Accurate determination of inner wall temperature fluctuations is critical for thermal fatigue assessment in sodiumcooled fast reactors(SFR)piping systems,but remains inaccessible for direct measurement due to extreme ...Accurate determination of inner wall temperature fluctuations is critical for thermal fatigue assessment in sodiumcooled fast reactors(SFR)piping systems,but remains inaccessible for direct measurement due to extreme operational conditions involving high temperature and chemical activity of liquid sodium.To overcome this challenge,this study proposes a self-adaptive Gaussian process regression(GPR)approach.The large eddy simulations(LES)of hot and cold liquid sodium mixing in T-junction pipes are conducted to quantify intense thermal-fluid interactions,revealing that inner wall temperature fluctuations are significantly higher than those at the outer walls.Building on these insights,we develop a self-adaptive GPR approach that integrates tree-structured composite kernel optimization with gradient-based hyperparameter tuning.The resulting approach accurately predicts inner wall temperature fluctuations using only outer wall measurements and corresponding operational parameters,achieving a predictive performance of determination coefficient R^(2)>0.95,and retaining robustness(R^(2)>0.75)even when trained on limited datasets.The proposed self-adaptive GPR approach offers non-intrusive,real-time thermal diagnostics for SFR piping systems,utilizing composite kernels that afford clear physical interpretability.Moreover,it provides a promising tool for safety monitoring in reactor cores,heat exchangers,and other nuclear components requiring high-fidelity thermal transient analysis.展开更多
In the present study,the effects of Nb addition on Charpy impact properties of TiVTa refractory high-entropy alloy with high strength-ductility trade-off were systematically studied by using the instrumented Charpy im...In the present study,the effects of Nb addition on Charpy impact properties of TiVTa refractory high-entropy alloy with high strength-ductility trade-off were systematically studied by using the instrumented Charpy impact testing machine.The experimental results showed that the impact toughness was remarkably improved by Nb addition in TiVTa to form TiVTaNb alloy.The crack initiation energy and propagation energy of TiVTaNb were 67.3%and 24.9%higher than that of TiVTa,indicating that Nb addition simultaneously reinforced the resistance to crack initiation and propagation.The impact fracture of TiVTaNb exhibited larger bending degree of shear lips,deeper dimples and more secondary cracks which effectively dissipated more impact energy.The deformation mechanism of TiVTa alloy was dominated by dislocation activities.While in TiVTaNb,the deformation mechanism was synergized by dislocation activities and deformation twinning,which were the main contributors for the improved impact properties and the stronger crack resistance of TiVTaNb alloy under impact loading.展开更多
Based on isentropic flow and thermal equilibrium assumptions, a model was derived to calculate discharge flow rate, which unified the rules of room temperature water discharge, high temperature and high pressure water...Based on isentropic flow and thermal equilibrium assumptions, a model was derived to calculate discharge flow rate, which unified the rules of room temperature water discharge, high temperature and high pressure water discharge, two-phase critical flow, saturated steam and superheated steam critical flow, and gave a method to calculate critical condition. Because of the influence of friction, the entropy is increased in the actual discharge process, and the discharge flow rate in thermal equilibrium condition can be obtained by the original model multiplied by an appropriate correction coefficient. The model calculated results agreed well with the experiment data of long nozzle critical flow.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52175224,52205262,52235005)。
文摘Accurate determination of inner wall temperature fluctuations is critical for thermal fatigue assessment in sodiumcooled fast reactors(SFR)piping systems,but remains inaccessible for direct measurement due to extreme operational conditions involving high temperature and chemical activity of liquid sodium.To overcome this challenge,this study proposes a self-adaptive Gaussian process regression(GPR)approach.The large eddy simulations(LES)of hot and cold liquid sodium mixing in T-junction pipes are conducted to quantify intense thermal-fluid interactions,revealing that inner wall temperature fluctuations are significantly higher than those at the outer walls.Building on these insights,we develop a self-adaptive GPR approach that integrates tree-structured composite kernel optimization with gradient-based hyperparameter tuning.The resulting approach accurately predicts inner wall temperature fluctuations using only outer wall measurements and corresponding operational parameters,achieving a predictive performance of determination coefficient R^(2)>0.95,and retaining robustness(R^(2)>0.75)even when trained on limited datasets.The proposed self-adaptive GPR approach offers non-intrusive,real-time thermal diagnostics for SFR piping systems,utilizing composite kernels that afford clear physical interpretability.Moreover,it provides a promising tool for safety monitoring in reactor cores,heat exchangers,and other nuclear components requiring high-fidelity thermal transient analysis.
基金financially supported by the China National Nuclear Corporation(CNNC)Science Fund for Talented Young Scholars(No.FY202307000120)the Continuous Basic Scientific Research Project(No.WDJC-2019-10)the National Natural Science Foundation of China(No.U1867217).
文摘In the present study,the effects of Nb addition on Charpy impact properties of TiVTa refractory high-entropy alloy with high strength-ductility trade-off were systematically studied by using the instrumented Charpy impact testing machine.The experimental results showed that the impact toughness was remarkably improved by Nb addition in TiVTa to form TiVTaNb alloy.The crack initiation energy and propagation energy of TiVTaNb were 67.3%and 24.9%higher than that of TiVTa,indicating that Nb addition simultaneously reinforced the resistance to crack initiation and propagation.The impact fracture of TiVTaNb exhibited larger bending degree of shear lips,deeper dimples and more secondary cracks which effectively dissipated more impact energy.The deformation mechanism of TiVTa alloy was dominated by dislocation activities.While in TiVTaNb,the deformation mechanism was synergized by dislocation activities and deformation twinning,which were the main contributors for the improved impact properties and the stronger crack resistance of TiVTaNb alloy under impact loading.
文摘Based on isentropic flow and thermal equilibrium assumptions, a model was derived to calculate discharge flow rate, which unified the rules of room temperature water discharge, high temperature and high pressure water discharge, two-phase critical flow, saturated steam and superheated steam critical flow, and gave a method to calculate critical condition. Because of the influence of friction, the entropy is increased in the actual discharge process, and the discharge flow rate in thermal equilibrium condition can be obtained by the original model multiplied by an appropriate correction coefficient. The model calculated results agreed well with the experiment data of long nozzle critical flow.
