核电用节流管伺服调压阀控制系统研究

介绍了节流管调控式调压阀用低功率高精度控制系统,包括系统原理与组成、以PLC为中枢的控制系统、软件设计和调试试验等,该控制系统功率低,控制精度高,可靠性好,满足核电用节流管伺服调压阀的使用要求。     

一种高压容器检测仪的设计原理

因当前国内各行业各领域对于高压、高精度气密性或耐压性检测的迫切需求,研制出一种典型的气密与耐压检测仪(型号为HP-0811).详细地介绍了该检测仪耐压性检测以及使用压差传感器进行气密性检测的工作原理,特别阐述了在高压下进行气密性检测时容器气体泄漏量的计算方法.该仪器可对不同体积、不同测试压力、不同精度要求的各容器、阀体、管材等进行气密和耐压检测,且气密测试压力最高可达到35 Mpa,耐压测试压力可达到60 Mpa.     

4m口径SiC反射镜原位检测用静压支撑系统

研制了一套用于4m SiC反射镜原位检测的静压支撑系统,以降低超大口径SiC反射镜离线检测的风险,提高其制造效率。首先,推导了单元刚度的解析式,确定了其中关键因素;然后,对支撑单元进行抽样测试,结合解析式预测了支撑群组中单元的工作刚度。最后,通过密封性测试和反射镜原位检测,验证了支撑系统的稳定性;通过有限元模拟,计算了系统的重力卸载面形精度。结果表明:5个单元连组时,单元刚度约为1.9kN/mm,刚度值分布在±3%误差区间;独立单元刚度可高至15kN/mm;3种分组单元刚度预测值分别为1.7,1.1和0.8kN/mm。支撑系统空载时管路压强变化缓慢,表明密封性良好;用该系统支撑4m反射镜时,11天内高度绝对变化量小于50μm,相对变化量小于20μm。54个单元刚度随机分布时,镜面面形高阶残差(RMS)为20nm。提出的系统基本满足原位检测的稳定性和精度要求。     

Effects of Fluid Film Pressure on Hydrodynamic Lubrication

The effect of pressure upon hydrodynamic lubrication is reflected by the variation of the density and viscosity of the lubricant.

Proceeding from the function that relates density to pressure in the case of liquids, the author obtains the generalized differential equation of a variable π upon which pressure distribution, as well as other characteristics, depends. This equation is integrated in the case of two-dimensional motion; as an application, the problem of plane surfaces and constant viscosity is discussed and it is shown that parameter K ? 6Vμ₁l/βh₂ ²(h¹/h₂? 1) has an important influence.

For circular cylindrical surfaces, the density depends on an integral expression the solution of which is obtained by means of conventional graphical and numerical computations.

By admitting finally that the viscosity also varies with pressure, a general method is given for solving the two-dimensional problem.     

高精度原油储罐液位计研究

通过对数字式电容液位计及等值基准电容补偿法的研究，提出将数字式电容液位计与压差法相结合，由数字式电容液位计测量原油液位和油水界面的高度，等值基准电容法补偿由于环境温度、极板腐蚀和油液粘结带来的测量误差，采用压差法测量混油密度，依据混油密度和液位高度求得油重及容积；通过高精度A/D板采集模拟和数字信号，连续对储罐内原油的液位、密度、温度等各种参数进行运算，并由智能监测仪实施全自动显示，其测量精度可达到毫米级。     

Hydrolysis of a Disiloxane/Ester Fluid in a Simulated Hydraulic System at 275 F

Data are presented on the changes in the properties of a disiloxane/ester fluid resulting from water concentrations as small as 200 ppm while undergoing mechanical stress at 275 F in a simulated aircraft hydraulic system. The response of fluid flash point, viscosity, neutralization number, and hydraulic system filter differential pressure are discussed for hydraulic fluid water concentrations as high as 18,900 ppm. The efforts of previous investigators, employing bench tests and simulated systems, are reviewed. The limitations and sources of error of methods of determining fluid degradation and level of water contamination, as determined by this study, are noted. Attention is given to the importance of reacted water, for which no routine method of determination has been developed, as apposed to free water as determined by the Karl Fischer method of analysis.     

