Subjects: Mine Engineering Technology >> Development Engineering of Oil and Gas Well Subjects: Mechanics >> Hydromechanics submitted time 2020-12-25
Abstract: Gas-liquid two-phase displacement are widely observed in oil and gas reservoir. The traditional seepage theory holds that the phase pressures and Darcy velocities must be continuous at the jump interface, and we have falsified them in previous studies. In this paper, the jump interface condition of two-phase seepage is extended from incompressible fluids to compressible. Taking gas-water displacement as an example, the new connection conditions of phase pressures and Darcy velocities at the gas-water displacement front in porous media were built. The results show that at the flood front, the global pressure is continuous, but not the fluid pressure are. (2) The total Darcy velocity can be discontinuous with a specific functional relationship;(3) The phase Darcy velocity of each phase of the fluid is discontinuous.
Peer Review Status:Awaiting Review
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc. submitted time 2018-01-05 Cooperative journals: 《工程热物理学报》
Abstract:本文针对蒸汽轮机末级湿蒸汽形成现象,分析湿蒸汽非平衡凝结流动的控制方程及物理模型。对Moses andStein 喷嘴进行了计算分析,得出湿蒸汽形成过程的特点,并与实验结果相比,契合度可以证明数值计算模型及方法的正确性。最后对某汽轮机静叶进行数值计算,分析湿度及过冷度分布,提出一种新型的静叶除湿结构,并对除湿效果进行计算分析。结果表明,随着通道直径的增加,静叶出口位置的平均湿度降低,湿汽损失减小。
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-11-07 Cooperative journals: 《工程热物理学报》
Abstract: The research, analyzed the governing equations and physical models of wet steam non-equilibrium condensation flow, carried out a numerical calculation on the Moses and Stein nozzle and the correctness of the numerical calculation is proved by comparing with the experimental results which is mainly aiming at the wet steam formation phenomenon in the last stage of the steam turbine. Besides, a fresh dehumidification structure was proposed and the numerical calculation was performed based on a specific steam turbine after analyzed the distribution of wetness and supercooling. The results show that: as passage diameter increasing, both of the average wetness in the outlet position of the stator and the wetness loss decrease.
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-05-24 Cooperative journals: 《工程热物理学报》
Abstract:考虑蒸发冷却效应、气相物质扩散、气液两相传热及界面变形,采用任意拉格朗日-欧拉法数值模拟研究了接触角θ、蒸发数Ec、Ma数对0.65cSt硅油液滴固定接触角模型蒸发及Marangoni对流的影响。发现:液滴无量纲体积V*变化与接触角θ、Ma数有关,而与Ec数无关;且V*2/3随时间线性减少。当θ0.479 rad时,仅存在热毛细涡流结构。当0.105 rad0.401 rad时,热毛细涡流结构与多个BM涡流结构的分界Ma数随θ增大而增大。
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-05-24 Cooperative journals: 《工程热物理学报》
Abstract:对于具有孔隙结构和微尺度效应的低渗透储层,其渗流现象的介观机理逐渐受到人们的重视。本文采用微流控技术在硅片上加工出微通道作为微观模型,模拟岩心内部的孔隙结构,对微通道中单相和油水两相的渗流规律进行了实验研究。研究结果表明,微观模型中带有喉道段的微通道存在启动压力梯度,这揭示了孔隙中的喉道是低渗透储层中产生启动压力梯度的主要介观因素。启动压力与孔隙结构和驱替介质的性质有关,在此基础上建立了适用于单相和油水两相渗流的启动压力预测模型。
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2017-03-22 Cooperative journals: 《工程热物理学报》
Abstract:本文针对微通道内气粒间流动传热过程开展数值研究,所建模型中气体处理为可压缩/变物性流体,并在气固交界处采用速度滑移和温度跳跃边界条件以考虑其微尺度效应。在数值研究基础上,分析了微通道受限空间、克努森数、气体流速以及颗粒表面温度对微通道内气粒换热的影响。研究结果表明,受限空间结构将强化气粒间换热过程,颗粒表面平均传热努赛尔数随微通道气体流量增大而增大,克努森数增大以及颗粒表面温度升高都将导致颗粒表面平均传热努赛尔数减小。
Subjects: Mechanics >> Basic Mechanics submitted time 2023-04-24 Cooperative journals: 《应用力学学报》
Abstract: This paper is intended for the study of a right-angle flexible elbow with a large bending diameter ratio.A numerical simulation on the erosion characteristics of gas-solid two-phase flow in the elbow is conducted employing the Fluent simulation software package,in which such factors as gas inlet velocity,mass flow rate of entrained solid particles,elbow ribs and bending diameter ratio under different working cases are considered based on the discrete phase model and the General erosion model.The results show that the velocity distribution of the gas-solid two-phase flow field in the longitudinal section of the elbow is separated.The maximum erosion rate of elbow varies exponentially with the increase of the gas inlet velocity,and linearly with the increase of the particle mass flow rate.As the number of ribs embedded in the inner wall of elbow increases,the erosion ratio firstly decreases and then slightly increases and finally stabilizes.The strength of the secondary flow in the large bend is smaller than that in the elbow,and the erosion resistance of the elbow improves to a certain extent due to the existence of ribs.The severely eroded area in the elbow occurs in the area where the elbow deflects along the flow direction at an angle of about 26° and presents V-shaped erosion morphology,which is caused by the special particle movement trajectory at the elbow.The groove-like erosion morphology appears within the angle range of 60°-80° along the flow direction,which is due to the secondary and multiple collisions of particles in the elbow.
