Modeling and simulation of thermal-fluid systems are very important in industrial numerical simulation and play key roles in their design and control. In this paper, the modeling and simplification method of one-dimen...Modeling and simulation of thermal-fluid systems are very important in industrial numerical simulation and play key roles in their design and control. In this paper, the modeling and simplification method of one-dimensional thermal-fluid network with variable-property are presented, including matrix representation of the network, simplification algorithm for series/parallel connection based on matrix operation and generation of flow equations based on system topology. This simplification is suitable for the simulation of thermal-fluid systems with arbitrary topological structure. The method to treat reflux during iteration is proposed. The outstanding features of the simplification algorithm are the significant reduction in the thermal-fluid network and therefore the number of the related governing equations, as well as the computation burden. The example in this paper shows that the number of the governing equations for flow is reduced by about 45% and the calculation time of flow calculation is reduced by an average of 32% after the simplification.展开更多
The complex curvature of turbomachinery rotor blade channels combined with strong rotational effect and clearance leakage brings on intricate internal flow phenomenon.It is necessary to study the internal flow and ene...The complex curvature of turbomachinery rotor blade channels combined with strong rotational effect and clearance leakage brings on intricate internal flow phenomenon.It is necessary to study the internal flow and energy loss mechanism to reveal the influence law of the key parameters and to achieve its optimal design.Considering features of flow and temperature fields in rotor passage,the concept of synergy analysis derived from equation of energy conservation was put forward.Typical NASA low-speed centrifugal compressor(LSCC)rotor was chosen for analysis using CFD.Numerical results showed remarkable agreement with experiment datum in both the tendency of the performance characteristics and quantitative pressure values.Under different flow rates and inlet total temperatures conditions,thermal-fluid interaction effect and losses were studied by synergy analysis.Results showed that peak synergy positive value zones located around blade leading edge,across the shroud wall and hub wall,and at the position where tip-leakage flow was mixing with the bulk flow and high entropy zones existed.Increasing flow rate from design condition,positive and negative synergy areas both changed tiny around leading edge and trailing edge.Reducing flow rate,positive synergy areas tended to increase and negative areas decreased at same positions.The relationship between flow separation,heat transfer and losses in turbomachinery rotor can be revealed based on synergy analyses.展开更多
Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the...Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.展开更多
By taking a 2.3 MW double-fed asynchronous generator as an example,a new method for fast simulation analysis of ventilation cooling system inside generator is proposed based on the one-dimensional simulation software ...By taking a 2.3 MW double-fed asynchronous generator as an example,a new method for fast simulation analysis of ventilation cooling system inside generator is proposed based on the one-dimensional simulation software FLOWMASTER.The thermal-fluid coupling simulation model of ventilation cooling system inside generator is established.Under the stable running state of the generator,the flow velocity distribution and temperature rise of the key parts of the generator are analyzed.The results prove that the ventilation structure design of the generator meets the temperature rise limit.The simulation results are compared with the theoretical calculation results and the experimental results,which verify the correctness of the thermal-fluid coupling simulation method proposed in this paper.展开更多
The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kin...The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kinds of grooves are obtained. The influence of inlet temperature, inlet pressure, velocity and film thickness on performance is analyzed compared with air DGS. The average film pressure, open force and leakage decrease while the average face temperature and flow velocity increase as the spiral groove number increases. The average film pressure, average face temperature, open force and leakage of DGS with radial different deep groove are higher than those of DGS with circumferential different deep groove respectively under the same spiral groove number while the average flow velocity is the opposite. SCO_2 DGS can generate larger average film pressure, open force and leakage with lower average face temperature than air DGS. SCO_2 DGS could maintain better sealing performance despite larger leakage with the variations of inlet temperature, inlet pressure, velocity and film thickness. The variables hold a more remarkable influence on SCO_2 DGS compared with air DGS.展开更多
由于电缆不规则排列导致其温度场和载流量与规则排列电缆不同,针对沟槽内不规则排列电缆群的温度场和载流量计算,提出了电缆的磁-热-流耦合模型。该模型以110 k V交联聚乙烯电缆为例,利用多物理场耦合分析软件COMSOL Multiphysics对沟...由于电缆不规则排列导致其温度场和载流量与规则排列电缆不同,针对沟槽内不规则排列电缆群的温度场和载流量计算,提出了电缆的磁-热-流耦合模型。该模型以110 k V交联聚乙烯电缆为例,利用多物理场耦合分析软件COMSOL Multiphysics对沟槽内规则与不规则排列电缆群的温度场和载流量进行计算。结果表明:电缆不规则排列可能导致其缆芯温度升高,载流量降低;利用电缆的磁-热-流耦合模型,可以准确计算沟槽内不规则电缆群的流场和温度场分布,从而准确计算沟槽内不规则排列电缆群的载流量。展开更多
文摘Modeling and simulation of thermal-fluid systems are very important in industrial numerical simulation and play key roles in their design and control. In this paper, the modeling and simplification method of one-dimensional thermal-fluid network with variable-property are presented, including matrix representation of the network, simplification algorithm for series/parallel connection based on matrix operation and generation of flow equations based on system topology. This simplification is suitable for the simulation of thermal-fluid systems with arbitrary topological structure. The method to treat reflux during iteration is proposed. The outstanding features of the simplification algorithm are the significant reduction in the thermal-fluid network and therefore the number of the related governing equations, as well as the computation burden. The example in this paper shows that the number of the governing equations for flow is reduced by about 45% and the calculation time of flow calculation is reduced by an average of 32% after the simplification.