基于MSP430的智能化冲击试验机的研制

介绍冲击试验机的工作原理及试验机的关键部件摆锤的打击中心、摆动中心及质心三者之间存在内在相互关系，通过推导找出了上述三者间的关系，即冲击中心与摆动中心重合，与质心不重合。给出智能化冲击试验机的软、硬件设计方案，选用，TI公司的16位单片机MSP430F449为核心，实现试验机的智能化，使测量效率、测量精度大大提高。     

精密空气密度测量仪的计量特性

利用精密温度、湿度、压力传感器,便携式空气密度精密测量仪实现了对空气密度的高精度测量。本文介绍了该仪器的基本原理和主要功能,并以实验数据为基础,验证了该仪器性能的可靠性。     

Direct continuous measurements of thermal expansion coefficients of liquids and solids using flow microcalorimetry

A differential heat capacity flow microcalorimeter is used to monitor in a continuous mode the thermal expansion of a sample during a programmed temperature scan. The sample may consist of liquids, suspensions, or bulk solids in a confining liquid and the typical temperature scanning rate is of the order of 1 K/min. The technique has a precision better than 1% and a detection limit of 10(-6) ml s(-1). In contrast to conventional dilatometers, this technique offers variable sensitivity and is not limited by the magnitude of the total volume change during the experiment. Various expansibility data obtained in the temperature range 10-55 degrees C are reported for several systems, namely water, benzene, carbon tetrachloride, and aqueous solutions of sodium chloride. The volume changes for the thermal transition of Teflon and the phase separation of 2-butoxyethanol/water mixtures further illustrate the possibilities of this new technique.     

精密恒压泵控制系统软件设计

介绍了以MCS-51单片机为核心的精密恒压泵控制系统应用软件的设计思想、结构和功能。该设计利用了检测与自动控制原理，精密恒压泵控制系统采用闭环控制结构，通过PID控制算法实现压力的精确控制。实地测试结果表明，该设计思想能够满足系统的功能要求与精度要求。     

竖直运动平台气动配重的研究

提出了一种利用气缸推力对竖直方向运动的超精密运动平台进行配重的新方法,使电机趋动力减小,提高运动精度。建立了重物配重及气动配重的力学模型,指出重物配重时,电机的推力至少要能够克服摩擦力,而用气动配重方法,当平台运动方向发生变化时,改变气缸压力,使平台在垂直运动时所需的电机推力小,甚至达到零负载,使其运动精度得以提高。并给出了一种控制气缸推力的解决方案。     

探针系统反应特性与参数选择研究

用于流场测量的探针针孔孔径小,压力反应缓慢,影响试验精度和进度。本文提出了探针系统针孔压力给定测量粗度的反应时间的计算方法,对三种系统测定水流场和测定空气流场的反应特性进行了比较,分析了压力反应时间的影响因素,给出了合理的系统和系统参数,以提高测试精度,缩短试验时间。     

常温液体粘度-密度-表面张力多参数快速测试仪的研制

本文研制了一种能够同时快速测量常温液体粘度、密度和表面张力的多参数综合测试仪。该测试仪以80C196KC单片机为检测与控制核心构建，粘度和密度的测量分别采用旋转柱体法和静力称衡法，表面张力采用一种新的测试方法——气泡幅频当量法。文中对各参数的测试原理、仪器总体结构、计算机测控单元等部分作了详细介绍，并给出了利用该仪器测定常见液体粘度、密度和表面张力的结果。试验结果表明，该测试仪具有较好的测试精度和工作稳定性。     

Characterization of thermally stable compliant structures with internal fluidic channels

This paper represents a novel method to suppress the thermal effects of flexure mechanism-based nanopositioning system by fluid (air or water) flow under certain pressure conditions through the internal fluidic channels of the compliant structure. The nanopositioning system made of stainless steel was additively manufactured, and the rectangular fluidic channels were formed on each side of the double compound type flexure mechanism-based compliant structure. The motion behavior was characterized by measuring the stiffness and frequency responses of the compliant structure with the hammering test while filling compressed air or the water through the fluidic channels. The thermal behavior was characterized by measuring the temperature distribution over the compliant structure and thermal displacement under the various compressed air pressure and water flow-rate conditions. Dynamic behaviors of the nanopositioning system under various fluid-fed conditions were also characterized by the Finite Element Method and were validated with experimental results. As a result, the compressed air- or water-fed mechanisms have the following characteristics: (1) the damping may increase when the fluid exists in the channels, (2) the compressed air-fed mechanism can move the stage with nanometer precision with fast response time, and (3) the media filled in the fluidic channels significantly lower the temperature increase and reduce thermal displacement error. Interestingly, two-fluid flows of the compressed air and water showed a similar tendency in suppressing the temperature increase. The proposed method is expected to meet the increasing needs for nanometer motion accuracies and the efforts achieving high precision in the thermally stable environments requiring from semiconductor industries and precision machine tool industries.     

