流量计量仪表软维护中的若干问题

文章从贯彻执行流量测量有关标准和规程出发,阐述了统一流量数学模型和计算参数的问题,以及应用流量测量工具软件对流量测量系统进行评估和管理.     

湿度对临界流文丘利喷嘴流量特性的影响

本文分析了湿度对临界流文丘里喷嘴的流出系数、湿空气的气体常数和等熵指数的影响,对不同来流条件下由此引起的流量测量误差进行了计算,并给出空气质量流量的准确计算方法。计算结果表明：空气湿度对喷嘴流出系数的影响很小,工程测量中往往忽略不计,而湿空气的气体常数与等熵系数对质量流量的影响却可达１．１％,是不可忽视的,需进行正确的修正。     

旋进漩涡流量调节装置流量调节特性研究

采用实验方法,对旋进漩涡流量计-锥形阀组合式流量调节装置的流量测量与调节特性,进行了研究.首先在有无锥形阀情况下,对旋进漩涡流量计的输出特性进行了测试,发现无论上游有无锥形阀,所测得压力信号的脉动频率与流量之间均呈现良好的线性关系,且同一流量时,锥形阀的存在引起的压力脉动频率变化小于5%.测量结果说明,在这种组合式的流量调节装置中,旋进漩涡流量计能够正常工作.装置的流量调节特性测试中,在进口压力为0.11～0.23MPa、阀芯行程0～8mm的范围内,测量了流量的变化情况.结果发现,进口压力不变时,流量随着开度的增大而增大,流量与开度之间呈线性关系;当进口压力增大时,通过的流量也增大;反之亦然.     

准确度为万分之五的流量标准装置系统的分析

流量测量是民航油料行业经营、管理必不可少的手段之一。流量参数是计算加油量的重要参数之一。目前，民航油料系统普遍采用准确度为of％的二等标准流量计对准确度为0．2％的工作流量计进行量值传递，而准确度为0．l％的二等标准流量计的溯源问题始终难于解决。为了统一民航油料流量量值、开展量值传递、满足民航油料事业的发展对流量测量的要求，中国航空油料华北公司建立了准确度为万分之五的流量标准装置。装置的组成及工作原理1．标准装置的原理图（见右图）。2．标准装置的工作原理门）被检流量计测得的体积值的确定该装置是采用比较法…     

调节阀的流量特性校正

由于在控制系统设计时一般都假定调节阀前后压差为常数,而实际上压差总会随着阀的开度变化而变化,这种误差会导致调节阀流量特性的畸变,对系统的控制性能有一定的影响。通过设计调节阀的流量特性校正装置,可以较好地克服调节阀的畸变,使调节阀的工作特性维持在比较理想的工作状态。实验证明这种校正对阀的工作特性改善非常明显。     

短管节流流量特性实验研究

通过毛细管与短管节流气态流量特性的实验研究,对比分析两者的气态流量特性,得出节流短管气态流量与孔径的函数关系,证明节流短管内制冷剂的流量函数与N2的流量函数类似,短管节流与毛细管节流具有相似的气态流量特性,可以将节流短管当作长度较短的毛细管进行研究。     

间冷冰箱风道系统流量分配特性的模块化计算方法

本文提出了一种用于计算间冷冰箱风道系统流量分配特性的模块化计算方法。首先将整体风道根据风道串并联位置划分成若干个模块,单独得出每个模块的流量阻力特性公式,其次将各模块按照冰箱实际串并联关系连接成网络,根据网络图构建模块的流量阻力方程并联立求解,最终获得整个风道系统的流量分配特性。通过实验对模型进行了验证,结果表明应用模块化计算方法得出的系统风量值与实验测量值误差在5%以内。风道系统流量分配特性的模块化计算方法具有计算准确、方便建模与求解、通用性强等优点,可应用在间冷冰箱的实际设计中。     

主动式活塞体积管流量标准装置阶跃特性研究

动态流量测量在研发和生产过程中越来越重要,为了开展流量计的动态响应特性相关试验,使用激光干涉仪对燃油流量标准装置的活塞位移进行了动态测量,并分析了该装置的阶跃特性。试验结果表明,在一定阶跃流量范围内,该装置的时间常数在7~60 ms之间。建议进一步优化装置的传动结构和伺服控制参数,改善装置的阶跃特性。     

气管道流量特性参数理论分析与实验研究

 根据ISO6358关于流量特性参数声速流导C值和临界压力比b值的定义,结合相关气动理论,给出了气管道流量特性参数的计算方法,并编制了相应的计算机程序进行了仿真。利用仿真结果和最小二乘拟合方法,提出了计算气管道流量特性参数的近似公式,并通过实验进行了验证。     

气缸缓冲特性计算机辅助测试系统

 为研究气缸缓冲特性计算机辅助测试(CAT)系统，设计了气动回路、电磁阀驱动电路。配置了虚拟仪器的硬件，用LabVIEW 设计虚拟仪器的软件． 此CAT 系统可以测试气缸的压力、输出力、位移和振动加速度，并绘制相应的实验结果曲线．实验表明此CAT 系统操作简便、测量精度高、实用性强，可对缓冲特性、速度特性、瞬态特性等多种气缸性能进行检测．     

大功率气动元件综合试验台的设计

 介绍了一种大功率气动元件综合试验台的主要结构、控制方式及其数据采集处理方法．此实验台的建立为研究设计高性能新型气动元件提供了可靠的保证．     

气动肌肉驱动关节参数的优化设计

 在气动肌肉驱动关节的设计中,关节参数的确定通常采用试凑法,此时不能保证结果是最优的．为解决这个问题,提出了确定最佳参数的图示解法,利用气动肌肉的等压特性曲线求得气动肌肉的最佳初始长度．在关节直径的设计中,为保证能够得到最大转角,对关节直径进行了优化分析．提出的方法具有简便易行的特点．     

