气体非牛顿流体两相流动.docx
- 文档编号:24106678
- 上传时间:2023-05-24
- 格式:DOCX
- 页数:9
- 大小:18.24KB
气体非牛顿流体两相流动.docx
《气体非牛顿流体两相流动.docx》由会员分享,可在线阅读,更多相关《气体非牛顿流体两相流动.docx(9页珍藏版)》请在冰豆网上搜索。
气体非牛顿流体两相流动
气体非牛顿流体两相流动
气体/非牛顿流体两相流动
与气/水两相流动阻力特性的比较
劳力云吴应湘郑之初李东晖石在虹
(中国科学院力学研究所应用流体力学研究室)
提要本文基于常用的均相流动模型~主要针对油/气/水混输管道中经常遇到的气体
/幂律液体水平管道两相流动~对其阻力特性进行了阐述~其中包括流动基本模型和方程、
常用的经验估算方法等方面~将它与气/水两相流动中对应的有关问题进行了比较。
SummaryInthispaper,thepressurelosscharacteristicsofthegasandpower-lawliquidtwo-phaseflowthatwasoftenmetwithinoil/gas/waterconcurrent
--oneofthetransportationpipelinewerepresented.Basedthehomogeneousmodelfrequentlyadaptedmodels,theissuesoffundamentalmodelandequationsoftheflowandtheestimationmethodsofpressurelosseswereincluded.Theseresultswerealsocomparedwiththecorrespondentsrelatedtogas/watertwo-phaseflows.
关键词均相模型气液两相流非牛顿流体
Keywordshomogeneousmodel,gas/liquidtwo-phaseflow,non-Newtonianfluid
1引言
在海洋石油资源开发中,油气混输正在成为一种越来越重要的油气输运手段。
为了了解
油气混输管道中的能耗,进行混输管线与增压系统的合理设计,在油气混输过程中对油、气、
水等介质进行有效准确的计量,以及对整个混输系统的运行状态进行监控等等,需要深入了
解油气混输管道的流动阻力特性。
另一方面,油气混输问题实际上属于气液两相流动中的气
体/非牛顿液体的流动问题。
而目前在国内外,气液两相流研究主要集中于对气体/牛顿液体
(尤其是气/水两相流)的流动特性上,对于气体/非牛顿液体流动问题的研究相对较少,尚
无比较成熟的结果。
因此,对气体/非牛顿液体的流动阻力特性进行研究,不但具有重要的
工程价值,也具有较大的学术意义。
实际测试结果表明,我国油田所生产的原油,在常温输送时,其流变特性表现为幂率流
ndu,,,K,,,,dr[1,2],,体的特性——流动剪应力与剪应变呈现为幂率关系(对于管流即)。
其主
edgesshouldbecleaned,aftermakingsurethatnodefectshallbemarkedwithamarkerpentowritedownweldingneartheweld,includingthesloganofwelding,welders,etc.(16)weldingQianPreheatandtheweldingHouheattreatmentpipeweldingQianPreheatandtheweldingHouheattreatmentprocessconditionsweldingQianPreheatandtheweldingHouheattreatmenttemperaturetableprojectmaterialweldingQianpreheattemperature(?
)weldingHouheattreatmentandtheinsulationtime(?
/H)wallthick(mm)temperature(?
)wallthick(mm)temperature(?
)20?
26100~200>36600~650/1-1.515CrMo?
10150~200>10670~700/1.2-2Preheatandtheheattreatmentprocessinthe,Innerandouterwalltemperatureshallbekeptuniform,inordertoavoidinternalstresses.Preheatingbeforeweldingandpostweldheattreatment,shallmeasureandrecordthetemperature,temperaturemeasurementlocationsandnumberofpointsarereasonable.Pronetowelddelayedcrackofsteel,postweldheattreatmentafterweldingshouldbecarriedoutpromptly,whennotconductingtimelypostweldheattreatment,shouldbeuniformlyheatedto200~300?
