同轴差速式热量表的结构设计

文章介绍了一种用于采暖供热系统进行热计量的同轴差速式热量表的工作原理．结构组成、应用特点．重点介绍了同轴差速式热量表的结构组成及其运作过程。     

基于AMESim的大流量调距桨液压系统泵源设计与分析

针对船舶主机PTO转速不断变化,调距桨液压系统流量变化较大的情况,设计了三联齿轮泵组合式泵源以满足系统快速调距时的大流量和精确调距时小流量的需求。对使用此组合式泵源液压系统进行仿真计算和分析,结果表明三联泵泵源可以满足调距桨液压系统的流量变化要求。同时对影响泵源流量特性的相关参数和系统热性能进行了分析,其结果为组成泵源的元器件和系统换热器选型提供参考依据。     

差压式流量传感器测量一般气体流量时的温度压力补偿方法

简要介绍使用差压式流量传感器进行一般气体流量测量时的温压补偿方法;指出了差压方式流量传感器测量一般气体的通用流量温压补偿公式,并写出了公式的推导过程;与线性流量传感器温压补偿方法进行对比,强调指出了采用差压式流量传感器时进行温压补偿的注意要点.对公用工程中的一般气体的流量计量工作有一定的指导作用.     

基于虚拟仪器技术的温差测定仪及其应用

介绍了基于虚拟仪器技术的温差测定仪及在燃烧热实验中的应用,该虚拟温差测定仪不仅在测量精度、自动化程度和成本方面是传统温差仪无法相比的,而且还具有自动数据处理、多通道同时测量、整个系统一次性标定、便于系统集成等优点。     

Application of small size cavitating venturi as flow controller and flow meter

The cavitating venturi is using to provide constant mass flow rate of liquid which is passing through a passage, independent of downstream pressure changes. The flow rate is a function of the upstream pressure, the throat area, the density and saturation pressure of the liquid. An experimental setup with capability of supplying water flow rate and constant upstream pressure was designed and manufactured. Three cavitating venturis with throat diameter of 5, 2.5, and 1 mm were designed and built to investigate the effect of venturi size on its mass flow rate. Three different sets of experiments were conducted to investigate the performance of the venturis. In the experiments, the mass flow rates were examined under different downstream and upstream pressure conditions and time varying downstream pressure. The results show for the ratio of downstream pressure to upstream pressure less than 0.8, the mass flow rate is constant and independent of the downstream pressure. Whenever the pressure ratio exceeds 0.8, the venturi acts like an orifice. This pressure ratio has been predicted analytically to highlight the affecting parameters, mainly the geometry of the venturi and viscous losses. It is found that the venturi size has no effect on its expecting function to keep mass flow rate constant. Also, it is shown that by applying a discharge coefficient and using only upstream pressure, the cavitating venturi can be used as a flowmeter with a high degree of accuracy in a wide range of mass flow rate.     

Application of variable area cavitating venturi as a dynamic flow controller

The variable area cavitating venturi is an effective means to throttle the mass flow rate of liquid. The mass flow rate is a function of the upstream pressure, the pintle stroke, the density and saturation pressure of the liquid, independent of the downstream pressure. In this paper, a variable area cavitating venturi is designed and four different sets of experiments are conducted to investigate the performance of the variable area cavitating venturi. In these experiments, the mass flow rates are examined under different pintle positions, upstream pressures, downstream pressures and dynamic motions of the pintle. The experimental results indicate that the mass flow rate is independent of the downstream pressure when the ratio of the downstream pressure to upstream pressure is less than 0.8. The mass flow rate is almost linearly dependent on the pintle stroke for a constant upstream pressure. The discharge coefficient is a function of the pintle stroke, whereas the upstream and downstream pressures have rare influence on the discharge coefficient. The variable area cavitating venturi can control and measure the mass flow rate dynamically by determining the pintle stroke and the upstream pressure.     

