Gas-liquid flow(GLF),especially slug and annular flows in oil and gas gathering and transportation pipelines,become particularly complex inside elbows and can easily exacerbate pipeline corrosion and damage.In thisstu...Gas-liquid flow(GLF),especially slug and annular flows in oil and gas gathering and transportation pipelines,become particularly complex inside elbows and can easily exacerbate pipeline corrosion and damage.In thisstudy,FLUENT was used to conduct 3D simulations of slug and annular flow in elbows for different velocitiesto assess the ensuing changes in terms of pressure.In particular,the multifluid VOF(Volume of Fraction)modelwas chosen.The results indicate that under both slug and annular flow conditions,the pressure inside the elbow islower than the outside.As the superficial velocity of liquid and gas increase,the pressure and liquid flow velocityat different positions of the elbow also increase,while the secondary flow weakens.Under annular flow conditions,the liquid film on the outer side of the elbow is thicker than that on the inner side,and the liquid velocityin the main liquid film zone is the lowest.展开更多
This research introduces a spectrum-based physics-informed neural network(SP-PINN)model to significantly improve the accuracy of calculation of two-phase flow parameters,surpassing existing methods that have limitatio...This research introduces a spectrum-based physics-informed neural network(SP-PINN)model to significantly improve the accuracy of calculation of two-phase flow parameters,surpassing existing methods that have limitations in global and continuous data sampling.SP-PINNs address the challenges of traditional methods in terms of continuous sampling by integrating the spectral analysis and pressure correction into the Navier-Stokes(N-S)equations,enhancing the predictive accuracy especially in critical regions like gas-phase boundaries and velocity peaks.The novel introduction of a pressure-correction module within SP-PINNs mitigates prediction errors,achieving a substantial reduction to 1‰compared with the conventional physics-informed neural network(PINN)approaches.Experimental applications validate the model’s ability to accurately and rapidly predict flow parameters with different sampling time intervals,with the computation time of predicting unsampled data less than 0.01 s.Such advancements signify a 100-fold improvement over traditional DNS calculations,underscoring the model’s potential in the real-time calculation and analysis of multiphase flow dynamics.展开更多
A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The sw...A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The swirling blades are used to transform the complex flow pattern into a forced annular flow.Drawing on the research of existing blockage flow meters and also exploiting the single-phase flow measurement theory,a formula is introduced to measure the phase-separated flow of gas and liquid.The formula requires the pressure ratio,Lockhart-Martinelli number(L-M number),and the gas phase Froude number.The unknown parameters appearing in the formula are fitted through numerical simulation using computational fluid dynamics(CFD),which involves a comprehensive analysis of the flow field inside the device from multiple perspectives,and takes into account the influence of pressure fluctuations.Finally,the measurement model is validated through an experimental error analysis.The results demonstrate that the measurement error can be maintained within±8%for various flow patterns,including stratified flow,bubble flow,and wave flow.展开更多
A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two...A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two-fluid model is used to calculate both gas and liquid phases’flow characteristics.The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced.Moreover,energy conservation is applied for obtaining the liquid film thickness distribution along the circumference.Liquid film thickness distribution is calculated accordingly for different cases;its values are compared with other models and available experimental data.As a result,the newly proposed model is tested and good performances are demonstrated.The liquid film thickness distribution in small pipes and inclined pipes is also studied,and regime transition is revealed by liquid film profile evolution.The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference,when the circle angle ranges between 30°and 50°for gas-liquid stratified flow with small superficial velocities.展开更多
When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located do...When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located downstream.In order to investigate these aspects and,more specifically,the so-called bias phenomenon(all gas and liquid flowing to one pipe,while the other pipe is a liquid column that fluctuates up and down),laboratory experiments were carried out by using a T-junction connected to two parallel vertical pipes.Moreover,a GLTPF prediction model based on the principle of minimum potential energy was introduced.The research results indicate that this model can accurately predict the GLTPF state in parallel risers.The boundary of the slug flow and the churn flow in the opposite pipe can be predicted.Overall,according to the results,the pressure drop curves of the two-phase flow in the parallel risers are basically the same when there is no bias phenomenon,but the pressure drop in the parallel riser displays a large deviation when there is a slug flow-churn flow.Only when the parallel riser is in a state of asymmetric flow and one of the risers produces churn flow,the two-phase flow is prone to produce the bias phenomenon.展开更多
