An Experimental Study of the Flowrate Transients in Slug Flow

An investigation of the characteristics of flowrate transientswithin slug flow was conducted in a large- scale outdoor testingfacility. The test section consisted of a 378 m long, 7.62 cmdiameter stainless steel pipe. Air and water were used as the testfluids. The response to a change of flowrate of either phase or twophases Was measured using a series of pressure transducers anddifferential pressure transducers. An increase or decrease In gasflowrate caused a pressure overshoot above the value at new steadystate or led to a pressure undershoot To form a temporary stratifiedflow.

Flowrate behavior and clustering of self-driven robots in a channel

In this paper,the collective motion of self-driven robots is studied experimentally and theoretically.In the channel,the flowrate of robots increases with the density linearly,even if the density of the robots tends to 1.0.There is no abrupt drop in the flowrate,similar to the collective motion of ants.We find that the robots will adjust their velocities by a serial of tiny collisions.The speed-adjustment will affect both robots involved in the collision,and will help to maintain a nearly uniform velocity for the robots.As a result,the flowrate drop will disappear.In the motion,the robots neither gather together nor scatter completely.Instead,they form some clusters to move together.These clusters are not stable during the moving process,but their sizes follow a power-law-alike distribution.We propose a theoretical model to simulate this collective motion process,which can reproduce these behaviors well.Analytic results about the flowrate behavior are also consistent with experiments.

Analysis on optimal working fluid flowrate and unstable power generation for miniaturized ORC systems

For efficient utilization of a limited geothermal resource in practical projects,the cycle parameters were comprehensively analyzed by combining with the heat transfer performance of the plate heat exchanger,with a variation of flowrate of R245 fa.The influence of working fluid flowrate on a 500 W ORC system was investigated.Adjusting the working fluid flowrate to an optimal value results in the most efficient heat transfer and hence the optimal heat transfer parameters of the plate heat exchanger can be determined.Therefore,for the ORC systems,optimal working fluid flowrate should be controlled.Using different temperature hot water as the heat source,it is found that the optimal flowrate increases by 6-10 L/h with 5 ℃ increment of hot water inlet temperature.During experiment,lower degree of superheat of the working fluid at the outlet the plate heat exchanger may lead to unstable power generation.It is considered that the plate heat exchanger has a compact construction which makes its bulk so small that liquid mixture causes the unstable power generation.To avoid this phenomenon,the flow area of plate heat exchanger should be larger than the designed one.Alternatively,installing a small shell and tube heat exchanger between the outlet of plate heat exchanger and the inlet of expander can be another solution.

The Measurement of Oil,Gas and Water Flowrates in Three-Phase Slug Flow

Three-sphase flow invo1ving oil-water two immiscible liquids and gas which is often foundin the fields of petroleum production has been studied in this paper.A new method with thecombination of a horizontal tube,a downward flow vertica1 tube and an orifice to measure theflowrates is presented.In this method the frictional pressure drop in the downward vertical tube isreplaced by that in the horizontal tube,the void fraction is derived from the gravitational pressuredrop,then the volume fraction of the individual phase can also be obtained.The individual flowratescan be calculated when the water fraction is known.This method is applicable for many kinds ofoil-wells to measure the flowrates of crude oil,natural gas and water.Compared with other methods,the presented method involves fewer measuring parameters.The experimental results proved quitegood accuracy of the method,with measurement deviation within 10%,and reliable results wereobtained under high Dressure conditions.

An experimental study on flowrate and stability for 600MW supercritical steam-turbine control valve

An experimental study on flowrate and stability of a type of control valve of 600MW supercritical steam-turbine was presented by measuring instruments of static, dynamic pressure and vibration in self-designed test rig. The investigation shows that flow coefficient is 30% up more than that of the control valve of GX-1 type used widely in domestic power plants now, as small-medium lifts. If the relative lift (h/D) is less than 20%, the valve can always work steadily in all the pressure ratios. When the h/D is between 20% to 24%, big vibration of valve stem occurs if the pressure ratio is between 0.7 to 0.8. When h/D is more than 25%, relatively great vibration happens in a wide range of pressure ratios of 0.4 to 0.85.

Evaluation of the Air Leakage Flowrate in Sintering Processes

Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.

某单缸发动机冷却系统数值模拟及优化

为研究某单缸发动机冷却系统的冷却性能及工作流量,采用CFD方法对该单缸发动机冷却系统开展流场分析及工作流量提升研究。实验结果表明:该发动机冷却系统原方案的工作流量为34 L/min,不满足当发动机转速8 000 r/min时工作流量43.75 L/min的设计要求。通过优化水套阻力和提升冷却水泵性能,冷却系统的工作流量提升至44 L/min,增幅为29.4%。研究结果可为该单缸发动机冷却系统的冷却性能评估及结构改进提供仿真数据支撑。

