Based on a new second-order neutron transport equation, self-adjoint angular flux (SAAF) equation, the spherical harmonics (PN) method for neutron transport equation on unstructured-meshes is derived. The spherical ha...Based on a new second-order neutron transport equation, self-adjoint angular flux (SAAF) equation, the spherical harmonics (PN) method for neutron transport equation on unstructured-meshes is derived. The spherical harmonics function is used to expand the angular flux. A set of differential equations about the spatial variable, which are coupled with each other, can be obtained. They are solved iteratively by using the finite element method on un- structured-meshes. A two-dimension transport calculation program is coded according to the model. The numerical results of some benchmark problems demonstrate that this method can give high precision results and avoid the ray effect very well.展开更多
The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in China. Rail, road and water transportation have competed against each other for container transportation in the Chang-ji...The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in China. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifically in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line.展开更多
Colloidal gas aphrons (CGAs) were first reported by Sebba (1971) as micro bubbles (25-125 μm), composed of a gas nucleus surrounded by a thin surfactant film and created by intense stirring of a surfactant solution. ...Colloidal gas aphrons (CGAs) were first reported by Sebba (1971) as micro bubbles (25-125 μm), composed of a gas nucleus surrounded by a thin surfactant film and created by intense stirring of a surfactant solution. Since then, these colloidal dispersions have been used for diverse applications, with a particular focus on separation processes. However, exploitation of CGAs in petroleum industry is only at the outset. CGAs were first used in west Texas in 1998, under the name Aphron drilling fluids. This kind of fluid is characterized as having a continuous phase, a high viscosity at a low shear rate and containing, as an internal phase, micro air or gas bubbles, non-coalescing and recirculating. In this paper, we illuminate the physical and chemical properties of aphron drilling fluid and its processing mechanism.展开更多
The 5-axis NC machining offers the potential of efficient and accuratemachining. However, the present CAM system for 5-axis control is still an unsolved problem due tointerference between tool and surrounding objects....The 5-axis NC machining offers the potential of efficient and accuratemachining. However, the present CAM system for 5-axis control is still an unsolved problem due tointerference between tool and surrounding objects. A new method is presented. There are two steps inthis procedure. First, it detects the interference by calculating the shortest distance between thetool-axis and the surrounding surfaces. Then upon the maximum gouging, the interference-free toolposture for 5-axis NC cylindrical milling free-form surfaces is obtained by adjusting tool. Thevalidity of the proposed method has been confirmed by machining an impeller.展开更多
The 3-D turbulent flow in the impeller of sewage pump is simulated. Thetime-averaged N-S equations and the kappa-epsilon turbulent model is modified. The calculation iscarried out in body-fitted coordinated grid by ap...The 3-D turbulent flow in the impeller of sewage pump is simulated. Thetime-averaged N-S equations and the kappa-epsilon turbulent model is modified. The calculation iscarried out in body-fitted coordinated grid by applying SIMPLE-C algorithm. The calculated velocity,pressure distributions of the turbulent flow in the sewage pump are obtained for the first time,which will be helpful for the optimal design and performance prediction of sewage pumps on the basisof flow field simulation.展开更多
Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the re...Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the reasons for the losses are also explored.Results show that qualitative and quite fair quantitative agreements are achieved between thepredicted and measured flowfields. The influence of the impeller wake on the convexity surface ofdiffuser is great. The potential repercussion of the diffuser on the suction surface of the impelleris much larger than on the pressure surface. Effect of the unsteady interaction is strongest in theradial gap. The unsteady flow itself may compensate for the loss generated in stage, and the stageefficiency is inversely proportional to the entropy production.展开更多
