管壳式换热器内气液两相流冲刷垂直管速的阻力特性研究

本文对垂直布置的管壳式换热器中，气液两相液冲刷管束时的流动阻力进行了实验研究。实验段采用管壳式换热器模型，其圆形外壳内的管束由４９根管子组成，并沿长度方向用三块折流板将管束分成四个冲刷流程，当气液两相流自下而上冲刷管束时，分别测量摩擦阻力和局部阻力，并用分相流动模型进行分析，得到良好的计算关联式。     

水平管气液两相间歇流含气率研究

对大直径水平管内气液二相流动进行了实验，实验结果表明大直径水平管与小直径水平管具有不同的气液二相流动特征。分析和提出了适用于大直径水平管内间歇流液弹含气率模型，其计算值与实验值非常接近。     

微重力气液两相流动与池沸腾传热

综述了近年来中国科学院微重力重点实验室(国家微重力实验室)完成的一系列微重力气液两相流动与池沸腾传热方面的地基实验、飞行实验和理论研究等方面获得的主要成果.在微重力气液两相流动方面,提出了半理论Weber数模型用于预测微重力条件下气液两相弹-环状流转换,并采用Monte Carlo方法,针对气泡初始尺寸对泡-弹状流转换的影响进行数值研究.通过俄罗斯"和平号"空间站与IL-76失重飞机实验,获得了微重力下的气液两相流型图,与此同时在地面利用小尺度毛细管模型模拟了微重力气液两相流动特征.实验测量了微重力气液两相流压降,并基于微重力流动特性建立了一个泡状流压降关联模型.在微重力池沸腾传热方面,利用我国返回式卫星完成了两次空间实验,其中,第22颗返回式卫星搭载铂丝表面R113池沸腾实验采用控制温度的稳态加热方式,而实践8号育种卫星搭载平面FC-72池沸腾实验则采用控制加热电压的准稳态加热方式.同时,还进行了地面常重力和落塔短时微重力条件下的对比实验研究.观察到丝状加热表面微重力时轻微的传热强化现象,而平板加热表面微重力核态池沸腾低热流时传热强化、高热流时传热恶化.微重力实验中观察到气泡脱落前存在横向运动现象,据此分析了气泡行为与传热之间关系,并提出了一个预测丝状加热表面气泡脱落直径的半理论模型.旨在对相关领域的进一步发展和空间两相流系统的应用提供数据及理论支持.     

不同重力条件下管内冷凝现象研究进展

本文对不同重力环境中水平管内冷凝气液两相流动与传热现象的研究现状进行了全面评介, 重点关注于航天应用中的小管径、低流量和以氨为工质的情形,以及部分重力条件下冷凝现象中的重力效应. 冷凝现象中管壁四周液膜的存在,导致水平管内冷凝气液两相流与沸腾或绝热气液两相流在构型上存在着明显的不同, 表面张力的作用增大,向波状和分层流转换所对应的临界Bond数也随之增大, 进而使小管径、低流量水平管内冷凝气液两相流动与传热现象中的重力效应减弱,甚至可以忽略不计. 实验发现该情形中摩擦压降要小于基于常规气液两相流实验数据的经验关联式的预测结果, 而更接近光滑环状流情形; 对冷凝两相传热系数的预测,只有采用基于空隙率与界面剪切率相互耦合的模型, 才能够给出较好的结果.      

气液两相瞬变流的流固耦合模型研究

传统的气液两相流瞬态分析和管道动力响应计算是分开的，存在一定的缺陷．针对石油工业中常见的多相混输问题，介绍了常见的气液两相流瞬态模型和流固之间存在的耦合机理，在不作薄壁管假设的前提下推导出了气液两相瞬变流的流固耦合模型．与现有相似模型的对比分析表明，这一模型比较全面地考虑了流体和管道的特性以及不同的耦合形式，可以适应实验和／或仿真研究的需要．     

