不调频叶片设计改型研究

工业汽轮机与发电用汽轮机不同，它通常都是在一个很大的转速范围内长期运行，这就使得动叶片常常会在共振点上长期运行，对级组的动叶片特别是末级动叶片的安全性提出了更高的要求。本文将计算固体力学分析、三维计算流体动力学分析以及流固耦合技术与传统的常规计算方法和汽轮机行业安全性准则相结合，来综合判断动叶片在其共振点上运行的安全性。     

某汽轮机低压缸次末级叶片安全性分析

火电灵活性技术的发展使大型火电汽轮机的运行工况更为复杂,这对汽轮机叶片的安全性提出了更高要求。基于有限元分析方法,对某汽轮机低压缸次末级叶片的安全性进行了分析计算,得到了叶片的静应力分布、振动避开率以及动应力分布等相关数据,表明了次末级叶片安全性满足强度设计要求。研究成果可为叶片的安全性判定以及机组的安全稳定运行提供理论支撑。     

汽轮机带冠单叶片结构的动强度分析

通过级组动应力的扩大计算及叶冠运行间隙的确定，表明带冠单叶片结构的共振态基本上处于较低的切向B0振型动应力水平，对比其它结构，更适宜于作为不调频叶片。提出了结构措施以扩大其在中长或较长叶片上的应用。     

GE350MW汽轮机叶片静叶片静频测试及振动安全性分析

某电厂GE350MW机组检修期间,利用SCHENCK VIBROPORT41频谱分析仪对其叶片进行现场静态频率测试,并进行了叶片振动安全性分析,测试结果表明该机组次末两级叶片(组)可在工作转速下安全稳定运行。     

某厂汽轮机叶片静频率测试及振动安全性分析

介绍了一种利用振动信号分析仪测试叶片静频率的新方法,并通过某厂1号汽轮机叶片静频率的现场测试数据,进行了叶片振动特性及安全性分析。试验结果表明该机最末3级叶片(组)在工作转速下运行时是安全的。     

引进型300MW、600MW汽轮机次末级叶片安全性分析的思路

阐述了引进型300MW、600MW汽轮机次末级“474”、“475”叶片安全性分析的思路,指出了“474”、“475”叶片二阶频率振型的不同是“474”叶片失效、“475”叶片安全运行的关键。     

汽轮机调节级叶片三维接触有限元强度可靠性分析

汽轮机运行转速通常存在波动,叶片材料特性也存在不确定性。为评估调节级叶片强度可靠度,假设汽轮机转速、叶片材料弹性模量及密度服从正态分布,建立三维有限元接触模型,自编程序完成了调节级叶片多个样本的静态应力分析,然后应用多项式响应面法拟合以及Monte Carlo模拟方法得到了叶片可靠度。建立的叶片强度可靠性分析方法具有计算效率和精度高的优点,分析结果对保证叶片安全性具有重要参考意义。     

超超临界1000MW汽轮机动叶片静频试验研究

汽轮机动叶片振动问题是叶片运行过程中的主要问题之一。为使机组安全运行,通常需要测定和调整叶片的静频。该丈针对1000MW超超临界汽轮机指定级叶片的静频试验内容与方法进行介绍,并对试验数据进行总结分析,给出了各级叶片静频数据及振型特性,并与理论计算值进行比对分析,为理论计算修正提供参考。     

汽轮机末级动叶片出口边水蚀特性及疲劳裂纹扩展的研究

空冷汽轮机组、调峰汽轮机组及热电联产汽轮机低压缸在小容积流量工况下运行时，末级动叶片根部分离流区的回流会将排汽缸湿蒸汽中的水滴带回叶栅通道，使动叶片吸力面出口区侵蚀并引发疲劳裂纹。为了确定机组负荷工况对叶片水蚀特性及叶片安全性的影响，首先利用流线曲率法发展出一种计算回流气动特性及水滴撞击叶片速度的方法。并用以分析了一台200MW汽轮机末级动叶根部出口边水蚀的特性，分析结果与实际情况较一致。此后，采用断裂力学理论研究了出口边水蚀缺口处的裂纹萌生期与扩展的增长率，计算结果与实际裂纹发展情况较为符合。所发展的方法为研究预防叶片出口边水蚀方法和合理制定机组检修周期提供了有用手段。     

汽轮机叶片损坏的原因分析及处理

某公司C145／N200-130-535／535型汽轮机组末级叶片在运行中发生断裂。通过对叶片断裂原因的分析,提出叶片断裂的原因,并对处理方法进行详细的介绍。     

Thermal design and CFD analysis of the radial inflow turbine for a CO2-based mixture transcritical Rankine cycle

