Investigation and numerical simulation of inner-flow of an axial mineflow fan under low flow rate conditions

Because of unstable properties of axial mine flow fans working under conditions of low flow rates, the safety and reliability of fans in their operational zone is reduced. At times, serious vibration may bring about the destruction of equipment or even jeopardize the safety of entire factories. By means of oil flow visualization techniques and numerical simulation, we have investigated the inner-flow of an axial mine flow fan working under low flow rate conditions. The fundamental reasons of complex flow phenomena of the inner-flow of the flow fan under these stated conditions were revealed. At the same time and in order to improve the inner-flow under conditions of low flow rates, a blade separator and air separator were designed. From our tests we found that the blade separator and air separator are two kinds efficient methods to improve the unstable working characteristics of the axial mine flow fan operating under low flow rate conditions. The effect of the improvement of the air separator is stronger than that of the blade separator.

Methodology for production logging in oil-in-water flows under low flow rate and high water-cut conditions

This study aimed to obtain the production profiles of oil-in-water flow under low flow rate and high water-cut conditions in oil wells.A combination production profile logging composed of an arc-type conductance sensor(ATCS)and a cross-correlation flow meter(CFM)with a center body is proposed and experimentally evaluated.The ATCS is designed for water holdup measurement,whereas the CFM with a center body is proposed to obtain the mixture velocity.Then,a drift-flux model based on flow patterns is established to predict the individual-phase superficial velocity of oil-in-water flows.Results show that the ATCS possesses high resolution in water holdup measurement and that flow pattern information can be deduced from its signal through nonlinear time series analysis.The CFM can enhance the correlation of upstream and downstream signals and simplify the relationship between the cross-correlation velocity and mixture velocity.On the basis of the drift-flux model,individual-phase superficial velocities can be predicted with high accuracy for different flow patterns.

Design and Experiment of Streamlined Piezoelectric Pump with Low Vortex and Large Flow Rate

Valveless piezoelectric pump is widely used in the medical,however,there is a general and difficult problem to be solved:Low vortex and large flow rate are not compatible,resulting in the blood prone to thrombosis during blood delivery.In this paper,a new valveless piezoelectric(PZT)pump with streamlined flow tubes(streamlined pump)is proposed.The design method and the working principle of the pump are analyzed.The velocity streamlines are simulated,and the results demonstrate that there are no obvious vortexes in the flow tube of the streamlined pump.Five prototype pumps(two cone pumps and three streamlined pumps)are designed and fabricated to perform flow rate and flow resistance experiments.The experimental results illustrate that the maximum flow rate of the streamlined pump is 142 mL/min,which is 179%higher than that of the cone piezoelectric pump,demonstrating that the streamlined pump has a large flow rate performance.This research provides an inspiration for future research on simple structure,low vortex and large flow rate volume-type pumps,and also provides a useful solution for thrombosis preventing.

Simplified graphical correlation for determining flow rate in tight gas wells in the Sulige gas field

The Sulige tight gas reservoir is characterized by low-pressure, low-permeability and lowabundance. During production, gas flow rate and reservoir pressure decrease sharply; and in the shut- in period, reservoir pressure builds up slowly. Many conventional methods, such as the indicative curve method, systematic analysis method and numerical simulation, are not applicable to determining an appropriate gas flow rate. Static data and dynamic performance show permeability capacity, kh is the most sensitive factor influencing well productivity, so criteria based on kh were proposed to classify vertical wells. All gas wells were classified into 4 groups. A multi-objective fuzzy optimization method, in which dimensionless gas flow rate, period of stable production, and recovery at the end of the stable production period were selected as optimizing objectives, was established to determine the reasonable range of gas flow rate. In this method, membership functions of above-mentioned optimizing factors and their weights were given. Moreover, to simplify calculation and facilitate field use, a simplified graphical illustration （or correlation） was given for the four classes of wells. Case study illustrates the applicability of the proposed method and graphical correlation, and an increase in cumulative gas production up to 37% is achieved and the well can produce at a constant flow rate for a long time.

