两相流电容层析成象技术研究

本介绍了两相流的电容层析成象方法,研究了电容测量技术和实现该技术的电路;并了电容层析成象的计算机仿真过程;最后给出了工程实现的流程图。     

两相流电容层析成像系统

本文较系统地介绍了电容层析成像系统结构原理,包括抗杂散电容影响的微小检测技术,并行数据采集与处理单元设计以及基于总变差正则化的图像重建算法.与此同时,结合研制的双截面电容成像系统进行试验研究,结果表明该系统不仅可给出实时流型识别,同时能输出表征的特征参数.     

两相流电容层析成像系统

本文较系统地介绍了电容层析成像系统结构原理,包括抗杂散电容影响的微小检测技术,并行数据采集与处理单元设计以及基于总变差正则化的图像重建算法.与此同时,结合研制的双截面电容成像系统进行试验研究,结果表明该系统不仅可给出实时流型识别,同时能输出表征的特征参数.     

用于气固两相流在线测量的ECT电容测量电路

电容层析成像(ECT)技术是目前最具发展前景的多相流参数检测方法.介绍了12电极ECT成像系统的测量原理及设计方法.研制了一种交流激励的微电容测量电路,该电路具有较强的抗杂散电容性能、结构简单、容易实现等优点,较好地解决了电子开关的电荷注入效应对测量分辨力的影响问题.经试验证明可达到的实际分辨力为0.04fF.     

油水两相流浓度电容层析成像的测量方法

以8电极油水两相流电容层析成像系统为研究对象,分析了油水两相流电容层析成像系统的测量原理,依据二重积分微元原理建立了油水两相流相浓度分布信息的数学模型,采用ART图像重建的方法完成油水两相流的浓度测量,并在重建算法中引入了阈值以提高图像重建质量和含率计算的准确性,测量误差在1%左右,较好地解决了其他测量方法速度慢,成本高,安全性差等缺陷,为油水两相流浓度的测量提供了一种新方法.     

A Capacitance Ultrasonic Transducer With Micromachined Backplate for Fast Flow Measurements in Hot Pulsating Gases

A novel high-temperature resistant capacitance ultrasonic transducer is presented. It is designed for an ultrasonic transit-time gas flowmeter and meets two main requirements not fulfilled by common piezoelectric transducers: First, a special construction based on an oxidized and patterned silicon backplate combined with a metallic membrane enables transducer operation at elevated gas temperatures of up to 600$^circhboxC$. Second, the geometry and material parameters were chosen to obtain a broadband device that allows high signal slew rates and pulse repetition rates. As proven by measurements in an automotive combustion engine test bed environment, this new transducer suits for internal combustion engine exhaust flow measurements in between the catalytic converter and the end of the exhaust pipe. Preliminary results for the exhaust mass flow (up to 160 kg/h) of a typical automotive engine measured with these novel transducers are given and compared with the mass flow calculated from fuel consumption and air/fuel ratio$(lambda)$.     

两相流流型辨识方法研究

本文提出了一种基于模糊聚类分析和神经网络辨识两相流流型的新方法。该方法首先通过对极板电容测量数据进行聚类分析,然后根据聚类结果和电容值的隶属度,利用神经网络进行流型辨识。仿真结果表明：此方法在两相流流型辨识中具有较高的判别精度和较快的软件运动速度,为两相流流型在线辨识提供了一种有效的手段。     

Low-Noise Signal Processing Chain for High Capacitance Sensors

A low-noise readout array is proposed for use with high capacitance detectors. The readout array is composed of a preamplifier/amplifier chain. The signal processing chain is designed for use with CdZnTe gamma ray detectors employed by NASA for radiation detection. This approach employs correlated double sampling and capacitive matching to increase the signal-to-noise ratio (SNR). The readout array is custom designed to fit into one detector pixel. The preamplifier/amplifier chain is designed and fabricated in 0.13 $mu$m CMOS8RF IBM technology. The readout array results show that the SNR is significantly improved compared to previous work done in this field.      

The Use of Capacitance Sensors for Phase Percentage Determination in Multiphase Pipelines

A variety of capacitance designs are considered for determining the volume fractions in two-phase pipelines. Experimental results are compared for the most promising structures and for slug (SL) and stratified (ST) flow patterns. It is concluded that the most practical linear sensor is the double helix capacitance, although in some instances a four concave-plate structure may be preferred for greater sensitivity and simplicity of construction if the flow pattern is known.     

