环形管流量计测量气液两相流研究

提出了一种基于环形管流量计的新型气液两相流流量测量方法.设计了多圈环形管流量传感器,通过对多圈环形管的水平直径上和垂直直径上四个差压信号进行分析,建立了不同位置差压信号与总体积流量和总质量流量的关系模型,并由此获得气液两相流的混合密度,实现了气液两相流分相流量的测量.     

新型内外管差压流量计弹状流双参数测量研究

为实现气液两相流相含率及流量的双参数测量,设计新型内外管差压流量计测量装置。利用该装置在单相水流量为1～11 m3/h范围内进行实验测试,拟合单相流出系数C的数学模型。单相水流量测量值与实际值的最大示值相对误差在±1.6%以内。气液两相流测量特性研究在水流量范围为2～6 m3/h,气流量范围为0.12～0.6 m3/h进行实验,在已知含率的情况下求得弹状流的两相总质量流量预测模型,通过分析压损比与XLM变化规律,分段建立压损比和Frg与XLM的数学模型,得到分相含率。预测结果表明:弹状流液相含率相对误差在±2%以内,两相总质量流量相对误差在±3%以内。通过差压及压损比实现相含率及流量的双参数测量,为气液两相流不分离测量提供一种参考方法。     

双锥流量计气液两相流空隙率测量研究

设计了一种结构简单、对加工工艺要求较低的双锥流量计,并用于气液两相流参数的测量.提取双锥流量计的差压波动信号的特征值,采用无量纲分析方法建立分相含率的测量模型,通过优化方法获得局部最佳的模型参数.在气液两相流实验装置上开展了实验研究.结果表明,所建立的分相含率测量模型可在一定的空隙率范围内对气液两相流含气率进行有效的测量.     

基于流体诱发管道振动的气液两相流型识别

通过对不同流型的气液两相流流经管道时诱发的管道振动特性的实验研究,提出了基于流体诱发振动的非接触式在线两相流流型识别新方法.通过安装于测试管道外壁的振动传感器测量不同流型下气液两相流诱发的振动信号;采用小波包分析提取了表征流型变化的振动信号能量特征向量;以能量特征向量作为模型输入,建立了概率神经网络模型用于识别分层流、...     

基于声发射技术的气液两相流相含率测量方法

气液两相流动广泛存在于石油、化工、管道运输、核反应堆等领域,利用声发射检测技术的非侵入式优势,对管内两相流动系统的进行无干扰,通过检测气液两相流动噪声,实现气液两相流相含率的测量。通过提取垂直管气液两相流流动噪声信号特征参数,在时域、频域分析方面分辨单相流动与两相流动的差别,研究两相流动的流动机理、流型过渡特性、流动噪声与流动形态之间的关系。在垂直管弹状流流型下,利用重标极差分析法(R/S分析法)对所测得垂直管气液两相流流动噪声进行分析,提取的垂直管两相流声发射信号作为输入量,利用支持向量机回归的方法,克服两相流声发射信号的非线性关系,成功建立相含率测量模型。     

基于近红外差压技术的气液两相流双参数测量

为实现气液两相流相含率及流量的双参数测量,对基于近红外光谱技术的轴向安装气液两相流测量装置进行优化。利用近红外吸收衰减技术实现两相流液相含率测量,同时结合差压技术通过测量实验管段前后差压值得到流量信息。利用该装置进行单相水、单相气的相关测试并得到单相流量测量模型,实验结果表明其相对误差分别在±1.25%和±1.5%以内。选取液相含率高于85%的35个工况点进行气液两相流动测试,结合朗伯比尔定律及双流体模型,分别得到相含率及流量预测模型。预测结果表明:上述模型的相对误差分别在±3.0%和±6.0%以内。通过结合近红外技术与差压技术,同时实现相含率及流量的双参数在线测量,为后续气液两相流不分离测量奠定基础。     

数学形态滤波在两相流差压信号分析中的应用

气液两相流信号作为非平稳信号,传统的滤波方法对其分析结果不理想。为了更好地研究其动态特性,采集水平管道内的两相流差压信号,利用数学形态方法对其进行滤波。通过分析滤波前后信号功率谱可知,泡状流40~100Hz之间的信号被作为噪声滤除,弹状流10~20Hz以及80~100Hz之间的信号被作为噪声滤除,塞状流20~30Hz之间的信号被作为噪声滤除。研究表明,数学形态滤波对两相流信号存在很明显的滤波效果,为进一步研究其动态特性奠定了基础。     

双锥流量计气液两相流测量模型研究

设计了一种直径比为0.8的新型双锥流量计.在管道内径为50 mm、干度范围为0.002 5～0.04的工况下,采用该流量计对水平管道气液两相流流量的测量进行了实验研究.在水流量标准装置上对该流量计进行了标定,分析了其流出系数.基于均相流和James模型,提出了一种混合密度的修正方法.利用双锥流量计的差压信号,分别对均相流模型、James模型以及修正的模型进行气液两相流总流量测量误差分析.实验结果显示,经密度修正的模型对总流量测量的相对误差可控制在6%以内,均方根误差为2.94%,表明修正后的模型可对总流量进行有效的测量,双锥流量计用于气液两相流测量可以获得较好的效果.     