基金support from the National Key R&D Plan(Grant No.2017YFB0903602)the Transformational Technologies for Clean Energy and Demonstration,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21070200)+1 种基金the Frontier Science Research Project of CAS(Grant No.QYZDB-SSW-JSC023)International Partnership Program,Bureau of International Cooperation of Chinese Academy of Sciences(Grant No.182211KYSB20170029)。
文摘The complex curvature of turbomachinery rotor blade channels combined with strong rotational effect and clearance leakage brings on intricate internal flow phenomenon.It is necessary to study the internal flow and energy loss mechanism to reveal the influence law of the key parameters and to achieve its optimal design.Considering features of flow and temperature fields in rotor passage,the concept of synergy analysis derived from equation of energy conservation was put forward.Typical NASA low-speed centrifugal compressor(LSCC)rotor was chosen for analysis using CFD.Numerical results showed remarkable agreement with experiment datum in both the tendency of the performance characteristics and quantitative pressure values.Under different flow rates and inlet total temperatures conditions,thermal-fluid interaction effect and losses were studied by synergy analysis.Results showed that peak synergy positive value zones located around blade leading edge,across the shroud wall and hub wall,and at the position where tip-leakage flow was mixing with the bulk flow and high entropy zones existed.Increasing flow rate from design condition,positive and negative synergy areas both changed tiny around leading edge and trailing edge.Reducing flow rate,positive synergy areas tended to increase and negative areas decreased at same positions.The relationship between flow separation,heat transfer and losses in turbomachinery rotor can be revealed based on synergy analyses.
基金ACKNOWLEDGMENTS The work was supported by the National Nature Science Foundation of China （Nos.11161002 and 41001320）, Natural Science Foundation of Jiangxi province （No.20114BAB201016）. Thanks for the useful advices of the editors and the reviewers.
基金Project(51974278)supported by the National Natural Science Foundation of ChinaProject(E2018203446)supported by the Natural Science Foundation of Hebei Province Distinguished Young Fund Project,ChinaProject(2018YFA0707303)supported by the National Key Research and Development Project of China。
文摘Unequal diameter twin-roll casting(UDTRC)can improve the formability,surface conditions,and production efficiency during the fabrication of clad strips.Using Fluent software,a numerical simulation is used to study the asymmetric heat transfer characteristics of Cu/Al clad strips fabricated by UDTRC.The effects of roller velocity ratio,Cu strip thickness,and inclination angle on the kissing point position,as well as the entire temperature distribution are obtained.The heat transfer model is established,and the mechanism is discussed.The Cu strip and rollers are found to be the main causes of asymmetric heat transfer,indicating that the roller velocity ratio changes the liquid zone proportion in the molten pool.The Cu strip thickness determines the heat absorption capacity and the variations in thermal resistance between the molten Al and the big roller.The inclination angle of the small roller changes the cooling time of big roller to molten Al.Moreover,the microstructure of Al cladding under different roller velocity ratios is examined.The results show significant grain refinement caused by the shear strain along the thickness direction of Al cladding and the intense heat transfer at the moment of contact between the metal Al cladding and Cu strip.
文摘By taking a 2.3 MW double-fed asynchronous generator as an example,a new method for fast simulation analysis of ventilation cooling system inside generator is proposed based on the one-dimensional simulation software FLOWMASTER.The thermal-fluid coupling simulation model of ventilation cooling system inside generator is established.Under the stable running state of the generator,the flow velocity distribution and temperature rise of the key parts of the generator are analyzed.The results prove that the ventilation structure design of the generator meets the temperature rise limit.The simulation results are compared with the theoretical calculation results and the experimental results,which verify the correctness of the thermal-fluid coupling simulation method proposed in this paper.
基金financial support provided by 111 project (Grant No.B16038)
文摘The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kinds of grooves are obtained. The influence of inlet temperature, inlet pressure, velocity and film thickness on performance is analyzed compared with air DGS. The average film pressure, open force and leakage decrease while the average face temperature and flow velocity increase as the spiral groove number increases. The average film pressure, average face temperature, open force and leakage of DGS with radial different deep groove are higher than those of DGS with circumferential different deep groove respectively under the same spiral groove number while the average flow velocity is the opposite. SCO_2 DGS can generate larger average film pressure, open force and leakage with lower average face temperature than air DGS. SCO_2 DGS could maintain better sealing performance despite larger leakage with the variations of inlet temperature, inlet pressure, velocity and film thickness. The variables hold a more remarkable influence on SCO_2 DGS compared with air DGS.
文摘由于电缆不规则排列导致其温度场和载流量与规则排列电缆不同,针对沟槽内不规则排列电缆群的温度场和载流量计算,提出了电缆的磁-热-流耦合模型。该模型以110 k V交联聚乙烯电缆为例,利用多物理场耦合分析软件COMSOL Multiphysics对沟槽内规则与不规则排列电缆群的温度场和载流量进行计算。结果表明:电缆不规则排列可能导致其缆芯温度升高,载流量降低;利用电缆的磁-热-流耦合模型,可以准确计算沟槽内不规则电缆群的流场和温度场分布,从而准确计算沟槽内不规则排列电缆群的载流量。