土样含水量快速测定传感技术研究

土壤含水量的速测受土壤电导和土壤类型等诸多因素的影响，如何确保测试精度是实现土壤含水量速测的关键。首先分析了土壤含水量速测传统方法存在的问题，并从低成本快速测试的目标出发提出了实现土样含水量测试的电容传感技术、传感器结构和原理，并给出了传感器的信号检测处理电路。使用速测技术设计而成的测定仪器测试结果与常规烘干称重法对比，其精度达到土样含水量测定的要求。     

Water-Assisted Injection Molding System Based on Water Hydraulic Proportional Control Technique

Water-assisted injection molding(WAIM), an innovative process to mold plastic parts with hollow sections, is characterized with intermittent, periodic process and large pressure and flow rate variation. Energy savings and injection pressure control can not be attained based on conventional valve control system. Moreover, the injection water can not be supplied directly by water hydraulic proportional control system. Poor efficiency and control performance are presented by current trial systems, which pressurize injection water by compressed air. In this paper, a novel water hydraulic system is developed applying an accumulator for energy saving. And a new differential pressure control method is proposed by using pressure cylinder and water hydraulic proportional pressure relief valve for back pressure control. Aiming at design of linear controller for injection water pressure regulation, a linear load model is approximately built through computational fluid dynamics(CFD) simulation on two-phase flow cavity filling process with variable temperature and viscosity, and a linear model of pressure control system is built with the load model and linearization of water hydraulic components. According to the simulation, model based feedback is brought forward to compensate the pressure decrease during accumulator discharge and eliminate the derivative element of the system. Meanwhile, the steady-state error can be reduced and the capacity of resisting disturbance can be enhanced, by closed-loop control of load pressure with integral compensation. Through the developed experimental system in the State Key Lab of Fluid Power Transmission and Control, Zhejiang University, China, the static characteristic of the water hydraulic proportional relief valve was tested and output pressure control of the system in Acrylonitrile Butadiene Styrene(ABS) parts molding experiments was also studied. The experiment results show that the dead band and hysteresis of the water hydraulic proportional pressure relief valve are large, but the control precision and linearity can be improved with feed-forward compensation. With the experimental results of injection water pressure control, the applicability of this WAIM system and the effect of its linear controller are verified. The novel proposed process of WAIM pressure control and study on characteristics of control system contribute to the application of water hydraulic proportional control and WAIM technology.     

USB数据采集系统在风压测试中的应用

介绍了基于USB数据采集系统构建风机风压自动测试的方法,同时设计了风压自动测试系统的硬件和软件,实现了风机性能试验中静压和全压的自动采集和处理,现场试验证明该数据采集设备具有测量数据可信,测量精度高,用户接口界面友好,操作方便,扩展灵活等特点.     

High-accuracy differential measurement of ultrasonic velocity in liquids

An improved technique for measuring very accurately the difference in sound velocity between two liquids is described. The technique, which can be used over a frequency range from 1 to 100 MHz, uses a differential cell that is completely submerged in a thermostatically controlled fluid and a phase-sensitive detection scheme accurate to 2x10(-4) signal periods. Measurements of the velocity difference between water and dilute NaCl solutions (3x10(-5) to 6.6x10(-4) M), accurate to +/-0.02 cm s(-1) (relative accuracy 1 part in 10(7)), are presented.     

Influence of Certain Vapors and Liquids on the Frictional Properties of Molybdenum Disulfide

The influence of certain vapors and liquids on the coefficient of friction of molybdenum disulfide has been studied under boundary conditions. The vapors investigated were those of water, butanol, benzene, and heptane. The liquids used were water, glycol, glycerol, dodecanol, dodecylamine, dodecane, hexadecane, ocladecane, white paraffin oil with and without additions of nonanoic acid and nonyl alcohol, and commercial mineral oil. The tests were performed on various friction testing machines, viz., on the LFW-1, LFW-2, Almen-Wieland, and Reichert machines. The test results show that the coefficient of friction of molybdenum disulfide is lowest in absence of the vapors or liquids studied, and under these conditions is independent of load. With increasing polarity of the vapor or liquid the coefficient of friction of molybdenum disulfide increases.