垂直向下管内两相流泡状-弹状流型转换研究

建立实验系统,在维持管道出口压力为0.2MPa的条件下,对内径分别为15mm、25mm、40mm、65mm的垂直向下管内空气-水气液两相流动进行了实验研究,获得了两相流泡状-弹状流型分布。实验研究发现:管径对于泡状流与弹状流流型特征有较大影响,并且进一步影响流型转换边界,随着管径增加,泡状流-弹状流的流型转换边界向折算气速减小的方向移动。基于理论推导及实验数据,建立了垂直向下管内气液两相流泡状流-弹状流流型转换预测模型,该模型对本文实验工况条件下的垂直向下管内空气-水气液两相流流型转换具有良好的预测效果,预测模型的计算结果与实验数据之间的误差小于10%。     

换热器管束中的流体弹性不稳定性

文中重点讨论了管壳式换热器管束中的流体弹性不稳定性．从工程实用的观点出发，应用了Ｌｅｖｅｒ与Ｗｅａｖｅｒ的“流管”模型，在建立管子振动的基本方程时则认为管子作周期性的衰减（或发散）运动，以复数解法进行求解．根据所获得的对比流速与质量阻尼参数之间的关系画出的稳定区图，可用来确定管子的流体弹性不稳定性或该时的临界流速．实验数据表明，理论计算结果是令人满意的．     

柱体形状对气液两相涡街的影响

本文试验研究了柱体形状对气液两相涡街的影响，得出了在气液两相流中的最佳涡街发生体和发生两相涡街时，两相斯托拉赫数，来流截面含气率，水流量三者之间的关系。试验工质为水和空气，混合物流动方向垂直向上。参数范围：相对压强０．０－０．２ＭＰａ；来流截面含气率０．０－０．３５；水流量０．０－２６ｍ３／ｈ。     

水平管内气液两相螺旋流实验研究

为研究水平管内气液两相螺旋流的流动特性,开展了以空气和水为实验介质,含气率为10％～90％,气相折算速度为0.01～3.4m/s,液相折算速度为0.05～2.7m/s的气液两相螺旋流实验.利用高速摄影机记录并参考借鉴相关研究结果分析和划分了不同工况下的流型;给出了水平管内气液两相螺旋流的流型图;研究了不同流速、不同起旋参数对流动特性(压降、流型衰减、螺距、螺旋直径以及流型转换边界等)的影响.实验结论如下:将水平管内气液两相螺旋流的流型划分为螺旋波状分层流、螺旋泡状流、螺旋团状流、螺旋线状流、螺旋轴状流、螺旋弥散流6种;将绘制的流型图与经典Mandhane流型图进行对比,出现了线状流、弥散流和轴状流3种新的流型;泡状流的分布基本不变,层状流的分布发生变化,当气相流速在2m/s以内时是线状流和轴状流,而不是层状流;随着液相流速的提高,管内两相流动的损失逐渐变大,流型的衰减程度变弱,螺旋扭矩逐渐变大,螺旋直径逐渐变小.另外,随着叶轮角度的增大或者随着叶片面积的减小,流型转换边界均向进气量增大的方向推移.而当进气量一定时,随着叶轮角度的增大或者随着叶片面积的减小,同样流型转换边界趋于进水量增大的方向.最后,随着起旋角度的增大或者随着叶片面积的减小,压降均有逐渐变大的趋势.     

板壳式换热器波纹倾角对换热和阻力性能影响

研究了波纹倾角（α=45°，60°，75°）对板壳式换热器单流道内单相流动与换热过程的影响，分析了波纹流道内的速度分布、湍动能分布、压力分布和温度分布；基于范宁摩擦阻力因子f和Nu与Re的关系，提出了板壳式换热器不同波纹倾角下换热特性和流动阻力特性的预测关联式；通过计算不同波纹倾角下的综合性能评价指标（performance evaluation criteria,PEC）和面积质量因子（j/f）综合评价了流动与换热性能。结果表明：波纹倾角是影响圆形板间流体流动形态的因素之一，随着波纹倾角增大，会出现“十字交叉流”向“曲折流”转变；所提出的关联式能够很好地预测板壳式换热器内阻力与换热性能，阻力特性偏差在±14%范围内，换热特性偏差在±7%范围内；α为45°时，j/f较大，流道内阻力相对小；α为60°时，PEC较大，流道内换热性能相对强。     

