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.

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.

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。

高炉中修开炉关键技术及宝钢实践

结合宝钢高炉中修开炉实践,对高炉中修开炉关键技术如开炉料结构、上下部操作制度、加风节奏的把控、炉缸的加热,以及第一炉渣铁的排放等进行了总结。认为高炉开炉采用开放中心的布料制度能够快速形成中心气流,有利于炉况的稳定顺行;根据炉料化学反应的进程,加风节奏建议按照四个阶段进行控制;开炉第一炉铁水温度比新开高炉要低,不必追求第一炉铁水1500℃以上的高温;出好第一炉铁非常关键,采用预埋氧枪的方式有利于渣铁的排放,按照体积置换计算实际装入的料批数作为开铁口时机是科学合理的。

河口航道双丁坝影响下异重流运动特性

在河口地区,由密度梯度驱动而产生的异重流是影响航道内泥沙输移的重要因素之一。作为航道整治中常见的建筑物,丁坝群可以缓解航道的泥沙淤积问题、提高通航能力。为探究双丁坝对异重流运动特性的影响,运用粒子图像测速系统(PIV)开展了开闸式异重流实验,研究了在不同束窄系数情况下,航道异重流稳定阶段内的流场及湍流特性,并对比分析了异重流在两个丁坝位置特征断面处的单宽流量及总流量。结果表明,双丁坝改变了航道内的流场,异重流在经过束窄断面后会向第二个丁坝后部区域横向扩散,进而使得流速加大、高度降低;异重流在两个丁坝束窄断面的单宽流量近似相同,且与束窄系数无关;异重流在束窄断面的总流量与断面宽度成正比,在实际工程中可以通过适当调整丁坝长度来控制侵入航道的异重流总量。

基于双线结构光双目视觉的干排渣机排渣流量检测方法研究

实现电站锅炉干排渣机传送钢带上渣量的实时检测,对提高锅炉运行的经济性和可靠性具有重要意义。针对锅炉底部无纹理炉渣在线检测,本文提出了耦合双线结构光和双目视觉的干排渣机流量在线检测方法,在双线结构光照射下,双目相机采集连续2帧带有红蓝颜色激光线图像,通过对图像RGB通道分离、图像处理和亮点匹配,计算激光线处炉渣厚度;进一步利用互相关算法获得物料移动速度,进而结合炉渣横截面积和速度,计算获得炉渣无纹理对象的体积流量。构建了双线结构光双目视觉测量系统,并开展了系统标定与实验评价研究。结果表明:双目相机标定重投影平均误差为0.07个像素,具有较高精度;横截面积测算误差均小于2.1%,时均速度测算误差均小于2.1%,体积流量测算误差均小于2.6%。结合炉渣经验堆积密度,本文方法可满足燃煤电站锅炉底部排渣量在线测量工业现场应用要求,为炉渣冷却风调整提供渣量数据支持。

发动机冷却水泵CFD数值模拟及性能优化

以某发动机冷却水泵为研究对象,基于计算流体力学(ComputationalFluid Dynamics,CFD)方法搭建了冷却水泵性能分析模型,并对3种叶轮改进方案进行了对比。采用自主搭建的水泵性能实验台对水泵性能进行了试验,并与发动机转速10000 r/min时的水泵性能仿真结果进行对比,发现水泵扬程仿真值与实验值变化趋势一致,误差在5%以内,验证了水泵性能分析模型的可靠性。3种叶轮改进方案的性能对比分析结果表明:叶轮加高30%并加宽16%时水泵扬程在发动机转速10000 r/min时可提升37%,效率提升4%,轴功率增大50 W。采用优化叶轮的冷却系统工作流量点提升了11.8%,表明水泵性能优化效果明显,可为冷却水泵的选型及结构改进提供理论参考。

马钢1号高炉操作炉型的优化措施

2020年上半年,马钢1号高炉存在炉腹冷却壁热流强度偏低、炉身中部冷却壁周向热负荷不均匀的问题,操作炉型发生变化,高炉主要技术经济指标明显下滑。通过采取调整初始煤气流、内推料面平台、监控炉体热负荷等操作炉型的优化措施,1号高炉生产效果逐渐显现:炉腹冷却壁热流强度升高、渣皮变薄,能接受较大的炉腹煤气量;炉身中部冷却壁热负荷周向均匀性、稳定性提高,产生异常气流的概率大幅降低;主要技术经济指标明显改善,2021年12月,1号高炉日产量达到6660t/d,煤比升高至148kg/t。

发动机冷却系统数值模拟分析及优化研究

为了给发动机冷却系统性能评估及优化提供理论指导,本文以某四缸发动机为研究对象,采用CFD方法对其冷却系统进行数值模拟分析及优化,结果表明:油水交换器及散热器流阻的CFD仿真值与实验值误差小于10%,说明搭建的冷却系统性能仿真模型是可靠的;缸体水套排气侧上部区域冷却液流速较低,缸头水套上鼻梁区冷却液流速低于1.5 m/s且分布不均匀。为提升冷却系统散热性能和水套内部流动均匀性,对水泵性能、管路直径及水套结构进行了优化,优化后冷却系统在发动机转速10000 r/min时流量提升至90 L/min,水套流动均匀性提升,缸体水套排气侧区及缸头水套鼻梁区冷却液流速均满足1.5 m/s的冷却液流速设计要求。