高浓度水煤浆的流变特性与壁面滑移效应试验研究

在水煤浆综合输送试验装置上,采用直径分别为25 mm、32 mm、40mm和50 mm的圆管,对质量分数为65.3%、67.1%和68.2%的高浓度水煤浆进行了流动特性和滑移特性试验研究.从合理假设的滑移速度模型和流动结构出发,得出滑移速度和真实流变特性的确定方法,获得了不同浓度和管径下试验水煤浆的滑移速度及真实流变特性.结果表明:所采用的滑移速度模型能很好地描述所试验水煤浆的宏观滑移流动规律;煤浆浓度较高时,呈现显著的非牛顿流体特性,壁面滑移效应显著;壁面滑移效应与煤浆的真实流变特性关系密切,两者共同支配管内流动,对流动特性影响显著.     

水煤浆流经局部管件的阻力特性研究进展

水煤浆流经局部管件阻力特性的研究对水煤浆管道输送的工业应用和设计有重要意义。论文对水煤浆流经局部管件的阻力特性的研究方法进行了较为全面的阐述,包含了其影响因素、实验方法、数值模拟及实验结果分析等方面的一些研究进展。与此同时,笔者也对局部管件的几何定义、压差分析及阻力特性参数等方面提出一些新的观点,并对局部管件中水煤浆的阻力特性研究作了几点展望。     

高浓度水煤浆的流动特性

讨论和分析了高浓度水煤浆的管内流动特性,阐述了影响水煤浆流动特性的若干因素,综述了水煤浆管内流动阻力特性的理论和计算方法。在分析探讨水煤浆“滑移层”的机理及其对管内流动影响和修正的基础上,介绍了表征水煤浆流动状态的相似准则数——广义雷诺数,可以应用于工程上的简化计算。     

高浓度水煤浆流动的滑移现象及对其管内流动特性的影响

本文采用理论分析与实验研究相结合的方法,讨论了高浓度水煤浆在圆管内流动的滑移现象。分析了“滑移层”的存在在对水煤浆管内流动特性的影响,并提出了一种用管流法确定水煤浆的真实本构关系的滑移修正方法。     

水煤浆的流变特性研究进展

总结了水煤浆流变特性的国内外研究进展,对水煤浆的流变学属性、流变特性的研究方法、流变特性的影响因素和流变机理等方面的研究现状和研究成果进行了概述,重点对水煤浆流变特性的影响因素和流变机理的研究进展进行了详细地阐述,指出了目前水煤浆流变特性研究中存在的问题,探讨性地提出了今后的研究方向。     

90°水平弯管内水煤浆的阻力特性试验研究

在水煤浆综合输送中试试验台上,将管径为50mm的90°水平弯管配以不同弯径比,对神华煤水煤浆进行了阻力特性试验研究。根据试验结果,对弯管内水煤浆的局部压力损失、摩擦阻力损失及弯管内流动有效长度等方面的一些特性进行总结。结果表明:采用合理的定义及方法,水煤浆弯管内流动的一些特性存在较为明显的规律。     

高浓度水煤浆流变特性和稳定性试验研究

水煤浆是由液固两相组成的非牛顿流体,流变性和稳定性十分复杂,影响因素也很多,其流变特性和稳定特性对管道输送和燃烧性能起着决定性的作用.借助于水煤浆粘度计对质量浓度为60%以上的水煤浆进行流变性测量,研究了温度、浓度和添加剂对煤浆流变性的影响,水煤浆的表观粘度随温度的升高而降低,随浓度增加而增大,添加剂的加入大大改善水煤浆的流变特性.通过对水煤浆稳定性的研究,得出了水煤浆的稳定性随浓度增加而增加,与煤种有关,适量的添加剂能改善稳定性,稳定性随温度升高而降低.从输送水煤浆总体经济角度看,水煤浆的输送温度在20y～40℃为宜.     