Polymer-Based Micro Flow Sensor with Alternative Electronic Signal Interfaces for Low and High Flow Rates

The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by principle a calorimetric flow sensor produced as a micro system on a glass substrate by means of photolithography and glass etching technology. These structures are arranged as a platinum micro heater and sensor in a Wheatstone bridge. The subsequent etching process produces an exposed area of polyimide membrane that is only a few microns thick and includes the resistive sensor structure as the active area. In addition, the RTD （resistance temperature detector） technology included on the sensor allows for the implementation of a variety of electronic biasing and signal processing modes. Since the sensor can be powered and the bridge can be measured in both CTA （constant temperature anemometer） and calorimetric mode, new possibilities are presented for both low and high flow rates with regard to temperature compensation, self-calibration and self-monitoring.

化疗患者行个体化低流率腹部增强CT:双源CT低管电压高管电流的可行性分析

目的 探讨在癌症患者中使用双源CT结合低流速和低管电压方案的可行性。方法 共纳入90名进行上腹部增强CT扫描的患者,并随机分为A组、B组和C组(每组30人)。在A组中,患者使用120kVp和448mgl/kg对比剂量进行扫描。B组患者以100kVp和336 mgl/kg对比剂量进行扫描。C组患者以70kVp和224mgI/kg对比剂量进行扫描。对CT值、标准差、信噪比、对比噪声比、主观评分、对比剂剂量和流速进行测量。结果 在三组中,除了肾脏外,主观图像评分无统计学差异(均P>0.05)。与其他组相比,C组在大多数感兴趣区域(ROIs)中显示出显著更高的CT值、更低的噪声水平以及更高的SNR和CNR值(P<0.05)。与A组相比,C组所用对比剂剂量减少了47.3%(79.2±13.7 vs.41.7±8.9,P<0.01),对比剂注射速率降低了19.2%(2.6±0.5 vs.2.1±0.4,P<0.01)。结论 在化疗后血管受损的患者中使用70kVp管电压结合高管电流的方法,在保证图像质量和诊断信心的同时降低流速是可行的。

叶顶间隙对低比转数小流量泵性能的影响

为建立叶顶间隙对低比转速小流量泵性能的影响关系,采用数值计算的方法,以叶顶间隙宽s和叶轮出口宽b的比值(s/b)表征间隙大小,对不同间隙下泵的性能展开对比分析。分析发现,随着间隙的增加,泵的扬程和效率均逐渐降低,最大和最小间隙下的扬程和效率差分别达15.4%,5.5%。当间隙较小即s/b<0.2时,扬程曲线在小流量工况会出现不稳定的“驼峰”现象,在s/b>0.3后,设计工况附近效率的降幅显著增大。从流动特性来看,随着叶顶间隙的增大,间隙泄漏流对叶轮内主流区影响加剧,会诱导严重的二次流和旋涡的产生,同时间隙内不稳定流动也会产生能量损失,造成扬程和效率下降。为低比转数小流量泵的设计与优化提供借鉴意义。

基于CFD仿真的浮子流量传感器设计

针对小流量测量精度低等问题,文中提出了一种基于6DOF模型和浮子流量传感器工作原理的浮子流量传感器CFD仿真方法,基于该仿真方法,设计了一种流量范围为60~600 mL/h用于水流量检测的浮子流量传感器。结果显示:当传感器的关键结构参数锥管锥半角为0.1°、浮子直径为2.98 mm时,浮子流量传感器性能达到最优。通过实流实验验证了设计方案的可行性。

