Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelm...Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This vertical shear of mean flow is to some extent weakened by thermal forcing.展开更多
Flow accelerated corrosion(FAC)is the main failure cause of the secondary circuit carbon steel piping in nuclear power plants.The piping failures caused by FAC have resulted in numerous unplanned outages and tragic fa...Flow accelerated corrosion(FAC)is the main failure cause of the secondary circuit carbon steel piping in nuclear power plants.The piping failures caused by FAC have resulted in numerous unplanned outages and tragic fatalities.The existing researches focus on the main factors contributing to FAC,which include metallurgical factors,environmental factors and hydrodynamic factors.Some effective FAC management methods and programs with long term monitoring and inspection data analysis are recommended.But a comprehensive FAC management system should be developed in order to mitigate and manage FAC systematically.In this paper,the FAC influencing factors are analyzed in combination with the operating conditions of the secondary circuit piping in the Third Qinshan Nuclear Power Plant(TQNPP),China(Third Qinshan Nuclear Power Company Limited,China).A comprehensive FAC mitigation and management system is developed for TQNPP secondary circuit piping.The system is composed of five processes,viz.materials substitution,water chemical optimization,long-term monitor strategy for the susceptible piping,integrity evaluation of the local thinning defects,and repair or replacement.With the implementation of the five processes,the material of FAC sensitive pipe fittings are modified from carbon steel to stainless steel,N_2H_4 and NH_3 are finally selected as the water chemical regulator of secondary circuit,the secondary circuit pips are classified according to FAC susceptibility in order to conduct long term monitoring strategy,and an integrity evaluation flow for local thinning caused by FAC in carbon steel piping is developed.If the component with local thinning defects is not fit-for-service,corresponding repair or replacement should be conducted.The comprehensive FAC mitigation and management system with five interrelated processes would be a cost-effective method of increasing personnel safety,plant safety and availability.展开更多
Vortex double layers (VDLs) and vortex projectiles (VPs) are the essential coherent structures which emerge in the shock excited (s/f/s) planar parallel "curtain" simulations of a 2D shock tube with PPM. The...Vortex double layers (VDLs) and vortex projectiles (VPs) are the essential coherent structures which emerge in the shock excited (s/f/s) planar parallel "curtain" simulations of a 2D shock tube with PPM. These opposite signed layers, formed by shock induced baroclinic deposition of vorticity, "ind" and are strongly affected by secondary reflected shocks and vortex interactions. In our visiometric mode of working, we quantify several of these processes and introduce time epochs to discuss the emerging phenomena and normalizations to scale (collapse) the data at M =1.5 and 2.0. This versatile configuration, easily obtained in the laboratory, allows us to study the formation, evolution and reacceleration of VPs and stratified turbulence and mixing.展开更多
A number of piping components in the secondary system of nuclear power plants (NPPs) have been exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, LDIE (Liquid Droplet Impingeme...A number of piping components in the secondary system of nuclear power plants (NPPs) have been exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, LDIE (Liquid Droplet Impingement Erosion), and SPE (Solid Particle Erosion). Those mechanisms may lead to thinning, leaking, or the rupture of components. Due to the pipe ruptures caused by wall thinning of Surry Unit 2 in 1986 and Mihama Unit 3 in 2004, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage the wall thinning of pipes caused by FAC and erosion, KEPCO-E & C has developed ToSPACE program. It can predict both FAC & erosion phenomena, and also be utilized in the pipe wall thinning management works such as susceptibility analysis, UT (Ultrasonic Test) data evaluation as well as establishment of long-term inspection plan. Even though the ToSPACE can predict the five aging mechanisms mentioned above, only the FAC prediction result using ToSPACE was compared herein with the experimental result using FACTS (Flow Accelerated Corrosion Test System) to verify the ToSPACE’s capability. In addition, the FAC prediction result using ToSPACE was also compared with that of CHECWORKS that is widely used all over the world.展开更多
Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change o...Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer.The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport.Meanwhile,the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer,which is caused by the dissolution of Cr ions increased by increasing the DO concentration.Meanwhile,the chromium ion concentration increases with the dissolved oxygen concentration,which leads to a decrease in the thickness of the electric double layer,weakening the electrodynamic effect.The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees.This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.展开更多
