In nuclear reactors,temperature fluctuations of fluids may cause fatigue damage to adjacent structures;this is referred to as thermal striping.Research on thermal striping in the upper plenum has mainly focused on flu...In nuclear reactors,temperature fluctuations of fluids may cause fatigue damage to adjacent structures;this is referred to as thermal striping.Research on thermal striping in the upper plenum has mainly focused on fluid fields.Few experimental studies have been reported on solid structures in a fluid field with a coaxial jet.This study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial jet.The temperature fluctuations of the fluid and plate surfaces located at different heights were analyzed.The cause of the temperature fluctuation was analyzed using a transient temperature distribution.The results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial direction.The average surface temperatures tended to be consistent.When the jet reaches the plate surface,the swing of the jet center,contraction and expansion of the cold jet,and changes in the jet shape result in temperature fluctuations.The intensity of the temperature fluctuation was affected by the position.More attention should be paid when the plate is located at a lower height,and between the hot and cold-fluid nozzles.展开更多
To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blas...To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast loading.First,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage test.Second,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation method.Finally,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact block.The calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the model.The residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged panel.The results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.展开更多
Most hydrodynamic fluidized bed models, including CFD codes, neglect any effects of the plenum chamber volume. Experiments were performed in a 0.13 m ID fluidization column to determine plenum chamber volume effects o...Most hydrodynamic fluidized bed models, including CFD codes, neglect any effects of the plenum chamber volume. Experiments were performed in a 0.13 m ID fluidization column to determine plenum chamber volume effects on fluidized bed hydrodynamics for FCC and glass particles. Two low-pressure-drop distributors were used, one with a single orifice, and the other with 33 orifices and the same total open area as the single orifice. The results show two peaks in the frequency spectra for the single-orifice distributor, one representing bubble eruption at the bed surface and the other of higher frequency corresponding to the bubbling frequency at the distributor. The latter decreased slightly with increasing plenum volume and with increasing bed depth. For the multi-orifice distributor, broad frequency spectra from pressure measurements became narrower and moved towards higher frequency with decreasing plenum volume.展开更多
The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly af...The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.展开更多
Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of...Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system,which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge.For further verification,a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study.In the first case,an additional test point is set on the wall of the plenum to detect the system response.Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions,the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated.In the second case,a screen is mounted at the compressor outlet to prevent positive feedback from the plenum.The experimental results demonstrate that in the absence of system feedback,it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge.In addition,three flow phenomena in the second case are discussed,including the occurrence of the single pulse,the unstable process during the stall evolution and the switch of instability inception.展开更多
Hydraulic performance of an inlet plenum in a printed-circuit heat exchanger has been analyzed using three-dimensional Reynolds-Averaged Navier-Stokes equations. The numerical model of the inlet plenum was constructed...Hydraulic performance of an inlet plenum in a printed-circuit heat exchanger has been analyzed using three-dimensional Reynolds-Averaged Navier-Stokes equations. The numerical model of the inlet plenum was constructed through grid dependency test, calculation domain tests, and turbulence model and numerical scheme selections. Shear stress transport turbulence model was used for analysis of turbulence. Non-uniformity of the flow in zigzag flow channels was evaluated for the reference case. Parametric studies have been performed with the angle of the inlet plenum wall, radius of curvature of the inlet plenum wall, and width of the inlet pipes. The effects of these parameters on the flow uniformity and friction performance were evaluated.展开更多
基金supported by the National Natural Science Foundation of China (No. 52075173)the Overseas Expertise Introduction Project for Discipline Innovation (No. B13020)
文摘In nuclear reactors,temperature fluctuations of fluids may cause fatigue damage to adjacent structures;this is referred to as thermal striping.Research on thermal striping in the upper plenum has mainly focused on fluid fields.Few experimental studies have been reported on solid structures in a fluid field with a coaxial jet.This study entailed an experimental study of the temperature fluctuations in the fluid and on a plate surface caused by a coaxial jet.The temperature fluctuations of the fluid and plate surfaces located at different heights were analyzed.The cause of the temperature fluctuation was analyzed using a transient temperature distribution.The results show that the mixing of the hot and cold fluids gradually becomes uniform in the positive axial direction.The average surface temperatures tended to be consistent.When the jet reaches the plate surface,the swing of the jet center,contraction and expansion of the cold jet,and changes in the jet shape result in temperature fluctuations.The intensity of the temperature fluctuation was affected by the position.More attention should be paid when the plate is located at a lower height,and between the hot and cold-fluid nozzles.
