Reliability based multidisciplinary design optimization of cooling turbine blade considering uncertainty data statistics

Considering the coupling among aerodynamic, heat transfer and strength, a reliability based multidisciplinary design optimization method for cooling turbine blade is introduced. Multidisciplinary analysis of cooling turbine blade is carried out by sequential conjugated heat transfer analysis and strength analysis with temperature and pressure interpolation. Uncertainty data including the blade wall, rib thickness, elasticity Modulus and rotation speed is collected. Data statistics display the probability models of uncertainty data follow three-parameter Weibull distribution. The thickness of blade wall, thickness and height of ribs are chosen as design variables. Kriging surrogate model is introduced to reduce time-consuming multidisciplinary reliability analysis in RBMDO loop. The reliability based multidisciplinary design optimization of a cooling turbine blade is carried out. Optimization results shows that the RBMDO method proposed in this work improves the performance of cooling turbine blade availably.

     

Structural analysis of francis turbine runners using ADINA

ADINA is used as the primary design tool in the structural analysis of Francis turbine runners at Kværner Energy. An in-house developed finite-element mesh generator is used for quick and efficient modelling of any runner or runner vane segment in THREEDSOLID elements. The finite-element analyses include frequency analyses in order to avoid structural amplification of dynamic loads and static-strength analyses in order to obtain a uniform stress distribution in the runner. Comparison of the convergence has been carried out with respect to mesh density and order of the elements. The high-order elements (20- and 27-nodes) compute both smaller displacements and lower natural frequencies in comparison to eight-node elements. For stress calculations, only high-order elements are used. Poor structural design is one explanation of failures in some runners. Knowledge of structural performance secures structural integrity and reveals the potential for reducing weight.     

Optimal blank design based on finite element method for blades of large Francis turbines

Metal pressing process that is widely used in industries has advantages over casting process for producing large Francis turbine blades from thick plates. Prior to the pressing process, blank design is firstly performed to determine flat blanks. The traditional trial and error approach is not applicable to blade design for Francis turbines that are not standard due to hydraulic characteristics of power plant sites. The rapid development of computing technology makes it possible to obtain optimal flat blanks by numerical modelling and simulation. In this paper, inverse finite element approach is investigated for blank design and an elasto-plastic model has been built using the well-known commercial software ANSYS. Numerical simulations for blade unfolding models with thick shell elements, solid elements and shell elements have given results with negligible differences. Unfolding tests with simple geometries have been carried out and the numerical results agree well with the analytical solutions. A large and thick shape of a Francis turbine blade for a hydropower plant has been successfully unfolded by inverse FE model. Sensibility analysis shows that the middle surface of the flat blank is independent of blade thickness. For ensuring the machining of the blade after the pressing process, a new contour is obtained by extending the boundary of the flat blank provided by the numerical model. This research may provide a useful tool for optimal blank design of Francis turbine blades.     

On the optimal design of the form of hydroturbine impeller blades

When designing a hydraulic turbine, a machine of better performance characteristics and primarily of the highest possible efficiency should be created. In the process, a designer is given a numer of restrictions concerning dam height, impeller diameter, etc. The turbine efficiency can be increased by varying the impeller blade profile or the angular velocity of the impeller rotation and by some other design techniques.The problem of optimization of hydroturbine parameters has been investigated in a number of works (see e.g. Fedorov 1983, 1984; Klimovich and Fedorov 1984; Kazachkov and Provad 1989). This paper presents some optimum decisions obtained for one-and two-dimensional axisymmetrical flow models. The turbine efficiency and local cavitation coefficients are accepted as the goal functionals. Necessary optimizing conditions are described, and calculated optimum characteristics of blade systems are given.     

VBA在水轮机辅助设计中的应用

为更好地综合运用计算机自动绘图技术和混流式水轮机叶片设计理论,通过Microsoft Excel的VBA编程工具进行二次开发控制AutoCAD自动绘制水轮机部分图形,完成叶片三维绘形和速度三角形绘形,实现水轮机叶片参数计算与绘图一体化.该方法可提高工作效率,大大减少重复性工作量,为水轮机叶片参数优化和设计优化提供参考.     