油管的疲劳强度分析

疲劳断裂是油管失效的形式之一,本文针对抽油机井常用油管(J55,2 ")在循环载荷作用下的断裂问题进行了理论与实验研究。实测了井口处油管载荷谱与应变谱,得到了油管载荷的变化规律,同时通过在室内建立模拟油管工况的试验台,得到了油管从上扣到加载的全过程中油管螺纹段内壁的环向、轴向、剪应变等的变化规律。并且采用油管螺纹段轴对称接触模型进行了弹塑性有限元分析,计算了油管螺纹内的应力应变场,发现油管内第一啮合齿齿根处应力应变最大,应力已经进入屈服阶段,油管是在高应力应变水平和低应力应变幅状态下工作。并利用局部应力应变法进行了相应的疲劳实验,得到油管的疲劳断裂条件,当油管内的应力应变进入强化段εeq>10-2ε,塑性应变幅超过4×10-5ε时,油管就会发生疲劳断裂。     

油管的疲劳强度分析

疲劳断裂是油管失效的一种形式 ,本文针对抽油机井常用油管 (J5 5 ,2 1/ 2″)在循环载荷作用下的疲劳断裂问题进行了理论与实验研究。在实测油管载荷谱与应变谱的基础上应用弹塑性有限元法计算油管螺纹内的应力应变场 ,并进行了有关的疲劳实验 ,以得到油管的疲劳强度。油管内第一啮合齿齿根处应力应变最大 ,应力已经达到屈服阶段 ,油管是在高应力应变水平和低应力应变幅状态下工作。当油管内的应力应变进入强化段εeq >1 0 - 2 ε,塑性应变幅超过 4× 1 0 - 5ε时 ,油管就会发生疲劳断裂     

Instantaneous Squeeze-Film Force Between a Heat Exchanger Tube and a Support Plate for Arbitrary Tube Motion

The instantaneous squeeze-film force between a heat exchanger tube and a support plate is studied. Based on a two-dimensional rectangular plate model, a short-sleeve squeeze-film model for arbitrary tube motion is developed. The instantaneous squeeze-film force is expressed in normal and tangential directions. The normal squeeze-film force consists of four nonlinear terms, the viscous, unsteady inertia, convective inertia and centripetal inertia terms. Three nonlinear terms, the viscous, unsteady inertia and Coriolis inertia terms, make up the tangential squeeze-film force. An experimental apparatus was developed in order to evaluate the theoretical models against measurements of a finite length squeeze film. A modified model based on the experimental data is obtained where the viscous terms for both directions are multiplied by the instantaneous Reynolds number. All the inertia terms are multiplied by constant coefficients. The modified model is in good agreement with most experimental cases for unsymmetrical linear motion, approximate circular motion and elliptical motion. The form of the modified model is suitable for predicting instantaneous squeeze-film forces in the simulation of heat exchanger tube vibration. Further work using different sized components and fluid properties is required in order to finalize coefficient values.     

