PRESSURE DROP IN THE VERTICAL PNEUMATIC PIPE FOR POWDER CONVEYING

Based on the former research work of the authors,the resistance of differentsolid particle suspension flow in a vertical pipe is analysed,and investigatedexperimentally.The applicable formulas of pressure drop are presented.Two types of par-ticles,talcum powder and glass beads,are convcyed in the test which has been carried outat various air vclocities of 10 to 28 m/s and at the ratio of solids-air mass flow rateranged from 0 to 2.The experimental results show a good agreement with the calculatedones.

Pressure Drop of Liquid–Solid Two-Phase Flow in the Vertical Tube Bundle of a Cold-Model Circulating Fluidized Bed Evaporator

A cold-model vertical multi-tube circulating fluidized bed evaporator was designed and built to conduct a visualization study on the pressure drop of a liquid–solid two-phase flow and the corresponding particle distribution.Water and polyformaldehyde particle(POM)were used as the liquid and solid phases,respectively.The effects of operating parameters such as the amount of added particles,circulating flow rate,and particle size were systematically investigated.The results showed that the addition of the particles increased the pressure drop in the vertical tube bundle.The maximum pressure drop ratios were 18.65%,21.15%,18.00%,and 21.15%within the experimental range of the amount of added particles for POM1,POM2,POM3,and POM4,respectively.The pressure drop ratio basically decreased with the increase in the circulating flow rate but fluctuated with the increase in the amount of added particles and particle size.The difference in pressure drop ratio decreased with the increase in the circulating flow rate.As the amount of added particles increased,the difference in pressure drop ratio fluctuated at low circulating flow rate but basically decreased at high circulating flow rate.The pressure drop in the vertical tube bundle accounted for about 70%of the overall pressure drop in the up-flow heating chamber and was the main component of the overall pressure within the experimental range.Three-dimensional phase diagrams were established to display the variation ranges of the pressure drop and pressure drop ratio in the vertical tube bundle corresponding to the operating parameters.The research results can provide some reference for the application of the fluidized bed heat transfer technology in the industry.

A Pressure-Drop Model for Oil-Gas Two-Phase Flow in Horizontal Pipes

The accurate prediction of the pressure distribution of highly viscous fluids in wellbores and pipelines is of great significance for heavy oil production and transportation.The flow behavior of high-viscosity fluids is quite different with respect to that of low-viscosity fluids.Currently,the performances of existing pressure-drop models seem to be relatively limited when they are applied to high-viscosity fluids.In this study,a gas-liquid two-phase flow experiment has been carried out using a 60 mm ID horizontal pipe with air and white oil.The experimental results indicate that viscosity exerts a significant influence on the liquid holdup and pressure drop.At the same gas and liquid volume,both the liquid holdup and pressure drop increase with an increase in the viscosity.Combining two existing models,a modified pressure drop method is developed,which is applicable to horizontal pipes for different viscosities and does not depend on the flow pattern.This new method displays a high accuracy in predicting the new experimental data presented here and other published data in literature.

Heat Transfer Characteristics and Pressure Drop in a Horizontal Circulating Fluidized Bed Evaporator

A vapor-liquid-solid horizontal circulating fluidized bed evaporation setup was constructed to study the thermal-exchange properties and pressure change.The influences of the operating variables,including the amount of added particles,heat flux,and circulating flow velocity,were systematically inspected using resistance temperature detectors and pressure sensors.The results showed that the heat transfer eff ect was improved with the increase in the amount of added particles,circulating flow velocity,and particle diameter,but decreased with increasing heat flux.The pressure drop fluctuated with the increase in operating parameters,except circulating flow velocity.The enhancing factor reached up to 71.5%.The enhancing fac-tor initially increased and then decreased with the increase in the amount of added particles and circulating flow velocity,fluctuated with increasing particle diameter,and decreased with increasing heat flux.Phase diagrams showing the variation ranges of the operation variables for the enhancing factor were constructed.