The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the sti...The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.展开更多
In the industrial production, the mixing of gas-liquid flow with vapor and gas-solid flow is a very common problem. In the process of the mixing, solid particle-clusters will form, and will have steady radii when the ...In the industrial production, the mixing of gas-liquid flow with vapor and gas-solid flow is a very common problem. In the process of the mixing, solid particle-clusters will form, and will have steady radii when the effect of the gathering of particles is balanced withthat of the breaking of particle-clusters. Then, the population distribution function of size of particles per unit length per unit volume is introduced, and its governingequation is derived on the analogy of the molecular kinetic theory. Finally, when the gas flow is very slow, the expression of steady average radius of particle-clusters is obtained.展开更多
A viscous Kelvin-Helmholtz criterion of the interfacial wave instability is proposed in this paper based on the linear stability analysis of a transient one-dimensional two-fluid model. In thismodel, the pressure is e...A viscous Kelvin-Helmholtz criterion of the interfacial wave instability is proposed in this paper based on the linear stability analysis of a transient one-dimensional two-fluid model. In thismodel, the pressure is evaluated using the local momentum balance rather than the hydrostatic approximation. The criterion predicts well the stability limit of stratified flow in horizontal and nearly horizontal pipes. The experimental and theoretical investigation on the effect of pipe inclination on the interfacial instability are carded out. It is found that the critical liquid height at the onset of interfacial wave instability is insensitive to the pipe inclination. However, the pipe inclination significantly affects critical superficial liquid velocity and wave velocity especially lor low gas velocities.展开更多
Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by et...Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.展开更多
In many gasliquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gasliquid flow pattern. Bubble formation models for variant gasliquid flow pat t...In many gasliquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gasliquid flow pattern. Bubble formation models for variant gasliquid flow pat terns have been developed based on force balance. The effects of the orientation of gasliquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient airwater system, thesultable gasllquid flow pattern is important to obtain smaller bubbles under the low velocity liquid crossflow con ditions with stainless steel spargers. Among the four types of gasliquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found tobe insgnifican whenliq.uid velocity is.higher than. 3.2 m;sa or theorifice diameter is small enough.展开更多
Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by et...Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.展开更多
To clarify the countercurrent flow in a PWR hot leg under reflux condensation, numerical simulations of countercurrent air-water flow for a 1/15th scale model of the PWR hot leg were conducted using the two-fluid mode...To clarify the countercurrent flow in a PWR hot leg under reflux condensation, numerical simulations of countercurrent air-water flow for a 1/15th scale model of the PWR hot leg were conducted using the two-fluid model implemented in CFD software. In this paper, the effect of expansion of the inclined pipe, which is the actual plant geometry, was evaluated. When increasing the air velocity, CCFL characteristics and the mechanism of flow pattern transition had significant differences between the case with and without expansion of the inclined pipe. CCFL characteristics were mitigated in the case with expansion. The effect of computational grid size was also discussed. When the supplied water velocity was small, the predicted flow pattern transition point agreed well with the measured data by increasing the number of cells. On the other hand, when the air velocity was decreasing, there were no significant differences in each case.展开更多
A computational code is developed for the numerical solution of onedimensional transient gas-liquid flows using drift-flux models,in isothermal and also with phase change situations.For these two-phase models,classica...A computational code is developed for the numerical solution of onedimensional transient gas-liquid flows using drift-flux models,in isothermal and also with phase change situations.For these two-phase models,classical upwind schemes such as Roe-and Godunov-type schemes are generally difficult to derive and expensive to use,since there are no treatable analytic expressions for the Jacobian matrix,eigenvalues and eigenvectors of the system of equations.On the other hand,the highorder compact finite difference scheme becomes an attractive alternative on these occasions,as it does not make use of any wave propagation information from the system of equations.The present paper extends the localized artificial diffusivity method for high-order compact finite difference schemes to solve two-phase flows with discontinuities.The numerical method has simple formulation,straightforward implementation,low computational cost and,most importantly,high-accuracy.The numerical methodology proposed is validated by solving several numerical examples given in the literature.The simulations are sixth-order accurate and it is shown that the proposed numerical method provides accurate approximations of shock waves and contact discontinuities.This is an essential property for simulations of realistic mass transport problems relevant to operations in the petroleum industry。展开更多