Based on three-dimensional （3D） acceleration sensing, an intelligent particle spy capable of detecting, transferring, and storing data, is proposed under the name of Particle Measurement Sensor （PMS）. A prototype ...Based on three-dimensional （3D） acceleration sensing, an intelligent particle spy capable of detecting, transferring, and storing data, is proposed under the name of Particle Measurement Sensor （PMS）. A prototype 60-mm-dia PMS was tested to track its freefall in terms of velocity and displacement, and served as a particle spy in a fluidized bed delivering the in situ acceleration information it detects. With increasing superficial gas velocity in the fluidized bed, the acceleration felt by PMS was observed to increase. The variance of the signals, which reflect the fluctuation, increased at first, reaching a maximum at the gas velocity （Uc） which marks the transition from bubbling to turbulent fluidization. Through probability density distribution （PDD） analysis, the PDD peak can be divided into the emulsion phase peak and the bubble phase peak. The average acceleration of emulsion and bubble phase increased, while the variance of both phases reached a maximum at Uc, at the same time. However, the difference between the variances of two phases reached the maximum at Uc. Findings of this study indicate that PMS can record independent in situ information. Further, it can provide other in situ measurements when equipped with additional multi-functional sensors.展开更多
Collision among particles plays a significant role in governing the structure of gas-solids flow in a riser, especially in the dense and acceleration region. The inter-particle collision is the major cause not only fo...Collision among particles plays a significant role in governing the structure of gas-solids flow in a riser, especially in the dense and acceleration region. The inter-particle collision is the major cause not only for the kinetic energy dissipation （in terms of additional pressure drop beyond the solids hold-up） but also for the control of solids acceleration （in terms of a balancing force to prevent a free acceleration of solids）. A neglect of the balancing force of inter-particle collision against the hydrodynamic force in the solids momentum equation would simply overestimate the solids acceleration or concentration while underestimate the axial gradient of pressure along the riser by a large margin, typically by up to two orders of magnitude. This paper aims to illustrate the importance of the collision on the characteristic of the gas-solids riser flow. Our analysis shows that the collision force should be of the same order of magnitude as that of the drag force in the dense and acceleration region, which can be far beyond that of gravitational force on solids. A simple formulation of the collision force is therefore proposed to bear a similar format of drag force, with regard to the dependence upon local solids properties.With the inclusion of the proposed correlation of collision force in the solids momentum equation, our model would be able to yield reasonable phase distributions of gas-solid flows, which can be validated, in a bulk range, against available measurements of solids volume fraction and axial gradient of pressure.展开更多
基金Research Project No.[75-09-01] on medium-range numerical weather forecasts.
文摘Non-acceleration theorem in a primitive equation system is developed to investigate the influences of waves on the mean flow variation against external forcing. Numerical results show that mechanical forcing overwhelms thermal forcing in maintaining the mean flow in which the internal mechanical forcing associated with horizontal eddy flux of momentum plays the most important roles. Both internal forcing and external forcing are shown to be active and at the first place for the mean flow variations, whereas the forcing-induced mean meridional circulation is passive and secondary. It is also shown that the effects on mean flow of external mechanical forcing are concentrated in the lower troposphere, whereas those due to wave-mean flow interaction are more important in the upper troposphere. These act together and result in the vertically easterly shear in low latitudes and westerly shear in mid-latitudes. This vertical shear of mean flow is to some extent weakened by thermal forcing.
文摘Flow accelerated corrosion(FAC)is the main failure cause of the secondary circuit carbon steel piping in nuclear power plants.The piping failures caused by FAC have resulted in numerous unplanned outages and tragic fatalities.The existing researches focus on the main factors contributing to FAC,which include metallurgical factors,environmental factors and hydrodynamic factors.Some effective FAC management methods and programs with long term monitoring and inspection data analysis are recommended.But a comprehensive FAC management system should be developed in order to mitigate and manage FAC systematically.In this paper,the FAC influencing factors are analyzed in combination with the operating conditions of the secondary circuit piping in the Third Qinshan Nuclear Power Plant(TQNPP),China(Third Qinshan Nuclear Power Company Limited,China).A comprehensive FAC mitigation and management system is developed for TQNPP secondary circuit piping.The system is composed of five processes,viz.materials substitution,water chemical optimization,long-term monitor strategy for the susceptible piping,integrity evaluation of the local thinning defects,and repair or replacement.With the implementation of the five processes,the material of FAC sensitive pipe fittings are modified from carbon steel to stainless steel,N_2H_4 and NH_3 are finally selected as the water chemical regulator of secondary circuit,the secondary circuit pips are classified according to FAC susceptibility in order to conduct long term monitoring strategy,and an integrity evaluation flow for local thinning caused by FAC in carbon steel piping is developed.If the component with local thinning defects is not fit-for-service,corresponding repair or replacement should be conducted.The comprehensive FAC mitigation and management system with five interrelated processes would be a cost-effective method of increasing personnel safety,plant safety and availability.
