The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanizatio...The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction(XRD) and Fourier-transform infrared spectroscopy(FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature(Tg) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and Tg shifted towards to higher temperature.展开更多
The rotating stall mechanism is of high importance for the stability of centrifugal compressors and thermal power cycles.The majority of research concerning this topic has concentrated on the initial stall phase.Howev...The rotating stall mechanism is of high importance for the stability of centrifugal compressors and thermal power cycles.The majority of research concerning this topic has concentrated on the initial stall phase.However,the evolution of stall cells in wide-long diffusers has not been comprehensively studied.In this paper,the causes of rotating stall in the wide-long diffuser and the three-dimensional evolution mechanism of stall cells during the stall process were thoroughly analyzed.During the stall induction phase,an annulus vortex structure was found in the reverse-flow zone near the hub side of the diffuser outlet,which was the initial form of stall cells.The whole evolution process of stall cells was divided into three phases as the flow rate decreased.During the initial stall phase,the dynamic equilibrium was built under effects of the impeller wake and the adverse pressure gradient.As a result,the number of stall cells was kept at seven and the size of stall cells remained constant.During the transition phase,the flow in the diffuser became unstable.Stall cells extended to the impeller outlet,and the effect of the wake flow was strengthened significantly.Stall cells started integrating and separating regularly.As a result,the number and propagation speed of stall cells varied periodically at a constant mass flow rate.During the deep stall phase,the size of stall cells remained unchanged,and the number of stall cells kept at one.This study has important practical guidance and engineering value for the high-efficiency design and safe operation of centrifugal compressors.展开更多
基金Founded by the Central Public-interest Scientific Institution Basal Research Fund for Chinese Academy of Tropical Agricultural Sciences(No.1630122018005)
文摘The natural rubber/zinc disorbate composite was prepared by the in situ formation of zinc disorbate from zinc oxide and sorbic acid in natural rubber. The structure variations of fillers during mixing and vulcanization processes were studied by X-ray diffraction(XRD) and Fourier-transform infrared spectroscopy(FTIR). The effects of zinc disorbate amount on processing performance and glass transition temperature(Tg) of compounds and the mechanical properties of vulcanizates were also determined. The XRD and FTIR analyses results indicate that the zinc disorbate is formed from the reaction of zinc oxide and sorbic acid during the mixing procedure followed by graft copolymerizing with NR molecules to form composite networks during vulcanization, which is initiated by dicumyl peroxide. Thus the mechanical properties of NR-based composite are increased significantly and Tg shifted towards to higher temperature.
基金supports of National Natural Science Foundation of China(No.52076079)Natural Science Foundation of Hebei Province(E2022502048,E2020502013)+1 种基金Fundamental Research Funds for the Central Universities(No.2022MS085,2023MS121)Post-graduate's Innovation Fund Project of Hebei Province(No.CXZZSS2024162,No.CXZZBS2024165)。
文摘The rotating stall mechanism is of high importance for the stability of centrifugal compressors and thermal power cycles.The majority of research concerning this topic has concentrated on the initial stall phase.However,the evolution of stall cells in wide-long diffusers has not been comprehensively studied.In this paper,the causes of rotating stall in the wide-long diffuser and the three-dimensional evolution mechanism of stall cells during the stall process were thoroughly analyzed.During the stall induction phase,an annulus vortex structure was found in the reverse-flow zone near the hub side of the diffuser outlet,which was the initial form of stall cells.The whole evolution process of stall cells was divided into three phases as the flow rate decreased.During the initial stall phase,the dynamic equilibrium was built under effects of the impeller wake and the adverse pressure gradient.As a result,the number of stall cells was kept at seven and the size of stall cells remained constant.During the transition phase,the flow in the diffuser became unstable.Stall cells extended to the impeller outlet,and the effect of the wake flow was strengthened significantly.Stall cells started integrating and separating regularly.As a result,the number and propagation speed of stall cells varied periodically at a constant mass flow rate.During the deep stall phase,the size of stall cells remained unchanged,and the number of stall cells kept at one.This study has important practical guidance and engineering value for the high-efficiency design and safe operation of centrifugal compressors.