Subjects: Mechanics >> Hydromechanics Subjects: Mine Engineering Technology >> Development Engineering of Oil and Gas Well submitted time 2022-05-12
Abstract:
Almost all the oil or gas reservoirs have sharp interfaces. The key to establish the corresponding mathematical flow model is to find the reasonable phase pressures and velocities connection conditions at the sharp interfaces. In the existing seepage mechanics theory, it is generally recognized that the velocity and pressure of each phase of fluid are continuous at the sharp interface (named CPVCM). However, we can find that CPVCM contradicts some other multiphase seepage phenomena or theories: (1) The saturation distribution of fluid in the real world does not always obey the fluids distribution rules that CPVCM required;(2) Near the flood front, CPVCM conflicts with Rankine-Hugoniot Interface Conditions;(3)It has been proved that the formula of phase fluxes across the sharp interface which are derived from CPVCM, harmonic average of transmissibility, possible give non-physical results in some cases, so that they have been replace by single points upstream weighting method(SPU) and other high order method, such as TVD,ENO,WENO et al. . Therefore, we retraced the way that how to derive the CPVCM based on the mass conservation law in the early lectures, and find that the two particles on both sides of the interface which mentioned in the interface condition has been misplaced on the same interface, therefore, the proof process is essentially equivalent to preset the continuity of velocity and pressures of each phase and prove they are continuous. Such proof is invalid self-proof. Then, taking the incompressible two-phase fluids flow in the porous media as an example, the interface condition with discontinuous velocity and pressure of each phase (JPVCM) is obtained according to the same laws of mass conservation and two-phase Darcy’s law. Finally, it is suggested that, as for the incompressible two-phase flow in porous media, the jump conditions should be (1) total velocity of the two phases are equal, (2) the velocity of each phase at the sharp interface adopt the upstream ones.
Peer Review Status:Awaiting Review
Subjects: Mine Engineering Technology >> Development Engineering of Oil and Gas Well Subjects: Mechanics >> Hydromechanics submitted time 2021-01-06
Abstract: Jump interface in porous media exists widely in oil and gas reservoirs during development. The traditional seepage theory holds that the pressure and Darcy velocity are continuous at the discontinuous interface, and we have falsified them in previous studies. In this paper, taking gas-water phase as an example and considering the compressibility of the fluids, the connection conditions of phase pressures and Darcy velocities at the immovable jump interface are established. The results show that :(1) the total pressure is always continuous, but the phase pressure of each phase can be discontinuous;(2) The total Darcy velocity at the both sides are equal, but the phase Darcy velocity probably discontinuous;(3) The connection conditions of fixed jump interface do not comfort to Rankine - Hugoniot conditions, which are different from mobile jump interface, i.e. flood front.
Peer Review Status:Awaiting Review
Subjects: Dynamic and Electric Engineering >> Engineering Thermophysics submitted time 2018-02-01 Cooperative journals: 《工程热物理学报》
Abstract: In this work, a new optical diagnostic technique (high-speed two-color PIV) was developed and applied to simultaneously measure the flow-fields of a multi-hole GDI fuel spray and its ambient gas. The interaction process between the fuel spray and ambient gas was investigated under various superheated conditions based on this technique. The results showed that on one hand the momentum transfer from the fuel spray to the surrounding ambient gas was enhanced with the superheat degree due to the expanded two-phase interaction area and decreased spray droplet-size. On the other hand the reaction of the ambient gas motion on the fuel spray was observed. The complicated relationship between the spray injection inertia force and the aerodynamic force was provided with a preliminary explanation.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The influence of pipebend parameters on flow field of liquid-solid two-phase flow and the erosion of pipes was studied by means of computational fluid dynamics (CFD). The relation of the erosion of pipe with the variation of the diameter, curvature-to-diameter ratio and bending angle of the pipe, as well as the particles induced erosion of the pipe wall were mainly concerned. The results show that: (1) the erosion rate varies with the varying pipeline parameters, among them the diameter is the main factor, the curvature-to-diameter ratio the next, and the bending angle the last; (2) the areas of serious erosion mainly exist in the side walls of joints as well as the outside of the joints between export of straight pipe and elbow. However, the location of the most serious erosion is uncertain, which will change along with the variation of the bend pipe parameters.
Subjects: Geosciences >> Geography submitted time 2023-11-13 Cooperative journals: 《干旱区地理》
Abstract:古尔班通古特沙漠南缘处在风、水两相营力作用的交汇区域,沉积环境独特,对气候变化响应敏感,是研究中国西北沙区全新世环境演变的理想区域。选取古尔班通古特沙漠南缘荒漠-绿洲过渡带3个风积-冲积交互地层剖面,在实地观察岩性特征、沉积序列的基础上,通过光释光(OSL)测年建立年代标尺,结合粒度参数、磁化率和石英颗粒表面微形态特征的对比分析,综合判别研究区全新世以来的沉积环境演化过程。结果表明:研究区地层序列主要反映了河流过程和风沙过程的消长,并且表现出同期异相特征。约11.8~10.2 ka,天山北麓冲积作用活跃,辫状河深入沙漠,局部发育河流沉积;约10.2~6.0 ka,研究区进入全新世适宜期,沙漠北退,河湖、湿地广泛发育;约6 ka至今,研究区冲积作用减弱,风沙活动频繁,沙漠环境与河流环境交替出现。近千年以来,研究区沉积环境表现出风沙活动增强、河流冲积萎缩的特点,古尔班通古特沙漠总体上有南侵扩张趋势。本区全新世湿润环境的出现主要受制于西风环流的强弱变化和位置变动,此外,北半球夏季太阳辐射与天山冰川的耦合作用及北大西洋冷事件引发的气候波动可能也是影响本区全新世沉积环境变迁的重要因素。