低流速、低对比剂注射方案在老年患者肺动脉CTA检查中的应用价值

目的:探讨低流速、低对比剂注射方案在老年患者肺动脉CT血管造影(computedtomographyangiography,CTA)检查中的应用价值。方法:选取2020年4月至2023年1月于某院接受肺动脉CTA检查的60例老年患者,根据对比剂注射方案的不同,将患者分为对照组(30例)和实验组(30例)。对照组采用常规对比剂注射方案,实验组采用低流速、低对比剂的优化对比剂注射方案。观察2组患者的肺动脉强化程度、肺动脉主干和分支的显示情况以及图像血管边缘的锐利程度、上腔静脉对比剂硬化伪影程度并进行主观评分,对2组患者的肺动脉干、左肺静脉及右肺静脉的强化CT值进行客观评价,记录2组患者对比剂外渗情况。采用SPSS25.0软件进行统计学分析。结果:2组肺动脉CTA图像质量评分比较差异无统计学意义(P>0.05);实验组上腔静脉对比剂硬化伪影评分低于对照组,差异有统计学意义(P<0.05)。2组图像的肺动脉干、左肺静脉及右肺静脉CT值比较差异无统计学意义(P>0.05)。实验组未出现对比剂外渗患者;对照组出现1例严重外渗患者,4例轻、中度外渗患者。结论:在老年患者行肺动脉CTA检查时采用低流速、低对比剂注射方案能够在保证图像质量的前提下避免对比剂外渗,提升了患者的就医体验和安全性。

基于时域积分的温差流量传感器仿真与试验

目前对于温差流量传感器的研究处于摸索阶段,传感器温度场与流量关系不明确,开展传感器的模拟仿真和试验有助于进一步提高传感器的分辨率和稳定性。为此,通过COMSOL仿真软件对测速传感器温度场进行了仿真分析和试验研究,探究了流量和持水率对测速传感器温度场的影响规律,明确了流量和持水率与时域积分结果的关系。试验结果表明:流量和持水率与积分结果均呈单调递减关系,与仿真结果一致,且在流量0~30 m^(3)/d,持水率0~100%的条件下,测速传感器的分辨率达到了1 m^(3)/d。所得结论可为温差流量检测方法的应用提供理论参考。

边水气藏水侵动态分析方法及水侵主控因素

基于经典分流理论与气水渗流规律,推导了考虑气体高速非达西渗流的边水气藏分流方程,并根据四川盆地某边水气藏多口产水气井的基础资料,分析了水侵动态特征参数的变化规律及主控因素,探讨了延缓气藏水侵的技术思路与对策。研究结果表明:(1)新的改进分流方程能够确定不同开发时刻气藏(或气井)边水的整体推进情况及见边水时间,相较于传统的基于达西定律的分流方程,该计算结果更加可靠。(2)边水气藏水侵动态受制于多种因素的综合影响,其中储层渗透率对其影响最为显著,其次为非达西流系数、相对渗透率及孔隙度,而有效厚度、供气边界及水侵流量的影响程度较小。(3)充分发掘物性较均一的低渗致密段储层的开发潜力是提升边水气藏开发效果的关键,制定合理的气藏采气强度是主动控水、稳水的重要手段。

低瓦斯自燃采空区注氮工艺优化研究

为了分析注氮口埋深和注氮流量对采空区氧化带范围的影响,优化低瓦斯自燃煤层采空区注氮防灭火工艺,采用数值模拟和现场实测相结合的方法,分别模拟了未注氮,注氮流量为设计量且注氮口埋深为15 m、30 m、45 m、60 m和75 m,注氮口埋深为45 m且注氮流量为0.50倍、0.75倍、1.00倍、1.25倍、1.50倍和1.75倍设计量时采空区氧化带范围;现场实测了注氮口埋深为45 m且注氮流量为设计量时采空区氧化带范围。研究结果表明:随着注氮口埋深增加氧化带面积逐渐减小,注氮口埋深分别为15 m、30 m、45 m、60 m和75 m时,氧化带面积为未注氮时的100.8%、96.1%、90.5%、95.0%和79.1%;随着注氮流量增加,氧化带面积逐渐减小,注氮流量为0.50倍、0.75倍、1.00倍、1.25倍、1.50倍和1.75倍设计量时,氧化带面积为未注氮时的95.8%、93.4%、90.5%、87.1%、83.3%和79.2%;增加50%的注氮流量,氧化带面积减小7.9%,减少50%的注氮流量,氧化带面积增加5.9%。现场实测结果与数值模拟结果基本一致。对于9202工作面,合理的注氮口埋深为30~60 m,最佳注氮口埋深为45 m,注氮流量为设计量的1.00~1.50倍比较合适,最优注氮流量为设计量的1.25倍。