Development of a structural optimization strategy for the design of next generation large thermoplastic wind turbine blades

This paper presents the development of a structural optimization process for the design of future large thermoplastic wind turbine blades. The optimization process proposed in this paper consists of three optimization steps. The first step is a topology optimization of a short untwisted and non tapered section of the blade, with the inner volume used as the design domain. The second step is again a topology optimization, but on the first half of a blade to study the effect of non symmetry of the structure due to blade twist and taper. Results of this optimization step are then interpreted to build a shell model of the complete blade structure to perform composite size optimization based on a minimum mass objective subjected to constraints on deflection, composite strength and structural stability. Different blade models using ribs are then optimized and compared against conventional blade structure (box spar structure without ribs and single web structure without ribs). The use of ribs in wind turbine blade structures, which is more adapted to thermoplastic composite manufacturing than for thermoset composites, leads to slightly lighter blades than conventional blade structures.     

基于接触应力的高参数汽轮机叶片枞树形叶根型线优化

为提高汽轮机叶片叶根型线的设计效率和产品质量,基于接触应力约束下的枞树形叶片叶根型线设计,将传统的基于经验的设计与经典优化理论相结合,推导适合叶根型线的设计方法。采用移动渐近线法（method of moving asymptotes, MMA）进行结构拓扑优化,以某低压末级动叶片设计为例,优化前、后叶根和轮槽的VON Mises应力对比表明,所推导的方法能够快速得到所需的型线设计。该设计使得叶根与轮槽间的接触应力降低,叶片的使用寿命提高。     

涡轮气冷叶片传热分析数据提取技术研究

涡轮气冷叶片传热管网计算是涡轮气冷叶片传热设计的重要环节,针对涡轮气冷 叶片传热设计需求,提出了涡轮气冷叶片模型传热分析数据提取的方法,具体包括计算单元划 分、流路自动判断、网络图生成和传热数据提取等算法。结合涡轮气冷叶片结构特点,使用UG Open API 工具开发了传热分析数据提取系统,实现了涡轮气冷叶片传热分析数据的提取、管理 和输出功能,以用于后续的分析计算,提高了传热设计管网计算的自动化水平,并通过实例验 证了所提出方法的可行性。     

航空发动机轮盘参数化结构优化

为降低航空发动机轮盘的质量,提高发动机推质比,对发动机转子轮盘进行参数化结构优化设计.研究辐板不同高度处厚度与轮盘径向破裂裕度的关系,以简化轮盘辐板优化方法.以周向破裂转速裕度为约束条件,体积最小为优化目标函数,利用Isight软件和有限元数值模拟方法研究轮盘盘心优化方法,并通过算例计算验证其正确性.结果表明：在满足约束条件的基础上,轮盘体积减小8.66%,最大等效应力减少10.4%.该方法可为航空发动机轮盘轻量化开发提供参考.     

Recent advances in computerized aerospace structural analysis and design

This paper presents accomplishments at the Boeing Commercial Airplane Company in the areas of (1) large problem solutions, (2) practical structural design automation and (3) a hypothesis for stable crack growth.A turbine blade (3200 nodes 350 elements, 9500 freedoms, 15 million words of storage) and a sports stadium (3400 nodes, 9600 elements, 20,000 freedoms, 70 million words of storage) are presented in terms of problem definition, strategy of approach, data management and computer resources.The Boeing automated strength design capability in the ATLAS System is discussed in terms of user specified constraints on the automated strength resizing and local optimization, strength criteria, user control and convergence criteria. Cost and weight data are presented from large aircraft design studies (20,000 design variables).A new concept of crack stability based on non-linear stress/strain analysis is presented. Stable crack growth is modeled by a suitable failure criterion in the stress analysis procedure. A crack is extended by a simultaneous unloading of the newly created crack surface and the loading of the uncracked region. Test comparisons and numerical experiments support a new hypothesis based on material strength characteristics, plastic zone size/history and the residual plastic strains.     

