一种气泡流量超声波检测系统的研究

本文针对海底冷泉天然气渗漏参数进行数据采集的需要,利用超声波获取海水中被测对象的参数,研究出一种气泡流量超声波数据检测系统。同时,建立了模拟实验装置并进行了前期实验,验证了该系统的可行性,为工程实现提供了技术原型。

海底渗漏气泡流量测量过程的模糊控制

为了使海底天然气渗漏气泡流量测量过程具有稳定性和较高的测量精度,需要对气泡-水两相流介质的声场强度进行控制。根据测量装置的静态和动态特性以及声波线性传播方程,建立了声场强度的控制模型,针对被控环节的输入输出关系设计了模糊控制器。之后在MATLAB Simulink里面建立仿真模型,并进行了仿真实验。仿真结果表明,经过模糊控制器的调节,介质的声场强度可以跟踪被测介质中的气泡状态变化,其输出值的波动小于5%。该模糊控制器可用于海底渗漏气泡流量测量仪器的控制电路,从而实现了声波声场强度的控制。

基于气泡技术的阿牛巴式防堵抗腐污水流量计的设计

随着经济的快速发展,国家对水环境的污染治理越来越重视。现存污水流量计在进行流量检测时易受悬浮物、沉积物等杂质堵塞,影响测量结果。为了准确检测污水流量,以阿牛巴式传感器为基础,基于气泡技术,设计了具有防堵抗腐蚀的污水流量计进行流量测量。阐述了阿牛巴流量计的特点和测量原理,介绍了基于气泡技术的阿牛巴式防堵抗腐污水流量计的测量原理、硬件组成。

海底天然气渗漏流量声学测量方法及初步实验研究

测量每年海底渗漏释放到海洋水体及大气中的具有温室效应的甲烷的量具有重要的科学意义。文章提出了测量前调整气泡状态并用透射声波波形-幅度参数测量渗漏气泡流量的新方法。通过空间频谱分析得出声波测量窗口高度小于气泡流每秒上升的距离时,文章所设计的声波传感系统可以有效地测量气泡流速。根据求解声波方程的Born近似方法得出了气泡直径与测量声波波长的关系,该关系是确定测量系统结构参数的依据。实验表明,采用蜂窝芯板为主的结构可把气泡调整为直径小于3mm且空间分布均匀的状态,气泡流速测量精度可达±2%,透射声波幅度与截面含气率有近线性关系;初步验证了气泡流量测量方法的可行性。

液体区域控制单元流量控制阀在线更换可行性分析

液体区域控制系统(以下简称LZC系统)是重水堆的反应性控制机构之一,区域单元液位测量的准确性对反应堆的堆芯功率调节具有重要作用。液体区域控制单元流量控制阀故障会直接导致液体区域液位波动,影响堆芯功率调节功能。本文结合液位区域控制单元液位测量回路的构成及特点开展全面的风险分析和理论分析,通过构造恒定流动模型,计算出水在恒定流动下的流动时间并与实际的非恒定流动状态进行比较,分析了在线更换流量控制阀的可行性,对开展创新性维修工作有一定的指导意义。

Effects of bubbly flow on bending moment acting on the shaft of a gas sparged vessel stirred by a Rushton turbine

The bending moment acting on the overhung shaft of a gas-sparged vessel stirred by a Rushton turbine,as one of the results of fluid and structure interactions in stirred vessels,was measured using a moment sensor equipped with digital telemetry.An analysis of the shaft bending moment amplitude shows that the amplitude distribution of the bending moment,which indicates the elasticity nature of shaft material against bending deformation,follows the Weibull distribution.The trends of amplitude mean,standard deviation and peak deviation characteristics manifest an "S" shape versus gas flow.The "S" trend of the relative mean bending moment over gas flow rate,depending on the flow regime in gas-liquid stirred vessels,resulted from the competition among the nonuniformity of bubbly flow around the impeller,the formation of gas cavities behind the blades,and the gas direct impact on the impeller when gas is introduced.A further analysis of the bending moment power spectral density shows that the rather low frequency and speed frequency are evident.The low-frequency contribution to bending moment fluctuation peaks in the complete dispersion regime.

