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Recently,small hydroelectric generators have gained attention as a further development in water turbine technology for ultra low head drops in open channels.The authors have evaluated the application of cross-flow water turbines in open channels as an undershot type after removing the casings and guide vanes to substantially simplify these water turbines.However,because undershot cross-flow water turbines are designed on the basis of cross-flow water turbine runners used in typical pipelines,it remains unclear whether the number of blades has an effect on the performance or flow fields.Thus,in this research,experiments and numerical analyses are employed to study the performance and flow fields of undershot cross-flow water turbines with varying number of blades.The findings show that the turbine output and torque are lower,the fluctuation is significantly higher,and the turbine efficiency is higher for runners with 8 blades as opposed to those with 24 blades. 相似文献
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J. Sumner N. J. Simms W. Stamm J. E. Oakey 《Energy Materials: Materials Science and Engineering for Energy Systems》2016,11(4):1090-1099
Integrated gasification combined cycles can incorporate pre-combustion carbon capture. High-H2 syngas produces high H2O levels after combustion, potentially accelerating gas turbine component damage. Determining materials systems’ suitability for this novel environment requires exposures in representative environments. Thus, an existing 0.7?MW burner rig was modified to generate the combustion environment and incorporate a cascade of 15 air-cooled turbine blades. Computational fluid dynamic calculations using blade dimensions and flow requirements supported the cascade design and determined blade placement within the gas flow. Trials of the modified unit have shown that a simulated combusted H2-rich syngas composition was generated at gas temperatures ≤1440°C. A 1000?h exposure has been carried out with thermal barrier coated blades to demonstrate the operation of the unit.This paper is part of a thematic issue on the 9th International Charles Parsons Turbine and Generator Conference. All papers have been revised and extended before publication in Materials Science and Technology. 相似文献
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The primary focus of this work is in the development of an evolutionary optimization technique which gets progressively 'smarter' during the optimization process by learning from computed domain knowledge. In the approach, the influence of the design variables on the problem solution is recognized, and the knowledge learned is then generalized to dynamically create or change design rules during optimization. This technique, when applied to a constrained optimization problem, shows progressive improvement in convergence of search, as successive generations of rules evolve by learning from the environment. This method is applied to a complex aerodynamic optimization problem involving turbine airfoil design. In this investigation, the 3D geometry of an airfoil is optimized by simultaneously optimizing multiple 2D slices of the airfoil. Results from the optimization of a low pressure turbine nozzle are presented in the paper. Results obtained using standard numerical optimization techniques are also presented for comparison purposes. 相似文献
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The present paper investigates the effect of material coupling on static and modal characteristics of composite structures. Incorporation of stiffness and damping coupling terms into a beam formulation yields equivalent section stiffness and damping properties. Building upon the damping mechanics, an extended beam finite element is developed capable of providing the stiffness and damping matrices of the structure. Validation cases on beams and blades demonstrate the importance of all stiffness and damping terms. Numerical results validate the predicted effect of material coupling on static characteristics of composite box-section beams. The effect of the full coupling damping matrices on modal frequencies and structural modal damping of composite beams is investigated. Box-section beams and small blade models with various ply angle laminations at the girder segments are considered. Finally, the developed finite element is applied to the prediction of the modal characteristics of a 19 m realistic wind-turbine model blade. 相似文献
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在发动机叶片定向无余量精铸件的研制过程中,通过对叶片变形的分析,制定预防变形的措施,设计成型浇注系统、组合夹具等工装,加强控制手段,解决了超薄细长定向无余量叶片变形问题,提高了叶片的尺寸精度,研制出符合设计要求的无余量叶片. 相似文献
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泡沫陶瓷过滤器在带冠导叶熔模铸造中的应用 总被引:2,自引:0,他引:2
叙述了泡沫陶瓷过滤器在汽轮机带冠导叶铸造中的应用。使用泡沫陶瓷过滤器使除渣有显著效果,是获得少、无夹渣带冠导叶的一种有效途径。 相似文献
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Geometrical Error Analysis and Control for 5-axis Machining of Large sculptured surfaces 总被引:3,自引:2,他引:1
Si-Jie Yan Ji Zhou Fan-Yu Peng Yun-Fei Zhou Xi-De Lai 《The International Journal of Advanced Manufacturing Technology》2003,21(2):110-118
One of the important tasks in five-axis machining of large sculptured surfaces is to control and reduce the machined errors.
This paper presents the methods to control geometrical errors based on the establishment of the link between geometrical errors
and the parameters of tool path planning. Nonlinear errors, which are the majority of geometrical errors during five-axis
machining, are is strictly analysed and formulated. An adaptive step length method is proposed to control effectively the
cutter contact path error. The measures to reduce the scallop error in machining of the large sculptured surfaces are discussed
also. With the combination of this research with CAM software, both large Kaplan and Francis hydroturbine blades have been
successfully machined. It shows that the machined errors can be controlled effectively and the machining efficiency can be
improved in the machining of the large sculptured surfaces by the proposed methods. 相似文献