Differences of Gas Lift Design between Deviated and Vertical Wells and the Analysis of Sensitivity Parameters

尽管气举越来越多地被应用到大斜度井、水平井的举升采油中,但倾斜井气举设计与直井气举设计存在什么差异,这些差异随倾斜角度的增大将怎样变化,以及哪些气举设计所需参数对这种差异比较敏感,即如何对倾斜井气举设计所需参数进行合理选择,以便对倾斜井气举设计进行优化的研究较少,这也一直是倾斜井合理气举设计的难点问题。鉴于此,笔者以某油田一口倾斜井为例,通过实测数据进行了倾斜井产能预测方法优选和多相管流压力计算方法优选,然后在该基础上采用等套压降气举设计方法对比分析了倾斜井气举设计与同等条件下直井气举设计的差异,并逐一分析了各种气举设计所需重要参数分别取不同值时气举设计注气深度和产量随井斜角度的变化规律,从而得到了倾斜井气举设计的敏感性参数,可为倾斜井气举设计的参数优化和调整提供参考依据,是倾斜井气举高效生产的有力保障。

稀密两相状态监测实验平台设计

为了实际测量稀密两相对应的管道尺寸、风压和空气体积流量,设计了一个稀密两相状态监测实验平台。基于空气动力学理论和比例-积分-微分(PID)控制方法,将旁路调节系统应用到实验平台入口处,以控制管道入口空气体积流量,从而实现对物料稀密两相输送的实时监测与调控。该实验平台可实现稀密两相边界条件测试和流形稳定性分析等多项测试。最后,通过多次物料流形实验,验证了旁路调节系统在调控空气体积流量方面的有效性,以及气动测控系统维持物料流形的可行性。

Pressure recovery characteristics for a dilute gas-particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach

This work applies the Eulerian-Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas-particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid loading.To do so,the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion;a satisfactory agreement was obtained.Initially,the effect of the two significant numerical parameters namely,the speculairty coefficient and the coefficient of restitution for particle-particle collisions were investigated and then,for fixed combinations of these parameters the effect of particle-phase volume fraction,particle density,particle size,and inlet slip ratio were studied.It was concluded that pressure recovery diminishes as the speculairty coefficient increases and the particle-particle coefficient of restitution decreases.Pressure recovery was found to increase with increasing solid volume fraction for coarse particles whereas,for fine particles,a critical volume fraction is obtained above which pressure recovery reduces.An increase in slip ratio is found to diminish pressure recovery.Similarly,at relatively higher solid volume fractions,a critical diameter was found,above and below which pressure recovery decreases.

竖直管气动物流传输系统管道压降和传送瓶输送特性

气动物流传输系统在医疗、化工等行业得到广泛应用,管道压降和特征速度是竖直管气动物流传输系统设计的关键参数,但目前相关报道很少。基于实验室自主搭建的竖直管气动物流传输系统,开展压缩气流输送传送瓶实验,进行输送特性分析以及管道压降和特征速度的建模研究。首先借助压降信号分析、高速摄像与数据处理等方法,分析了传送瓶输送特性,提出了基于管道压降信号分析的传送瓶运动状态识别方法;其次综合考虑流道结构特征,建立了竖直管气动物流传输系统的管道压降模型,并通过数据回归获得了管道阻力系数;最后基于力平衡分析、机械能守恒定律建立了竖直管气动物流传输系统特征速度的预测模型,为传送瓶状态识别及追踪监测提供了一种新方法。

浅埋矩形顶管背土效应全过程理论分析模型

针对浅埋矩形顶管顶进的背土效应,提出覆盖背土竖向扩展阶段、水平扩展阶段和整体背土阶段的全过程理论分析模型,确定顶管顶进的松动土压力、管土摩擦力、侧壁剪切约束力和前端阻力的计算方法,得到背土启动和发展全过程的理论计算公式.结果表明:背土是否启动主要由顶管上覆土层的厚度、地层土体特性和管土摩擦特性决定,与顶进长度无直接关系;背土竖向扩展阶段的背土区域厚度和水平扩展阶段的地表扩展宽度都随着顶进长度的增加而非线性增长;理论分析结果与矩形顶管顶进全过程三维有限元模拟结果和现场实测结果吻合较好,理论公式可为矩形顶管背土发展全过程预测分析提供一种有效而简便的方法.

水滴形热管阵列预冷器综合换热特性数值研究

提出了一种应用于高超声速飞行器进气预冷的水滴形热管阵列预冷器构想,以实现进气预冷的高效换热和低流动损失。基于将热管处理为恒定温度导热体的简化模型假设,采用数值模拟方法研究了水滴形热管预冷器的流动换热特性以及水滴热管形状、纵向间距和来流马赫数的影响,并与具有相同截面积的圆形热管预冷器进行了对比分析。结果表明,水滴外形减少了外掠高温来流在热管尾缘脱落涡的产生,流动变得平滑。与圆形热管预冷器相比,水滴形热管预冷器极大地减小了高温来流流动损失,仅为圆形热管阵列的30%。虽然温降有所降低,但综合性能因子大于圆形热管预冷器。在本文的研究参数范围内,存在相对较优的水滴形状和热管纵向间距,可以获得更高的综合换热特性;随着来流马赫数增大,预冷器的综合换热特性有所提升。