水煤浆真实流变特性的研究

在中试规模的浆体输送装置上,通过改变浓度、温度、煤粉粒度和管道直径,系统地考察了当存在壁面滑移现象时水煤浆在直管内的流动特性.利用经典Mooney滑移修正方法的模型检验功能和Tikhonov正则化方法的准确可靠性,确定了水煤浆的真实流变特性.得到如下结论:随着浓度升高,水煤浆的真实剪切粘度和非牛顿流体特性显著增加;升高温度和增大煤粉粒径,可有效降低水煤浆的真实剪切粘度,但温度改变对浆体的非牛顿流体特性基本无影响;当固相体积份额/最大填充率(/m)低于0.9时,极限剪切粘度随浓度缓慢增加,当/m高于0.9时,极限剪切粘度急剧增加;极限剪切粘度与温度的关系遵循Arrhenius定律,且浓度对流动活化能基本无影响.     

温度对高浓度水煤浆流变特性的影响

对高浓度的水煤浆流变特性影响因素很多,温度是其中的一个重要因素.借助于水煤浆粘度计在不同温度、不同剪切速率下对3种浓度的水煤浆进行粘度测度,得出在各个剪切速率下粘度与温度的关系.结果表明,在给定的剪切速率下,水煤浆的表观粘度与温度关系可以用近似Arrhenius关系式表示.采用Herschel-Bulkley模型拟合出水煤浆的流变参数,发现水煤浆的流变参数随温度变化呈现出规律性地变化.     

增压流化床用水煤膏在管内流动特性

通过试验研究水煤膏在中小管道中的流变特性和阻力特性,分析了各影响因素对水煤膏流变特性的影响,给出了水煤膏管内流动阻力的计算方法。研究表明,适当配比的水煤膏可以在很低水份下（22.16%）顺利流动,石灰石的添加和温度的提高可以降低水煤膏在管道内的流动阻力,水煤膏的流变特性可用Herschel-Bulkley模型描述。在层流状态下,水煤膏的阻力系数可用类似于牛顿流体的广义雷诺数表征,λ=64/Reg。     

Combined effects of homogeneous and heterogeneous reactions on peristalsis of Ree-Eyring liquid: Application in hemodynamic flow

This research examines the influence of homogeneous and heterogeneous chemical reactions on the peristaltic flow via an inclined permeable channel. The current investigation emphasizes on modeling the flow of blood in narrow arteries by taking convective and wall properties into account. The Ree-Eyring non-Newtonian model is used to govern the fluid flow due to its significance in understanding the behavior of dilatant, pseudoplastic, and viscous liquids. The variation in variable viscosity and thermal conductivity is considered for analyzing the complex rheological behavior of blood. The similarity transformations are used in the process of nondimensionalization. The series solution procedure is adopted to solve the governing nonlinear differential equations. The expressions for velocity, temperature, concentration, and trapped bolus are obtained. The computational results are analyzed with the help of graphs for shear thickening, shear thinning, and Newtonian fluid models. One of the significant findings of the current model is that an introduction of variable liquid properties improves the temperature and velocity profiles for Newtonian and pseudoplastic fluid models. Compared with the other theoretical models developed, the rheological and flow properties of various biological fluids can be derived from the model used in the present investigation.     

Exact solution of two phase stratified flow through the pipes for non-Newtonian Herschel–Bulkley fluids

Steady state, laminar and fully developed stratified two phase flow including two immiscible fluids through the pipe has been studied analytically. One of the phases is Newtonian and the other one is non-Newtonian which obeys the Herschel–Bulkley fluid model. The dimensionless velocity distribution, Martinelli correction factor and non-Newtonian liquid holdup have been reported. The effect of interface curvature and wide range of viscosity ratio of two phases on flow behavior has been investigated. The results illustrate that the non-Newtonian rheological properties have significant effects on dimensionless velocity and consequently on two phase flow pressure drop specially for larger viscosity ratio.     