This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practi...This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practical engineering fields,such as in short take-off and vertical landing(STOVL)aircraft.Nowadays many intricate phenomena associated with impinging jet flows remain inadequately elucidated,which limits the ability to optimize aircraft design.Given a boundary condition in the inlet,the impinging jet problem is transformed into a Bernoulli-type free boundary problem according to the stream function.Then the variational method is used to study the corresponding variational problem with one parameter,thereby the wellposedness is established.The main conclusion is as follows.For a 3D axisymmetric finitely long nozzle and an infinitely long vertical wall,given an axial velocity in the inlet of nozzle,there exists a unique smooth incom‑pressible impinging jet flow such that the free boundary initiates smoothly at the endpoint of the nozzle and extends to infinity along the vertical wall at far fields.The key point is to investigate the regularity of the corner where the nozzle and the vertical axis intersect.展开更多
The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow ...The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.展开更多
The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because o...The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because of its straightforward,single-solution evolution framework.However,a potential draw-back of IGA is the lack of utilization of historical information,which could lead to an imbalance between exploration and exploitation,especially in large-scale DPFSPs.As a consequence,this paper develops an IGA with memory and learning mechanisms(MLIGA)to efficiently solve the DPFSP targeted at the mini-malmakespan.InMLIGA,we incorporate a memory mechanism to make a more informed selection of the initial solution at each stage of the search,by extending,reconstructing,and reinforcing the information from previous solutions.In addition,we design a twolayer cooperative reinforcement learning approach to intelligently determine the key parameters of IGA and the operations of the memory mechanism.Meanwhile,to ensure that the experience generated by each perturbation operator is fully learned and to reduce the prior parameters of MLIGA,a probability curve-based acceptance criterion is proposed by combining a cube root function with custom rules.At last,a discrete adaptive learning rate is employed to enhance the stability of the memory and learningmechanisms.Complete ablation experiments are utilized to verify the effectiveness of the memory mechanism,and the results show that this mechanism is capable of improving the performance of IGA to a large extent.Furthermore,through comparative experiments involving MLIGA and five state-of-the-art algorithms on 720 benchmarks,we have discovered that MLI-GA demonstrates significant potential for solving large-scale DPFSPs.This indicates that MLIGA is well-suited for real-world distributed flow shop scheduling.展开更多
Due to the complex high-temperature characteristics of hydrocarbon fuel,the research on the long-term working process of parallel channel structure under variable working conditions,especially under high heat-mass rat...Due to the complex high-temperature characteristics of hydrocarbon fuel,the research on the long-term working process of parallel channel structure under variable working conditions,especially under high heat-mass ratio,has not been systematically carried out.In this paper,the heat transfer and flow characteristics of related high temperature fuels are studied by using typical engine parallel channel structure.Through numeri⁃cal simulation and systematic experimental verification,the flow and heat transfer characteristics of parallel chan⁃nels under typical working conditions are obtained,and the effectiveness of high-precision calculation method is preliminarily established.It is known that the stable time required for hot start of regenerative cooling engine is about 50 s,and the flow resistance of parallel channel structure first increases and then decreases with the in⁃crease of equivalence ratio(The following equivalence ratio is expressed byΦ),and there is a flow resistance peak in the range ofΦ=0.5~0.8.This is mainly caused by the coupling effect of high temperature physical proper⁃ties,flow rate and pressure of fuel in parallel channels.At the same time,the cooling and heat transfer character⁃istics of parallel channels under some conditions of high heat-mass ratio are obtained,and the main factors affect⁃ing the heat transfer of parallel channels such as improving surface roughness and strengthening heat transfer are mastered.In the experiment,whenΦis less than 0.9,the phenomenon of local heat transfer enhancement and deterioration can be obviously observed,and the temperature rise of local structures exceeds 200℃,which is the risk of structural damage.Therefore,the reliability of long-term parallel channel structure under the condition of high heat-mass ratio should be fully considered in structural design.展开更多
Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel...Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel traffic modelling framework for aggregate traffic on urban roads. The main idea is that road traffic flow is random, even for the recurrent flow, such as rush hour traffic, which is predisposed to congestion. Therefore, the structure of the aggregate traffic flow model for urban roads should correlate well with the essential variables of the observed random dynamics of the traffic flow phenomena. The novelty of this paper is the developed framework, based on the Poisson process, the kinematics of urban road traffic flow, and the intermediate modelling approach, which were combined to formulate the model. Empirical data from an urban road in Ghana was used to explore the model’s fidelity. The results show that the distribution from the model correlates well with that of the empirical traffic, providing a strong validation of the new framework and instilling confidence in its potential for significantly improved forecasts and, hence, a more hopeful outlook for real-world traffic management.展开更多
This paper presents an optimized strategy for multiple integrations of photovoltaic distributed generation (PV-DG) within radial distribution power systems. The proposed methodology focuses on identifying the optimal ...This paper presents an optimized strategy for multiple integrations of photovoltaic distributed generation (PV-DG) within radial distribution power systems. The proposed methodology focuses on identifying the optimal allocation and sizing of multiple PV-DG units to minimize power losses using a probabilistic PV model and time-series power flow analysis. Addressing the uncertainties in PV output due to weather variability and diurnal cycles is critical. A probabilistic assessment offers a more robust analysis of DG integration’s impact on the grid, potentially leading to more reliable system planning. The presented approach employs a genetic algorithm (GA) and a determined PV output profile and probabilistic PV generation profile based on experimental measurements for one year of solar radiation in Cairo, Egypt. The proposed algorithms are validated using a co-simulation framework that integrates MATLAB and OpenDSS, enabling analysis on a 33-bus test system. This framework can act as a guideline for creating other co-simulation algorithms to enhance computing platforms for contemporary modern distribution systems within smart grids concept. The paper presents comparisons with previous research studies and various interesting findings such as the considered hours for developing the probabilistic model presents different results.展开更多
基金supported by the Ministry of Industry and Information Technology High Tech Ship Special Project(Grant No.CBG3N21-2-6).
文摘Gas-liquid flow(GLF),especially slug and annular flows in oil and gas gathering and transportation pipelines,become particularly complex inside elbows and can easily exacerbate pipeline corrosion and damage.In thisstudy,FLUENT was used to conduct 3D simulations of slug and annular flow in elbows for different velocitiesto assess the ensuing changes in terms of pressure.In particular,the multifluid VOF(Volume of Fraction)modelwas chosen.The results indicate that under both slug and annular flow conditions,the pressure inside the elbow islower than the outside.As the superficial velocity of liquid and gas increase,the pressure and liquid flow velocityat different positions of the elbow also increase,while the secondary flow weakens.Under annular flow conditions,the liquid film on the outer side of the elbow is thicker than that on the inner side,and the liquid velocityin the main liquid film zone is the lowest.
基金Supported by the National Natural Science Foundation of China(No.62304022)。
文摘This research introduces a spectrum-based physics-informed neural network(SP-PINN)model to significantly improve the accuracy of calculation of two-phase flow parameters,surpassing existing methods that have limitations in global and continuous data sampling.SP-PINNs address the challenges of traditional methods in terms of continuous sampling by integrating the spectral analysis and pressure correction into the Navier-Stokes(N-S)equations,enhancing the predictive accuracy especially in critical regions like gas-phase boundaries and velocity peaks.The novel introduction of a pressure-correction module within SP-PINNs mitigates prediction errors,achieving a substantial reduction to 1‰compared with the conventional physics-informed neural network(PINN)approaches.Experimental applications validate the model’s ability to accurately and rapidly predict flow parameters with different sampling time intervals,with the computation time of predicting unsampled data less than 0.01 s.Such advancements signify a 100-fold improvement over traditional DNS calculations,underscoring the model’s potential in the real-time calculation and analysis of multiphase flow dynamics.
基金Supported By Open Fund of Hubei Key Laboratory of Oil and Gas Drilling and Production Engineering(Yangtze University),YQZC202309.
