High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_(2).However,there are still issues and associated risks that have to be effectively addressed ...High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_(2).However,there are still issues and associated risks that have to be effectively addressed and adequately understood.It is well known that a strong JouleThomson Cooling effect can occur when pressurized CO_(2) flows through a choke valve.Thus,to investigate the choking characteristics especially the temperature drop of high pressure CO_(2),a new laboratory scale experimental setup(total length of 14.85 m and the inner diameter of 15 mm)was constructed.Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO_(2) in various initial phases.The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow.For transient choked flow of various initial phases,all the flows downstream would transfer from single phase to gas-liquid twophase flow.Furthermore,the effect of water on transient choked flow of supercritical CO_(2) pipeline was investigated,and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO_(2)pipelines when throttling by the choke valves.展开更多
The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relev...The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relevant results anddata in the literature, in the present study, we concentrate on the experimental determination of the flow coefficientfor the annular orifice, the pressure distribution in the MCOP, and the characteristics of the choked flow itself. Asconfirmed by the experimental results, the Reynolds number, the orifice plate thickness, the plug taper, and theeccentricity have an obvious influence on the aforementioned flow coefficient. The pressure drop in the MCOPis mainly generated near the orifice plate, and the pressure upstream of the orifice plate is slightly reduced in theflow direction, while the pressure downstream of the orifice plate displays a recovery trend. The choked flow rateof the MCOP can be adjusted by replacing the spring with a maximum flow control deviation of 4.91%.展开更多
The choked back pressure characteristic of the steam turbine unit with air cooled condenser is very different with the unit with wet cooling technology, and the understanding of the choked back pressure performance ch...The choked back pressure characteristic of the steam turbine unit with air cooled condenser is very different with the unit with wet cooling technology, and the understanding of the choked back pressure performance change with operation load is important to guide the economic operation of the unit. One simplified Variable Operation Condition Analysis Method was put forward for calculation of the unit output-turbine back pressure characteristics. Based on this method, the choked back pressure for each operation load can be determined. An example was given for a super-critical, regenerative single-shaft, 2-casing with 2-exhaust steam turbine generation unit with air cooled condenser. The calculation result was provided and compared with the result of the unit with wet cooling technology.展开更多
We report a case of grave and rare surgical complications nowadays, which calls out to us on the necessity of a bigger raising sensitization on the coverage of the constrictions hernial at the adult. It is about a cas...We report a case of grave and rare surgical complications nowadays, which calls out to us on the necessity of a bigger raising sensitization on the coverage of the constrictions hernial at the adult. It is about a case of right inguino-scrotal hernia choked secondarily complicated with a scrotal coecostomie at a 64-year-old man. The delay in the care was in touch with a traditional treatment but also in the poverty of the patient which was a needy the total care of which was assured by the social services department of the hospital. The perioperative exploration found a cecostomy the mucous membrane of which was inverted in the opening of the stoma, an ulceration of the peristomial scrotum with a normal macroscopic aspect of the testicle homolateral. The care was made at single time: parage and scrotal suture more resection segmental of the coecum followed by an anastomosis ileocolic terminoterminal and a cure of the hernia according to Shouldice. The operating suites were simple with ablation of the threads to operating J12 comment and the liberation of the patient the next day. The clinical evolution was satisfactory with a backward movement of 4 years.展开更多
Particle-gas two-phase flows show significantly different behaviors compared to single gas flow through a convergent-divergent nozzle. Non-equilibrium effects, thermal and velocity lag results to the inefficiency of n...Particle-gas two-phase flows show significantly different behaviors compared to single gas flow through a convergent-divergent nozzle. Non-equilibrium effects, thermal and velocity lag results to the inefficiency of nozzle performance. In the present studies, theoretical analysis and numerical simulations were carried out to investigate particle-gas flows in a C-D nozzle. Homogeneous equilibrium model that no lag in velocity and temperature occurs between particles and gas phase was used to derive mass flow rate and sound speed of multiphase flows. Two-phase flows are regarded as isentropic flows that isentropic relations can be used for homogeneous equilibrium model. Discrete phase model （DPM） where interaction with continuous phase and discrete random walk model were considered was used to calculate particle- gas flows. Particle mass loadings were varied to investigate their effects on choking phenomena of particle-gas flows. Mass flow rate and sound speed of mixture flows were theoretically calculated by homogeneous equilibrium model and compared with numerical results. Shock wave structure and particle number density were also obtained to be different at different particle mass loading and operating pressure conditions.展开更多
Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field ch...Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field characteristics and aerodynamic heating effect of hyperloop is in its infancy,and that on the flow field structure is lacking.In this study,the nozzle theory was used to make a preliminary judgment on the choked flow phenomenon in the hyperloop.Based on the flow results obtained under different working conditions,the identification basis of the choked flow phenomenon in the hyperloop was obtained.Furthermore,the effect of the choked/unchoked flow on the flow structure,temperature,and pressure distribution of the annular space in the tube was analyzed.Based on traditional high-speed railway aerodynamics,according to relevant theories and calculation in aerospace field,and combined with the model test data,the reliability verification analysis on the characteristics of the flow field are carried out.The structure of the flow filed in the tube can be divided into choked and unchoked.The judgment is dependent on whether the throat reaches the speed of sound.Under the choked flow,a normal shock wave is formed in front of the tube train.The temperature rise of the local flow field exceeds 50 K;the temperature rise of the stagnation region exceeds 88 K,and the pressure is approximately 1.7 times that of the initial pressure in the tube.When the flow is unchoked,differences arise in the distribution of the flow field corresponding to different incoming Mach numbers.When the incoming flow is supersonic,the flow field maintains a supersonic speed,and a bow-shaped shock wave is formed at the front of the tube train.Owing to the shock wave or expansion wave,the local flow field exhibits significant fluctuations in temperature and pressure.Conversely,when the incoming flow is subsonic,the flow field in the tube maintains a subsonic speed,and no shock wave structure is observed.展开更多
When sonic nozzles of significantly smaller diameter are used as standard flow meters,the critical back pressure ratio is affected by the boundary layer at the nozzle throat.However,the effect of the boundary layer on...When sonic nozzles of significantly smaller diameter are used as standard flow meters,the critical back pressure ratio is affected by the boundary layer at the nozzle throat.However,the effect of the boundary layer on choking criteria is still controversial.Then,the choking phenomenon of a convergent nozzle flow has been experimentally investigated using four convergent nozzles with the same diameter followed by a straight pipe of a variable length.As a result,it is shown that the critical back pressure ratio is smaller than that for the steady one-dimensional is-entropic flow and decreases as the boundary layer thickness increases.Moreover,the main flow Mach number at the nozzle exit is supersonic when the back pressure ratio is equivalent to the choking condition,and the Mach number increases as the boundary layer thickness increases.展开更多
The cavitation is ubiquitous in the water delivery system of high hydraulic head navigation locks.This paper studies the choked cavitation characteristics of the gap flows in the valve lintel of the navigation locks a...The cavitation is ubiquitous in the water delivery system of high hydraulic head navigation locks.This paper studies the choked cavitation characteristics of the gap flows in the valve lintel of the navigation locks and analyzes the critical self-aeration conditions.The cavitation gap flow in the valve lintel is experimentally and numerically investigated.A visualized 1:1 full-scale slicing model is designed,with a high-speed camera,the details of the cavitation flow is captured without the reduced scale effect.Moreover,the numerical simulations are conducted to reveal the flow structures in the gap.The experimental results show that the flow pattern of the gap flow in the valve lintel could be separated into four models,namely,the incipient(1)the developing,(2),the intensive,(3),and the choked(4)cavitation models.The numerical simulation results are consistent with the experimental data.The choked cavitation conditions are crucial to the gap flow in the valve lintel.When the choked cavitation occurs,the gap is entirely occupied by two cavitation cloud sheets.The gap pressure then decreases sharply to the saturated water vapor pressure at the operating temperature.This water vapor pressure is the ultimate negative pressure in the gap that remains unchanged with the continuous decrease of the downstream pressure.The volumetric flow rate reaches a peak,then remains constant,with the further decrease of the pressure ratio or the cavitation number.At the choking point,the volumetric flow rate is proportional to the root mean square of the difference between the upstream pressure(absolute pressure)and the saturated pressure of the water.Moreover,the pressure ratio is linearly correlated with the downstream cavitation number with a slope of(1+ζc).展开更多
基金Key laboratory of oil&gas storage&transportation PetroChina(GDGS-KJZX-2016-JS-379)supported by the National Science and Technology Special Project(2016ZX05016-002).