An Investigation of Stokes' Second Problem for Non-Newtonian Fluids

ABSTRACT

Stokes flow produced by an oscillatory motion of a wall is analyzed in the presence of a non-Newtonian fluid. A total of eight non-Newtonian models are considered. A mass balance approach is introduced to solve the governing Equations. The velocity and temperature profiles for these models are obtained and compared to those of Newtonian fluids. For the power law model, correlations for the velocity distribution and the time required to reach the steady periodic flow are developed and discussed. Furthermore, the effects of the dimensionless parameters on the flow are studied. For the temperature distribution, an analytical solution for Newtonian fluid is developed as a comparative source. To simulate the rheological behavior of blood at unsteady state, three non-Newtonian constitutive relationships are used to study the wall shear stress. It is found that in the case of unsteady stokes flow, although the patterns of velocity and wall shear stress is consistent across all models, the magnitude is affected by the model utilized.     

竖直弯管内水煤浆局部阻力特性的研究

在中试试验台上对水煤浆流经竖直弯管的局部阻力特性进行了研究,分析了水煤浆在竖直弯管内流动的最佳弯径比,并利用多种阻力特性分析方法对试验结果进行了处理.结果表明:水煤浆流经竖直弯管时存在最佳弯径比;竖直弯管内的流动有效长度和摩擦阻力损失比存在较明显的变化趋势,且受弯径比影响较大;利用经验公式对竖直弯管内的局部阻力损失系数与雷诺数的关系进行拟合,尽管存在弯径比的影响,但拟合误差较小,能满足工程实际应用;将De改进为De′,对摩擦阻力损失与De′的关系进行拟合,可以很好地消除弯径比的影响,得出拟合误差更小、能更好地指导工程实际应用的经验公式.     

Study on local resistance of non-Newtonian power law fluid in elbow pipes

This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved90° bend pipe with circular cross-sections,which are widely used in industrial applications.By employing numerical simulation and theoretical analysis the properties of the flow and local resistance of power law fluid under different working conditions are obtained.To explore the change rule the experiment is carried out by changing the Reynolds number,the wall roughness and different diameter ratio of elbow pipe.The variation of the local resistance coefficient with the Reynolds number,the diameter ratio and the wall roughness is presented comprehensively in the paper.The results show that the local resistance force coefficient hardly changes with Reynolds number of the power law fluid;the wall roughness has a significant impact on the local resistance coefficient.As the pipe wall roughness increasing,the coefficient of local resistance force will increase.The main reason of the influence of the roughness on the local resistance coefficient is the increase of the eddy current region in the power law fluid flow,which increases the kinetic energy dissipation of the main flow.This paper provides theoretical and numerical methods to understand the local resistance property of non-Newtonian power law fluid in elbow pipes.     

水煤浆流经渐缩管段的局部阻力特性

在中试试验台上研究了水煤浆流经渐缩管的局部阻力特性,分析了滑移产生的机理,采用一种新的滑移修正方法确定了水煤浆的真实流变模型,同时获得了水煤浆流经渐缩管时局部能量损失的计算方法.运用非均相流模型和量纲理论,提出了水煤浆流经渐缩管段时局部阻力系数的准则式,发现随着广义雷诺数的增加,渐缩管局部能量损失系数先下降然后逐渐趋于稳定,同时根据试验结果获得了计算局部能量损失系数的经验公式.     

Steady revolving flow and heat transfer of a non-Newtonian Reiner–Rivlin fluid

The steady revolving flow and heat transfer of a non-Newtonian Reiner–Rivlin fluid is studied. The momentum equation gives rise to a highly nonlinear boundary value problem. Attempt has been made to study the properties of the solution of the momentum equation analytically before proceeding for numerical solution. The effects of non-Newtonian fluid characteristic on the velocity and temperature fields have been discussed in detail and shown graphically.