文摘A new measurement device,consisting of swirling blades and capsule-shaped throttling elements,is proposed in this study to eliminate typical measurement errors caused by complex flow patterns in gas-liquid flow.The swirling blades are used to transform the complex flow pattern into a forced annular flow.Drawing on the research of existing blockage flow meters and also exploiting the single-phase flow measurement theory,a formula is introduced to measure the phase-separated flow of gas and liquid.The formula requires the pressure ratio,Lockhart-Martinelli number(L-M number),and the gas phase Froude number.The unknown parameters appearing in the formula are fitted through numerical simulation using computational fluid dynamics(CFD),which involves a comprehensive analysis of the flow field inside the device from multiple perspectives,and takes into account the influence of pressure fluctuations.Finally,the measurement model is validated through an experimental error analysis.The results demonstrate that the measurement error can be maintained within±8%for various flow patterns,including stratified flow,bubble flow,and wave flow.
基金support provided by Shandong Provincial Science and Technology Plan Project(No.2023TSGC0625)Natural Resources Defense Council(NRDC,K94).
文摘A model is proposed for liquid film profile prediction in gas-liquid two-phase flow,which is able to provide the film thickness along the circumferential direction and the pressure gradient in the flow direction.A two-fluid model is used to calculate both gas and liquid phases’flow characteristics.The secondary flow occurring in the gas phase is taken into account and a sailing boat mechanism is introduced.Moreover,energy conservation is applied for obtaining the liquid film thickness distribution along the circumference.Liquid film thickness distribution is calculated accordingly for different cases;its values are compared with other models and available experimental data.As a result,the newly proposed model is tested and good performances are demonstrated.The liquid film thickness distribution in small pipes and inclined pipes is also studied,and regime transition is revealed by liquid film profile evolution.The observed inflection point demonstrates that the liquid film thickness decreases steeply along the circumference,when the circle angle ranges between 30°and 50°for gas-liquid stratified flow with small superficial velocities.
基金supported by the Research Project of the Technical Inspection Center of Sinopec Shengli Oilfield Company.
文摘When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located downstream.In order to investigate these aspects and,more specifically,the so-called bias phenomenon(all gas and liquid flowing to one pipe,while the other pipe is a liquid column that fluctuates up and down),laboratory experiments were carried out by using a T-junction connected to two parallel vertical pipes.Moreover,a GLTPF prediction model based on the principle of minimum potential energy was introduced.The research results indicate that this model can accurately predict the GLTPF state in parallel risers.The boundary of the slug flow and the churn flow in the opposite pipe can be predicted.Overall,according to the results,the pressure drop curves of the two-phase flow in the parallel risers are basically the same when there is no bias phenomenon,but the pressure drop in the parallel riser displays a large deviation when there is a slug flow-churn flow.Only when the parallel riser is in a state of asymmetric flow and one of the risers produces churn flow,the two-phase flow is prone to produce the bias phenomenon.
基金the National Natural Science Foundation of China (No. 29792074) and SINOPEC.
文摘The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.
文摘In the industrial production, the mixing of gas-liquid flow with vapor and gas-solid flow is a very common problem. In the process of the mixing, solid particle-clusters will form, and will have steady radii when the effect of the gathering of particles is balanced withthat of the breaking of particle-clusters. Then, the population distribution function of size of particles per unit length per unit volume is introduced, and its governingequation is derived on the analogy of the molecular kinetic theory. Finally, when the gas flow is very slow, the expression of steady average radius of particle-clusters is obtained.
基金Supported by the National Natural Science Foundation of China （No.50521604） and Shanghai Jiao Tong University Young Teacher Foundation.
文摘A viscous Kelvin-Helmholtz criterion of the interfacial wave instability is proposed in this paper based on the linear stability analysis of a transient one-dimensional two-fluid model. In thismodel, the pressure is evaluated using the local momentum balance rather than the hydrostatic approximation. The criterion predicts well the stability limit of stratified flow in horizontal and nearly horizontal pipes. The experimental and theoretical investigation on the effect of pipe inclination on the interfacial instability are carded out. It is found that the critical liquid height at the onset of interfacial wave instability is insensitive to the pipe inclination. However, the pipe inclination significantly affects critical superficial liquid velocity and wave velocity especially lor low gas velocities.
基金Supported by the National Natural Science Foundation of China (No.20476072).
文摘Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.
基金Supported by the National Natural Science Foundation of China （20736009）.