液体微小流量测量技术研究进展

随着流体力学与生命科学、材料科学、医疗健康、能源环境和先进制造等多学科领域的交叉融合,微量液体与微流控技术逐渐在这些领域取得了广泛的应用.与此同时,液体微小流量(每分钟几微升、几纳升,甚至更低)的测量需求逐渐凸显出来.随着特征尺度的减小,原有的液体流量测量技术已经无法满足测量准确度的要求,因此,需要流量测量技术的进一步发展来满足微小流量测量和传感器微尺度集成的需求.文章介绍了液体微小流量的应用背景和面临的主要问题,首先,根据测量过程中是否引入外界能量(例如电能、热能等),将现有的和正在开发的液体微小流量测量技术分为有源流量测量技术和无源流量测量技术;其次,分别对其包含的具体测量技术展开论述,主要包括质量流量测量技术(科里奥利和微谐振器)、热式流量测量技术(热损失型、热分布型和热脉冲型)、光流控流量测量技术(光致褪色)、压力转换流量测量技术(压差式、悬臂式和柔性膜形变)、粒子测速技术、重力测量技术和弯月面追踪技术等,并讨论了上述测量技术的传感测量原理、测量性能指标和优缺点;最后,结合液体微小流量测量技术的发展和先进测量体系的建设,总结了液体微小流量测量的应用前景和有待解决的挑战.

基于流量预测的波纹管泵流量脉动抑制控制方法

随着晶圆内部线宽减小,在晶圆制造的湿法清洗工艺中对超纯水杂质颗粒的数量和直径提出了更严格的要求,以提高晶圆生产的产量,因此,对作为流控部件的波纹管泵(BsP)有更高的要求。针对波纹管泵运行过程中流量脉动导致的超洁净水颗粒杂质增加和晶圆良品率下降的问题,提出了一种基于神经网络流量预测模型的流量脉动抑制控制方法。首先,阐述了波纹管泵的工作原理和流量脉动产生的原因;然后,介绍了波纹管泵流固耦合模型的搭建方法,使用神经网络流量预测模型建立了流量脉动前馈控制的理论方法;最后,使用COMSOL仿真进行了流量预测模型验证研究,基于Simulink仿真平台开展了前馈控制应用于流量脉动抑制的验证研究。研究结果表明:在流量为[3.39,5.01]L/min时,预测的绝对流量误差范围为[8.0×10^(-1),1.6×10^(-1)]L/min;当流量为5.0 L/min时,最大流量脉动可从1.6 L/min降至4.0×10^(-1) L/min。在仿真验证中,该方法对波纹管泵脉动抑制有显著的效果,还可以有效提高波纹管的性能。

S型皮托管对向和非对向测量方法准确度实验研究

S型皮托管的对向和非对向测量方法准确度在不同工况下有较大差异。通过风洞实流实验对风速、流速攻角和结构参数对S型皮托管对向和非对向测量方法准确度的影响进行了研究。结果表明:风速由5 m/s变化至30 m/s时,在不同流速攻角下S型皮托管对向和非对向测量准确度最大差异超过10%;对向和非对向测量中静压孔的压力变化是皮托管在较大流速攻角下造成测量误差的主因;外径较小、总静压孔距较大、测量端弯曲角度在15°至30°间、取压孔内径更小的S型皮托管在对向和非对向测量中都有更高的测量准确度;俯仰角取正值时对向测量准确度全面优于非对向测量,在俯仰角和偏航角同为45°时测量准确度差异达到最大值,大于70%。

中试装置中流量计的设计选型探讨

中试装置与常规工业装置相比,其工艺物料流量和管道尺寸都很小,给流量计的设计选型带来一定的困难。依托某聚烯烃中试装置项目的工程设计实践,结合微小流量的检测需求,总结了5种常用流量计的适用场合,分别通过理论计算给出不同流量计的测量下限,并提出选型建议,为微小流量工况的仪表选型形成标准化设计提供思路。

液压快换接头压力降-流量特性试验台的设计及不确定度分析

为测试不同流体介质、流量等工况下液压快换接头的流通能力,设计一套液压快换接头压力降-流量特性试验台,完成配套测试处理软件的开发。该试验台可采用46号液压油或水作为试验介质,其流量测试范围为40~1000 L/min,被测快换接头的进、出口压力降测量范围为0~5.0 MPa,被测快换接头的适用公称通径范围为12.5~51 mm。在此基础上,依据ISO 9110-1:2020和ISO 9110-2:2020标准,建立被测快换接头压降值测量的数学模型,并分别计算得到了使用46号液压油或水作为试验介质时的合成不确定度。该试验台的技术参数符合GB/T 5861—2003,也可用于测量快换接头的流量系数和流阻系数。

自流充填系统的管道压力与流量特征研究

以某高浓度自流充填矿山为例,采用理论分析、室内试验及实测验证相结合的方式,研究了自流充填系统管网参数与阻力特征。结果表明,自流充填系统工序多,正常充填的流量波动范围可达100~240 m^(3)/h,压力1.2~2.2 MPa。管道具体点位的流量呈似正态分布,均值为190 m^(3)/h;压力具有2个区间特征峰,分别为1.86 MPa和3.04 MPa,单一点位的管道参数不能用于分析与判断堵管、泄漏等工况。管道区间压力差和流量差具有显著的正态分布特征,统计数学期望值分别为4.62 m^(3)/h和0.64 MPa,可用瞬时流量差和压力差判断管道堵泄状态。用Swamee-Aggarwal公式预测层流-紊流过渡区的管流阻力为2.08 MPa/km,与实测值2.15 MPa/km相吻合。