低渗透率油藏二流量试井影响因素

为解决低渗透率油藏二流量试井测试成功率低、解释误差大的问题,从低渗透率油藏二流量试井技术的测试原理和解释原理出发,结合低渗透率油藏的地质特征、生产特征,围绕现场测试、井底压力折算、地层参数计算进行重点分析;剖析低渗透率油藏二流量试井现场测试、井底压力折算、地层参数计算过程中存在的主要问题及影响因素,针对各环节存在的问题针对性地提出改进措施并在现场进行应用。现场应用结果证明改进措施能有效提高低渗透率油藏二流量试井的测试成功率和解释符合率,该技术的推广应用有助于为油田生产及措施调整提供数据支撑。

CT血管造影应用双流速低剂量对比剂对冠脉各节段图像质量的影响

目的目的探究CT血管造影应用双流速低剂量对比剂对冠脉各节段图像质量的影响。方法方法选取2021年2月~2022年3月在本院进行CT造影检查的患者108例,根据入院时间将纳入研究对象分为两组,观察组54例,对照组54例。对照组使用常规对比剂进行检查,观察组使用双流速低剂量对比剂,比较两组图像质量评分及冠状动脉各部分CT值。结果图像质量评分:对照组(2.91±0.63)分,观察组(3.18±0.61)分,差异有意义(P=0.026);观察组和对照组患者主动脉根部、右冠状动脉起始部、回旋支中段及前降支远端CT值比较,差异无意义(P>0.05);观察组左冠状动脉起始部及右冠状动脉远端CT值较低与对照组,差异有意义(P<0.05)。结论CT血管造影应用双流速低剂量对比剂能提高冠脉各节段图像质量,对冠状动脉各部位CT值无较大影响,满足临床诊断要求。

高价值低流速备品备件管理体系构建与实施

秦山核电针对备件价值高、流速慢的特点,以备品备件需求类型为主轴,通过备品备件的需求管理带动供应链管理。通过备品备件基础信息管理、备品备件数量管理和备品备件的质量管理,实现备品备件全生命周期管理。引入虚拟分库概念,建立基于需求的分库管理模型,形成“以计划为核心的预防性维修备件管理”“以可靠性为核心的随机备件管理”“建立以精细化为目标的待梳理备件管理”“以跨核电厂调用为目标的虚拟库一体化管理”的业务模式,实现了秦山核电不同法人单位之间的备品备件高效流转,有效降低了企业备品备件的管理成本。高价值低流速备品备件管理体系的构建,以数字化平台为抓手,整合碎片化的备品备件业务数据,通过识别备品备件需求类型,建立备品备件采购动态调整机制,使企业具备了备品备件全业务流的快速响应能力,有效解决了备件价值高、制造周期长的核电企业备品备件管理难点。

基于正交试验的低比转数离心泵高效设计

为了研究叶轮结构参数对离心泵效率提升的影响,以某单级单吸立式离心泵(比转数n_(s)=40~60)为研究对象,选取叶轮出口宽度b_(2)、叶片数Z、叶片出口安放角β2和叶片包角φ为试验因素,建立L_(9)(4^(3))正交试验方案,在0.75Q_(d)~1.20Q_(d)(Q_(d)为额定流量)工况下进行各方案模型的数值计算,分析各因素对水力性能的影响,继而得到该泵叶轮结构的最佳参数组合.随后按照最佳尺寸修改叶轮,将优化后水泵外特性试验结果与原泵进行比较.结果表明:高效设计时,低比转数离心泵叶轮结构参数对效率影响程度由大到小依次为b_(2),β_(2),φ,Z,影响水力性能的主要因素为b_(2);确定了高效设计时叶轮结构参数的最优水平组合;优化后泵效率较原泵整体提高近2.85%,高效区扩宽至0.75Q_(d)~1.20Q_(d)工况范围;最后得到修正系数k′_(b_(2)),k′_(Z),k′_(φ),用于指导低比转数离心泵的高效设计.