In this work, an efficient AgVO3/MoS 2 composite photocatalyst was successfully synthesized via a hydrothermal method. The photocatalytic activity of the as-prepared photocatalyst was evaluated by using it for assessi...In this work, an efficient AgVO3/MoS 2 composite photocatalyst was successfully synthesized via a hydrothermal method. The photocatalytic activity of the as-prepared photocatalyst was evaluated by using it for assessing the degradation of different organic pollutants under visible-light irradiation. The composite 3%-AgVO3/MoS 2 catalyst demonstrated a significantly enhanced photocatalytic activity compared to the pure compounds（AgVO3 and MoS2）. The reason behind the excellent photocatalytic performance was the modification of MoS 2 by AgVO3 to facilitate O2 adsorption/activation. In addition, the composite catalyst facilitates the two-electron oxygen reduction reaction whereby H2O2 is generated on the surface of MoS 2 to produce additional reactive oxygen species（ROSs）. ESR coupled with the POPHA fluorescence detection method and a free radical capture experiment were used to elucidate the mechanism of formation of the ROSs, including ·OH, ·O2- and H2O2. Furthermore, the generation of additional ROSs could accelerate electron consumption, leaving behind more holes for the oxidation of organic pollutants. A possible photocatalytic mechanism of the composite is also discussed.展开更多
The compressor of composite gear teeth is a new type of rotor compressor withpartial built-in compression process. Analysis of its thermodynamic process indicates that thebuilt-in process is incomplete. The thermodyna...The compressor of composite gear teeth is a new type of rotor compressor withpartial built-in compression process. Analysis of its thermodynamic process indicates that thebuilt-in process is incomplete. The thermodynamic process of the compressor of composite gear teethcan be considered as five processes; the suction process, the isometric process, the compressionprocess, the pressure-balance process at high pressure and low pressure gas, and discharge process.Here, it is necessary to explain further the pressure-balance process. The pressure-balance processis isometric process. It is found that the isometric process of gas in chamber A whose capacity is83 percent of total work volume can be eliminated basically through extending the discharge port toconnect early the discharge port with the chamber B. By the above-mentioned method, the loss ofenergy will be reduced.展开更多
This paper discusses the flowing process inside a nozzle, especially the formation mechanism of cavitations within the nozzle and puts forward a nozzle flow model, which takes account of the injection conditions and n...This paper discusses the flowing process inside a nozzle, especially the formation mechanism of cavitations within the nozzle and puts forward a nozzle flow model, which takes account of the injection conditions and nozzle geometry. By the model being implemented to the KIVA codes, the spray characteristics (e. g., spray penetration and cone angle) of diesel and dimethyl ether (DME) are simulated. The comparisons between the computational and experimental results are performed, which show that the liquid spray characteristics could be more truly demonstrated by considering the existence of the cavitations. Key words nozzle model - spray characteristics - cavitation - atomization CLC number O 35 - TK 402 Foundation item: Supported by the National Natural Science Foundation of China (50376018) and the National 973 Basic Research Program of China (2001CB209207)Biography: WEI Ming-rui (1967-), male, Associate professor, Ph. D, research direction: computational combustion, computational fluid dynamics.展开更多
Fault diagnosis is confronted with two problems; how to '' measure'' the growthof a fault and how to predict the remaining useful lifetime of such a failing component or machine.This paper attempts to ...Fault diagnosis is confronted with two problems; how to '' measure'' the growthof a fault and how to predict the remaining useful lifetime of such a failing component or machine.This paper attempts to solve these two problems by proposing a model of fault prognosis usingwavelet basis neural network. Gaussian radial basis functions and Mexican hat wavelet frames areused as scaling functions and wavelets, respectively. The centers of the basis functions arecalculated using a dyadic expansion scheme and a k-means clustering algorithm.展开更多
This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for prof...This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for profile description was coupled with ablade-to-blade flow calculation and a real-coded genetic algorithm. A low solidity vaned diffuser of0.89 in solidity was obtained through the present optimum design. Numerical analysis andexperimental test were made to evaluate the hydrodynamic performance of the centrifugal pump withthe designed low solidity vaned diffuser and original vaned diffuser. The obtained resultsdemonstrate that the centrifugal pump with the optimized vaned diffuser has compact size comparedwith the original one while the performance requirements have been met.展开更多
Numerical simulation has been performed to investigate the characteristics ofthe turbulent jet issuing obliquely into a crossflow, at the injection angles of 90° and 60°. TheSIMPLEC algorithm in the body-fit...Numerical simulation has been performed to investigate the characteristics ofthe turbulent jet issuing obliquely into a crossflow, at the injection angles of 90° and 60°. TheSIMPLEC algorithm in the body-fitted coordinates and the wall-function method using the RNG k-εturbulence model have been adopted to simulate this flow at two jet-to-crossflow velocity ratios, 2and 4. The numerical results are good agreement with the experimental measurements, the jettrajectories have been given, the separation events in the lee of the jet exit have been found, andthe forming mechanism has been analyzed.展开更多
