一种测量气--液两相流的线列阵传感器设计

针对气—液两相流研究对含气率测量的需求,基于线列阵测量技术原理,设计了一种可移动式线列阵两相流测量传感器,该传感器具有较高的空间分辨率（3 mm）和极高的时间分辨率（2500 Hz）,设计了线列阵传感器标定和含气率算法,实现了瞬时二维局部含气率的测量。经过射流冲击试验验证表明：该线列阵传感器结构稳定,基于原始测量数据,采用标定和含气率求解算法,可计算气泡夹带现象在水平截面的平均含气率分布情况。     

气体流速流向传感器

设计并研制了一种气体流速流向测量传感器 ,流速测量范围为 3～ 30m/s,流向测量范围为± 45°。实验结果表明 ,流速测量的非线性度为 0 .5 %FS ,流向测量分辨率为 0 .45°。     

水平管段塞流相界面参数的超声相控阵测量及分析

段塞流是两相流的一种典型流型,其流动的间歇性、不稳定性在传输过程中会带来许多问题。本文采用超声相控阵技术对段塞流相界面进行了测量和分析。通过设计聚焦法则,确定扫描声束、偏转角度和实验参数,在气液两相流装置上开展了18种流动条件下的实验测量。结合扇扫界面的数据分析,利用四阶多项式方程拟合方法获取了气液相界面曲线,提取了两相界面中心点处液位高度和截面含气率两个特征值。结果表明,当气相表观流速一定时,随着液相表观流速的增加,液位高度增加。当液相表观流速一定时,随着气相表观流速的增加,液位高度下降。通过比较数据得出气相表观流速的变化对段塞流液位高度影响更加显著。此外,气相和液相表观流速滑差的增大会导致液位高度升高,截面含气率降低,气液表观流速之差较小时,气液界面波动较大,液位高度和截面含气率变化明显。该测量方法为段塞流流动参数测量奠定了基础。     

基于LS-SVM的多传感器气体质量流量测量

针对流量测量中流速分布不规则对气体流量测量精度的影响,提出了一种多传感器气体质量流量测量新方法。该方法基于均速管测量原理,在测量管道中按照对数线性法分布了4个热式气体流量传感器,采集不同特征位置的流量。通过流量标定实验,获得不同质量流量下测量管道内4个传感器的电压。然后利用GA和LS-SVM算法,将传感器电压和气体的质量流量作为训练集,建立了气体流量模型。实际测量中由4个传感器的电压计算出气体的质量流量。不规则流场的流量实验结果表明该方法是有效的。     

微机在电导法测量中的应用

本文研制了一种在气-液两相流和液相流中流动特性的在线测量系统,扩展了电导法的应用领域。它可以测量气泡速度、气泡直径、含气率、混匀时间和停留时间分布等;它对采集的数据进行实时的在线处理;每次采样只需几个微秒;整个系统结构简单、操作方便、实用性强。实验证实此法可行。     

固阀塔内颗粒夹带特性研究

对固阀塔内泡沫层中颗粒浓度分布及塔板上方分离空间颗粒夹带速率进行研究。实验表明在泡沫层内并不是所有颗粒都处于悬浮状态,悬浮颗粒浓度分布与泡沫层高度、颗粒粒径及气液流量等因素有关。颗粒悬浮百分含量与颗粒粒径和泡沫层高度成反比,与气体流量大小成正比。对于给定的表观气速和泡沫层高度,悬浮颗粒百分含量受液体内颗粒浓度影响较小。泡沫层表面颗粒浓度随着表观气速的增加和溢流堰高度的降低而增大。随气体流量增加及泡沫层表层颗粒浓度增大,颗粒夹带量会增加;随泡沫层高度增加,颗粒夹带量减少。泡沫层上方颗粒夹带速率受板间距、表观气速和泡沫层表层颗粒浓度影响较大。通过对颗粒在气泡尾涡内的受力分析,建立了泡沫层内颗粒浓度分布模型,并且结合塔板上方分离空间的雾沫夹带速率,建立了固阀塔板上方颗粒夹带速率模型     

方向选择性流速传感器研制

该文提出具有方向选择性并通过热平衡检测流速的方法,隔热套管与流体接触面之间平行安装,并保持有一特殊距离,实现方向选择性,通过检测流体接触面的温度来测量流体流速。用这种方法研制了一种单方向流速测量传感器,扩展用于构成三维风速传感器。该传感器可广泛应用于风力发电、气象预报、空间飞行器、工业锅炉等领域的气体和液体速度场、流量场测量。     

微小尺度射流流量传感器的设计与仿真分析

在许多新型传感器和微系统中均存在微量流体自动、精确地驱动和控制问题,而这有赖于微小尺度下对流量的精确测量。基于射流振荡原理设计了一种新型的无反馈通道微小尺度流量传感器,采用计算流体动力学(CFD)方法对该流量传感器的测量特性进行了仿真研究。通过观测振荡腔内部流场,分析了振荡器内部流动形态和射流振荡过程。通过对监测点压力变化曲线的分析,获得了不同入口速度下流体振荡频率,建立了流体流速与振荡频率的函数关系。研究结果表明,该微小尺度射流振荡器振荡平稳,主射流切换灵活,在较宽的流速范围内,流速与振荡频率具有线性关系,具有0.3%的较低的相对压力损失并可达到较小的测量下限,易于加工成型。     

