In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakag...In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakage rate and amount cannot be accurately calculated through critical pressure conditions.In this paper,a micro-element body of the pipeline was intercepted for calculation.The relationship between radial displacement and pressure of pipe wall was studied based on the stress-strain equation.Then,the strain response of pipeline volume with pipeline pressure was obtained.The change in volume expansion of pipeline was used to characterize leakage of incompressible fluid.Finally,the calculation model of leakage amount of incompressible fluid was obtained.To verify the above theory,the pipeline expansion model under pressure was established by COMSOL software for simulation.Both simulation results and deduction equations show that the volumetric change has a quadratic parabolic relationship with the change of pipeline pressure.However,the relationship between them can be approximately linear when the pressure change is not too large.In addition,the leakage of incompressible fluid under the pressure of 0 MPa-0.8 MPa was obtained by experiments.The experimental results verify the linear relationship between leakage of incompressible fluid and the change of pipeline pressure.The theoretical and experimental results provide a basis for the calculation of leakage of incompressible fluid in the pipeline.展开更多
A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is compos...A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is composed of a gear pump, a reversing valve, a relief valve and other components. By using the steady penetration method, the permeability and non-Darcy flow β factor of broken coal samples under five different porosity levels were measured, the grain diameters of the coal samples were selected as 2.5-5 mm, 5-10 mm, 10-15 mm, 15-20 mm, 20-25 mm and 2.5-25 ram, respectively. After measuring the permeability under each porosity, the overfall pressure of the relief valve continuously increased until the coal sample was broken down. In this way, the flow type of liquid inside the broken coal samples changed from seepage to pipe flow. The correlation between breakdown pressure gradient （BPG） and porosity was analyzed, and the BPG was compared with the pressure gradient when seepage instability occurred. The results show that, ①the non-Darcy flow β factor was negative before broken coal samples with six kinds of diameters were broken down; ②the BPG of coal samples with a grain size of 2.5-25 mm was lower than that of the others; ③ the BPG of coal samples with a single diameter under the same porosity increased as the grain size increased; ④ the BPG could be fitted by an exponential function with porosity, and the exponent decreased as the grain size increased for coal samples with a single diameter; ⑤ the BPG was slightly less than the seepage instability pressure gradient. The change in liquid flow type from seepage to pipe flow could be regarded as the performance of the seepage instability.展开更多
The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gra...The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.展开更多
文摘In practical engineering,only pressure sensors are allowed to install to detect leakage in most of oil transportation pipelines,while flowmeters are only installed at the toll ports.For incompressible fluid,the leakage rate and amount cannot be accurately calculated through critical pressure conditions.In this paper,a micro-element body of the pipeline was intercepted for calculation.The relationship between radial displacement and pressure of pipe wall was studied based on the stress-strain equation.Then,the strain response of pipeline volume with pipeline pressure was obtained.The change in volume expansion of pipeline was used to characterize leakage of incompressible fluid.Finally,the calculation model of leakage amount of incompressible fluid was obtained.To verify the above theory,the pipeline expansion model under pressure was established by COMSOL software for simulation.Both simulation results and deduction equations show that the volumetric change has a quadratic parabolic relationship with the change of pipeline pressure.However,the relationship between them can be approximately linear when the pressure change is not too large.In addition,the leakage of incompressible fluid under the pressure of 0 MPa-0.8 MPa was obtained by experiments.The experimental results verify the linear relationship between leakage of incompressible fluid and the change of pipeline pressure.The theoretical and experimental results provide a basis for the calculation of leakage of incompressible fluid in the pipeline.
基金Supported by the National Natural Science Foundation of China （50974107） the University Graduate Research and Innovation Project in Jiangsu Province （CXZZI2_0924）+1 种基金 the Applied Basic Research Project of Yancheng Institute of Technology （XKR2010010） the State Key Laboratory Open Foundation of Deep Geomechanics and Underground Engineering of China University of Mining and Technology （SKLGDUEK1014）
文摘A test system of the permeability of broken coal samples mainly consists of a CMT5305 electronic universal test machine, crushed rock compaction containing cylinder and a self-designed seepage circuit, which is composed of a gear pump, a reversing valve, a relief valve and other components. By using the steady penetration method, the permeability and non-Darcy flow β factor of broken coal samples under five different porosity levels were measured, the grain diameters of the coal samples were selected as 2.5-5 mm, 5-10 mm, 10-15 mm, 15-20 mm, 20-25 mm and 2.5-25 ram, respectively. After measuring the permeability under each porosity, the overfall pressure of the relief valve continuously increased until the coal sample was broken down. In this way, the flow type of liquid inside the broken coal samples changed from seepage to pipe flow. The correlation between breakdown pressure gradient （BPG） and porosity was analyzed, and the BPG was compared with the pressure gradient when seepage instability occurred. The results show that, ①the non-Darcy flow β factor was negative before broken coal samples with six kinds of diameters were broken down; ②the BPG of coal samples with a grain size of 2.5-25 mm was lower than that of the others; ③ the BPG of coal samples with a single diameter under the same porosity increased as the grain size increased; ④ the BPG could be fitted by an exponential function with porosity, and the exponent decreased as the grain size increased for coal samples with a single diameter; ⑤ the BPG was slightly less than the seepage instability pressure gradient. The change in liquid flow type from seepage to pipe flow could be regarded as the performance of the seepage instability.
基金the Scientific Project of Ministry of Land and Resource of Chinathe National Natural Science Foundation of Chinathe Doctoral Station Foundation of Ministry of Education of China
文摘The pressure gradient of the lithosphere is a key to explaining various geological processes, and varies also in time and space similar to the geothermal gradient. In this paper a correlation formula of geothermal gradients and pressure gradients was built with the thermocomprestion coefficients. Based on this formula, the article has studied the relation between the pressure gradients and the geothermal gradients in the lithosphere, and the results indicate that the pressure gradient in the lithosphere is nonlinear, and its minimum value is the lithostatic gradient, and that the pressure gradient of the lithosphere will increase obviously with the contribution of both geothermal and gravity, and could be twice times more than the lithostatic gradient.