超薄空间复杂边界条件下气体流动压降实验

随着超薄热管等元件进一步超薄化,蒸汽腔厚度减小导致蒸汽流动压降急剧增大,传热热阻增加,传输极限降低。搭建了超薄受限空间气体流动压降实验装置,开展空气流动实验,获得了不同通道高度(0.1~0.5 mm)、不同表面丝网孔径(0.036~0.104 mm)和不同流速(1~10 m/s)下的压降变化。结果表明:通道高度和流速对压降产生显著影响,而表面丝网孔径并不会;3个影响因素按显著程度依次为通道高度、流速、表面丝网孔径;随表面丝网孔径的减小,压降逐渐增大;随通道高度的减小,压降先缓慢增大,在减至0.3 mm后压降开始剧烈上升;随流速的增加,压降增大且近似呈正比例变化关系。最后基于实验数据修正了微通道层流情况下沿程阻力系数相关性预测关联式,以便更准确地预测气体压降。

沟埋式管道垂直土压力模拟试验研究

为研究沟埋式管道的垂直土压力,以甘肃某大型管道工程为研究背景,采用PFC3D数值分析方法,建立埋地管道三维离散元模型,模拟土体工后沉降过程中管土相互作用过程,分析不同埋深、管径条件下的管顶土压力分布规律和管顶垂直土压力,并与现场试验和理论计算进行对比验证。结果表明:沉降过程中土颗粒位移持续增大,最后趋于稳定,在管顶位置与土的接触处力达到最大。现场试验和数值模拟所得的管顶土压力分布规律一致,近似呈“中间大,两侧小”的抛物线分布形式,管顶垂直土压力随管道埋深的增加而增大。管径对管顶垂直土压力的影响较小,整体随着管径增大呈现出逐渐减小的趋势。数值模拟与折学森土压力计算理论更为接近,Marston计算理论偏于保守。

大管径90°弯头压降数值模拟与计算分析

本文对大管径90°弯头的流动阻力损失进行了数值研究,分析了空气流过弯头时的内部流场特性,并研究了流体流过大管径90°弯头的流动阻力损失影响因素。然后,选取了不同的常用计算弯头阻力系数的公式,比较了当量长度法和阻力系数法计算弯头流动阻力损失的可靠性,为设计者提供参考。

CHARACTERISTICS OF PRESSURE DROP AND CORRELATION OF FRICTION FACTORS FOR SINGLE-PHASE FLOW IN ROLLING HORIZONTAL PIPE

Gas-liquid two-phase flow occurs increasingly in some dynamic devices operating in the oceanic condition. The relative data are limited with respect to flow characteristics, so the present study is to investigate systematically single-phase pressure drop, and to develop the theory for frictional factor under the roiling condition. Using deionized water as the test fluid, a series of experiments of single-phase flow were conducted in pipe with the inner diameter of 34.5 ram. The test section was horizontally settled on the rolling apparatus, and its regularity was similar to simple harmonic motion. It is found that the pressure drop during rolling motion fluctuate with the change of the rolling period and rolling angle, which is significantly different from fluid motion in a steady state. By the contrast between experiment results and stable-state theory values, existing correlations can not predict present frictional factor very well. Therefore, in the present article, the single-phase frictional factor is correlated with the Reynolds number for rolling motion, and its computated results agree well with experimental data.

ERRATUM TO “CHARACTERISTICS OF PRESSURE DROP AND CORRELATION OF FRICTION FACTORS FOR SINGLE-PHASE FLOW IN ROLLING HORIZONTAL PIPE”

This is the erratum to the article [zhang Jin-hong, Yan Chang-qi, Gao Pu-zhen, Journal of Hydrodynamics, 2009, 21(5)]. The Fig.5 is corrected.

锥形溢流管开缝水力旋流器流场特性与分离性能研究

为降低旋流分离器压降,达到节能减排的目的,设计溢流管底部开缝结构的旋流器。通过固液分离试验与数值模拟相结合,对常规溢流管(型号Ⅰ)、溢流管双切开缝(型号Ⅱ)、溢流管单切开缝(型号Ⅲ)的旋流器入口流量由780 mL/s逐渐增至1000 mL/s时的分离性能进行分析研究。研究结果表明:随入口流量的增加,锥型溢流管开缝对旋流器分离效率的影响逐渐减小,压降降幅逐渐增大,入口流量为980 mL/s时,两种改进后旋流器分离效率达到最高值,相较于型号Ⅰ旋流器,型号Ⅱ和型号Ⅲ旋流器的分离效率均基本保持不变,而压降分别降低高达到22.85%,27.46%,节能效果显著。模拟结果显示改进后旋流器的轴向速度、切向速度、压强均有所下降,溢流管开缝对轴向速度影响较大,中心处轴向速度降低明显,对切向速度影响较小。为深入探究旋流器内部流场的规律和旋流器结构改进提供了依据。