文摘Vortex double layers (VDLs) and vortex projectiles (VPs) are the essential coherent structures which emerge in the shock excited (s/f/s) planar parallel "curtain" simulations of a 2D shock tube with PPM. These opposite signed layers, formed by shock induced baroclinic deposition of vorticity, "ind" and are strongly affected by secondary reflected shocks and vortex interactions. In our visiometric mode of working, we quantify several of these processes and introduce time epochs to discuss the emerging phenomena and normalizations to scale (collapse) the data at M =1.5 and 2.0. This versatile configuration, easily obtained in the laboratory, allows us to study the formation, evolution and reacceleration of VPs and stratified turbulence and mixing.
文摘A number of piping components in the secondary system of nuclear power plants (NPPs) have been exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, LDIE (Liquid Droplet Impingement Erosion), and SPE (Solid Particle Erosion). Those mechanisms may lead to thinning, leaking, or the rupture of components. Due to the pipe ruptures caused by wall thinning of Surry Unit 2 in 1986 and Mihama Unit 3 in 2004, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage the wall thinning of pipes caused by FAC and erosion, KEPCO-E & C has developed ToSPACE program. It can predict both FAC & erosion phenomena, and also be utilized in the pipe wall thinning management works such as susceptibility analysis, UT (Ultrasonic Test) data evaluation as well as establishment of long-term inspection plan. Even though the ToSPACE can predict the five aging mechanisms mentioned above, only the FAC prediction result using ToSPACE was compared herein with the experimental result using FACTS (Flow Accelerated Corrosion Test System) to verify the ToSPACE’s capability. In addition, the FAC prediction result using ToSPACE was also compared with that of CHECWORKS that is widely used all over the world.
基金financially supported by the National Natural Science Foundation of China(51901254,52001336)the Foundation Research Funds for the Central Universities(19lgpy22)the Shenzhen Science and Technology Program(2022A007)
文摘Effects of dissolved oxygen(DO)on the deposition characteristics of corrosion-related unidentified deposit(CRUD)were investigated by using 304 stainless steel micro-orifices.The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer.The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport.Meanwhile,the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer,which is caused by the dissolution of Cr ions increased by increasing the DO concentration.Meanwhile,the chromium ion concentration increases with the dissolved oxygen concentration,which leads to a decrease in the thickness of the electric double layer,weakening the electrodynamic effect.The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees.This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.
基金supported by the Foundation for Natural Scientific Foundation of China (No. 20606020, No. 20736004, No. 20736007)
文摘Based on three-dimensional （3D） acceleration sensing, an intelligent particle spy capable of detecting, transferring, and storing data, is proposed under the name of Particle Measurement Sensor （PMS）. A prototype 60-mm-dia PMS was tested to track its freefall in terms of velocity and displacement, and served as a particle spy in a fluidized bed delivering the in situ acceleration information it detects. With increasing superficial gas velocity in the fluidized bed, the acceleration felt by PMS was observed to increase. The variance of the signals, which reflect the fluctuation, increased at first, reaching a maximum at the gas velocity （Uc） which marks the transition from bubbling to turbulent fluidization. Through probability density distribution （PDD） analysis, the PDD peak can be divided into the emulsion phase peak and the bubble phase peak. The average acceleration of emulsion and bubble phase increased, while the variance of both phases reached a maximum at Uc, at the same time. However, the difference between the variances of two phases reached the maximum at Uc. Findings of this study indicate that PMS can record independent in situ information. Further, it can provide other in situ measurements when equipped with additional multi-functional sensors.
文摘Collision among particles plays a significant role in governing the structure of gas-solids flow in a riser, especially in the dense and acceleration region. The inter-particle collision is the major cause not only for the kinetic energy dissipation （in terms of additional pressure drop beyond the solids hold-up） but also for the control of solids acceleration （in terms of a balancing force to prevent a free acceleration of solids）. A neglect of the balancing force of inter-particle collision against the hydrodynamic force in the solids momentum equation would simply overestimate the solids acceleration or concentration while underestimate the axial gradient of pressure along the riser by a large margin, typically by up to two orders of magnitude. This paper aims to illustrate the importance of the collision on the characteristic of the gas-solids riser flow. Our analysis shows that the collision force should be of the same order of magnitude as that of the drag force in the dense and acceleration region, which can be far beyond that of gravitational force on solids. A simple formulation of the collision force is therefore proposed to bear a similar format of drag force, with regard to the dependence upon local solids properties.With the inclusion of the proposed correlation of collision force in the solids momentum equation, our model would be able to yield reasonable phase distributions of gas-solid flows, which can be validated, in a bulk range, against available measurements of solids volume fraction and axial gradient of pressure.