Optimal design of laminated composite beam structures

This work deals with design sensitivity analysis and optimal design of composite structures modelled as thin-walled beams. The structures are treated as a torsion-bending resistant beams. The analysis problem is discretized by a finite element technique. A two-node Hermitean beam element is used. The beam sections are made from an assembly of elements that correspond to flat layered laminated composite panels. Optimal design is performed with respect to the lamina orientations and thickness of the laminates. The structural weight is considered as the objective function. Constraints are imposed on stresses, displacements, critical load and natural frequencies. Two failure criteria are used to limit the structural strength: Tsai-Hill and maximum stress. The Tsai-Hill criterion is also adopted to predict the first-ply-failure loads. The design sensitivity analysis is analytically formulated and implemented. An adjoint variable method is used to derive the response sensitivities with respect to the design. A mathematical programming approach is used for the optimization process. Numerical examples are performed on three-dimensional structures.     

Experimental validation of the utility of structural optimization

This paper addresses the topic of validating structural optimization methods by use of experimental results. The paper describes the need for validating the methods as a way of effecting a greater and an accelerated acceptance of formal optimization methods by practicing engineering designers. The range of validation strategies is defined which includes comparison of optimization results with more traditional design approaches, establishing the accuracy of analyses used, and finally experimental validation of the optimization results. The remainder of the paper describes examples of the use of experimental results to validate optimization techniques. The examples include experimental validation of the following: optimum design of a trussed beam; combined control-structure design of a cable-supported beam simulating an actively controlled space structure; minimum weight design of a beam with frequency constraints; minimization of the vibration response of helicopter rotor blade; minimum weight design of a turbine blade disk; aeroelastic optimization of an aircraft vertical fin; airfoil shape optimization for drag minimization; optimization of the shape of a hole in a plate for stress minimization; optimization to minimize beam dynamic response; and structural optimization of a low vibration helicopter rotor.     

Performance optimization of gas turbine engine

Performance optimization of a gas turbine engine can be expressed in terms of minimizing fuel consumption while maintaining nominal thrust output, maximizing thrust for the same fuel consumption and minimizing turbine blade temperature. Additional control layers are used to improve engine performance. This paper presents an evolutionary approach called the StudGA as the optimization framework to design for optimal performance in terms of the three criteria above. This approach converges fast and can potentially save on computing cost. Model-based experimental results are used to illustrate this approach.     

Design of heterogeneous turbine blade

Constantly rising operating pressure and temperature in turbine drivers push the material capabilities of turbine blades to the limit. The recent development of heterogeneous objects by layered manufacturing offers new potentials for the turbine blades. In heterogeneous turbine blades, multiple materials can be synthesized to provide better properties than any single material. A critical task of such synthesis in turbine blade design is an effective design method that allows a designer to design geometry and material composition simultaneously.This paper presents a new approach for turbine blade design, which ties B-spline representation of a turbine blade to a physics (diffusion) process. In this approach, designers can control both geometry and material composition. Meanwhile, material properties are directly conceivable to the designers during the design process. The designer's role is enhanced from merely interpreting the optimization result to explicitly controlling both material composition and geometry according to the acquired experience (material property constraints).The mathematical formulation of the approach includes three steps: using B-spline to represent the turbine blade, using diffusion equation to generate material composition variation, using finite element method to solve the constrained diffusion equation. The implementation and examples are presented to validate the effectiveness of this approach for heterogeneous turbine blade design.     

Implementation of a crack propagation constraint within a structural optimization software

A crack propagation constraint related to the stress intensity factor is examined for the minimum-weight design optimization of a composite blade-stiffened panel. A low-fidelity approach uses a closed-form solution for the stress intensity factor, while a high-fidelity approach uses the stress distribution around the crack. Structural optimizations are performed by low- and high-fidelity approaches for a number of panels configured with different values of the load, crack length, and blade height. Response surface (RS) approximations are then constructed for the optimal weight as a function of the three configuration variables. The computational cost, numerical noise, and accuracy for the two approaches are compared. An additional constraint in the low-fidelity solutions is found to be active for some of the configurations, increasing the difference between the low-fidelity and high-fidelity optima. It is shown that outlier analysis helps to identify the configurations with the largest difference.     