文摘High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_(2).However,there are still issues and associated risks that have to be effectively addressed and adequately understood.It is well known that a strong JouleThomson Cooling effect can occur when pressurized CO_(2) flows through a choke valve.Thus,to investigate the choking characteristics especially the temperature drop of high pressure CO_(2),a new laboratory scale experimental setup(total length of 14.85 m and the inner diameter of 15 mm)was constructed.Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO_(2) in various initial phases.The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow.For transient choked flow of various initial phases,all the flows downstream would transfer from single phase to gas-liquid twophase flow.Furthermore,the effect of water on transient choked flow of supercritical CO_(2) pipeline was investigated,and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO_(2)pipelines when throttling by the choke valves.
基金the Foundation of the Educational Commission of Hubei Province of China[Grant No.Q20191310]。
文摘The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relevant results anddata in the literature, in the present study, we concentrate on the experimental determination of the flow coefficientfor the annular orifice, the pressure distribution in the MCOP, and the characteristics of the choked flow itself. Asconfirmed by the experimental results, the Reynolds number, the orifice plate thickness, the plug taper, and theeccentricity have an obvious influence on the aforementioned flow coefficient. The pressure drop in the MCOPis mainly generated near the orifice plate, and the pressure upstream of the orifice plate is slightly reduced in theflow direction, while the pressure downstream of the orifice plate displays a recovery trend. The choked flow rateof the MCOP can be adjusted by replacing the spring with a maximum flow control deviation of 4.91%.
文摘The choked back pressure characteristic of the steam turbine unit with air cooled condenser is very different with the unit with wet cooling technology, and the understanding of the choked back pressure performance change with operation load is important to guide the economic operation of the unit. One simplified Variable Operation Condition Analysis Method was put forward for calculation of the unit output-turbine back pressure characteristics. Based on this method, the choked back pressure for each operation load can be determined. An example was given for a super-critical, regenerative single-shaft, 2-casing with 2-exhaust steam turbine generation unit with air cooled condenser. The calculation result was provided and compared with the result of the unit with wet cooling technology.
文摘We report a case of grave and rare surgical complications nowadays, which calls out to us on the necessity of a bigger raising sensitization on the coverage of the constrictions hernial at the adult. It is about a case of right inguino-scrotal hernia choked secondarily complicated with a scrotal coecostomie at a 64-year-old man. The delay in the care was in touch with a traditional treatment but also in the poverty of the patient which was a needy the total care of which was assured by the social services department of the hospital. The perioperative exploration found a cecostomy the mucous membrane of which was inverted in the opening of the stoma, an ulceration of the peristomial scrotum with a normal macroscopic aspect of the testicle homolateral. The care was made at single time: parage and scrotal suture more resection segmental of the coecum followed by an anastomosis ileocolic terminoterminal and a cure of the hernia according to Shouldice. The operating suites were simple with ablation of the threads to operating J12 comment and the liberation of the patient the next day. The clinical evolution was satisfactory with a backward movement of 4 years.
文摘Particle-gas two-phase flows show significantly different behaviors compared to single gas flow through a convergent-divergent nozzle. Non-equilibrium effects, thermal and velocity lag results to the inefficiency of nozzle performance. In the present studies, theoretical analysis and numerical simulations were carried out to investigate particle-gas flows in a C-D nozzle. Homogeneous equilibrium model that no lag in velocity and temperature occurs between particles and gas phase was used to derive mass flow rate and sound speed of multiphase flows. Two-phase flows are regarded as isentropic flows that isentropic relations can be used for homogeneous equilibrium model. Discrete phase model （DPM） where interaction with continuous phase and discrete random walk model were considered was used to calculate particle- gas flows. Particle mass loadings were varied to investigate their effects on choking phenomena of particle-gas flows. Mass flow rate and sound speed of mixture flows were theoretically calculated by homogeneous equilibrium model and compared with numerical results. Shock wave structure and particle number density were also obtained to be different at different particle mass loading and operating pressure conditions.
