Fluid forces on kayak paddle blades of different design   总被引：1，自引：1，他引：0  

D.?SumnerEmail author  E.?J.?Sprigings  J.?D.?Bugg  J.?L.?Heseltine 《Sports Engineering》2003,6(1):11-19

Three kayak paddle blades of different design (Conventional, Norwegian, Turbo) were tested in a low-speed wind tunnel at a maximum chord Reynolds number of Re = 2.2–2.7 × 10⁵ (corresponding to speed through water of ≈1 m/s). The mean drag force and side force acting on each blade were measured, as the yaw and pitch angles were varied. The results were compared with those recorded for a finite rectangular flat plate of similar area and aspect ratio. For zero pitch angle of the blades, the results indicate that the drag coefficient was mostly independent of the blade design as the yaw angle was varied between ± 20°, with only the Norwegian blade design displaying a marginally higher drag coefficient than either of the other two blades or the flat plate. Increasing the pitch angle to 30°, while maintaining the yaw angle at zero, resulted in a 23% reduction of the drag coefficient for the flat plate, but only a 15% reduction of the drag coefficients for the three blades. For all designs, the drag coefficient reduction followed a simple cosine relationship as the pitch angle or yaw angle was increased. The wind tunnel experiments revealed that the side force coefficients for all three paddle blade designs were entirely independent of the blade design and were indistinguishable from those recorded for a flat plate. In summary, the study showed that the nondimensional force coefficients are largely independent of the paddle blade design.  相似文献   

基于主控逻辑的风电机组叶片断裂原因分析     

黄权开  卢成志  洪志刚  魏超  刘永生 《实验室研究与探索》2021,(1):22-26,57

梳理了风电机组的运行流程,并阐述了主控系统与主控逻辑对风电机组安全运行的重要性,提出从主控逻辑是否完善的角度对机组叶片断裂事故进行原因分析.当排除叶片制造质量问题或风速超过限值、失速、电气故障或是否遭受雷击等外因后,可从机组主控系统控制逻辑出发,分析机组本身是否存在控制方面的重大安全隐患,结合机组的运行数据记录和控制系...  相似文献   

带冷气掺混的涡轮级三元流场分析     

赵晓路  李维  罗建桥 《中国科学院大学学报》2003,20(2):155-159

航空发动机向大幅度提高推重比和降低油耗的方向发展.涡轮进口温度在不断的提高.随着叶片热负荷的加大,冷却用气量也不断加大,最多已占到涡轮进口流量的20%左右.冷却气的喷射对高压涡轮级的三元流场会产生不可忽略的影响.在多叶片排三元N-S方程并行解的基础上,采用冷却气射流源项模型,研究了某带冷气掺混的高压涡轮级的流场和温度场分布特点.  相似文献   

The “Hands Together” method of nonsterile scalpel blade mounting and removal          下载免费PDF全文

Jon Cornwall 《Anatomical sciences education》2014,7(2):161-166

Scalpels are utilized by many different user groups for such purposes as medical procedures and dissection. Injuries caused by scalpels are a potential risk for scalpel users, and include injuries that may occur while mounting and removing the scalpel blade. Between 10% and 20% of all scalpel injuries in education and healthcare settings are reported to occur while scalpel blades are being mounted or removed. At present there are few published or “best practice” demonstrations of safe technique for scalpel blade mounting and removal. This brief article outlines a variation of the procedure for scalpel blade mounting and removal. It includes strategies developed to minimize risk or injury for the scalpel user, including providing a stable base for the hands and arms so as to prevent unnecessary large amplitude movements that may lead to injury of the scalpel user or a third party. Such a technique may promote scalpel safety, contribute to the development of “best practice” scalpel use, and help decrease injuries that may be caused while mounting or removing scalpel blades. Anat Sci Educ 7: 161–166. © 2013 American Association of Anatomists.  相似文献   

基于nRF9E5的无线热力特性测试系统硬件设计     

周珊  蔡长青  赵殿纯 《科技通报》2014,(9)