温度分布测量装置

本发明阐述的是温度测量和显示装置。更具体地说,是关于无触点测温的装置。这种装置可以测量大面积的温度分布,并以很高的分辨率显示出示。这种装置进行无触点测温采用多个辐射测量传感器来实现。每个传感器都具有确定的视界,瞄准要测温的物体。传感器的输出信号经加工处理使其在要求的温度范围内产生最高的灵敏度,而在这个温度范围之外,灵敏度则很低,或者几乎没有。把经过处理和放大的每个传感器的输出信号加以比较分类,经过比较而产生的电信号送到列阵显示器,这个列阵显示器与每个传感器都连接。列阵显示器显示出温度范围,指示出每个传感器的输出信     

锁相放大技术在光学式甲烷气体传感器中的应用

设计了一种基于近红外可调谐半导体激光吸收光谱的光学式甲烷气体传感器,传感器针对甲烷气体位于1653.722nm处的吸收谱线,应用锁相放大技术提取微弱的一次谐波幅度信号,实现对气体浓度的测量。重点分析了在光学式甲烷气体传感器中应用锁相放大的原理及关键技术。结果表明该传感器响应时间为10s,测量精度可达0.02%VOL。     

A quantitative sub-grid air entrainment model for bubbly flows - plunging jets

The accurate prediction of air entrainment is critical in simulating various important multiphase (air/water) flows. In this paper, we present a sub-grid air entrainment model that quantitatively predicts the rate of air entrainment and subsequent disperse bubbly flow for a plunging jet. The derivation of this model is based on the two-stage (i.e., low and high liquid jet velocity) air entrainment mechanisms suggested by Sene [Sene KJ. Air entrainment by plunging jets. Chem Eng Sci 1988;43(10):2615-23]. This model was validated against extensive experimental data for water jets in air over a wide range of liquid velocities (from around 1 to 10 m/s) for the total rate of air entrainment. It was then implemented into an Eulerian/Eulerian two-fluid computational multiphase fluid dynamics (CMFD) model, wherein the liquid and the bubbles are modeled as two distinct continua. This multiphase model, supplemented by the new sub-grid air entrainment model, was used to predict the void fraction distribution underneath plunging water jets at different depths and water jet velocities. It was found that this approach yields results that match the experimental observations very well.     

A sub-grid air entrainment model for breaking bow waves and naval surface ships

Direct numerical simulations (DNS) of air entrainment by the breaking bow waves of naval surface ships are outside of the computational reach of the most powerful computers in the foreseeable future. This creates a need for physically-based models of air entrainment for applications in numerical simulations for ship design. Due to the non-linear dependence of the terminal bubble velocity with diameter most air entrainment flows have a high void fraction region immediately below the free surface. We present a model that locates this region employing the local liquid velocity and the distance to the interface. Using this model and the bubble size distributions measured by Deane and Stokes [Deane BD, Stokes MD. Scale dependence of bubble creation mechanisms in breaking waves. Nature 2002;418:839-44] we have simulated the air entrainment in the breaking wave experiments of Wanieski et al. [Waniewski TA, Brennen CE, Raichlen F. Measurement of air entrainment by bow waves. J Fluids Eng 2001;123:57-63]. Comparison against these experimental data is good. We then apply this model to simulate the flow around naval combatant DTMB 5415 and the research vessel Athena. The model predicts air entrainment in regions where it was actually observed at sea, namely the breaking bow wave, along the water/air/hull contact line and in the near-wake. To the best of our knowledge this is the first model of air entrainment that compares favorably with data at laboratory scale and also presents the right trends at full-scale.     

Prediction of penetration depth in a plunging water jet using soft computing approaches

The flow characteristics of the plunging water jets can be defined as volumetric air entrainment rate, bubble penetration depth, and oxygen transfer efficiency. In this study, the bubble penetration depth is evaluated based on four major parameters that describe air entrainment at the plunge point: the nozzle diameter (D _N), jet length (L _j), jet velocity (V _N), and jet impact angle (θ). This study presents artificial neural network (ANN) and genetic expression programming (GEP) model, which is an extension to genetic programming, as an alternative approach to modeling of the bubble penetration depth by plunging water jets. A new formulation for prediction of penetration depth in a plunging water jets is developed using GEP. The GEP-based formulation and ANN approach are compared with experimental results, multiple linear/nonlinear regressions, and other equations. The results have shown that the both ANN and GEP are found to be able to learn the relation between the bubble penetration depth and basic water jet properties. Additionally, sensitivity analysis is performed for ANN, and it is found that D _N is the most effective parameter on the bubble penetration depth.     