用于两相流测量的差动自相关测量系统研究

本文提出了差动自相关测量两相流流速的新方法,介绍了所使用的电容式传感器及其测量电路的原理.应用所研制的传感器及测量系统做了大量实验,并给出了实验结果.     

A Model of Polydisperse Vapor–Droplet Mixture Flow in a Vortex Chamber

Journal of Engineering Physics and Thermophysics - A thermo- and hydrodynamic model of polydisperse vapor–droplet mixture flow in a vortex evaporation chamber has been described. The motion...     

Regimes of Two-Phase Flow in Short Rectangular Channel

Experimental study of two-phase flow in the short rectangular horizontal channel with height 440 μm has been performed. Characteristics of liquid motion inside the channel have been registered and measured by the Laser Induced Fluorescence technique. New information has allowed determining more precisely the characteristics of churn regime and boundaries between different regimes of two-phase flow. It was shown that formation of some two-phase flow regimes and transitions between them are determined by instability of the flow in the lateral parts of the channel.     

A Digital Special-Purpose Signal Processor for Two-Phase Flow Real-Time Analysis

In the statistical study of two-phase flow real-time control of experiments is often needed. Furthermore, in industrial processes involving boiling units control or two-phase gas-liquid transport control, real-time signal processing is required to check the status of two-phase flows. An instrument is described for the measurement of the fundamental characteristic parameters of two-phase flows. The measurement technique employs extensively high speed digital computation. It is based on a discrimination of the probe output signal into two signals, representing, respectively, a "bubble" flow and a slug flow. The parameters are measured on averaging times ranging from 10 ms to 104 s. Measurement errors and limitations of this high-resolution measurement technique are pointed out. Its utility in evaluating the fundamental statistical parameters of two-phase flows is demonstrated.     

Further Developments in the Photography of Two-Phase Gas-Liquid Flow

Equipment and techniques for photography of two-phase flow are described. The application of photography to the determination of flow patterns, to the study of climbing and falling liquid film systems and to the study of two-phase flow accompanied by vapour generation, is discussed. The work has included the use of X-radiography, the use of microscopic techniques in studying the interface of a falling film, the use of axially directed photography in evaluating climbing film flow and the use of photography in studying droplet mass transfer.     

Accurate Thermal Conductance and Impedance Measurements of Transition Edge Sensors

Past measurements of the thermal coupling of superconducting transition edge sensor (TES) calorimeters suspended on SiN membranes produced wide-ranging values for the exponent of the thermal coupling through the membranes. We present a measurement technique that is less susceptible to current dependence of the phase transition than the previous measurements. An initial measurement produced the expected exponent for a 2-D phonon gas: thermal conductance is proportional to T ². In doing these measurements, we employ a modification to Lindeman’s equivalent circuit technique for measuring TES complex impedance.      

板翅式换热器两相流封头设计及其分配特性

提出了三种两相流板翅热器封头形式，即水帘式，打孔管式，孔板工，在允许的压降范围内，明显改善了两相流分配的不均匀状况。实验结果表明，孔板式封头的两相分配性能最佳。     

Automated Digital Measurements of CV Curves and Derivatives, and of Capacitance Transients for Semiconductor Evaluation

A system of instruments is presented for automated digital measurements of voltage and/or time dependent capacitances. The system has been designed for the evaluation of semiconductor materials and devices. It is based on a fast capacitance-inverse-to-frequency converter (FCFC), where a direct conversion is obtained with high accuracy, and where the device to be tested can be subject to dc, modulated, and pulsed voltage bias. The output frequency (of the order of 1 MHz) accurately foliows capacitance variations, even if occurring in short times (less than 100 Ms). Biasing circuits, a multichannel scaler, and logic interface circuits complete the system. Stationary and nonstationary CV curves and time variations of capacitances can be accuratety measured. The precision can be improved by averagng over many repetitions of the measurement. Derivatives (first and higher orders) of CV curves can also be directly and accurately measured by using a technique based on voltage modulation and synchronous reversible counting. This feature also makes it possible to obtain accurate measurements of doping profiles in semiconductors. Representative experimental results obtained with the system are shown.