文摘To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast loading.First,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage test.Second,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation method.Finally,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact block.The calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the model.The residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged panel.The results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.
基金the Natural Sciences and Engineering Research Council of Canada for supporting this project financially
文摘Most hydrodynamic fluidized bed models, including CFD codes, neglect any effects of the plenum chamber volume. Experiments were performed in a 0.13 m ID fluidization column to determine plenum chamber volume effects on fluidized bed hydrodynamics for FCC and glass particles. Two low-pressure-drop distributors were used, one with a single orifice, and the other with 33 orifices and the same total open area as the single orifice. The results show two peaks in the frequency spectra for the single-orifice distributor, one representing bubble eruption at the bed surface and the other of higher frequency corresponding to the bubbling frequency at the distributor. The latter decreased slightly with increasing plenum volume and with increasing bed depth. For the multi-orifice distributor, broad frequency spectra from pressure measurements became narrower and moved towards higher frequency with decreasing plenum volume.
基金National Natural Science Foundation of China(No.62173307)the Key R&D Projects of Science and Technology Department of Zhejiang Province,China(Nos.2023C01158,2022C01065 and 2022C01188)the Fundamental Research Funds of Zhejiang Sci-Tech University,China(No.22242298-Y)。
文摘The plenum chamber of a heat setting machine is a key structure for distributing hot air to different air channels.Its outlet velocity uniformity directly determines the heating uniformity of textiles,significantly affecting the heat setting performance.In a traditional heat setting machine,the outlet airflow maldistribution of the plenum chamber still exists.In this study,a novel plenum chamber with an airfoil baffle was established to improve the uniformity of the velocity distribution at the outlet in a heat setting machine.The structural influence of the plenum chamber on the velocity distribution was investigated using a computational fluid dynamics program.It was found that a chamber with a smaller outlet partition thickness had a better outlet velocity uniformity.The structural optimization of the plenum chamber was conducted using the particle swarm optimization algorithm.The outlet partition thickness,the transverse distance and the longitudinal distance of the optimized plenum chamber were 20,686.2 and 274.6 mm,respectively.Experiments were carried out.The experimental and simulated results showed that the optimized plenum chamber with an airfoil baffle could improve the outlet velocity uniformity.The air outlet velocity uniformity index of the optimized plenum chamber with an airfoil baffle was 4.75%higher than that of the plenum chamber without an airfoil baffle and 5.98%higher than that of the conventional chamber with a square baffle in a commercial heat setting machine.
基金the support of National Natural Science Foundation of China(Nos.51706008,51636001,51976005 and 52006002)National Science and Technology Major Project,China(No.2017-Ⅱ-0005-0018)Aeronautics Power Foundation,China(No.6141B09050375)。
文摘Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region.Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system,which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge.For further verification,a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study.In the first case,an additional test point is set on the wall of the plenum to detect the system response.Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions,the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated.In the second case,a screen is mounted at the compressor outlet to prevent positive feedback from the plenum.The experimental results demonstrate that in the absence of system feedback,it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge.In addition,three flow phenomena in the second case are discussed,including the occurrence of the single pulse,the unstable process during the stall evolution and the switch of instability inception.
基金supported by the National Research Foundation of Korea (NRF), (Grant No. 2009-0083510)funded by the Korean government (MSIP) through the Multi-phenomena CFD Engineering Research Center
文摘Hydraulic performance of an inlet plenum in a printed-circuit heat exchanger has been analyzed using three-dimensional Reynolds-Averaged Navier-Stokes equations. The numerical model of the inlet plenum was constructed through grid dependency test, calculation domain tests, and turbulence model and numerical scheme selections. Shear stress transport turbulence model was used for analysis of turbulence. Non-uniformity of the flow in zigzag flow channels was evaluated for the reference case. Parametric studies have been performed with the angle of the inlet plenum wall, radius of curvature of the inlet plenum wall, and width of the inlet pipes. The effects of these parameters on the flow uniformity and friction performance were evaluated.