文摘In many gasliquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gasliquid flow pattern. Bubble formation models for variant gasliquid flow pat terns have been developed based on force balance. The effects of the orientation of gasliquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient airwater system, thesultable gasllquid flow pattern is important to obtain smaller bubbles under the low velocity liquid crossflow con ditions with stainless steel spargers. Among the four types of gasliquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found tobe insgnifican whenliq.uid velocity is.higher than. 3.2 m;sa or theorifice diameter is small enough.
基金the National Natural Science Foundation of China (No.20476072)
文摘Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.
文摘To clarify the countercurrent flow in a PWR hot leg under reflux condensation, numerical simulations of countercurrent air-water flow for a 1/15th scale model of the PWR hot leg were conducted using the two-fluid model implemented in CFD software. In this paper, the effect of expansion of the inclined pipe, which is the actual plant geometry, was evaluated. When increasing the air velocity, CCFL characteristics and the mechanism of flow pattern transition had significant differences between the case with and without expansion of the inclined pipe. CCFL characteristics were mitigated in the case with expansion. The effect of computational grid size was also discussed. When the supplied water velocity was small, the predicted flow pattern transition point agreed well with the measured data by increasing the number of cells. On the other hand, when the air velocity was decreasing, there were no significant differences in each case.
基金CAPES-National Council for the Improvement of Higher Education(Grant No.88882.435210/2019-01).
文摘A computational code is developed for the numerical solution of onedimensional transient gas-liquid flows using drift-flux models,in isothermal and also with phase change situations.For these two-phase models,classical upwind schemes such as Roe-and Godunov-type schemes are generally difficult to derive and expensive to use,since there are no treatable analytic expressions for the Jacobian matrix,eigenvalues and eigenvectors of the system of equations.On the other hand,the highorder compact finite difference scheme becomes an attractive alternative on these occasions,as it does not make use of any wave propagation information from the system of equations.The present paper extends the localized artificial diffusivity method for high-order compact finite difference schemes to solve two-phase flows with discontinuities.The numerical method has simple formulation,straightforward implementation,low computational cost and,most importantly,high-accuracy.The numerical methodology proposed is validated by solving several numerical examples given in the literature.The simulations are sixth-order accurate and it is shown that the proposed numerical method provides accurate approximations of shock waves and contact discontinuities.This is an essential property for simulations of realistic mass transport problems relevant to operations in the petroleum industry。
文摘This paper mainly studies the well-posedness of steady incompressible impinging jet flow problem through a 3D axisymmetric finitely long nozzle.This problem originates from the physical phenomena encountered in practical engineering fields,such as in short take-off and vertical landing(STOVL)aircraft.Nowadays many intricate phenomena associated with impinging jet flows remain inadequately elucidated,which limits the ability to optimize aircraft design.Given a boundary condition in the inlet,the impinging jet problem is transformed into a Bernoulli-type free boundary problem according to the stream function.Then the variational method is used to study the corresponding variational problem with one parameter,thereby the wellposedness is established.The main conclusion is as follows.For a 3D axisymmetric finitely long nozzle and an infinitely long vertical wall,given an axial velocity in the inlet of nozzle,there exists a unique smooth incom‑pressible impinging jet flow such that the free boundary initiates smoothly at the endpoint of the nozzle and extends to infinity along the vertical wall at far fields.The key point is to investigate the regularity of the corner where the nozzle and the vertical axis intersect.
基金supported in part by Natural Science Foundation of Jiangsu Province under Grant BK20230255Natural Science Foundation of Shandong Province under Grant ZR2023QE281.
文摘The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.
基金supported in part by the National Key Research and Development Program of China under Grant No.2021YFF0901300in part by the National Natural Science Foundation of China under Grant Nos.62173076 and 72271048.