An expert system for predicting aeration performance of weirs by using ANFIS

A free overfall jet from a weir plunging into downstream water causes entrainment of the air bubbles if the free overfall jet velocity exceeds a certain critical value and hence aeration occurs. This study investigates the free overfall jets from triangular sharp-crested weirs and effect on their air entrainment rate and the aeration efficiency. An expert system based on adaptive network based fuzzy inference system (ANFIS) was obtained for predicting air entrainment rate and aeration efficiency of weirs. The performance of ANFIS model was compared with multi nonlinear and linear regression models. There were good agreements between the measured values and the values obtained using the ANFIS model.     

Unsteady viscous jet flow into stationary surroundings

The unsteady constant-property uniform pressure flow of a viscous laminar axisymmetric jet into stationary surroundings is analyzed with the aid of the boundary layer approximations and an integral method. Numerical solutions of the resulting non-linear system of equations are presented for the response of an initially steady jet to monotonic mass flow variations which are imposed at the initial axial station of the jet. Significant departures from quasi-steady behaviour arise for sufficiently large streamwise distances and/or rates of change of the boundary conditions. Among these effects are overshoots in mass and momentum flux, a dynamic effect on flow entrainment, and a tendency toward discontinous behavior. The influence of the kinematic viscosity on the transient flow is examined, and an estimate is made of the applicability of quasi-steady approximations in this problem.     

Induced co-flow and laminar-to-turbulent transition with synthetic jets

A detailed numerical solution of the fluid flow patterns engendered by a synthetic jet has been carried out. The synthetic jet is caused by a reciprocating piston assembly which is attached to a large, stationary cavity. It was found that a significant momentum efflux is produced by the synthetic jet assembly. Also, fluid entrainment by the synthetic jet causes a coincident flow around the exterior of the cavity (self-induced co-flow). Numerical solutions allow the investigation of the effect of reciprocation stroke length and piston speed on the resulting flow patterns and momentum flows. For all investigated cases, the contribution made by the co-flow to the momentum flowrate is found to be small. In order to account for the simultaneous existence of both laminar and turbulent regions, two numerical approaches were taken. One approach used the Shear Stress Transport (SST) turbulence model while the other used a newly devised transitional turbulence model. Of particular interest was a comparison between the predicted locations of the laminar-to-turbulent transition based on the two independent models. The excellent agreement between the two models reinforces the use of the SST model throughout the domain.     

A printed circuit board capacitive sensor for air bubble inside fluidic flow detection

This paper presents a three-electrode capacitive fluidic sensor for detecting an air bubble inside a fluidic channel such as blood vessels, oil or medical liquid channels. The capacitor is designed and fabricated based on a printed circuit board (PCB). The electrodes are fabricated by using copper via structure through top to bottom surface of the PCB. A plastic pipe is layout through the capacitive sensor and perpendicular to the PCB surface. Capacitance of sensor changes when an air bubble inside fluidic flow cross the sensor. The capacitance change can be monitored by using a differential capacitive amplifier, a lock-in amplifier, filter and an NI acquisition card. Signal is processed and calculated on a computer. Air bubble inside the liquid flow are detected by monitor the unbalance signal between the three electrode potential voltages. Output voltage depends on the volume of the air bubble due to dielectric change between capacitor’s electrodes. Output voltage is up to 53 mV when an 2.28 mm³ air bubble crosses the sensing channel. Air bubble velocity can be estimated based on the output pulse signal. This proposed fluidic sensor can be used for void fraction detection in medical devices and systems; fluidic characterization; and water–gas, oil–water and oil–water–gas multiphase flows in petroleum technology. That structure also can apply to the micro-size for detecting in microfluidic to monitor and control changes in microfluidic channels.     

气液两相流空隙率测量方法微重力环境应用研究

微重力环境下气液两相流空隙率测量是载人航天器需解决的关键技术之一。通过对当前常重力环境下气液两相流空隙率测量方法的特点和微重力环境对气液两相流空隙率测量的影响分析,提出了满足微重力环境气液两相流空隙率测量方法的基本要求,对当前空隙率测量方法在微重力环境应用的可行性进行了分析,并给出了相应建议。     

Development of a commercial code-based two-fluid model for bubble plumes

Bubble plume models are applied to study the de-stratification of lake water, aeration of reservoirs, wastewater treatment, and gas injection into liquid metals. Several existing models exemplify numerical modeling as problem-specific art, solve a mixture momentum equation, and have limitations in the availability of documentation, definition of boundary conditions, and post- and pre-processing capabilities. The transfer of problem-specific models to a client or to a multidisciplinary research and development team is a difficult process. The questions addressed in this study were as follows: (a) can one use a commercial code as a basis to develop a user-friendly, efficient model that simulates two-phase flow in bubble plumes? (b) what are the capabilities and limitations of such a model?The two-fluid model developed has flexibility in the definition of the multiphase and viscous models, easily understood definition of boundary conditions, simple definition of spatial dimensionality and time dependency, efficient numerical solution, clear documentation and user-friendly pre- and post-processing capabilities. Water and air phase velocities, water turbulent kinetic energy, and air volume fraction are predicted with accuracy similar to that of existing problem-specific models. A strategy to overcome some under-dispersion and include air–water mass transfer effects through user-defined functions is discussed.