蒸汽发生器排污能力不足问题原因分析和处理

田湾4号机组蒸汽发生器排污系统在进行排污时,其排污能力长期不能达到运行规程要求,且此时系统调节阀开度已超过90%,丧失了调节能力。另外由于原系统设备经过改造,相关参数特性发生改变,所以通过仿真建模计算分析原有管路阻力特性的方法无法进行。本文选择利用核电厂现有运行参数,直接计算整个管路的装置特性曲线,分析得出原因为泵能力不足,然后按照规程要求的系统流量,考虑调节阀开度问题,计算得出泵的最终扬程,完成新泵的选型,最终有效地解决了排污能力不足的问题,为后续核电厂改造中解决类似问题提供了参考依据。

基于参数映射的通风机流量全程测量的实验研究

该文基于风机无因次性能曲线中反映出的性能参数间稳定的映射规律,采用曲面拟合和神经网络的方法,逼近风机不同流量区域内的流量和全压、流量和功率的映射规律,并对逼近效果进行了比较。在此基础上,建立了基于参数映射的通风机全程流量测量模型,并对模型的应用进行了实验研究。同时针对风机相似定律适用范围的定量研究等相关的问题进行了实验研究。从而证明在相似定律范围内,该模型的测量精度可充分满足工程需要,在一定程度上解决了大管径流量的无节流准确测量的问题。

孔隙水流速对胶体在饱和多孔介质中运移的影响

采用室内石英砂柱出流实验和数学模型,研究了流速对自然土壤胶体、蒙脱石胶体和腐殖酸钠胶体在饱和多孔介质中运移的影响。结果表明:孔隙水流速影响着胶体在多孔介质中的运移过程,流速的提高可加速土壤胶体的出流过程,减小蒙脱石胶体和腐殖酸钠胶体的沉积率。胶体的运移过程除受孔隙水流速的影响外,胶体特性的不同亦决定着胶体运移过程的差异,由于胶体表面性质不同,与介质之间的作用力不同,决定了胶体运移过程中的沉积和释放。

探针测定大型水泵流量研究

用 5孔探针测定大型水泵流量 ,确定了测量断面和测点布置 ,根据断面轴向流速分布积分求得流量。着重研究了测量方法、影响测流精度的因素和提高精度的措施。本方法已在江苏省 5座大型泵站的 8台机组现场实测中成功应用 ,结果表明该方法设备简单、施测方便、工作量小、易于实现 ,测量精度小于 2 % ,可以推广应用。

一种同时测量流量和含水率的电导式传感器

介绍了一种可同时测量油水两相流流量和含水率的电导式传感器的结构。该传感器由 6个圆环形不锈钢电极镶嵌在绝缘的管道内壁上构成。流量是通过对传感器内上下游检测电极对所检测到的流体流动噪声进行互相关运算来获取的 ;含水率是通过油 /水混合相的电导与其中水相的电导相比来获取的。对传感器测量流量和含水率的原理进行了介绍 ;对电导式传感器在多相流模拟井上的流量测量和含水率测量的动态实验结果进行分析。动态实验表明 。

鄱阳湖流域洪峰流量和枯水流量变化趋势分析

利用鄱阳湖流域40多年来的实测流量数据,分析了该流域年最大流量、高于阈值的洪峰流量和枯水流量的变化趋势。分析表明,鄱阳湖流域洪峰流量变化的区域差异较大:多数地区趋势变化不明显,修水上游和抚河上游有增大的趋势,饶河流域是趋势变化最明显的地区——年最大流量、高于阈值的洪峰流量的强度与频率都呈现增大的趋势,这与降水量变化的空间分布基本一致;与洪峰流量变化趋势不同,40多年来,整个鄱阳湖流域枯水流量呈现显著上升趋势。这种趋势的变化在很大程度上是该流域气候变化及其对水循环影响的反映,同时也为研究人类活动对径流的影响提供有意义的参考。

微小流量离心压缩机叶轮流场性能模拟计算

设计了一种空气工质低压比的微小流量、高转速离心压缩机三元叶轮,并对其流场特性进行数值模拟.研究表明:该类叶轮出口与进口区域面积比小于1;采用高转速可以改善该类叶轮的效率;叶轮的最佳叶片数较源于大流量低转速离心压缩机理论的叶片数经验公式计算值要小;叶轮出口角一般在60°以上;叶尖顶部间隙增大时,叶轮总压比及效率显著下降.研究方法和结果为飞机高性能空气循环制冷系统和蒸汽压缩制冷系统中微小流量高转速离心压缩机的工程化设计提供了有益的参考.