Discrete Material and Thickness Optimization of laminated composite structures including failure criteria

This work extends the Discrete Material and Thickness Optimization approach to structural optimization problems where strength considerations in the form of failure criteria are taken into account for laminated composite structures. It takes offset in the density approaches applied for stress constrained topology optimization of single-material problems and develops formulations for multi-material topology optimization problems applied for laminated composite structures. The method can be applied for both stress- and strain-based failure criteria. The large number of local constraints is reduced by the use of aggregate functions, and the developed approach is demonstrated for optimization problems involving both constant and varying thickness laminated composites.     

Side-wall effect of runner casing on performance of Darrieus-type hydro turbine with inlet nozzle for extra-low head utilization

A ducted Darrieus-type turbine has been proposed for hydropower utilization of extra-low head less than 2 m.Though the hydro turbine system,in general,might consist of an intake,runner casing section and a draft tube for higher efficiency operation,it was clarified in previous experiment that there was no need of the side-walls of runner casing section and a draft-tube for keeping the efficiency high in the case of duct with an inlet nozzle.This would yield a simplification of the structure of the turbine s...     

COMPUTER AIDED PRELIMINARY DESIGN FOR ROTORS

An interactive computer aided preliminary design system has been developed mainly for gasturbine engine rotors. The design system covers three parts: disks, shafts and rotor dynamics. A nu-merical optimization package called MPOP is used to minimize the weight of disks, shafts and optimizethe arrangement or stiffness of bearings for rigid or flexible rotors subjected to certain constraints ofsizes, shapes, stresses, deflections, stiffness and frequencies. Various forms of disks, shafts, rotorsand structure-analysing result curves are displayed on the screen. Designer may select, inspect or modi-fy the results interactively. The integrated design of structure, optimization, strength and rotor dynamics has improved designquality and reduced turnaround time during preliminary design phase of gas turbine engine develop-ment. As an example, a real preliminary design of an aeroengine turbine rotor is described.     

Transient hydrodynamic analysis of the transition process of bulb hydraulic turbine

In this paper, a semi-implicit method for solving pressure coupled equations used to calculate the flow field, and dynamic mesh were employed to simulate the three-dimensional dynamic turbulent flow of whole flow channels, in start transition process and runaway transition process of bulb hydraulic turbine. In above processes, the transition process of pressure field and flow field were realistically modeled and simulated, which reflects the influence of water flow state, after passing through guide vanes on the inflow of the runner blades, and reveals the flow field variations in the transition process. The numerical results show that: during the start transition process, with the increase of guide vane opening, the flow circulation produced by water flowing through the guide vanes becomes smaller; therefore, the rotational acceleration of the runner decreases and the rotational speed value reduces. In the runaway transition process, the hydraulic turbine operating with load has a sudden load rejection and then, the hydraulic turbine rotational speed is rising with the guide vane closing, leading to pressure pulsations and severe vortex phenomenon, which will cause significant vibrations of swings.     

基于导叶位置数据分析的刘家峡水电厂导叶立面间隙调整方法改进

在水电厂水轮机检修过程中,水轮机导叶立面间隙调整是一项重要而精细的工作,其主要目的是将水轮机24片矩形导叶两两相靠,调整为一个密不透水的圆筒状。传统导叶立面间隙调整方法虽然能满足调整完成后两两导叶立面间隙为零的技术要求,但因缺乏精确的反馈量和监视量,调整过程费时费力,同时可能造成导叶之间压紧程度不一的现象,对后续调整产生一定影响。通过采集机组检修前导水机构各项数据,导入三维建模软件进行精确建模,在模型中进行多项初始条件下进行水轮机导叶立面间隙模拟调整,并与检修前数据比较,得出该检修状态下导叶的标准位置。在现场实际调整过程中,根据不同水轮机导叶立面间隙分布情况、机组检修级别,结合导叶标准位置提出差异化水轮机导叶立面间隙调整策略,极大提高了水轮机导叶立面间隙[3]调整效率和精度,保证了机组运行安全性。