基于热传导时域积分的井下流量测量方法

针对油田低产液生产井流量测量困难的问题,根据多相流体热力学理论,利用整个测量周期内探测器周围流体冲刷引起的热传导效应,提出了一种基于热传导时域积分的井下流量测量方法。首先,采用间歇式恒功率加热的方式,给探测器提供周期性能量;然后,采用积分法计算和分析了探测器内部温度在升温和降温过程中随外界流体流量变化的规律。理论分析与试验结果表明,时域积分面积与流量呈极好的相关性,尤其在低流量条件下具有较高的分辨率,该方法解决了传统涡轮流量计在流量较低情况下因涡轮无法启动导致失去检测能力的问题。基于热传导时域积分的井下流量测量方法,促进了油水两相流检测技术的发展,为低产液井流量测量提供了一种新的技术手段。

优化对比剂注射方案联合低剂量扫描模式在头颈部CTA中的应用

目的 探讨基于患者身高和体重的优化对比剂注射方案结合低剂量扫描在头颈CTA中的应用价值。方法 连续收集100例拟行头颈部CTA扫描的患者随机分成A、B两组,A组采用常规对比剂注射方式和常规剂量扫描方案。B组采用基于患者体重和身高的低对比剂注射方式和低剂量扫描方案。测量两组图像主动脉弓、颈总动脉、颈内动脉、大脑中动脉3个层面动脉血管的CT值和图像噪声,并比较两组图像质量,辐射剂量和碘摄入量,对图像质量进行主观评分和对比剂滞留评分。结果 两组图像质量均可满足临床诊断,但A组辐射剂量高于B组(P<0.05);上腔静脉和锁骨下静脉对比剂滞留伪影大,平均注射对比剂量、碘摄入量、注射速率和碘流率均高于B组(P<0.05)。结论 基于身高和体重的优化对比剂注射方案联合低剂量扫描行头颈CTA具有可行性,值得临床推广应用。

水力负荷和填料对华南冬季条件下潮汐流人工湿地去除氨氮的影响

供氧不足是导致传统人工湿地硝化速率和水力负荷低的关键因素。此外,低温条件下微生物活性下降会进一步加剧该问题。针对上述情况,构建两组供氧能力强的潮汐流实验柱,在华南冬季条件下考察水力负荷和填料对系统NH_(4)^(+)-N去除效率的影响。结果表明,NH_(4)^(+)-N去除负荷与水力负荷成正比。以沸石与碎石混合填充的潮汐流实验柱(TFCW-Z)对NH_(4)^(+)-N的平均去除率(67.20%~77.28%)显著高于以碎石填充的实验柱(TFCW-G)NH_(4)^(+)-N平均去除率(43.23%~51.77%)(p<0.05)。在日平均温度为6~19.5℃,水力负荷为4 m/d条件下,TFCW-Z出水中NH_(4)^(+)-N质量浓度始终低于黑臭水体标准值8 mg/L,此时NH_(4)^(+)-N平均去除率为67.20%,NH_(4)^(+)-N平均去除负荷高达47.96 g/(m2·d),表明潮汐流人工湿地在华南地区黑臭水体治理中具有良好的应用前景。

灌渠流速下的仿鱼尾双驱叶轮水动力性能分析

针对低流速灌渠中水轮机能量利用率低的问题,提出一种仿鱼尾双驱式垂直轴叶轮来提高发电功率,并采用CFD数值模拟与实物模型试验相结合的方法,对该叶轮的水动力性能和功率进行了局部和整体的分析。研究结果表明:对于应用在灌渠中的导流罩式的微水流水轮机,双驱设计可以提高垂直轴叶轮的能量利用率;仿鱼尾可以优化叶轮的旋转性能;仿鱼尾双驱垂直轴叶轮在微水流渠道中有着比普通水平叶轮更好的水动力性能。