Improved Correlation for the Volume of Bubble Formed in Air-Water System

In order to address the bubble formation and movement in air-water two-phase flow,single bubble rising in stagnant water is experimentally studied by digital image processing.Bubbles are released individually from the submerged orifices with different diameters(1.81 mm,2.07 mm,2.98 mm,3.92 mm)at different detachment frequency.Images are recorded by a high-speed video camera and processed by digital image processing technique. The factors impacting the formed volume of bubble are discussed.The experimental results showed that a threshold of gas flow rate(400 mm 3 ·s- 1)divides the bubble formation into two regimes:the constant volume regime and the growing volume regime.Especially for the growing volume regime,the surface tension is taken into account.The bubble volume is consisted of two parts:the surface tension impacting part and the gas volume flow rate impacting part.An improved correlation for bubble volume prediction is developed for the two regimes and better coincidence with the experiment data than the previous models is obtained.

Numerical simulation on melt flow with bubble stirring and temperature field in aluminum holding furnace

The numerical model for predicting the flow and temperature fields of the melt in holding furnace with porous brick purging system were set up using Euler-Lagrange approach.In this model,bubbles coalescence and disintegration were ignored based on the dimensionless analysis,and the bubble size was assumed to be obedient to Rosin-Rammler distribution with a mean size of 0.6 mm.The results show that on reference operating condition,during the heating and agitation process,melt mixes well in the furnace,and the melt velocity increases with the increase of gas flux.Holding the melt for 30 min causes the max temperature in the bulk melt to increase to 60 K.After holding the heat,the agitation processing restarts,and it takes 10 min for the stratified melt to retrieve the homogeneous temperature field when the gas flux is 10 L/min,which shows deficient alloying and degassing in the melt.With the increase of gas flux from 10 to 20,30 and 40 L/min,the necessary recovery time decreases from 10 to 6,5 and 4 min gradually,which shows the improvement of the stirring efficiency.Depending on the processing purposes,for both good degassing performance and gas saving,proper operating strategy and parameters (gas flux,primarily) could be adjusted.

Effect of bubbles addition on teetered bed separation

To improve the separation efficiency of a conventional Teetered Bed Separator(TBS) in beneficiation of fine coal with a wide size range,an Aeration TBS(A-TBS) was proposed in this investigation.The bubbles were introduced to A-TBS by a self-priming micro-bubble generator.This study theoretically analyzed the effect of bubbles on the difference in hindered settling terminal velocity between different density particles,investigated the impact of superficial water velocity(V_(SW)) and superficial gas velocity(V_(Sg)) on bed fluidization,and compared the performance of the TBS and A-TBS in treating 1-0.25 mm size fraction particles.The results show that the expansion degree of fluidized bed which was formed by different size particles or has different initial height,is increased by the introduction of bubbles.Compared with the TBS,at the same level of clean coal ash content,the A-TBS shows an increase in the combustible recovery of clean coal,ash content of tailings,and practical separation density by 5.26%,6.56%,and 0.088 g/cm3 respectively,while it shows a decrease in the probable error(E_p) and V_(SW) by 0.031 and 3.51 mm/s,respectively.The addition of bubbles at a proper amount not only improves the separation performance of TBS,but also reduces the upward water velocity.

Local Measurement of Gas-Liquid Bubbly Flow with a Double-Sensor Probe

A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubble frequency and bubble interface velocity. The authors paid special attention to the probe design and construction for minimizing measurement errors. Measures were also taken in the design of sensor ends for preventing corrosions in the flow. This is an effort to improve the current double-sensor probe technique to meet the ever-increasing needs to local parameter measurements in gas-liquid two-phase flows.

如何选择合适的流量计

文章描述了气泡流量计、多谱勒流量计、传播时间流量计、旋涡流量计和电磁流量计的基本设计参数，强调了每一类型流量计的优缺点，而且还讨论了每一种计量技术的工艺应用，并列表对这五种类型流量计的性能特点进行了对比。本文的目的不是评价出一种最适用的流量计，而是为大家在实际应用中选择合适的流量计提供最基本的知识。

Evaporating Momentum Force and Shear Force on Meniscuses of Elongated Bubble in Microchannel Flow Boiling

The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically.The concept of the effective evaporation region and the theory of the liquid layer supplement between elongated bubble and microchannel are proposed,and the analytical expressions of the evaporating momentum force and shear force have been obtained.The relative importance of both forces has been determined by the method of magnitude analysis and numerical simulation.It has been found that the evaporating momentum force can always be neglected in analyzing the bubble elongation process and the motion law of meniscus of elongated bubble in microchannel flow boiling,but whether the shear force should be considered or not is determined by its relative order of magnitude and the particular conditions such as channel dimension and the operating conditions.