在模拟实车制动工况条件下,检测系统通过输出快速响应的PWM信号控制进气电磁阀、排气电磁阀高速通断,以此实现对防滑阀性能的高精确检测。测试系统经重复性实验结果表明,阶段充排气性能的最大测量不确定度为0.834 kPa,密封性检测的最大不确定度为0.011 kPa。     

超低压力启动止加阀

对现有止回阀的性能、结构进行了分析,设计了一种可以随意安装于各种方向的管道中的超低压力启动止回阀。     

超低压力启动止回阀

对现有止回阀的性能、结构进行了分析，设计了一种可以随意安装于各种方向的管道中的超低压力启动止回阀。     

基于IPC的高压阀类产品性能参数采集与处理系统

采用基于IPC和工业组态软件的控制方案，解决了高压阀类产品性能参数的高速采集和存储问题，完成了对采集数据的显示和曲线分析；通过PLC高速计数功能对流量计进行高精度的实时测频，完成实时流量测量；对系统中使用的高压手动调节阀进行了创新型的改造，实现了高压下其行程的自动调节；设计出了通用的阀类产品测试平台。该系统已应用于某军品高压阀类产品性能参数的测试线中，采集速度最高达到了20次／秒，精度达到了0．3％以上。     

呼吸阀开启压力智能测试系统

开启正压和开启负压是呼吸阀最重要的特性参数。现有的呼吸阀开启压力确定方法有理论计算法和手动测试法,两者都存在精度低、自动化程度低的问题。该文研制可以检测呼吸阀实际开启压力的智能测试系统,采用高性能气压传感器、仪表放大器和A／D转换器获取高精度气压信号,采用实时时钟芯片存储时间信息和系统参数。系统提供良好的人机接口,能自动检测呼吸阀开启压力,判定呼吸阀是否合格,并打印检测报告。实验结果表明,该系统适用于呼吸阀生产厂家和使用单位。     

中/重型车辆坡道起步辅助系统气动控制电磁阀的设计与研究

目前手动挡汽车,尤其是中/重型车辆坡道起步时,需要驾驶员进行复杂的操作,操作不当易导致发动机熄火或溜车。通过系统结构设计原理分析,得到对电磁阀的功能和结构需求,设计了由1个膜片阀和1个二位三通常闭电磁阀集合而成的坡道起步控制电磁阀。借助该阀,驾驶员无需复杂的操作便可实现汽车坡道起步。此外,通过坡道起步控制电磁阀开关动作系统压力滞后特性试验研究得到:为了达到对制动力的精确控制,应根据系统特性适当选择坡道起步控制电磁阀开启与关闭时间,坡道起步控制电磁阀的断电时间至少应大于开启滞后时间32 ms,坡道起步控制电磁阀的通电时间至少要大于关闭滞后时间8 ms。