基于子波分析的气液两相流中气含率的测量

用热膜风速仪以高于对应最小湍流时间尺度的分辨率精细测量环流反应器内不同空间位置的气液两相流瞬时速度信号,用子波分析的能量最大准则辨识气液两相流中的相.利用子波分析方法自动识别气液两相流中的相,从而获得测量气液两相流中气含率的切实可行的方法.     

气液两相入流条件下离心泵内部流动诱导特性实验研究

搭建了泵送气液两相流实验台,以比转速n_s=132.2的离心泵为模型进行气液两相入流条件下的流动诱导特性研究,获得了在不同进口含气率下的外特性和压力脉动、振动信号的频谱和概率密度图。研究结果表明:气液两相入流条件下,离心泵在小流量工况时的性能对气体更加敏感;模型泵在入流含气率超过8%以后,性能急剧下降且可测试的工况范围变窄并比较紊乱,能达到的最大入流含气率为10%;气液两相入流条件下,泵出口压力脉动主频仍为叶频,叶频处幅值随着进口含气率的增大而增大,含气率越大低频区的宽频特性越明显;压力脉动信号和振动信号均服从正态分布,随着进口含气率的不断增大,压力脉动的概率密度函数(PDF)幅值逐渐减小而压力幅值跨度逐渐变宽,振动的PDF幅值呈先增大,然后减小,在进口含气率为5%时达到最小(仍大于纯水工况),然后再增大的趋势,两者均可作为流态监测的重要依据。     

侧壁式压水室离心泵小流量非稳态旋转失速特性

用数值计算方法研究具有特殊结构的侧壁式压水室离心泵,分析小流量工况时模型泵的非稳态旋转失速特性,用快速傅里叶变换(FFT)获得压力脉动信号的频谱特征。结果表明,小流量工况时模型泵的扬程曲线呈驼峰状,压水室不同位置处压力分布不均;受叶轮旋转产生的非稳态作用影响,叶轮不同叶片流道内流动结构差异较大。不同流量下,叶轮内部分离涡结构诱发的激励频率各异,0.4ФN工况时模型泵压力脉动频谱图出现0.5fR及高次谐波频率,压力脉动最大幅值出现于4fR频率处;0.2ФN流量时非定常流动结构会诱发0.18fR及高次谐波频率;0.05ФN流量时压力脉动频谱图同时出现0.1fR、0.28fR两种激励频率。旋转失速现象出现时,频谱图中叶频处压力脉动幅值不再起主导作用。     

Decorrelation-based blood flow velocity estimation: effect of spread of flow velocity,linear flow velocity gradients,and parabolic flow

In recent years, a new method to measure transverse blood flow, based on the decorrelation of the radio frequency (RF) signals has been developed. In this paper, we investigated the influence of nonuniform flow on the velocity estimation. The decorrelation characteristics of transverse blood flow using an intravascular ultrasound (IVUS) array catheter are studied by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers; moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals were measured. The correlation coefficient method was used to present the results. Three velocity profiles were simulated: random spread of blood-flow velocity, linear blood-flow velocity gradient, and parabolic blood-flow. Radio frequency and envelope signals were used to calculate the decorrelation pattern. The results were compared to the mean decorrelation pattern for plug blood-flow. The RF signals decorrelation patterns were in good agreement with those obtained for plug blood flow. Envelope decorrelation patterns show a close agreement with the one for plug blood flow. For axial blood flow, there is a discrepancy between decorrelation patterns. The results presented here suggest that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow probably will not be affected by different transverse blood-flow conditions     

环形管流量计多点差压信号自动采集系统的设计

为多圈环形管流量计设计了一个多点差压信号的自动数据采集系统,可用于测量和记录环形管不同位置上差压测点的数据,进而确定各测点位置差压信号与总流量之间的关系,以及研究环形管流量系数的变化趋势.该数据采集系统具有测量精度高,采集速度快,数据实时保存等特点.     

Investigation of forced liquid flows in open capillary channels

We investigate a forced flow through an open capillary channel consisting of two parallel plates under microgravity condition. The aim of the experiments is to determine the maximal volume flux that can be withdrawn from the channel. The theoretical approach with a one-dimensional Bernoulli equation leads to a non-linear ordinary differential equation for the radius of curvature along the free surface of the channel. Both laminar and entrance pressure losses are taken into account as well as the flow conditions before the inlet of the channel. Several experiments with different channels and fluid properties were performed in the Bremen drop tower. The theory shows good agreement with the experimental data for a wide range of the non-dimensional parameters Ohnesorge number, gap ratio and channel length. The knowledge of the maximum volume flux is necessary to prevent gas ingestion at the channel outlet which is un-desired for applications in surface tension tanks.     