A文件浅深层地温数据查异软件

在李氏地面气象月报辅助审核软件(1.0)版本的基础上,利用Visual Basic 6.0[1]计算机编程语言编写扩展了A文件40~320cm浅深层地温数据的查异功能,增设了地温层遇强降水出现小时温度突变时数据查异的多个临界筛选值,满足了各地气象台站在旱涝等不同天气状况下对各地温层数据的查异要求,有效地提高了软件的实用性和气象月报表的审核效果。     

温度补偿法在流量控制和标准气稀释中的研究及应用

分析了质量流量控制器中温度变化所引起的流量变化理论值与实际值之间的关系,提出一种实用的梯度温度补偿方法,即将环境温度划分为若干梯度,针对每一梯度配置不同修正系数,有效消除环境温度变化对标准气配气仪精度的影响。实验结果表明,该方法解决了环境温度的干扰问题,保证了流量控制及标准气稀释的精度,为其它温度敏感设备提供了参考。     

On the measurement of temperature and recovery factor in high-speed subsonic duct flow

The measurement of temperature in compressible flows is complicated by the fact that the dynamic component of temperature can be significant and may be difficult to discern from the sensor temperature. A so-called recovery temperature is measured when only a portion of the dynamic temperature is recovered at the sensor. Since it is normally the static (thermodynamic) temperature that is sought, it is essential to convert the temperature measured by a sensor into static temperature or, alternatively, to understand what the sensor temperature represents. To this end, experiments and computational fluid dynamics simulations have been conducted for moderate Mach number (0.3 < Ma < 0.6) airflow through a narrow duct (tube) wherein the temperature measured by a simple thermistor sensor is compared to the total temperature simultaneously measured by a highly-accurate instrument. An analytical approach is then presented to evaluate the local static temperature and recovery factor from measurements of mass flowrate, total temperature and local static pressure. The results show that the recovery factor is dependent on whether the sensor tip is aligned with the tube inner wall or protruding into the airflow. The results also confirm that accurate results are obtained for static temperature derived using the proposed approach.     

一种新型的快速无超调预测控制器及其应用

该文采用一种比例积分型结构，建立了一种无超调预测控制器，通过钻杆热处理的退火过程控制的仿真研究，验证了该控制器的有效性。     

Numerical solutions for unsteady flow past a semi-infinite inclined plate with temperature oscillations

A study of the velocity and thermal boundary layers on a semi-infinite inclined plate with temperature oscillations is presented in this work. The non-linear, coupled parabolic integro-partial differential equations governing flow and heat transfer have been solved numerically using an implicit finite difference scheme of Crank-Nicolson type. The numerical values for the flow field, temperature, shearing stress, and heat transfer coefficients are presented in a graphical form. It is observed that the velocity and temperature profiles decrease as the frequency parameter increases. This paper was recommended for publication in revised form by Associate Editor Yang Na G. Palani received his B.Sc. and M.Sc. degrees from Madras University, India, in 1991 and 1993, respectively, and his Ph.D. degree from Anna University, India in 2001. Dr. G. Palani is currently a Post Doctoral Research Fellow at the School of Mechanical Engineering of Inha University in Incheon, Korea. Kwang-Yong Kim received his B.S. degree from Seoul National University in 1978, and his M.S. and Ph.D. degrees from the Korea Advanced Institute of Science and Technology (KAIST), Korea, in 1981 and 1987, respectively. He is currently a professor and the chairman of the School of Mechanical Engineering of Inha University, Incheon, Korea. Professor Kim is also the current editor-inchief of the Transactions of Korean Society of Mechanical Engineers (KSME), the editor-in-chief of the International Journal of Fluid Machinery and Systems (IJFMS), and the chief vice president of the Korean Fluid Machinery Association (KFMA). He is likewise a fellow of the American Society of Mechanical Engineers (ASME).     

快速再制造成形温度场模拟中的热源模型对比研究

介绍了基于快速成形的熔覆快速再制造系统,对成形温度场模拟中的两种热源模型,即高斯热源模型和双椭球热源模型,使用单元生死技术模拟熔覆区动态成形过程,并做了相应的成形试验,采集了温度数据,将两种热源下的温度场数据进行对比.研究结果表明,双椭球热源模型的模拟结果更加接近试验结果.