A nucleation of two types can occur in the water steam flowing in a nozzle or in a turbine： homogeneous （spontaneous） and heterogeneous. The effects of chemistry on the flowing steam nucleation and condensation are...A nucleation of two types can occur in the water steam flowing in a nozzle or in a turbine： homogeneous （spontaneous） and heterogeneous. The effects of chemistry on the flowing steam nucleation and condensation are not quite explained. An approach is used in the paper which is based on binary nucleation of main impurity NaC1 and water. Physical and mathematical models are described and are applied on the steam flow with condensation in convergent-divergent nozzle. Binary nucleation numerical model is applied for the calculation of the flow with condensation in the nozzle with low expansion rate in divergent nozzle part ^- = 1,000 s^-1. Calculation results of pressure distribution are compared with experiments. The agreement between calculations and experiments is very good. The homogeneous nucleation and condensation of pure water steam in the same nozzle is also calculated. The results are discussed. Main features of the binary nucleation and condensation of water and NaCI and of the homogeneous nucleation of pure water are compared.展开更多
A general initial water penetration(seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration(hydraulic fracturing),other than microcracking,will occur in concrete struct...A general initial water penetration(seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration(hydraulic fracturing),other than microcracking,will occur in concrete structures in a severe high water pressure environment.The final regression,of the different macroscopic failure types in concrete to microscopic ModeⅠ c racking,allows the use of only one universal criterion to indicate the damage.Thus,a general initial water penetration fracture criterion is approximately defined as a strain magnitude of 1000×10-6,based on the concept of tensile strain derived from experimental results in the relevant literature.Then,the locations of harmful water penetration fracture(hydraulic fracture) in the high arch dam mass of the Jinping first class hydropower project are analyzed using the nonlinear finite element method(FEM) according to the proposed criterion.The proposed criterion also holds promise for other concrete structures in high water pressure environments.展开更多
文摘A nucleation of two types can occur in the water steam flowing in a nozzle or in a turbine： homogeneous （spontaneous） and heterogeneous. The effects of chemistry on the flowing steam nucleation and condensation are not quite explained. An approach is used in the paper which is based on binary nucleation of main impurity NaC1 and water. Physical and mathematical models are described and are applied on the steam flow with condensation in convergent-divergent nozzle. Binary nucleation numerical model is applied for the calculation of the flow with condensation in the nozzle with low expansion rate in divergent nozzle part ^- = 1,000 s^-1. Calculation results of pressure distribution are compared with experiments. The agreement between calculations and experiments is very good. The homogeneous nucleation and condensation of pure water steam in the same nozzle is also calculated. The results are discussed. Main features of the binary nucleation and condensation of water and NaCI and of the homogeneous nucleation of pure water are compared.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No 2007CB714104)the National Natural Science Foundation of China (Grant Nos 51079045, 50779009 and 51008114)
文摘A general initial water penetration(seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration(hydraulic fracturing),other than microcracking,will occur in concrete structures in a severe high water pressure environment.The final regression,of the different macroscopic failure types in concrete to microscopic ModeⅠ c racking,allows the use of only one universal criterion to indicate the damage.Thus,a general initial water penetration fracture criterion is approximately defined as a strain magnitude of 1000×10-6,based on the concept of tensile strain derived from experimental results in the relevant literature.Then,the locations of harmful water penetration fracture(hydraulic fracture) in the high arch dam mass of the Jinping first class hydropower project are analyzed using the nonlinear finite element method(FEM) according to the proposed criterion.The proposed criterion also holds promise for other concrete structures in high water pressure environments.
