Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation reg...Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.展开更多
In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulatio...In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are composed of the continuity, momentum, energy and k-e transport equations, based on isotropic eddy viscosity theory. Different valve plug displacement models were built to describe the double throttling process. Our analysis shows that the steam pressure drops twice and the degree of superheat increases. There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity. After modifying the structure, the numerical results show a better performance of steam flow.展开更多
Models that simulate the signature of single airguns form the basis for modeling the signals of airgun arrays. Most of the existing models assume that the air inside the produced bubble is ideal gas, which may lead to...Models that simulate the signature of single airguns form the basis for modeling the signals of airgun arrays. Most of the existing models assume that the air inside the produced bubble is ideal gas, which may lead to errors because of the high operating pressure of the airguns. In this study, we propose a model that precisely simulates the signals of single airguns by applying the Van der Waals equation based on the Ziolkowski algorithm. We also consider a thermodynamically open quasistatic system, the heat transition between water and gas, the throttling effect of the port and the bubble rise, and the effect of the sea surface. Modeling experiments show that(1) the energy of the source increases and the signal-tonoise ratio of the signature wavelet decreases with increasing seawater temperature,(2) the reflection coefficient of the sea surface under the actual state and depth of the source affects the notch caused by the surface reflection,(3) the computed signature with the proposed model is very close to the actual data, and(4) the proposed model accurately simulates the signature of single airguns.展开更多
Based on analyzing the limit of Ziolkowski＇s bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects ...Based on analyzing the limit of Ziolkowski＇s bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski＇s model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates：（1）gun port throttling controls the peak amplitude of ai gun pulse;（2）since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;（3）heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.展开更多
Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flo...Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flow coefficient of coupled throttling grooves is proposed to resolve that difficulty.With this purpose,an approach of a 3 D numerical simulation and an experimental bench were introduced based on the prototype of a commercial proportional valve.The results show consistency between the numerical simulation and the bench test.Based on that,the concept of‘saturation limit’is introduced to describe the value gap between the current and saturated flows,so that the flow-coefficient saturation limit of the prototype in the process can be deducted.Accordingly,an approximate flow coefficient suitable for coupled throttling grooves within finite variable space,which is based on three typical throttling structures(i.e.O-shape,U-shape,and C-shape)of the coupled throttling grooves,is obtained based on an orthogonal test.The model results are consistent with the numerical and experimental results,with maximum errors of less than 5.29%and 5.34%,respectively.This suggests that the proposed method is effective in approximating the flow coefficient.展开更多
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51104172,U1262202)the Pro-gram for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1086)
文摘Wellbore temperature field equations are established with considerations of the enthalpy changes of the natural gas during the deep-water gas well testing. A prediction method for the natural gas hydrate formation region during the deep-water gas well testing is proposed, which combines the wellbore temperature field equations, the phase equilibrium conditions of the natural gas hydrate formation and the calculation methods for the pressure field. Through the sensitivity analysis of the parameters that affect the hydrate formation region, it can be concluded that during the deep-water gas well testing, with the reduction of the gas production rate and the decrease of the geothermal gradient, along with the increase of the depth of water, the hydrate formation region in the wellbore enlarges, the hydrate formation regions differ with different component contents of natural gases, as compared with the pure methane gas, with the increase of ethane and propane, the hydrate formation region expands, the admixture of inhibitors, the type and the concentrations of which can be optimized through the method proposed in the paper, will reduce the hydrate formation region, the throttling effect will lead to the abrupt changes of temperature and pressure, which results in a variation of the hydrate formation region, if the throttling occurs in the shallow part of the wellbore, the temperature will drop too much, which enlarges the hydrate formation region, otherwise, if the throttling occurs in the deep part of the wellbore, the hydrate formation region will be reduced due to the decrease of the pressure.
基金Project (No. 2012C11018-1) supported by the Science and Technology Department of Zhejiang Province,China
文摘In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are composed of the continuity, momentum, energy and k-e transport equations, based on isotropic eddy viscosity theory. Different valve plug displacement models were built to describe the double throttling process. Our analysis shows that the steam pressure drops twice and the degree of superheat increases. There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity. After modifying the structure, the numerical results show a better performance of steam flow.
基金This research is financially supported by the National Science Foundation Project （Grant No. 41176077, 41230318） and the National 973 Program （Grant No. 2009CB219505）.
文摘Models that simulate the signature of single airguns form the basis for modeling the signals of airgun arrays. Most of the existing models assume that the air inside the produced bubble is ideal gas, which may lead to errors because of the high operating pressure of the airguns. In this study, we propose a model that precisely simulates the signals of single airguns by applying the Van der Waals equation based on the Ziolkowski algorithm. We also consider a thermodynamically open quasistatic system, the heat transition between water and gas, the throttling effect of the port and the bubble rise, and the effect of the sea surface. Modeling experiments show that(1) the energy of the source increases and the signal-tonoise ratio of the signature wavelet decreases with increasing seawater temperature,(2) the reflection coefficient of the sea surface under the actual state and depth of the source affects the notch caused by the surface reflection,(3) the computed signature with the proposed model is very close to the actual data, and(4) the proposed model accurately simulates the signature of single airguns.
基金supported by the National 973 Program(Grant No.2007CB209608)National 863 Program(Grant No.2007AA06Z218)
文摘Based on analyzing the limit of Ziolkowski＇s bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski＇s model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates：（1）gun port throttling controls the peak amplitude of ai gun pulse;（2）since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;（3）heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.
基金Project supported by the National Key R&D Program of China(No.2018YFC0810203)。
文摘Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flow coefficient of coupled throttling grooves is proposed to resolve that difficulty.With this purpose,an approach of a 3 D numerical simulation and an experimental bench were introduced based on the prototype of a commercial proportional valve.The results show consistency between the numerical simulation and the bench test.Based on that,the concept of‘saturation limit’is introduced to describe the value gap between the current and saturated flows,so that the flow-coefficient saturation limit of the prototype in the process can be deducted.Accordingly,an approximate flow coefficient suitable for coupled throttling grooves within finite variable space,which is based on three typical throttling structures(i.e.O-shape,U-shape,and C-shape)of the coupled throttling grooves,is obtained based on an orthogonal test.The model results are consistent with the numerical and experimental results,with maximum errors of less than 5.29%and 5.34%,respectively.This suggests that the proposed method is effective in approximating the flow coefficient.