The Arctic Oscillation (AO), though basically is a zonal symmetricphenomenon, also shows zonal asymmetric variation. The dynamics of this zonal variation isconsidered here from the point of view of the planetary propa...The Arctic Oscillation (AO), though basically is a zonal symmetricphenomenon, also shows zonal asymmetric variation. The dynamics of this zonal variation isconsidered here from the point of view of the planetary propagation on the earth sphere. Based onthe linear barotropic vorticity e-quation, the planetary wave ray path is calculated in the winterJanuary. It shows that NAO( North Atlantic Oscillation), AO and North Pacific could be linkedthrough the planetary wave propagation, which acts as the atmospheric bridge. The zonal symmetricand asymmetric structures both have association with these Rossby wave activities.展开更多
Hydrodynamic optimization design of the bend pipe from pump using theNavier-Stokes solver and evolutionary algorithms was conducted. The minimization of the totalpressure loss of the bend pipe was chosen as the design...Hydrodynamic optimization design of the bend pipe from pump using theNavier-Stokes solver and evolutionary algorithms was conducted. The minimization of the totalpressure loss of the bend pipe was chosen as the design object in order to obtain the uniform exitflows through suppressing the secondary flows. The 3-D Navier-Stokes solver was applied to evaluatethe hydrodynamic performance of the bend-pipe flows. A 7th-order Bezier curve was used toparameterize the meridional section and elliptic representation was adopted to represent thecross-section profiles of the bend pipe. Evolutionary algorithms were applied in optimization. Theobtained results show that the designed bend pipe shape has much more uniform exit flows comparedwith the initial one and much weaker secondary flows, and that the evolutionary algorithms and CFDtechnique are the powerful optimization tools for the fluid machinery desiga展开更多
In this paper, the differences in the characteristics of airflow around thevan-body truck and of the aerodynamic drag, which were caused by the installation of a winddeflector, were studied by experimentally and numer...In this paper, the differences in the characteristics of airflow around thevan-body truck and of the aerodynamic drag, which were caused by the installation of a winddeflector, were studied by experimentally and numerically. The results show that after theinstallation of the deflector, the airflow around the top and bottom of the truck becoms smooth, theintensity of tail-vortex is weakened and its contribution area lessened. It also indicates that theaerodynamic characteristics of the airflow are changed distinctly and the aerodynamic drag isreduced considerably. The effect of the thin-wall deflector is better than the solid one indecreasing the drag. It is also concluded that proper design of the gap between the deflector bottomand the top of the driver cab can enhance the effect of the deflector in reducing drag.展开更多
基金Supported by pre-research fund of State Key Laboratory (51479080201 JW0802)
文摘Based on a new second-order neutron transport equation, self-adjoint angular flux (SAAF) equation, the spherical harmonics (PN) method for neutron transport equation on unstructured-meshes is derived. The spherical harmonics function is used to expand the angular flux. A set of differential equations about the spatial variable, which are coupled with each other, can be obtained. They are solved iteratively by using the finite element method on un- structured-meshes. A two-dimension transport calculation program is coded according to the model. The numerical results of some benchmark problems demonstrate that this method can give high precision results and avoid the ray effect very well.
文摘The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in China. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifically in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line.
文摘Colloidal gas aphrons (CGAs) were first reported by Sebba (1971) as micro bubbles (25-125 μm), composed of a gas nucleus surrounded by a thin surfactant film and created by intense stirring of a surfactant solution. Since then, these colloidal dispersions have been used for diverse applications, with a particular focus on separation processes. However, exploitation of CGAs in petroleum industry is only at the outset. CGAs were first used in west Texas in 1998, under the name Aphron drilling fluids. This kind of fluid is characterized as having a continuous phase, a high viscosity at a low shear rate and containing, as an internal phase, micro air or gas bubbles, non-coalescing and recirculating. In this paper, we illuminate the physical and chemical properties of aphron drilling fluid and its processing mechanism.