基金This work was supported by Hebei Province Natural Science Foundation(E2022105032)National Natural Science Foundation of China(51978575,52172359).
文摘Hyperloop has become one of the key reserve technologies for future high-speed rail transit.The gas in the tube is compressed and rubbed,leading to a strong aerodynamic heating effect.The research on the flow field characteristics and aerodynamic heating effect of hyperloop is in its infancy,and that on the flow field structure is lacking.In this study,the nozzle theory was used to make a preliminary judgment on the choked flow phenomenon in the hyperloop.Based on the flow results obtained under different working conditions,the identification basis of the choked flow phenomenon in the hyperloop was obtained.Furthermore,the effect of the choked/unchoked flow on the flow structure,temperature,and pressure distribution of the annular space in the tube was analyzed.Based on traditional high-speed railway aerodynamics,according to relevant theories and calculation in aerospace field,and combined with the model test data,the reliability verification analysis on the characteristics of the flow field are carried out.The structure of the flow filed in the tube can be divided into choked and unchoked.The judgment is dependent on whether the throat reaches the speed of sound.Under the choked flow,a normal shock wave is formed in front of the tube train.The temperature rise of the local flow field exceeds 50 K;the temperature rise of the stagnation region exceeds 88 K,and the pressure is approximately 1.7 times that of the initial pressure in the tube.When the flow is unchoked,differences arise in the distribution of the flow field corresponding to different incoming Mach numbers.When the incoming flow is supersonic,the flow field maintains a supersonic speed,and a bow-shaped shock wave is formed at the front of the tube train.Owing to the shock wave or expansion wave,the local flow field exhibits significant fluctuations in temperature and pressure.Conversely,when the incoming flow is subsonic,the flow field in the tube maintains a subsonic speed,and no shock wave structure is observed.
文摘When sonic nozzles of significantly smaller diameter are used as standard flow meters,the critical back pressure ratio is affected by the boundary layer at the nozzle throat.However,the effect of the boundary layer on choking criteria is still controversial.Then,the choking phenomenon of a convergent nozzle flow has been experimentally investigated using four convergent nozzles with the same diameter followed by a straight pipe of a variable length.As a result,it is shown that the critical back pressure ratio is smaller than that for the steady one-dimensional is-entropic flow and decreases as the boundary layer thickness increases.Moreover,the main flow Mach number at the nozzle exit is supersonic when the back pressure ratio is equivalent to the choking condition,and the Mach number increases as the boundary layer thickness increases.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFC0402007)the National Nature Science Foundation of China(Grant No.51779151).
文摘The cavitation is ubiquitous in the water delivery system of high hydraulic head navigation locks.This paper studies the choked cavitation characteristics of the gap flows in the valve lintel of the navigation locks and analyzes the critical self-aeration conditions.The cavitation gap flow in the valve lintel is experimentally and numerically investigated.A visualized 1:1 full-scale slicing model is designed,with a high-speed camera,the details of the cavitation flow is captured without the reduced scale effect.Moreover,the numerical simulations are conducted to reveal the flow structures in the gap.The experimental results show that the flow pattern of the gap flow in the valve lintel could be separated into four models,namely,the incipient(1)the developing,(2),the intensive,(3),and the choked(4)cavitation models.The numerical simulation results are consistent with the experimental data.The choked cavitation conditions are crucial to the gap flow in the valve lintel.When the choked cavitation occurs,the gap is entirely occupied by two cavitation cloud sheets.The gap pressure then decreases sharply to the saturated water vapor pressure at the operating temperature.This water vapor pressure is the ultimate negative pressure in the gap that remains unchanged with the continuous decrease of the downstream pressure.The volumetric flow rate reaches a peak,then remains constant,with the further decrease of the pressure ratio or the cavitation number.At the choking point,the volumetric flow rate is proportional to the root mean square of the difference between the upstream pressure(absolute pressure)and the saturated pressure of the water.Moreover,the pressure ratio is linearly correlated with the downstream cavitation number with a slope of(1+ζc).
