Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplish...Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.展开更多
Enhancement in boiling heat transfer performance is significant for addressing thermal management bottlenecks of advanced electronic systems.Reduced graphene oxides(rGO)are regarded as promising candidates for thermal...Enhancement in boiling heat transfer performance is significant for addressing thermal management bottlenecks of advanced electronic systems.Reduced graphene oxides(rGO)are regarded as promising candidates for thermal management due to their excellent thermal properties,chemical stability and adjustable wettability.In this study,rGO coatings with micron pores and controllable oxygen contents are prepared on Al substrate via cathodic electrophoretic deposition and subsequent thermal annealing,leading to enhanced pool boiling performance.The heat transfer coefficient for Al/rGO450is 37.2 kW m-2K-1,which is increased by 112.6%compared with bare Al,also outperformed previously reported Al based substrates.It is assumed that the hydrophilic and aerophobic r GO coatings effectively promote the liquid infiltration and bubble departure during pool boiling process.Importantly,repeatability tests indicate the durable stability of vertically oriented rGO nanosheets.Reverse nonequilibrium molecular dynamics simulation indicates that the interfacial transmission coefficients of Al/rGO increase after thermal annealing,indicative of the enhanced heat transfer performance of heterogeneous interface.Our study opens a new avenue for endowing metal substrates with high pool boiling performance using porous carbon coating nanoengineering strategy with controllable morphology and components.展开更多
文摘Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.
基金supported by the National Natural Science Foundation of China(Grant No.51635005)the 111 Project(Grant No.B18017)。
文摘Enhancement in boiling heat transfer performance is significant for addressing thermal management bottlenecks of advanced electronic systems.Reduced graphene oxides(rGO)are regarded as promising candidates for thermal management due to their excellent thermal properties,chemical stability and adjustable wettability.In this study,rGO coatings with micron pores and controllable oxygen contents are prepared on Al substrate via cathodic electrophoretic deposition and subsequent thermal annealing,leading to enhanced pool boiling performance.The heat transfer coefficient for Al/rGO450is 37.2 kW m-2K-1,which is increased by 112.6%compared with bare Al,also outperformed previously reported Al based substrates.It is assumed that the hydrophilic and aerophobic r GO coatings effectively promote the liquid infiltration and bubble departure during pool boiling process.Importantly,repeatability tests indicate the durable stability of vertically oriented rGO nanosheets.Reverse nonequilibrium molecular dynamics simulation indicates that the interfacial transmission coefficients of Al/rGO increase after thermal annealing,indicative of the enhanced heat transfer performance of heterogeneous interface.Our study opens a new avenue for endowing metal substrates with high pool boiling performance using porous carbon coating nanoengineering strategy with controllable morphology and components.