Relative Permeability Analysis of Tube Bundle Models

The analytical solution for calculating two-phase immiscible flow through a bundle of parallel capillary tubes of uniform diametral probability distribution is developed and employed to calculate the relative permeabilities of both phases. Also, expressions for calculating two-phase flow through bundles of serial tubes (tubes in which the diameter varies along the direction of flow) are obtained and utilized to study relative permeability characteristics using a lognormal tube diameter distribution. The effect of viscosity ratio on conventional relative permeability was investigated and it was found to have a significant effect for both the parallel and serial tube models. General agreement was observed between trends of relative permeability ratios found in this work and those from experimental results of Singhal et al. (1976) using porous media consisting of mixtures of Teflon powder and glass beads. It was concluded that neglecting the difference between the average pressure of the non-wetting phase and the average pressure of the wetting phase (the macro-scale capillary pressure) – a necessary assumption underlying the popular analysis methods of Johnson et al. (1959) and Jones and Roszelle (1978) – was responsible for the disparity in the relative permeability curves for various viscosity ratios. The methods therefore do not account for non-local viscous effects when applied to tube bundle models. It was contended that average pressure differences between two immiscible phases can arise from either capillary interfaces (micro-scale capillary pressures) or due to disparate pressure gradients that are maintained for a flow of two fluids of viscosity ratio that is different from unity.     

管阵流体弹性不稳定性分析

在设计换热器、蒸汽发生器等核电站和石油化学工业设备的管阵时都会遇到横向流作用下的流体诱发振动问题.无论是从引起振动的可能性,还是从产生振动后的危害性来看,流体弹性不稳定性是管阵流体诱发振动的最重要机理.本文在比较、分析现行的流体弹性不稳定性数学模型的基础上,提出了一种新的数学模型,给出了不稳定性临界流速的计算方法,开发了相应的计算机程序.与实验结果和其它理论模型的计算结果比较表明:本文模型应用方便,得到的结果与实验结果基本一致.     

On the Permeability of Fractal Tube Bundles

The permeability of a porous medium is strongly affected by its local geometry and connectivity, the size distribution of the solid inclusions, and the pores available for flow. Since direct measurements of the permeability are time consuming and require experiments that are not always possible, the reliable theoretical assessment of the permeability based on the medium structural characteristics alone is of importance. When the porosity approaches unity, the permeability?Cporosity relationships represented by the Kozeny?CCarman equations and Archie??s law predict that permeability tends to infinity and thus they yield unrealistic results if specific area of the porous media does not tend to zero. The aim of this article is the evaluation of the relationships between porosity and permeability for a set of fractal models with porosity approaching unity and a finite permeability. It is shown that the tube bundles generated by finite iterations of the corresponding geometric fractals can be used to model porous media where the permeability?Cporosity relationships are derived analytically. Several examples of the tube bundles are constructed, and the relevance of the derived permeability?Cporosity relationships is discussed in connection with the permeability measurements of highly porous metal foams reported in the literature.     

传爆序列长通道冲击起爆的数值模拟

结合传爆序列长通道冲击起爆试验研究结果 ,给出了理论计算的简化模型 ,使用LS DYNA程序计算出薄底壳首发雷管爆炸输出沿长通道的压力及冲击波到达时间变化 ,分析了冲击波与爆炸产物分离的过程及继发雷管可靠起爆时的入射压力。     

关于毕托管标定的数据处理问题

毕托管标定是实验流体力学教学中最基本的实验之一，在以往的教学中大多用经典的最小二乘法把实验数据拟合成过坐标原点的直线。本文讨论了用一般最小二乘法拟合直线方程的方法，并得出下列结论：（１）用经典最小二乘法带来的误差随数据相关系数减小而增大；（２）一般情况下，应该用不过坐标原点的直线方程拟合实验数据。     

A New Shock Tube Facility for Tunnel Safety

In this paper, a new double diaphragm shock tube facility for studying the structural response of a circular plate resting on soil, when subjected to a shock wave, is described. The present shock tube has been designed in the framework of a more extensive research program aimed at the investigation of underground tunnel lining under blast and fire conditions. The innovative features of the facility are an end-chamber conceived to investigate soil-structure interaction and a burner equipment to heat the specimen in order to study to what extent thermal damage can affect the transmitted and reflected pressure wave as well as the structural response. Details of the shock tube design, construction and test procedure operations are discussed in the paper. Particular emphasis is placed on the principles that have driven the experimental equipment design choices. Numerical simulations have been performed to assess the ideal shock tube performance in terms of reflected pressure and test time duration as well as to evaluate how far the fire testing situation actually is from that normally used in tunnel design.