文摘The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because of its straightforward,single-solution evolution framework.However,a potential draw-back of IGA is the lack of utilization of historical information,which could lead to an imbalance between exploration and exploitation,especially in large-scale DPFSPs.As a consequence,this paper develops an IGA with memory and learning mechanisms(MLIGA)to efficiently solve the DPFSP targeted at the mini-malmakespan.InMLIGA,we incorporate a memory mechanism to make a more informed selection of the initial solution at each stage of the search,by extending,reconstructing,and reinforcing the information from previous solutions.In addition,we design a twolayer cooperative reinforcement learning approach to intelligently determine the key parameters of IGA and the operations of the memory mechanism.Meanwhile,to ensure that the experience generated by each perturbation operator is fully learned and to reduce the prior parameters of MLIGA,a probability curve-based acceptance criterion is proposed by combining a cube root function with custom rules.At last,a discrete adaptive learning rate is employed to enhance the stability of the memory and learningmechanisms.Complete ablation experiments are utilized to verify the effectiveness of the memory mechanism,and the results show that this mechanism is capable of improving the performance of IGA to a large extent.Furthermore,through comparative experiments involving MLIGA and five state-of-the-art algorithms on 720 benchmarks,we have discovered that MLI-GA demonstrates significant potential for solving large-scale DPFSPs.This indicates that MLIGA is well-suited for real-world distributed flow shop scheduling.
文摘Due to the complex high-temperature characteristics of hydrocarbon fuel,the research on the long-term working process of parallel channel structure under variable working conditions,especially under high heat-mass ratio,has not been systematically carried out.In this paper,the heat transfer and flow characteristics of related high temperature fuels are studied by using typical engine parallel channel structure.Through numeri⁃cal simulation and systematic experimental verification,the flow and heat transfer characteristics of parallel chan⁃nels under typical working conditions are obtained,and the effectiveness of high-precision calculation method is preliminarily established.It is known that the stable time required for hot start of regenerative cooling engine is about 50 s,and the flow resistance of parallel channel structure first increases and then decreases with the in⁃crease of equivalence ratio(The following equivalence ratio is expressed byΦ),and there is a flow resistance peak in the range ofΦ=0.5~0.8.This is mainly caused by the coupling effect of high temperature physical proper⁃ties,flow rate and pressure of fuel in parallel channels.At the same time,the cooling and heat transfer character⁃istics of parallel channels under some conditions of high heat-mass ratio are obtained,and the main factors affect⁃ing the heat transfer of parallel channels such as improving surface roughness and strengthening heat transfer are mastered.In the experiment,whenΦis less than 0.9,the phenomenon of local heat transfer enhancement and deterioration can be obviously observed,and the temperature rise of local structures exceeds 200℃,which is the risk of structural damage.Therefore,the reliability of long-term parallel channel structure under the condition of high heat-mass ratio should be fully considered in structural design.
文摘Road traffic flow forecasting provides critical information for the operational management of road mobility challenges, and models are used to generate the forecast. This paper uses a random process to present a novel traffic modelling framework for aggregate traffic on urban roads. The main idea is that road traffic flow is random, even for the recurrent flow, such as rush hour traffic, which is predisposed to congestion. Therefore, the structure of the aggregate traffic flow model for urban roads should correlate well with the essential variables of the observed random dynamics of the traffic flow phenomena. The novelty of this paper is the developed framework, based on the Poisson process, the kinematics of urban road traffic flow, and the intermediate modelling approach, which were combined to formulate the model. Empirical data from an urban road in Ghana was used to explore the model’s fidelity. The results show that the distribution from the model correlates well with that of the empirical traffic, providing a strong validation of the new framework and instilling confidence in its potential for significantly improved forecasts and, hence, a more hopeful outlook for real-world traffic management.
文摘This paper presents an optimized strategy for multiple integrations of photovoltaic distributed generation (PV-DG) within radial distribution power systems. The proposed methodology focuses on identifying the optimal allocation and sizing of multiple PV-DG units to minimize power losses using a probabilistic PV model and time-series power flow analysis. Addressing the uncertainties in PV output due to weather variability and diurnal cycles is critical. A probabilistic assessment offers a more robust analysis of DG integration’s impact on the grid, potentially leading to more reliable system planning. The presented approach employs a genetic algorithm (GA) and a determined PV output profile and probabilistic PV generation profile based on experimental measurements for one year of solar radiation in Cairo, Egypt. The proposed algorithms are validated using a co-simulation framework that integrates MATLAB and OpenDSS, enabling analysis on a 33-bus test system. This framework can act as a guideline for creating other co-simulation algorithms to enhance computing platforms for contemporary modern distribution systems within smart grids concept. The paper presents comparisons with previous research studies and various interesting findings such as the considered hours for developing the probabilistic model presents different results.
