Turbine blades and vans operated in an aggressive gas environment usually suffer from combined oxidation and cycle loading effects. The surface oxide layer will result in premature failure and lead to a significant re...Turbine blades and vans operated in an aggressive gas environment usually suffer from combined oxidation and cycle loading effects. The surface oxide layer will result in premature failure and lead to a significant reduction in the service lifetime. The effects of prior oxidation-induced damage under a simulated combustion-gas environment on the fatigue lifetime of the directionally solidified（DS） nickel-based superalloy DZ125 with and without an oxidation-resistant coating were presented. The fatigue lifetime of uncoated samples is adversely affected by prior oxidation exposure. The deterioration of fatigue lifetime in uncoated samples is associated with surface microstructural degradation, which occurs during prior exposure. However,the presence of MCrAlY coating is beneficial for the sample＇s lifetime under high stress. Further scanning electron microscopy（SEM） analysis demonstrates that the coating does not contribute to the initiation mode of fatigue cracks.展开更多
Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the ...Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the literature on sulfur hexafluoride(SF6)alternatives including the scientific understanding,control,and implementation of gas-solid systems in this type of power transmission.First,the structure-activity relationship between the molecular structure and physico-chemical properties of Environment-friendly insulating gases is presented.Then,the search and prediction of important physicochemical properties of gases are summarized.Subsequently,in view of the potential of environmental friendly insulating gases,the swarm parameters of gas discharge and breakdown properties in a quasi-uniform field,inhomogeneous field,and at the gas-solid interface,that need to be taken into account with industrialized DC GILs are discussed.The latest research progress on insulation characteristics,especially the polarity effect in DC gas-solid insulation systems,the sensitivity to the electrode surface state,and the non-uniformity of the electric field,and the influence of metal particles and their variation with air pressure,is highlighted.In addition,the heat transfer characteristics of insulating gases,related to DC GIL transmission with a large current-carrying capacity and the influence of alternative gases on the heat transfer characteristics are described.Finally,aiming at solving the contradiction of low environmental impact,high dielectric strength and low liquefaction temperatures in the selection of alternative gases,an coordinated regulation model for Environment-friendly gases in DC GILs is established.Considerations for future work on this topic are also presented.展开更多
基金financially supported by National Basic Research Program of China (No.2015CB057401)
文摘Turbine blades and vans operated in an aggressive gas environment usually suffer from combined oxidation and cycle loading effects. The surface oxide layer will result in premature failure and lead to a significant reduction in the service lifetime. The effects of prior oxidation-induced damage under a simulated combustion-gas environment on the fatigue lifetime of the directionally solidified（DS） nickel-based superalloy DZ125 with and without an oxidation-resistant coating were presented. The fatigue lifetime of uncoated samples is adversely affected by prior oxidation exposure. The deterioration of fatigue lifetime in uncoated samples is associated with surface microstructural degradation, which occurs during prior exposure. However,the presence of MCrAlY coating is beneficial for the sample＇s lifetime under high stress. Further scanning electron microscopy（SEM） analysis demonstrates that the coating does not contribute to the initiation mode of fatigue cracks.
基金This work was supported in part by the National Basic Research Program of China(973 Program)(2014CB239500).
文摘Environment-friendly gas insulating mediums adapted to a DC gas-insulated transmission line(GIL)electric field condition is the key to the next generation of Environment-friendly HVDC GILs.In this paper,we review the literature on sulfur hexafluoride(SF6)alternatives including the scientific understanding,control,and implementation of gas-solid systems in this type of power transmission.First,the structure-activity relationship between the molecular structure and physico-chemical properties of Environment-friendly insulating gases is presented.Then,the search and prediction of important physicochemical properties of gases are summarized.Subsequently,in view of the potential of environmental friendly insulating gases,the swarm parameters of gas discharge and breakdown properties in a quasi-uniform field,inhomogeneous field,and at the gas-solid interface,that need to be taken into account with industrialized DC GILs are discussed.The latest research progress on insulation characteristics,especially the polarity effect in DC gas-solid insulation systems,the sensitivity to the electrode surface state,and the non-uniformity of the electric field,and the influence of metal particles and their variation with air pressure,is highlighted.In addition,the heat transfer characteristics of insulating gases,related to DC GIL transmission with a large current-carrying capacity and the influence of alternative gases on the heat transfer characteristics are described.Finally,aiming at solving the contradiction of low environmental impact,high dielectric strength and low liquefaction temperatures in the selection of alternative gases,an coordinated regulation model for Environment-friendly gases in DC GILs is established.Considerations for future work on this topic are also presented.
