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1.
以H型垂直轴风力机及其内含圆柱形实体为研究对象,对NACA0018翼型的五叶片H型垂直轴风力机的气动性能进行数值模拟和实验验证。分析8种不同直径的内含圆柱体,在内含实体截面积占风轮迎风面积之比分别为21.2%、50.0%和76.9%时,风力机风能利用率的峰值分别下降8.04%、20.7%及74.3%。结果表明:随着内含实体直径的增大,风能利用率的峰值逐渐减小,开始较为缓慢,达到一定值时快速下降。小直径内含实体主要影响叶片在下风区的转矩,对风能利用率的影响较小,而大直径内含实体还会影响叶片在上风区的转矩,其风能利用率迅速减小。对于内含固定直径的实体,比如在现有建筑物外侧安装风力机时,其风轮半径的选择需综合考虑风能利用率和风力机的建造成本两方面的因素。研究结果可为建筑物与垂直轴风力机进行有效结合以提高风能的利用提供参考。 相似文献
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本文阐述了多轴正逆向制造发展趋势,基地建设的必要性,以五轴加工中心、五轴仿真模拟面板、三维扫描仪、3D打印机等为主的加工、逆向、快速成形先进前沿设备,形成多元化的先进制造实习链,满足、丰富实训内容,提升学生社会就业竞争力。 相似文献
3.
Benedetto Rocchio Claudio Chicchiero Maria Vittoria Salvetti Stefania Zanforlin 《风能》2020,23(4):915-938
The present study is focused on modeling of dynamic stall behavior of a pitching airfoil. The deep stall regime is in particular considered. A model is proposed, which has a low implementation and computational complexity but yet is able to deal with different types of dynamic stall conditions, including those characterized by multiple vortex shedding at the airfoil leading edge. The proposed model is appraised against an extensive data set of experimental (α,CL) curves for NACA0012. The results of an existing widely used model, having comparable complexity, are also shown for comparison. The proposed model is able to well reproduce not only the classic curves of deep dynamic stall but also the curves characterized by lift oscillations at high angles of attack due to the shedding of multiple vortices. Furthermore, the model appears to be robust to variations of its parameters from the optimal values and of the airfoil geometry. Finally, the model is successfully implemented in a commercial CFD software and applied to the simulation of a vertical axis wind turbine within the actuator cylinder approach. The accuracy of the prediction of the turbine power coefficient in the whole rotation cycle is very good for the optimal working condition of the turbine, for which the model parameters were calibrated. Fairly good accuracy is also obtained in significantly different working conditions without any further calibration. 相似文献
4.
针对王村煤业MG400/930-WD(3.3)型电牵引采煤机截割部扭矩轴在截割电机负载超载情况发生断裂不能实现对截割电机保护的问题,本文提出了一种截割部扭矩轴设计优化方案。方案主要进行了扭矩轴材料选择、表面处理工艺改进以及卸荷槽的再设计,并对卸荷槽进行了参数试验,优化后的扭矩轴可以在电机超载时及时断裂,有效保护截割电机。 相似文献
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In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value. 相似文献
10.
Xiangling Shu Yanjun Tong Ruijin Yang 《International Journal of Food Science & Technology》2022,57(7):4222-4233
Xylo-oligosaccharides (XOS) is a functional oligosaccharide with prebiotic properties, and could be fermented by gut microbiota. In this study, the modulatory effects of XOS on emotions and behaviours at different dose were investigated based on the mouse model of chronic unpredictable mild stress-induced depression. The result showed that 0.23 and 0.50 g kg−1 doses of XOS significantly increased sucrose preference index and decreased the immobility time in tail suspension and forced swimming tests. Meanwhile, the dose of 0.23 g kg−1 day−1 XOS significantly increased the concentration of neurotransmitters, such as 5-hydroxytryptamine and γ- aminobutyric acid. Furthermore, the analysis of the faecal microbiota with XOS intervention showed a higher relative abundance of Akkermansia, Bifidobacterium and Lactobacillus, fewer Desulfovibrio and the SCFA concentrations increased with XOS prevention treatment. These results suggested that the dietary supplementation XOS could improve chronic stress-induced depressive-like behaviour by modulating neurotransmitters and reverting gut microbiota changes in mice. These findings present XOS as a potential prebiotic targeting to the gut microbiota for mood disorders. 相似文献