Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface （AMI） method were presented. The governing equations were the unsteady Reyn...Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface （AMI） method were presented. The governing equations were the unsteady Reynolds-averaged Navier-Stokes （RANS） which were solved by the pimpleDyMFoam solver, and the AMI method was employed to handle mesh movements. The National Renewable Energy Laboratory （NREL） phase VI wind turbine in upwind configuration was selected for numerical tests with different incoming wind speeds （5, 10, 15, and 25 m/s） at a fixed blade pitch and constant rotational speed. Detailed numerical results of vortex structure, time histories of thrust, and pressure distribution on the blade and tower were presented. The findings show that the wind turbine tower has little effect on the whole aerodynamic performance of an upwind wind turbine, while the rotating rotor will induce an obvious cyclic drop in the front pressure of the tower. Also, strong interaction of blade tip vortices with separation from the tower was observed.展开更多
The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP sub...The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP substrate) by spin-coating with thickness of about 10 μm. It was observed that there was a large difference of the phase inversion region between the blend films cast on glass and on PP substrates. On glass substrate, the phase inversion occurred at about \%Φ\%_m=0 4(PS mass fraction) while at \%Φ\%_m=0 5 on PP substrate. This implies that there is a shift of the phase inversion region with the change of substrate in cast polymer blend films. In other words, phase inversion region depends on the substrate. ATR-FTIR analysis was used to detect the composition of the surface and the bottom of the films(about 100 μm thick) obtained by evaporating solvent from the polymer blend solution. The ATR-FTIR spectra of the surface and the bottom of the PMMA/PS blend thin films cast on glass substrate and PP substrate showed that PMMA component preferentially segregated to glass substrate and PS component was enriched on the PP substrate. This selective segregation was due to the difference of the wetting abilities of PS and PMMA on the two kinds of substrates. The polymer-substrate interfacial tension γ were calculated and the results supported the ATR-FTIR results. It could be inferred that the shift of the phase inversion region with the change of the substrate in PMMA/PS blend film was due to the fact that the composition of the blend in the bulk changed, owing to the selective enrichment of one component of polymer blend to the substrate. In other words, the affinity between polymer and substrate can strongly influence the phase morphologies and the phase inversion region in polymer blend films.展开更多
Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the...Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so far.Herein,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon nanocages.It realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 GHz.Meanwhile,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave absorption.This spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.展开更多
Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer.Here,a regulatable three-phase interface on a porous fixed-bed is constructed f...Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer.Here,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)reduction.The photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic reactor.We find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor.The larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.50739004 and 11072154.
文摘Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface （AMI） method were presented. The governing equations were the unsteady Reynolds-averaged Navier-Stokes （RANS） which were solved by the pimpleDyMFoam solver, and the AMI method was employed to handle mesh movements. The National Renewable Energy Laboratory （NREL） phase VI wind turbine in upwind configuration was selected for numerical tests with different incoming wind speeds （5, 10, 15, and 25 m/s） at a fixed blade pitch and constant rotational speed. Detailed numerical results of vortex structure, time histories of thrust, and pressure distribution on the blade and tower were presented. The findings show that the wind turbine tower has little effect on the whole aerodynamic performance of an upwind wind turbine, while the rotating rotor will induce an obvious cyclic drop in the front pressure of the tower. Also, strong interaction of blade tip vortices with separation from the tower was observed.
文摘The effect of substrate on the phase morphologies of PMMA/PS blend films was investigated by means of phase contrast microscope. PMMA/PS blend films were cast onto various substrates(such as glass substrate and PP substrate) by spin-coating with thickness of about 10 μm. It was observed that there was a large difference of the phase inversion region between the blend films cast on glass and on PP substrates. On glass substrate, the phase inversion occurred at about \%Φ\%_m=0 4(PS mass fraction) while at \%Φ\%_m=0 5 on PP substrate. This implies that there is a shift of the phase inversion region with the change of substrate in cast polymer blend films. In other words, phase inversion region depends on the substrate. ATR-FTIR analysis was used to detect the composition of the surface and the bottom of the films(about 100 μm thick) obtained by evaporating solvent from the polymer blend solution. The ATR-FTIR spectra of the surface and the bottom of the PMMA/PS blend thin films cast on glass substrate and PP substrate showed that PMMA component preferentially segregated to glass substrate and PS component was enriched on the PP substrate. This selective segregation was due to the difference of the wetting abilities of PS and PMMA on the two kinds of substrates. The polymer-substrate interfacial tension γ were calculated and the results supported the ATR-FTIR results. It could be inferred that the shift of the phase inversion region with the change of the substrate in PMMA/PS blend film was due to the fact that the composition of the blend in the bulk changed, owing to the selective enrichment of one component of polymer blend to the substrate. In other words, the affinity between polymer and substrate can strongly influence the phase morphologies and the phase inversion region in polymer blend films.
基金This work was financially supported by the National Natural Science Foundation of China(U21A2093 and 52102370)the Natural Science Foundation of Shaanxi Province(2022JM-260)+2 种基金the Shanghai Key Laboratory of R&D for Metallic Functional Materials(2021-01)and Open Fund of Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province(JBGS014)Open access funding provided by Shanghai Jiao Tong University
文摘Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so far.Herein,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon nanocages.It realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 GHz.Meanwhile,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave absorption.This spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.
基金S.J.Bai,H.R.Qiu,and M.M.Song contributed equally to this work.This work is supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103).We also thank C.Liao for drawing some pictures for this article.In addition,we thank Doc.N.Deng and Miss D.He at the Instrumental Analysis Center of Xi'an Jiaotong University for their assistance with GC-MS and TRPL measurement.
文摘Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer.Here,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)reduction.The photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic reactor.We find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor.The larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.