An Experimental Technique for the Analysis of Slug Flows in Pneumatic Pipelines Using Pressure Measurements

An experimental technique has been developed to measure the flow characteristics of slugs in dense phase pneumatic conveying using pressure measurements. This method is based on the unique characteristics of slug flows in pipes, i.e., an axial pressure fluctuation along the pipeline and a pressure difference in the radial direction at the back of a slug. Standard differential pressure transducers were used in this study and the influence of the finite response time of these transducers was considered. Experiments were conducted over a range of gas-solids flow conditions and experimental data were analyzed to describe the behavior of solids slugs through pipes. The calculated slug velocity and length using axial pressure measurements were confirmed by video recordings, and the synthesis between axial and radial pressure signals showed reasonable agreement in flow pattern analysis. This relatively simple measuring technique has been found effective in detecting solids slugs traveling through horizontal pipes and will distinguish various flow regimes. It provides a useful and easily applied tool for system optimizing and benchmarking in industrial applications.     

An Experimental Technique for the Analysis of Slug Flows in Pneumatic Pipelines Using Pressure Measurements

An experimental technique has been developed to measure the flow characteristics of slugs in dense phase pneumatic conveying using pressure measurements. This method is based on the unique characteristics of slug flows in pipes, i.e., an axial pressure fluctuation along the pipeline and a pressure difference in the radial direction at the back of a slug. Standard differential pressure transducers were used in this study and the influence of the finite response time of these transducers was considered. Experiments were conducted over a range of gas-solids flow conditions and experimental data were analyzed to describe the behavior of solids slugs through pipes. The calculated slug velocity and length using axial pressure measurements were confirmed by video recordings, and the synthesis between axial and radial pressure signals showed reasonable agreement in flow pattern analysis. This relatively simple measuring technique has been found effective in detecting solids slugs traveling through horizontal pipes and will distinguish various flow regimes. It provides a useful and easily applied tool for system optimizing and benchmarking in industrial applications.     

不同四塔组合形式对特大型冷却塔局部非高斯风压分布影响研究

非高斯脉动风压是引起冷却塔局部风荷载过大的重要因素之一,群塔干扰会显著改变冷却塔表面风压非高斯分布模式。四塔组合是火/核电厂冷却塔群最常见的组合形式之一,以在建世界最高冷却塔（220 m）为研究对象,针对工程中最典型的串列、矩形、菱形、L形和斜L形五种四塔方案进行刚体测压风洞试验。在此基础上,系统研究不同四塔组合形式冷却塔风压信号的幅域和时域特性,并针对考虑四塔干扰效应的冷却塔二维和三维峰值因子取值问题进行对比探讨,分析不同四塔组合方案对冷却塔风压非高斯特性的影响规律。研究表明,串列、矩形、菱形、L形和斜L形方案分别较单塔工况非高斯区域增加了11%、63%、56%、89%和30%,采用基于高斯分布假定的峰值因子法进行冷却塔群极值风压计算将引起较大的误差。串列和斜L形四塔方案峰值因子分布受塔群干扰影响较小,而矩形、菱形和L形方案峰值因子较单塔明显增大,部分区域峰值因子达到6.5以上。该文研究从机理上分析四塔组合冷却塔群局部风压过大的形成原因,也为进一步探讨不同四塔组合冷却塔群表面极值风压奠定了基础。     

Decorrelation characteristics of transverse blood flow along an intravascular array catheter

In recent years, a new method to measure transverse blood flow based on the decorrelation of radio frequency (RF) signals has been introduced. In this paper, we investigated the decorrelation characteristics of transverse blood flow measurement using an intravascular ultrasound (IVUS) array catheter by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers. Moving this scattering medium transversally across the acoustical beam represented flow. First-order statistics were evaluated, and the signal-to-noise ratio from the signals was measured. The correlation coefficient method was used to present the results. The decorrelation patterns for RF and for RF-envelope signals were studied. The decorrelation patterns from the RF signals were in good agreement with those obtained from theoretical beam profiles. This agreement suggests that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow can be assessed by measuring the ultrasound beam. A line of point scatterers, moved transversally across the acoustical beam (line spread function), can determine this decorrelation behaviour.     

基于EMD与神经网络的滚动轴承故障诊断方法

针对滚动轴承故障振动信号的非平稳特征，提出了一种基于经验模态分解(Empirical Mode Decomposition，简称EMD)和神经网络的滚动轴承故障诊断方法。该方法首先对原始信号进行了经验模态分解，将其分解为多个平稳的固有模态函数(Intrinsic Mode function，简称IMF)之和，再选取若干个包含主要故障信息的IMF分量进行进一步分析，由于滚动轴承发生故障时，加速度振动信号各频带的能量会发生变化，因而可从各IMF分量中提取能量特征参数作为神经网络的输入参数来识别滚动轴承的故障类型。对滚动轴承的正常状态、内圈故障和外圈故障信号的分析结果表明，以EMD为预处理器提取各频带能量作为特征参数的神经网络诊断方法比以小波包分析为预处理器的神经网络诊断方法有更高的故障识别率，可以准确、有效地识别滚动轴承的工作状态和故障类型。