Comparison of pitching and plunging effects on the surface pressure variation of a wind turbine blade section

Numerous experiments were conducted on an oscillating airfoil in a subsonic wind tunnel. The experiments involved measuring the surface pressure distribution when the model oscillated in two types of motion, pitch and plunge, at three different Reynolds numbers, 0.42, 0.63 and 0.84 million, and over a range of reduced frequencies, k = 0.03–0.09. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. Particular emphasis was placed on the effects of different types of motion on the unsteady pressure distribution of the airfoil at pre‐stall, near‐stall and post‐stall conditions. It was found that variations of the pressure distribution and aerodynamic loads with angle of attack were strongly sensitive to the displacement, oscillation frequency and mean angle of attack. The width of the hysteresis loop, position of the ‘figure‐8 shape’ and slope of the pressure coefficient curve are influenced by both types of motion, pitch and plunge. The main difference between plunging and pitching motions is due to the presence of the pitch rate for the pitching motion case, which was absent in the plunging case. Pitch rate had the strongest influence on pressure data in the near‐stall and post‐stall conditions. The trend of increasing the width of the hysteresis loops of lift coefficients with changing reduced frequency was different in two motions in the pre‐stall and post‐stall regions. The aerodynamic damping was greater for the pitching case than for the plunging one at higher reduced frequencies due to the existence of the pitch rate in the pitching oscillation, which was reversed at lower reduced frequencies. In the near‐stall region, at higher reduced frequency, the dynamic stall angle for the pitching oscillation increased while for the plunging one the effect was minimal. Increasing the oscillation amplitude was more effective for the plunging motion than for the pitching one. The effects of surface grit roughness on the pressure signature for both types of motion were also investigated. Applying the surface roughness near the leading edge affected the performance of the airfoil significantly. Copyright © 2008 John Wiley & Sons, Ltd.     

俯伪斜走向分段采煤法在急倾极薄煤层中应用

针对坚硬顶板的急倾斜极薄煤层安全开采技术问题,在对铁山南煤矿过去采煤方法应用的分析和总结基础上,把俯伪斜走向长壁采煤法的走向拦矸密集柱的挡矸防窜矸功能同俯伪斜柔性掩护支架采煤法的支架上垫层的作用与开切眼布置作用等有利因素有机地组合起来,形成了该矿的俯伪斜走向长壁分段采煤法。试验结果表明,该方法借助回风巷上方采空区矸石对工作面第1个走向拦矸密集柱进行充填,在回采推进过程中,利用对走向拦矸密集柱充填后,能使工作面作业空间与采空区完全隔离开来,达到防窜矸和对设备防滑底的作用;实现了多段平行落煤安全生产。     

和顺县恋思水库土坝工程干砌石护坡质量控制

干砌石护坡对于土坝迎水面的保护有重要作用,是土坝工程的主要组成部分。干砌石护坡不仅要求严格控制施工质量,而且要求外观完美,表面平整。文中结合和顺县恋思水库土坝工程干砌石施工实际,分析干砌石护坡的施工过程和质量控制。     

某天线稳定平台的结构设计

舰载雷达稳定平台系统能消除舰船纵横摇对雷达天线产生的影响,雷达稳定平台的结构形式、动态特性对舰载雷达的发射精度有至关重要的影响。文中详细论述了一种两轴稳定平台的结构设计方案,通过分析稳定平台的各项载荷,计算得到稳定平台所需要的驱动功率。利用ANSYS软件对天线稳定平台系统进行有限元建模和分析,根据分析结果评判结构设计的合理性。最终,通过使用该稳定平台,成功地消除了舰船纵横摇运动对某舰载天线工作的影响。     

高破断拉力集装箱起重机俯仰钢丝绳生产

研制公称直径36mm、最小破断拉力990kN、主股6根、主股结构1-7-7+7-14港口岸边集装箱起重机俯仰钢芯钢丝绳.分析国内外钢丝绳企业资料,将绳芯设计成压实股钢芯,确定钢丝绳结构为6×36WS-IWRC (K).给出配丝直径和捻距,以及主股拆股钢丝抗拉强度.生产出的3根钢丝绳破断拉力分别为1 000,1002,1...     

乳酸菌接种量对发酵猪耳西式火腿品质的影响

以猪耳为原料经乳酸菌发酵加工西式火腿，探讨了在发酵猪耳西式火腿加工过程中乳酸菌接种量对产品的物性（包括硬度、弹性、咀嚼性、凝聚性、粘着性和脆性）、出品率、pH值以及感官品质的影响。结果表明：以保加利亚乳杆菌（Lactobacillus bulgaricus）和植物乳杆菌（Lactobacillus plantarum）按l：l的比例组合。发酵24h计，乳酸菌接种量为15％（菌种培养液体积：浸泡液体积×100）时，产品可获得较为理想的酸度和感官评分，而乳酸菌接种量对产品的物性和出品率没有明显规律性影响。     

啤酒生产过程中影响乙醛含量的因素

影响成品啤酒风味物质-乙醛含量的因素较多，主要针对以下几个影响因素分析其对乙醛含量的影响，包括；发酵周期中不同代数酵母接种发酵周期乙醛含量的变化情况；发酵工艺条件-麦汁浓度差异对乙醛含量的影响；接种酵母质量对发酵末乙醛含量的影响；灭菌前清酒溶解氧含量与灭菌后啤酒中乙醛含量的关系；添加剂-酵母营养盐末乙醛含量的影响；污染微生物-发酵单胞菌的对乙醛含量的影响。     

DQ5030型斗轮堆取料机悬臂起升失灵故障分析及处理

对DQ5030型斗轮堆取料机悬臂起升失灵的原因进行分析,认为在补油系统及工作液压油油质、油温均正常的情况下,悬臂起升失灵为俯仰系统中某个部件发生故障导致,通过对各个部件的检查以及对有缺陷的部件进行检修,解决了俯抑系统存在的缺陷。     

不同速比下纵摇运动对立轴叶轮的性能影响

浮式立轴水轮机在波浪中会发生纵摇运动,为了研究纵摇对立轴水轮机的水动力性能影响,将浮式垂直轴叶轮在波浪作用下摇荡运动的复杂模型简化为叶轮在均匀流中叠加简谐摇荡运动,应用ANSYS-CFX软件,采用动网格和滑移网格相结合的技术建立了垂直轴叶轮旋转和摇荡运动的数值模拟方法,并和在均匀流中的水轮机作对比,而且对水轮机的推力系数和侧向力系数的时历曲线用最小二乘法进行拟合分析,得到水轮机阻尼系数和附加质量系数.结果表明:纵摇运动下的水轮机效率会稍微高于均匀流中的水轮机效率;纵摇运动下的水轮机推力和侧向力波动幅值有大幅增加,对水轮机结构强度及疲劳效应产生不利影响;阻尼力是水轮机纵摇运动中的主要成分,附加质量力占的影响较小.     

基于MATLAB的消防炮射流轨迹研究

通过对消防炮射流微元体进行受力分析,得到了各种环境影响因素作用下的射流轨迹运动方程。运用MATLAB中的Runge-Kutta算法对方程组进行计算,并且编写ODE45模拟程序进行仿真,得到了在各组不同实验测试参数条件下对应不同俯仰角的射流轨迹模拟仿真图。将模拟仿真与实验测量数据进行对比分析表明:俯仰角小于60°时的射流轨迹模拟仿真结果较正确,对灭火时迅速定位降低反应时间和提高灭火的效率有重要的意义。