The transport of oil and its derivates are done, mostly, by pipeline. The time to detect leaks has to be short for pre-venting big disasters in the nature and decreasing losses for industries. The techniques available...The transport of oil and its derivates are done, mostly, by pipeline. The time to detect leaks has to be short for pre-venting big disasters in the nature and decreasing losses for industries. The techniques available for leak detection vary from visual inspection to the use of computational techniques such as mathematical modeling. This paper aims to study the fluid dynamics of two-phase flow (water-oil) in the pipe with leakage. The equations of the mass and momentum conservation are numerically solved by using the ANSYSCFX commercial code with the aid of a structured mesh of a horizontal pipe with three holes of leaks. The Eulerian-Eulerian model was adopted considering the oil as continuous phase and water as dispersed phase, and constant fluid properties. With profiles of pressure and volume fraction along the time in the pipe, the influence of leakage on the single-phase (oil) and two-phase (water-oil) was evaluated.展开更多
In this work,numerical models were developed to investigate the critical inclination of a pipeline to eliminate the water accumulation at the floor of the pipe carrying oil-water fluid.Computational fluid dynamics sof...In this work,numerical models were developed to investigate the critical inclination of a pipeline to eliminate the water accumulation at the floor of the pipe carrying oil-water fluid.Computational fluid dynamics software was used to establish a geometric model of the pipe with various inclination angles,and a grid-independent verification was conducted to determine a reasonable meshing method.Quantitative relationships were determined between the pipe inclination angle and the affecting factors including the flow velocity,viscosity and the pipe diameter,where the water accumulation would not be able to occur.Generally,the critical inclination angle increases with the fluid flow velocity.The refluxing of water is the key mechanism causing the water accumulation at the bottom of the pipe.In addition to the fluid flow velocity,an increase in fluid viscosity and a decrease in the pipe diameter cause an increase of the critical inclination angle that the water phase can be carried away by oil.The model can be used to determine the critical inclination of pipelines carrying oil-water fluid to cause the water accumulation and the operating conditions that can eliminate the accumulation of water phase at the pipe floor.展开更多
There is nothing illogical in the concept that hydrates are easily formed in oil and gas pipelines owing to the low-temperature and high-pressure environment,although requiring the cooperation of flow rate,water conte...There is nothing illogical in the concept that hydrates are easily formed in oil and gas pipelines owing to the low-temperature and high-pressure environment,although requiring the cooperation of flow rate,water content,gas-liquid ratio,and other specific factors.Therefore,hydrate plugging is a major concern for the hydrate slurry pipeline transportation technology.In order to further examine potential mechanisms underlying these processes,the present paper listed and analyzed the significant research efforts specializing in the mechanisms of hydrate blockages in the liquid-rich system,including oil-based,water-based,and partially dispersed systems(PD systems),in gathering and transportation pipelines.In addition,it summarized the influences of fluid flow and water content on the risk of hydrate blockage and discussed.In general,flow rate was implicated in the regulation of blockage risk through its characteristic to affect sedimentation tendencies and flow patterns.Increasing water content can potentiate the growth of hydrates and change the oil-water dispersion degree,which causes a transition from completely dispersed systems to PD systems with a higher risk of clogging.Reasons of diversity of hydrate plugging mechanism in oil-based system ought to be studied in-depth by combining the discrepancy of water content and the microscopic characteristics of hydrate particles.At present,it is increasingly necessary to expand the application of the hydrate blockage formation prediction model in order to ensure that hydrate slurry mixed transportation technology can be more maturely applied to the natural gas industry transportation field.展开更多
为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型...为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型,并将压力驱动的Lee模型通过用户自定义函数嵌入Fluent求解器来模拟CO_(2)的非平衡相变过程,建立了高压CO_(2)管道泄漏的非平衡相变数值模型。通过与Botros等的试验数据进行对比分析,验证了该模型的准确性。在此基础上,对比了上述模拟方法与编译S-W(Span-Wagner)状态方程模拟方法的精度和效率,最后使用本模型研究了不同初始压力对高压CO_(2)管道泄漏瞬态特性的影响。结果表明:两种模拟方法精度接近,最大相差为7.37%,但提出的模拟方法效率明显优于编译S-W状态方程的模拟方法,计算时间相较缩短约86.9%;初始压力为11.27 MPa的最大总出口质量流量比4.36 MPa的大7.24 kg/s,而对应的气相CO_(2)出口质量流量却低0.14 kg/s;初始压力为11.27 MPa和4.36 MPa对应的近场最大射流流速分别为155.12 m/s和175.50 m/s;管内初始压力越低,泄漏后到达亚稳态时过热度越大,管内及泄漏口附近相变程度越剧烈,气相出口质量流量越大,近场射流峰值速度越大。这项研究可为工业规模管道泄漏的模拟和管道泄漏的三维模拟提供更高效的方式。展开更多
文摘The transport of oil and its derivates are done, mostly, by pipeline. The time to detect leaks has to be short for pre-venting big disasters in the nature and decreasing losses for industries. The techniques available for leak detection vary from visual inspection to the use of computational techniques such as mathematical modeling. This paper aims to study the fluid dynamics of two-phase flow (water-oil) in the pipe with leakage. The equations of the mass and momentum conservation are numerically solved by using the ANSYSCFX commercial code with the aid of a structured mesh of a horizontal pipe with three holes of leaks. The Eulerian-Eulerian model was adopted considering the oil as continuous phase and water as dispersed phase, and constant fluid properties. With profiles of pressure and volume fraction along the time in the pipe, the influence of leakage on the single-phase (oil) and two-phase (water-oil) was evaluated.