火电厂中经常需要对汽轮发电机热力特性进行测试试验,本文提出了一种用于汽轮机热力特性测试试验的基于nRF9E5无线数据采集模块的数据采集系统方案,具有抗干扰性强、低成本、低功耗等优点。  相似文献   

某国产600MW汽轮发电机组振动故障诊断及处理   总被引：1，自引：0，他引：1  

朱小红  姚杰新 《中国科技信息》2011,(16):107-108,110

某国产600MW汽轮发电机组投产以来存在低压转子支承轴承瓦振超标的故障问题。本文针对产生该振动问题的根本原因进行了分析,在此基础上在现场进行了增加低压缸支承轴承动刚度的尝试。最后利用机组几次临停机会,在机组低压1转子、低压2转子及低发对轮上加重,进行现场精细动平衡,将机组轴振降低到了50μm以内,从而使该机组低压缸瓦振得到控制。  相似文献   

叶片数控砂带磨床的磨削工艺分析及结构设计     

王树凤 《扬州职业大学学报》2007,11(3):27-29

针对汽轮机叶片的结构特点,结合砂带磨削的工艺特性,进行了叶片砂带磨削的工艺分析。在对叶片磨削运动分析的基础上,进行了叶片数控砂带磨床的总体结构设计,并对砂带磨床的关键结构件进行了力学性能有限元分析。  相似文献   

基于LabVIEW的风力机叶片振动特性与控制实验系统     

李迺璐  江文宇  杨华  朱卫军  曹九发 《实验室研究与探索》2021,(2):115-120,138

针对高校新能源、电气和自控专业学生普遍缺乏针对风力机叶片振动控制的实践环节,提出了基于LabVIEW的风力机叶片振动特性与控制仿真实验设计方案,该方案利用LabVIEW搭建了风力机叶片的经典颤振模型,建立叶片振动特性与控制仿真实验系统。整个仿真实验系统,可在多种典型风速场景下进行叶片振动特性实验,同时,可自行设计控制参数,进行叶片PID振动控制和自适应振动控制的仿真。通过直观的虚拟仿真交互系统,有效克服了场地和设备带来的时间、空间上的局限,促进学生对于风力机叶片振动特性的了解,增强了叶片振动控制设计的实践能力。  相似文献   

Selection environments, flexibility and the success of the gas turbine     

Jim Watson 《Research Policy》2004,33(8):1065-1080

This paper explains the success and failure of two technologies for electricity generation. Both the combined cycle gas turbine (CCGT) and fluidised bed boiler burn fossil fuels more cleanly than more traditional technologies. Whereas the CCGT has been used for an increasing number of new power plants during the past 15 years, the fluidised bed has struggled to attract attention outside a small-scale niche. The paper examines economic, institutional and political changes in the selection environment for power plant technologies to explain this success and failure. It demonstrates how the technological flexibility of the CCGT allowed it to benefit from different selection environments to become the electricity industry's current technology of choice.  相似文献   

黑河水电站水轮机主轴密封改造方案的研究     

马艳丽  周强  任江涛 《杨凌职业技术学院学报》2020,(1):1-3,17

黑河水电站是一座供水为主兼顾发电的水电站,水轮机主轴采用端面水压式密封,这种密封形式在电站运行初期取得良好的密封效果。随着运行年限和运行条件的变化,机组漏水加剧,甚至出现水淹机坑、导轴承进水等事故。通过对黑河电站运行条件及漏水原因的分析,提出了主轴密封的非接触式泵板密封和镜板改造密封两种方案,并对两种方案的设计原理和设计思路进行了深入的阐述。基于尽可能节约成本,不对水轮机本体结构做大的修改的条件下选择采取了前期进行镜板改造,后期采用非接触泵板改造方案两套备用方案。并在1号机组进行了镜板改造实施,通过两年的运行观测,前期改造方案取得了良好效果。  相似文献