immediatelyafterweldingandinsulationandslowcooling,...26mmmorethan20steelpipeweldingpreheatingbeforeweldingshouldbecarriedout,36mmtheaboveheattreatmentafterweldingshouldbedone.Beforeweldingandheattreatmentusedoxyacetyleneflameheating,heattreatmentafterweldingusingspecialheattreatmentafterweldingequipment.Hardnessafterheattreatmentofweldsneededtesting.6.5.4sidesofthedissimilarsteelweldingwhenwerenon-austeniticsteelorausteniticsteel,alloycontentaccordingtoloweronesideofthebasemetalorselectingweldingmaterialinbetween.Whenoneofthesidesofmaterialwhenausteniticsteels,shouldselectthe
要的参数为稠度系数K和幂率指数n。
本文中的非牛顿液体即指这一类流体。
下面根据两相流的均相流动模型和基本方程,针对油/气/水混输管道中经常遇到的气体/幂律液体水平两相流动的阻力特性进行了阐述,并讨论了对摩擦系数的经验估算方法,将它与气/水两相流动中对应的有关问题进行了比较。
2均相流动模型
在某些两相流态中,如果一相均匀地弥散在另一相中,两相间的动量传递和能量传递足够快,两相的局部平均速度和温度就基本相同。
此时,可以应用均相模型对两相流的流动特性进行研究。
均相模型的基本思路是用一等效可压缩流体代替两相流体。
一般,在研究气泡流、雾状流等流态下的流动特性时,常采用均相流模型。
均相模型的基本假设为:
u,u,uLHG
(1)
(1)气液两相具有相同的线速度,即(式中u表示介质线速度,
下标G,L和H分别表示气相、液相和均相,下同);
(2)
(2)两相间处于热平衡状态。
对于两相管流,设其轴线方向为z,根据连续性、动量守恒和能量守恒原理以及上述假设,可以得到:
ddu1dAHHu,,,,u,0HHHHdzdzAdz
(1)
Pdvdp2rH,,,,G,,gsin,H0dzAdz
(2)
dvdpdF2H,,,,G,,gsin,HHdzdzdz(3)
,0上列式中,为介质密度,A为流道截面积,p为管道中的压力,P为流道周长,为管r
1v,G,,u,HH道壁面剪应力,为质量流速,为介质比容,g为重力加速度,,为管道轴线的倾角,F为管道中摩擦力所引起的能量损失。
比较
(2)、(3)两式,易知由摩擦力引起的管道压降
2,,dp4f,uFPdFTPHH,,r,,,,,,,,H0dz2D,,dzAe(4)式中f两相摩擦系数,D为两相流动水力直径。
TPe
,dpFP,,r,,,,,0dz,,A实际上,
(2)式反映了这样一个事实,管道的总压降由管道摩擦压降、edgesshouldbecleaned,aftermakingsurethatnodefectshallbemarkedwithamarkerpentowritedownweldingneartheweld,includingthesloganofwelding,welders,etc.(16)weldingQianPreheatandtheweldingHouheattreatmentpipeweldingQianPreheatandtheweldingHouheattreatmentprocessconditionsweldingQianPreheatandtheweldingHouheattreatmenttemperaturetableprojectmaterialweldingQianpreheattemperature(?
)weldingHouheattreatmentandtheinsulationtime(?
/H)wallthick(mm)temperature(?
)wallthick(mm)temperature(?
)20?
26100~200>36600~650/1-1.515CrMo?
10150~200>10670~700/1.2-2Preheatandtheheattreatmentprocessinthe,Innerandouterwalltemperatureshallbekeptuniform,inordertoavoidinternalstresses.Preheatingbeforeweldingandpostweldheattreatment,shallmeasureandrecordthetemperature,temperaturemeasurementlocationsandnumberofpointsarereasonable.Pronetowelddelayedcrackofsteel,postweldheattreatmentafterweldingshouldbecarriedoutpromptly,whennotconductingtimelypostweldheattreatment,shouldbeuniformlyheatedto200~300?
immediatelyafterweldingandinsulationandslowcooling,...26mmmorethan20steelpipeweldingpreheatingbeforeweldingshouldbecarriedout,36mmtheaboveheattreatmentafterweldingshouldbedone.Beforeweldingandheattreatmentusedoxyacetyleneflameheating,heattreatmentafterweldingusingspecialheattreatmentafterweldingequipment.Hardnessafterheattreatmentofweldsneededtesting.6.5.4sidesofthedissimilarsteelweldingwhenwerenon-austeniticsteelorausteniticsteel,alloycontentaccordingtoloweronesideofthebasemetalorselectingweldingmaterialinbetween.Whenoneofthesidesofmaterialwhenausteniticsteels,shouldselectthe
,,,dpdpFAdv2,,H,,,,,,G,,,,dzdz,gsin,,,,,dzH管道加速压降和管道重力压降三部分构成的。
流体的流变特性不影响其中的加速压降和重力压降,但将通过影响两相摩擦系数而直接影响
摩擦压降。
3气/水两相流的摩擦系数计算
均相模型在本质上将两相流动视为单相流动,其摩擦系数的确定方法与单相流动类似。
在单相流动的摩擦阻力计算中,摩擦系数f与流体介质动力粘度,的关系比较简单,主要决
GDRe,,定于流动的Reynolds数(式中D为单相流动的水力直径)。
当Re低于2000时(层
流),摩擦系数为
f,16/Re(5)
当Re高于2000时(湍流),则应用Blasius公式:
0.25f,0.079,,Re(6)
[3]对于气体/牛顿液体的气液两相流,常采用以下三种方法计算粘度:
(1)取两相粘度为单相粘度。
当含气率较低时,取两相粘度为液相粘度
,,TPL(7)
当含液率较低时,取两相粘度为气相粘度
,,TPL(8)
(2)低浓度悬浮小球粘度计算式。
对于空隙率,低于0.05的气泡流,取两相粘度为
,,(1,,)TPL(9)
(3)经验拟合关系式。
常用下列几种
1x1,x,,,,,TPGLMcAdams:
(10)
,,(1,x),,xTPLGCicchitti:
(11)
,,(1,,),,,TPLGDukler:
(12)上列式中,x为质量含气率(干度),,为体积含气率。
edgesshouldbecleaned,aftermakingsurethatnodefectshallbemarkedwithamarkerpentowritedownweldingneartheweld,includingthesloganofwelding,welders,etc.(16)weldingQianPreheatandtheweldingHouheattreatmentpipeweldingQianPreheatandtheweldingHouheattreatmentprocessconditionsweldingQianPreheatandtheweldingHouheattreatmenttemperaturetableprojectmaterialweldingQianpreheattemperature(?