文摘The 5-axis NC machining offers the potential of efficient and accuratemachining. However, the present CAM system for 5-axis control is still an unsolved problem due tointerference between tool and surrounding objects. A new method is presented. There are two steps inthis procedure. First, it detects the interference by calculating the shortest distance between thetool-axis and the surrounding surfaces. Then upon the maximum gouging, the interference-free toolposture for 5-axis NC cylindrical milling free-form surfaces is obtained by adjusting tool. Thevalidity of the proposed method has been confirmed by machining an impeller.
文摘The 3-D turbulent flow in the impeller of sewage pump is simulated. Thetime-averaged N-S equations and the kappa-epsilon turbulent model is modified. The calculation iscarried out in body-fitted coordinated grid by applying SIMPLE-C algorithm. The calculated velocity,pressure distributions of the turbulent flow in the sewage pump are obtained for the first time,which will be helpful for the optimal design and performance prediction of sewage pumps on the basisof flow field simulation.
文摘Numerical simulation on the unsteady flow in a centrifugal compressor isperformed, and compared with the experimental data. The influence of the impeller-diffuserinteraction on the flow-fields is discussed, and the reasons for the losses are also explored.Results show that qualitative and quite fair quantitative agreements are achieved between thepredicted and measured flowfields. The influence of the impeller wake on the convexity surface ofdiffuser is great. The potential repercussion of the diffuser on the suction surface of the impelleris much larger than on the pressure surface. Effect of the unsteady interaction is strongest in theradial gap. The unsteady flow itself may compensate for the loss generated in stage, and the stageefficiency is inversely proportional to the entropy production.
基金supported by the National Natural Science Foundation of China(21706104)the Natural Science Foundation of Jiangsu Province(BK20150484)+1 种基金the China Postdoctoral Science Foundation(2015M570416)the financial support of the Research Foundation of Jiangsu University,China(14JDG148)~~
文摘In this work, an efficient AgVO3/MoS 2 composite photocatalyst was successfully synthesized via a hydrothermal method. The photocatalytic activity of the as-prepared photocatalyst was evaluated by using it for assessing the degradation of different organic pollutants under visible-light irradiation. The composite 3%-AgVO3/MoS 2 catalyst demonstrated a significantly enhanced photocatalytic activity compared to the pure compounds（AgVO3 and MoS2）. The reason behind the excellent photocatalytic performance was the modification of MoS 2 by AgVO3 to facilitate O2 adsorption/activation. In addition, the composite catalyst facilitates the two-electron oxygen reduction reaction whereby H2O2 is generated on the surface of MoS 2 to produce additional reactive oxygen species（ROSs）. ESR coupled with the POPHA fluorescence detection method and a free radical capture experiment were used to elucidate the mechanism of formation of the ROSs, including ·OH, ·O2- and H2O2. Furthermore, the generation of additional ROSs could accelerate electron consumption, leaving behind more holes for the oxidation of organic pollutants. A possible photocatalytic mechanism of the composite is also discussed.
文摘The compressor of composite gear teeth is a new type of rotor compressor withpartial built-in compression process. Analysis of its thermodynamic process indicates that thebuilt-in process is incomplete. The thermodynamic process of the compressor of composite gear teethcan be considered as five processes; the suction process, the isometric process, the compressionprocess, the pressure-balance process at high pressure and low pressure gas, and discharge process.Here, it is necessary to explain further the pressure-balance process. The pressure-balance processis isometric process. It is found that the isometric process of gas in chamber A whose capacity is83 percent of total work volume can be eliminated basically through extending the discharge port toconnect early the discharge port with the chamber B. By the above-mentioned method, the loss ofenergy will be reduced.