Transcritical carbon dioxide (CO₂) Rankine cycle has exhibited great potential in the field of low-temperature heat utilization. But its application is restricted by the condensing issue and the safety concern due to the relatively low critical temperature and high critical pressure of CO₂. Blending CO₂ with organic fluids for the transcritical Rankine cycle is regarded as an effective method to solve these problems. And the turbine performance has great influence on the performance of transcritical Rankine cycle. In this paper, the thermal design of the CO₂-based mixture turbine is firstly carried out based on the parametric optimization of the system. Then the computational fluid dynamics (CFD) analysis is performed to examine the turbine performance and validate the reliability of thermal design. Furthermore, the effects of blade tip clearance and nozzle-to-rotor clearance on the turbine performance are investigated. Results show that the turbine is well designed with an isentropic efficiency of 84.54%, and the CFD simulation results basically agree with the thermal design results. The influence of leakage flow on mainstream grows significantly as the blade tip clearance increases. When the blade tip clearance is 2 mm, the relative loss of power output could achieve as large as 7.81%. Larger nozzle-to-rotor clearance leads to more uniform distributions of Mach number and pressure, but the flow losses also increase. The effect of trailing edge disturbance on the flow field at the nozzle outlet is almost negligible if the nozzle-to-rotor clearance is 6 mm or more.     

Effect of rotor–tower interaction,tilt angle,and yaw misalignment on the aeroelasticity of a large horizontal axis wind turbine with composite blades

This paper presents a detailed analysis of the rotor–tower interaction and the effects of the rotor's tilt angle and yaw misalignment on a large horizontal axis wind turbine. A high‐fidelity aeroelastic model is employed, coupling computational fluid dynamics (CFD) and structural mechanics (CSM). The wind velocity stratification induced by the atmospheric boundary layer (ABL) is modeled. On the CSM side, the complex composite structure of each blade is accurately modeled using shell elements. The rotor–tower interaction is analyzed by comparing results of a rotor‐only simulation and a full‐machine simulation, observing a sudden drop in loads, deformations, and power production of each blade, when passing in front of the tower. Subsequently, a tilt angle is introduced on the rotor, and its effect on blade displacements, loads, and performance is studied, representing a novelty with respect to the available literature. The tilt angle leads to a different contribution of gravity to the blade deformations, sensibly affecting the stresses in the composite material. Lastly, a yaw misalignment is introduced with respect to the incoming wind, and the resulting changes in the blade solicitations are analyzed. In particular, a reduction of the blade axial displacement amplitude during each revolution is observed.     

Structural design of spars for 100-m biplane wind turbine blades

Large wind turbine blades are being developed at lengths of 75–100 m, in order to improve energy capture and reduce the cost of wind energy. Bending loads in the inboard region of the blade make large blade development challenging. The “biplane blade” design was proposed to use a biplane inboard region to improve the design of the inboard region and improve overall performance of large blades. This paper focuses on the design of the internal “biplane spar” structure for 100-m biplane blades. Several spars were designed to approximate the Sandia SNL100-00 blade (“monoplane spar”) and the biplane blade (“biplane spar”). Analytical and computational models are developed to analyze these spars. The analytical model used the method of minimum total potential energy; the computational model used beam finite elements with cross-sectional analysis. Simple load cases were applied to each spar and their deflections, bending moments, axial forces, and stresses were compared. Similar performance trends are identified with both the analytical and computational models. An approximate buckling analysis shows that compressive loads in the inboard biplane region do not exceed buckling loads. A parametric analysis shows biplane spar configurations have 25–35% smaller tip deflections and 75% smaller maximum root bending moments than monoplane spars of the same length and mass per unit span. Root bending moments in the biplane spar are largely relieved by axial forces in the biplane region, which are not significant in the monoplane spar. The benefits for the inboard region could lead to weight reductions in wind turbine blades. Innovations that create lighter blades can make large blades a reality, suggesting that the biplane blade may be an attractive design for large (100-m) blades.     

Fracture mechanics approach for failure of adhesive joints in wind turbine blades

Composite components of wind turbine blade are assembled with adhesive. In order to assess structural integrity of blades it is needed to investigate fracture of joints. In this study, finite element analysis based on fracture mechanics was conducted to characterize failure of adhesive joint for wind turbine blade. The cohesive zone model as proposed fracture mechanics approach was verified through the comparison of numerical results with experimental data. Finite element models of wind turbine were developed to predict damage initiation and propagation. Numerical results based on fracture mechanics showed that failure was initiated in the edge of the adhesive bond line due to high level of shear stress prior to reaching the extreme design loading and propagated progressively.     