整体式微通道换热器的性能分析

为了提升整体式微通道换热器的整体性能,建立了整体式微通道换热器的稳态换热模型,研究了结构参数与运行参数对其的影响规律。整体式微通道换热器以R245fa为工作工质,并在实验验证模型准确性的基础上,利用该模型模拟研究了换热器风量和换热器热管间距对系统整体热阻和空气侧压降等参数的影响。研究结果表明,当微通道换热器的蒸发段风量为0.41 m^(3)/s、冷凝段风量为0.21 m^(3)/s时,换热器的系统整体热阻为0.0380 m^(2)·K/W;随着冷凝段和蒸发段循环风量的增加,微通道换热器空气侧的压降增加,整体热阻均降低;微通道换热器的整体热阻的下降趋势随着风量的增加而逐渐减弱,得出在本研究范围内,蒸发段风量取0.45 m^(3)/s、冷凝段风量取0.69 m^(3)/s为宜;随着整体式微通道换热器热管间距的增加,微通道换热器整体热阻呈上升趋势,微通道换热器在蒸发段空气侧的压降呈下降趋势。当换热器热管间距为6 mm时,微通道换热器综合性能达到最佳。研究结果对通信基站冷却设备设计及微通道换热器结构与控制参数优化设计提供了参考依据。

压缩空气泡沫在长距离管路输送中压降的数值模拟

基于Fluent对压缩空气泡沫在长距离管道中的流动特性进行了数值模拟研究,将压缩空气泡沫近似为弥散流,采用Saplart-Allmaras模型模拟了不同管径下压缩空气泡沫以及不同泡沫原液浓度的AFFF泡沫在长距离管道内的流动及压降变化。模拟结果表明,随着距离变化,各管径管道内压降均呈现线性变化,且随着压缩空气泡沫的流动,压降线性增大。管道管径对管内压降变化具有显著影响,管道直径越小,管道内压降越大;泡沫原液浓度对压降的影响较小,且压缩空气泡沫在长距离输送中的压力随距离线性衰减。将模拟结果与长距离输送的试验结果进行了对比,误差在10%以内。

燃煤电厂超临界压力下垂直并联管组流量分配特性

为研究超临界压力下垂直并联管组流量分配等特性,建立了超临界压力下垂直并联管组水动力计算数学模型。对超临界压力下不同质量流速、不同长度垂直光管和垂直内螺纹管并联管组内压降、流量分布等进行计算,明确定管长下的并联管组临界质量流速及定质量流速下的临界管长。结果表明:在相同条件下,内螺纹管的正流量补偿特性弱于光管;定长垂直内螺纹管在临界质量流速(1600 kg/(m^(2)·s))以下保持良好的正流量补偿特性,超过该值其正流量补偿特性逐渐减弱直至消失并转化为负流量补偿特性;同等条件下,垂直内螺纹管在低质量流速下的正流量补偿特性优于高质量流速下的正流量补偿特性,并且低质量流速下所对应的临界管长要大于高质量流速下的临界管长。相关计算结果的确定为超临界压力下锅炉水冷壁的制造安装及安全运行提供理论依据和技术支撑。

基于泡沫携液实验的压降携液量CFD数值模拟

为了研究流体动力学(CFD)方法对泡沫排水采气的可行性及在实际井筒中的流动规律,通过分析直井在不同质量分数泡排剂的流型、压降和携液量,得到最优泡排剂质量分数,基于室内实验模型建立相同的CFD物理模型,并对多相流模型(Eulerian模型、VOF模型和Mixture模型)和紊流模型(Reynolds Stress、k-ε和k-ω模型)进行优选得到最适合泡沫排水采气的数学模型,最后在实际井筒温度压力条件下进行CFD模拟得到流型压降携液量规律。结果表明:泡排剂质量分数为0.3%时携液效果最好;优选得到的最优CFD数学模型为“VOF+k-ω”,模拟结果与实验结果对比,压降、携液量误差均在10%以内;在实际井筒条件下,随着温度和压力增至40℃和15 MPa,液、气量分别低于0.2 m^(3)/h、30 m^(3)/h时,流型转为弹状流,压降增加1.8倍,携液量减少0.72倍,泡排效果减弱。该计算方法计算简单、准确性高,可以为泡沫排水采气工艺技术的高效实施和方案优化提供理论指导。