文摘In this work,numerical models were developed to investigate the critical inclination of a pipeline to eliminate the water accumulation at the floor of the pipe carrying oil-water fluid.Computational fluid dynamics software was used to establish a geometric model of the pipe with various inclination angles,and a grid-independent verification was conducted to determine a reasonable meshing method.Quantitative relationships were determined between the pipe inclination angle and the affecting factors including the flow velocity,viscosity and the pipe diameter,where the water accumulation would not be able to occur.Generally,the critical inclination angle increases with the fluid flow velocity.The refluxing of water is the key mechanism causing the water accumulation at the bottom of the pipe.In addition to the fluid flow velocity,an increase in fluid viscosity and a decrease in the pipe diameter cause an increase of the critical inclination angle that the water phase can be carried away by oil.The model can be used to determine the critical inclination of pipelines carrying oil-water fluid to cause the water accumulation and the operating conditions that can eliminate the accumulation of water phase at the pipe floor.
基金supported by the Doctoral Research Start-up Fund Project of Liaoning Province(2019-BS-159)the Scientific Research Fund Project of Liaoning Education Department(L2019024)the Key Scientific Research Project of Liaoning Provincial Department of Education(L2020002).
文摘There is nothing illogical in the concept that hydrates are easily formed in oil and gas pipelines owing to the low-temperature and high-pressure environment,although requiring the cooperation of flow rate,water content,gas-liquid ratio,and other specific factors.Therefore,hydrate plugging is a major concern for the hydrate slurry pipeline transportation technology.In order to further examine potential mechanisms underlying these processes,the present paper listed and analyzed the significant research efforts specializing in the mechanisms of hydrate blockages in the liquid-rich system,including oil-based,water-based,and partially dispersed systems(PD systems),in gathering and transportation pipelines.In addition,it summarized the influences of fluid flow and water content on the risk of hydrate blockage and discussed.In general,flow rate was implicated in the regulation of blockage risk through its characteristic to affect sedimentation tendencies and flow patterns.Increasing water content can potentiate the growth of hydrates and change the oil-water dispersion degree,which causes a transition from completely dispersed systems to PD systems with a higher risk of clogging.Reasons of diversity of hydrate plugging mechanism in oil-based system ought to be studied in-depth by combining the discrepancy of water content and the microscopic characteristics of hydrate particles.At present,it is increasingly necessary to expand the application of the hydrate blockage formation prediction model in order to ensure that hydrate slurry mixed transportation technology can be more maturely applied to the natural gas industry transportation field.
文摘为准确高效地模拟高压CO_(2)管道泄漏的瞬态特性,基于Fluent仿真平台,利用用户自定义真实气体模型(User Defined Real Gas Model,UDRGM)和用户自定义函数(User Defined Function,UDF),结合查表法和双线性插值法建立CO_(2)的真实气体模型,并将压力驱动的Lee模型通过用户自定义函数嵌入Fluent求解器来模拟CO_(2)的非平衡相变过程,建立了高压CO_(2)管道泄漏的非平衡相变数值模型。通过与Botros等的试验数据进行对比分析,验证了该模型的准确性。在此基础上,对比了上述模拟方法与编译S-W(Span-Wagner)状态方程模拟方法的精度和效率,最后使用本模型研究了不同初始压力对高压CO_(2)管道泄漏瞬态特性的影响。结果表明:两种模拟方法精度接近,最大相差为7.37%,但提出的模拟方法效率明显优于编译S-W状态方程的模拟方法,计算时间相较缩短约86.9%;初始压力为11.27 MPa的最大总出口质量流量比4.36 MPa的大7.24 kg/s,而对应的气相CO_(2)出口质量流量却低0.14 kg/s;初始压力为11.27 MPa和4.36 MPa对应的近场最大射流流速分别为155.12 m/s和175.50 m/s;管内初始压力越低,泄漏后到达亚稳态时过热度越大,管内及泄漏口附近相变程度越剧烈,气相出口质量流量越大,近场射流峰值速度越大。这项研究可为工业规模管道泄漏的模拟和管道泄漏的三维模拟提供更高效的方式。