Influence of blade deformation and yawed inflow on performance of a horizontal axis tidal stream turbine

For a better design of tidal stream turbines operated in off-design conditions, analyses considering the effects of blade deformation and yawed inflow conditions are necessary. The flow load causes deformation of the blade, and the deformation affects the turbine performance in return. Also, a yawed inflow influences the performance of the turbine. As a validation study, a computational fluid dynamics (CFD) simulation was carried out to predict the performance of a horizontal axis tidal stream turbine (HATST) with rigid blades. The numerical uncertainty for the turbine performance with blade deformation and a yawed inflow was evaluated using the concept of the grid convergence index (GCI). A fluid–structure interaction (FSI) analysis was carried out to estimate the performance of a turbine with flexible composite blades, with the results then compared to those of an analysis with rigid blades. The influence of yawed inflow conditions on the turbine performance was investigated and found to be important in relation to power predictions in the design stages.     

Global sensitivity analysis of the blade geometry variables on the wind turbine performance

The need for implementing efficient blade designs gains relevance as wind turbine developments require longer blades. The design of blade geometry, traditionally divided in 2D airfoils and spanwise distributions, is usually addressed as an optimization problem. A correct identification of the design variables is crucial to avoid unnecessary computational cost or insufficient exploration of the design space. This paper deals with the identification of the design variables that affect the wind turbine performance. First, the number of design variables for an accurate airfoil representation is resolved. A methodology, based on statistical hypothesis testing applied to the airfoil approximation errors, is presented to assess the accuracy of types of B‐splines. Second, the study is extended to chord and twist distributions besides airfoil geometry with the purpose of assessing the sensitive blade variables in the wind turbine performance. Global sensitivity analysis as multi‐variable linear regressions and variance‐based methods are used. Latin hypercube sampling is applied to generate efficient inputs. MATLAB‐based code is developed to obtain outputs: annual energy production, maximum blade tip deflection, overall sound power level and blade mass. As result of the study, a list of non‐affecting variables is deduced. These variables can be avoided in the optimization without loss of gain in the performance. The method is a powerful tool to analyse in a preliminary phase a design problem involving a high amount of variables and complex physical relations by means of combining different multi‐disciplinar calculation codes and performing statistical treatments. Copyright © 2017 John Wiley & Sons, Ltd.     

基于CFD的水平轴风力机叶尖小翼增功研究

基于风力机叶片增功装置设计要求,以NREL 5 MW叶片为设计原型,以扭角、上反角及后掠角3种小翼外形参数为优化因素设计正交试验表,每种因素分别选取4个水平值,采用计算流体力学(CFD)方法对加装16种不同构型小翼的叶片进行数值模拟。计算结果表明,叶片整体可增功约1.466%,同时推力增加约1.570%;影响扭矩的最主要因素为扭角,影响推力的最主要因素为上反角;通过分析叶片近尾迹流场发现,优化的叶尖小翼布局可改变叶片叶尖涡强度分布,调整叶尖翼型截面气动力特性,进而改善叶片气动性能。     

风电叶片联接结构常规强度校核方法

风电叶片联接结构是联接叶片和轮毂的唯一结构，其安全性设计非常重要。文中介绍了风电叶片“T”型叶根联接结构的常规强度校核方法。     

A Study of 3D Aerodynamic Design for a Transonic Compressor Blading Optimized by the Locations of Aerofoil Maximum Thickness and Maximum Camber

A design procedure for improving the efficiency of a transonic compressor blading was proposed based on a rapid generation method for three-dimensional blade configuration and computational meshes, a three-dimensional Navier-Stokes solver and an optimization approach. The objective of the present paper is to design a transonic compressor blading optimized only by selection of the locations of maximum camber and maximum thickness for the airfoils at different span heights and to study how do these two design parameters affect the blade performance. The blading configuration and the computational meshes can be obtained very rapidly for any given combination of maximum camber and maximum thickness. The computational grid system generated is used for the Navier-Stokes solution to predict adiabatic efficiency, total pressure ratio and flow rate. As a main result of the optimization, adiabatic efficiency was successfully improved.     

Numerical simulation of ice accretion phenomena on rotor blade of axial blower

Ice accretion is the phenomenon that super-cooled water droplets impinge and accrete on a body. It is well known that ice accretion on blades and airfoils leads to performance degradation and severe accidents. For this reason, experimental investigations have been carried out using flight tests or icing tunnels. However, it is too expensive, dangerous, and difficult to set actual icing conditions. Hence, computational fluid dynamics is useful to predict ice accretion. A rotor blade is one of jet engine components where ice accretes. Therefore, the authors focus on the ice accretion on a rotor blade in this study. Three-dimensional icing phenomena on the rotor blade of a commercial axial blower are computed here, and ice accretion on the rotor blade is numerically investigated.