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In this paper, the air film formation behavior of air cushion belt conveyor with stable load is studied. The air cushion field is analyzed by means of theoretical derivation, numerical simulation and experimental research. An intelligent experiment platform is developed. Three dimensional pressure distribution of air film and the air film thickness distribution along the conveyor belt in the width direction are obtained. The experimental result is analyzed by comparing with theoretical calculation and numerical simulation. The numerical and theoretical results are in good agreement with those obtained from experiments. The air film formation behavior pattern of air cushion belt conveyor with stable load is presented. The optimized film thickness and pore distribution are obtained based on the comprehensive energy consumption. This study provides a basis for the optimization design of air cushion belt conveyor. 相似文献
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Hui Liu DongLi Li Wencai Xu Yabo Fu Ruijuan Liao Jiazi Shi Yajun Wang 《Packaging Technology and Science》2019,32(11):537-544
Silica‐polypropylene (PP) composite resins were prepared with nanosilica particles and PP resin through melt blending. This composite resin was used to prepare uniaxially oriented PP film under certain conditions. Surface and cross‐section morphologies of the PP films were analyzed by SEM, while the crystalline phase, crystalline orientation, and grain size of the PP films were analyzed by X‐ray diffraction (XRD). Crystallinity was analyzed by differential scanning calorimetry (DSC). The mechanical properties, heat resistance, and barrier properties of the film were tested and analyzed. The PP melts formed shish‐kebab structure when subjected to shearing or stretching at near‐melting temperatures. The ratio of the intensity of the XRD of 040 crystal surface to that of the 110 crystal surface was greater than 0.71. The modified polypropylene melt was subjected to tensile action at 30°C on a cooling roller, resulting in a specially oriented structure. However, the ratio of the intensity of the XRD of the 040 crystal surface to that of the 110 crystal surface did not change. Under the same processing conditions (ie, low cooling temperature and high unidirectional tension), a transverse 040 wafer was formed on the surface of the unmodified film, but polypropylene film modified by nanosilica was not found. The fiber‐like shish‐kebab structure with regular arrangement appeared on the film. The change in the microstructure of the modified polypropylene film resulted in a material with excellent mechanical properties, toughness, barrier property, and heat resistance. 相似文献
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以玉米秸秆为原料,研究其提取制备微晶纤维素的工艺及产品性能。探讨酸解温度、硫酸体积分数、酸解时间对微晶纤维素聚合度及得率的影响,并对微晶纤维素的理化性质进行了分析。结果表明:玉米秸秆微晶纤维素最佳制备工艺条件为:反应温度85℃,硫酸体积分数8%,水解时间90 min,此时制得微晶纤维素聚合度为292,纯度92.6%,得率76.48%,结晶度为74.5%。在此条件下,玉米秸秆微晶纤维素在保留形态结构的同时具有较高的结晶度和热稳定性,具备较好的应用性能和价值。 相似文献
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This article presents a process for preparing organovermiculite by ball‐milling expanded vermiculite (EVMT) in water‐based ethylene vinyl acetate (EVA) latex. In this process, the vermiculite (VMT) is exfoliated to prepare a kind of EVMT/EVA modifying agent, in which EVA serves as both intercalating polymer into VMT and compatibilizer between VMT and polypropylene (PP). During melt blending between EVMT/EVA and PP, shear force exfoliates VMT sheets, dispersing them relatively well in the PP matrix. Compared with raw PP, EVMT‐modified cast polypropylene (CPP) are better when EVMT loading ranged from 0.5 to 1.0%, with improvement in both the strength and toughness of the EVMT/EVA‐modified CPP film. Specifically, tensile strength was increased by 44–54%, yield stress increased by 26%, stress at break increased by 37–43%, energy at break (toughness) increased by 29–34%, oxygen transmission rate decreased by 6.2–12.9%, the water vapor transmission rate was not significantly affected, the peel bond strength of laminated CPP film increased by 18–27%, and the processability and melt flow index (MFI) of EVMT/EVA/PP composites were improved as well. Increasing MFI attributes facilitated the processing and formation of EVMT/EVA/PP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40954. 相似文献
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Two-dimensional steady Reynolds-averaged Navier-Stokes(RANS) equations with transition shear stress transport(SST) model were solved to investigate the effects of Gurney flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 m/s. The chord length(C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76×10~5. Gurney flaps with the heights ranging from 0.25%C to3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack(3°), Gurney flap with the height of 0.5%C.can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gurney flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gurney flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack(≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition. 相似文献