文摘This paper discusses the flowing process inside a nozzle, especially the formation mechanism of cavitations within the nozzle and puts forward a nozzle flow model, which takes account of the injection conditions and nozzle geometry. By the model being implemented to the KIVA codes, the spray characteristics (e. g., spray penetration and cone angle) of diesel and dimethyl ether (DME) are simulated. The comparisons between the computational and experimental results are performed, which show that the liquid spray characteristics could be more truly demonstrated by considering the existence of the cavitations. Key words nozzle model - spray characteristics - cavitation - atomization CLC number O 35 - TK 402 Foundation item: Supported by the National Natural Science Foundation of China (50376018) and the National 973 Basic Research Program of China (2001CB209207)Biography: WEI Ming-rui (1967-), male, Associate professor, Ph. D, research direction: computational combustion, computational fluid dynamics.
文摘Fault diagnosis is confronted with two problems; how to '' measure'' the growthof a fault and how to predict the remaining useful lifetime of such a failing component or machine.This paper attempts to solve these two problems by proposing a model of fault prognosis usingwavelet basis neural network. Gaussian radial basis functions and Mexican hat wavelet frames areused as scaling functions and wavelets, respectively. The centers of the basis functions arecalculated using a dyadic expansion scheme and a k-means clustering algorithm.
文摘This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for profile description was coupled with ablade-to-blade flow calculation and a real-coded genetic algorithm. A low solidity vaned diffuser of0.89 in solidity was obtained through the present optimum design. Numerical analysis andexperimental test were made to evaluate the hydrodynamic performance of the centrifugal pump withthe designed low solidity vaned diffuser and original vaned diffuser. The obtained resultsdemonstrate that the centrifugal pump with the optimized vaned diffuser has compact size comparedwith the original one while the performance requirements have been met.
文摘Numerical simulation has been performed to investigate the characteristics ofthe turbulent jet issuing obliquely into a crossflow, at the injection angles of 90° and 60°. TheSIMPLEC algorithm in the body-fitted coordinates and the wall-function method using the RNG k-εturbulence model have been adopted to simulate this flow at two jet-to-crossflow velocity ratios, 2and 4. The numerical results are good agreement with the experimental measurements, the jettrajectories have been given, the separation events in the lee of the jet exit have been found, andthe forming mechanism has been analyzed.
文摘The Arctic Oscillation (AO), though basically is a zonal symmetricphenomenon, also shows zonal asymmetric variation. The dynamics of this zonal variation isconsidered here from the point of view of the planetary propagation on the earth sphere. Based onthe linear barotropic vorticity e-quation, the planetary wave ray path is calculated in the winterJanuary. It shows that NAO( North Atlantic Oscillation), AO and North Pacific could be linkedthrough the planetary wave propagation, which acts as the atmospheric bridge. The zonal symmetricand asymmetric structures both have association with these Rossby wave activities.
文摘Hydrodynamic optimization design of the bend pipe from pump using theNavier-Stokes solver and evolutionary algorithms was conducted. The minimization of the totalpressure loss of the bend pipe was chosen as the design object in order to obtain the uniform exitflows through suppressing the secondary flows. The 3-D Navier-Stokes solver was applied to evaluatethe hydrodynamic performance of the bend-pipe flows. A 7th-order Bezier curve was used toparameterize the meridional section and elliptic representation was adopted to represent thecross-section profiles of the bend pipe. Evolutionary algorithms were applied in optimization. Theobtained results show that the designed bend pipe shape has much more uniform exit flows comparedwith the initial one and much weaker secondary flows, and that the evolutionary algorithms and CFDtechnique are the powerful optimization tools for the fluid machinery desiga
文摘In this paper, the differences in the characteristics of airflow around thevan-body truck and of the aerodynamic drag, which were caused by the installation of a winddeflector, were studied by experimentally and numerically. The results show that after theinstallation of the deflector, the airflow around the top and bottom of the truck becoms smooth, theintensity of tail-vortex is weakened and its contribution area lessened. It also indicates that theaerodynamic characteristics of the airflow are changed distinctly and the aerodynamic drag isreduced considerably. The effect of the thin-wall deflector is better than the solid one indecreasing the drag. It is also concluded that proper design of the gap between the deflector bottomand the top of the driver cab can enhance the effect of the deflector in reducing drag.