气动弯曲关节的特性研究

 通过应用弹性力学理论来确定人造气动弯曲关节的弯曲角度和压缩空气压力之间的关系． 建立了系统的数学模型，并且通过数字仿真从理论上研究系统的脉冲响应．通过实验方法测试表明，这种人造关节对于信号的输入具有快速的响应，并且适合模拟人体关节的弯曲和伸展运动．     

Flow characteristics and flow rate prediction of pulverized coal through a regulation valve

In this paper, experiments of dense-phase pneumatic conveying of pulverized coal were carried out in an industrial-scale system to study the control characteristics of the regulation valve and to predict the solid mass flow rate. Firstly, effects of valve sweeping gas on conveying stability and solid mass flow rate were investigated and the optimum valve sweeping gas was determined. Second, effects of valve opening on pressure distribution and solid mass flow rate were investigated by conducting experiments at different conveying pressure drops and different valve openings. A good linear relationship between the valve pressure drop ratio and the valve opening was found, and as the valve opening increased from 13 % to 70 % the solid mass flow rate increased gradually. Limit operating conditions of the regulation valve including flow blockage and control failure were consequently determined and analyzed. Finally, a robust model was established to predict the solid mass flow rate by introducing the valve sensitivity coefficient into the traditional pressure drop ratio model. The model can predict the solid mass flow rate well by providing errors mostly within ± 10 %. This study will provide certain reference for solid mass flow rate regulation in the dry coal gasification process.     

新型船用气动数字阀动态特性仿真的MATLAB实现

新型船用气动数字阀属于闭环机构的结构设计,所以要同时提高它的稳定性、快速性和精度等性能指标是不可能的,改变阀机构的模型结构参数和工作参数对上述性能指标的影响也是非线性、非单调的。因此,为了提高该数字阀的综合性能,必须对其特性作进一步的分析。通过MATLAB编程对该数字阀动态特性进行仿真,仿真结果对工程实践有一定指导意义,对类似的研究项目也有一定的参考价值。     

The effect of oscillating flow on a horizontal dilute-phase pneumatic conveying

ABSTRACT

A horizontal dilute-phase pneumatic conveying system using vertically oscillating soft fins at the inlet of the gas–particle mixture was studied to reduce the power consumption and conveying velocity in the conveying process. The effect of different fin lengths on horizontal pneumatic conveying was studied in terms of the pressure drop, conveying velocity, power consumption, particle velocity, and intensity of particle fluctuation velocity for the case of a low solid mass flow rate. The conveying pipeline consisted of a horizontal smooth acrylic tube with an inner diameter of 80 mm and a length of approximately 5 m. Two types of polyethylene particles with diameters of 2.3 and 3.3 mm were used as conveying materials. The superficial air velocity was varied from 10 to 17 m/s, and the solid mass flow rates were 0.25 and 0.20 kg/s. Compared with conventional pneumatic conveying, the pressure drop, MPD (minimum pressure drop), critical velocities, and power consumption can be reduced by using soft fins in a lower air velocity range, and the efficiency of fins becomes more evident when increasing the length of fins or touching particles stream by the long fins. The maximum reduction rates of the MPD velocity and power consumption when using soft fins are approximately 15% and 26%, respectively. The magnitude of the vertical particle velocity for different lengths of fins is clearly lower than that of the vertical particle velocity for a non-fin conveying system near the bottom of the pipeline, indicating that the particles are easily suspended. The intensities of particle fluctuation velocity of using fins are larger than that of non-fin. The high particle fluctuation energy implies that particles are easily suspended and are easily conveyed and accelerated.     

流量控制电磁阀的小流量特性分析

介绍可调无级输出流量控制电磁阀在小流量输出区域的输出原理与特性。通过改变小流量区域的流道几何结构,改变电磁阀小流量区域的流量性能。     

Dynamical characteristics of wave-excited channel flow

This paper is part of a study on the receptivity characteristics of the shear flow in a channel whose walls are subjected to a wave-like excitation. The small amplitude forced wavy wall motion is characterised by a wave number vectorλ ₁,λ ₂ and a frequencyω _g . The basic flow in the problem is a superposition of the Poiseuille flow and a periodic component that corresponds to the wave excitation of the wall. The aim of the study is to examine the susceptibility of this flow to transition. The problem is approached through studying the stability characteristics of the basic flow with respect to small disturbances. The theoretical framework for this purpose is Floquet theory. The solution procedure for solving the eigenvalue problem is the spectral collocation method. Preliminary results showing the influence of the amplitude and the wave number of the wall excitation on the stability boundary of the flow are presented.     

任意分布参数的机械零件的可靠性稳健设计（一）：理论部分

 将可靠性优化设计理论、可靠性灵敏度技术和稳健设计方法相结合，讨论了具有任意分布参数的机械零件的可靠性稳健设计问题，提出了可靠性稳健设计的计算方法．把可靠性灵敏度融入可靠性优化设计模型之中，将可靠性稳健设计归结为满足可靠性要求的多目标优化问题．在基本随机参数的前四阶矩已知的情况下，通过计算机程序可以实现具有任意分布参数的机械零件的可靠性稳健设计，迅速准确地得到具有任意分布参数的机械零件的可靠性稳健设计信息。