)weldingHouheattreatmentandtheinsulationtime(?
/H)wallthick(mm)temperature(?
)wallthick(mm)temperature(?
)20?
26100~200>36600~650/1-1.515CrMo?
10150~200>10670~700/1.2-2Preheatandtheheattreatmentprocessinthe,Innerandouterwalltemperatureshallbekeptuniform,inordertoavoidinternalstresses.Preheatingbeforeweldingandpostweldheattreatment,shallmeasureandrecordthetemperature,temperaturemeasurementlocationsandnumberofpointsarereasonable.Pronetowelddelayedcrackofsteel,postweldheattreatmentafterweldingshouldbecarriedoutpromptly,whennotconductingtimelypostweldheattreatment,shouldbeuniformlyheatedto200~300?
immediatelyafterweldingandinsulationandslowcooling,...26mmmorethan20steelpipeweldingpreheatingbeforeweldingshouldbecarriedout,36mmtheaboveheattreatmentafterweldingshouldbedone.Beforeweldingandheattreatmentusedoxyacetyleneflameheating,heattreatmentafterweldingusingspecialheattreatmentafterweldingequipment.Hardnessafterheattreatmentofweldsneededtesting.6.5.4sidesofthedissimilarsteelweldingwhenwerenon-austeniticsteelorausteniticsteel,alloycontentaccordingtoloweronesideofthebasemetalorselectingweldingmaterialinbetween.Whenoneofthesidesofmaterialwhenausteniticsteels,shouldselectthe
4气体/幂率流体流动的摩擦系数计算
对于气体/幂率流体两相流,在进行摩擦系数的计算时,其基本思路类似于气/牛顿液体,
但是应根据液相的流变特性进行必要的修正。
[4]幂率液相的Renoalds数可以采用下式计算:
n2,n,DuLLRe,Ln3n,1,,n,18K,,4n,,(13)
(Re)c其临界Renoalds数也与幂率指数有关:
610(2n,1)(3n,2)(4n,3)(Re),c3(3n,1)(14)
在气相层流、气相紊流和液相层流时,可以参照牛顿流体的Blasius公式计算单相状态摩擦
系数;对于液相紊流时,则采用修正的Blasius公式计算液相摩擦系数:
af,Lb,,ReL(15)
0.133,0.217a,0.3164n,b,0.25n其中。
f,f(1,x),fxTPLG获得气、液两相的摩擦系数后,可以根据计算出两相流摩
擦系数f。
而实际的均相摩擦系数还应进行修正。
文献[2]根据三种管径的泡状流提出以下TP
的修正公式:
Bˆf,AfTPTP(16)
参数A、B仅与幂率指数有关,
2.0255A,0.3804n(17)
0.8448B,0.8911n(18)
需要指出,上述计算中,涉及介质的速度时应取介质的表观速度。
5结论
在气体/幂率液体两相流各种流态中,气泡流和雾状流流态表现出较好的介质均布性,
如各参数沿流道的变化率不大,可以采用均相流模型。
对于流动阻力中的重力分量和加速分
量,可以通过管道尺寸以及流动工况进行直接计算;对于流动摩擦阻力,需要根据实际数据
回归出经验关系进行估算。
与气/水两相流相比较,需要进一步考虑液相引起流动摩擦系数
edgesshouldbecleaned,aftermakingsurethatnodefectshallbemarkedwithamarkerpentowritedownweldingneartheweld,includingthesloganofwelding,welders,etc.(16)weldingQianPreheatandtheweldingHouheattreatmentpipeweldingQianPreheatandtheweldingHouheattreatmentprocessconditionsweldingQianPreheatandtheweldingHouheattreatmenttemperaturetableprojectmaterialweldingQianpreheattemperature(?
)weldingHouheattreatmentandtheinsulationtime(?
/H)wallthick(mm)temperature(?
)wallthick(mm)temperature(?
)20?
26100~200>36600~650/1-1.515CrMo?
10150~200>10670~700/1.2-2Preheatandtheheattreatmentprocessinthe,Innerandouterwalltemperatureshallbekeptuniform,inordertoavoidinternalstresses.Preheatingbeforeweldingandpostweldheattreatment,shallmeasureandrecordthetemperature,temperaturemeasurementlocationsandnumberofpointsarereasonable.Pronetowelddelayedcrackofsteel,postweldheattreatmentafterweldingshould
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 气体 牛顿 流体 两相 流动
![提示](https://static.bdocx.com/images/bang_tan.gif)