Hashin Failure Theory Based Damage Assessment Methodology of Composite Tidal Turbine Blades and Implications for the Blade Design

A damage assessment methodology based on the Hashin failure theory for glass fiber reinforced polymer(GFRP)composite blade is proposed. The typical failure mechanisms including the fiber tension/compression and matrix tension/compression are considered to describe the damage behaviors. To give the flapwise and edgewise loading along the blade span, the Blade Element Momentum Theory(BEMT) is adopted. In conjunction with the hydrodynamic analysis, the structural analysis of the composite blade is cooperatively performed with the Hashin damage model. The damage characteristics of the composite blade, under normal and extreme operational conditions,are comparatively analyzed. Numerical results demonstrate that the matrix tension damage is the most significant failure mode which occurs in the mid-span of the blade. The blade internal configurations including the box-beam, Ibeam, left-C beam and right-C beam are compared and analyzed. The GFRP and carbon fiber reinforced polymer(CFRP) are considered and combined. Numerical results show that the I-beam is the best structural type. The structural performance of composite tidal turbine blades could be improved by combining the GFRP and CFRP structure considering the damage and cost-effectiveness synthetically.

Optimized Design of Bio-Inspired Wind Turbine Blades

To enhance the aerodynamic performance of wind turbine blades,this study proposes the adoption of a bionic airfoil inspired by the aerodynamic shape of an eagle.Based on the blade element theory,a non-uniform extraction method of blade elements is employed for the optimization design of the considered wind turbine blades.Moreover,Computational Fluid Dynamics(CFD)is used to determine the aerodynamic performances of the eagle airfoil and a NACA2412 airfoil,thereby demonstrating the superior aerodynamic performance of the former.Finally,a mathematical model for optimizing the design of wind turbine blades is introduced and a comparative analysis is conducted with respect to the aerodynamic performances of blades designed using a uniform extraction approach.It is found that the blades designed using non-uniform extraction exhibit better aerodynamic performance.

涡轮叶片气动设计软件BladeDesign

涡轮叶片气动设计软件BladeDesign将涡轮气动设计中迭代最频繁的叶栅几何设计、S1流面计算、叶片积叠三个环节集成起来,极大地提高了涡轮部件设计的效率。叶栅型线设计采用目前流行的Bezier曲线,叶栅造型方法充分考虑了工程实际。集成的S1流面计算网格划分采用ANSYS ICEM CFD 11.0,分析采用ANSYS CFX 11.0。软件提供了与ANSYS TurboGrid的接口,用于生成叶片排的全三维流场计算网格。

Research on Low Cycle Fatigue Reliability-based Robust Design Optimization of Turbine Blade

针对涡轮叶片低周疲劳可靠性稳健设计优化问题，对叶片材料进行了高温疲劳试验，采用定量方程随机化方法处理试验数据，获得叶片材料的概率-应变-寿命曲线。采用贝塞尔曲线描述叶片型线方程，建立了涡轮叶片结构及流场的参数化模型，采用热-流-固耦合有限元法对涡轮流场和叶片进行了数值分析，得到叶片动能效率和应力应变分布特性。建立了叶片疲劳可靠性稳健设计优化模型，并采用响应面法获得叶片结构性能函数和极限状态函数，将叶片低周疲劳可靠性作为基本约束条件，采用序列二次规划优化法得到设计优化结果。研究结果表明，优化后的叶片低周疲劳可靠性以及稳健性显著提高，模型及方法正确可行，可用于涡轮叶片以及其他复杂结构的低周疲劳可靠性稳健设计优化。

Convergence Analysis of the Numerical Solution for Cathode Design of Aero-engine Blades in Electrochemical Machining

As a main difficult problem encountered in electrochemical machining （ECM）, the cathode design is tackled, at present, with various numerical analysis methods such as finite difference, finite element and boundary element methods. Among them, the finite element method presents more flexibility to deal with the irregularly shaped workpieces. However, it is very difficult to ensure the convergence of finite element numerical approach. This paper proposes an accurate model and a finite element numerical approach of cathode design based on the potential distribution in inter-electrode gap. In order to ensure the convergence of finite element numerical approach and increase the accuracy in cathode design, the cathode shape should be iterated to eliminate the design errors in computational process. Several experiments are conducted to verify the machining accuracy of the designed cathode. The experimental results have proven perfect convergence and good computing accuracy of the proposed finite element numerical approach by the high surface quality and dimensional accuracy of the machined blades.

The Development of Highly Loaded Turbine Rotating Blades by Using 3D Optimization Design Method of Turbomachinery Blades Based on Artificial Neural Network & Genetic Algorithm

In order to improve turbine internal efficiency and lower manufacturing cost, a new highly loaded rotating blade has been developed. The 3D optimization design method based on artificial neural network and genetic algorithm is adopted to construct the blade shape. The blade is stacked by the center of gravity in radial direction with five sections. For each blade section, independent suction and pressure sides are constructed from the camber line using Bezier curves. Three-dimensional flow analysis is carried out to verify the performance of the new blade. It is found that the new blade has improved the blade performance by 0.5%. Consequently, it is verified that the new blade is effective to improve the turbine internal efficiency and to lower the turbine weight and manufacturing cost by reducing the blade number by about 15%.

The Design of Stall-Regulated Wind Turbine Blade for a Maximum Annual Energy Output and Minimum Cost of Energy Based on a Specific Wind Statistic

The design of a stall-regulated wind turbine to achieve a maximum annual energy output is still a formidable task for engineers. The design could be carried out using an average wind speed together with a standard statistical distribution such as a Weibull with k = 2.0. In this study a more elaborated design will be attempted by also considering the statistical bias as a design criterion. The wind data used in this study were collected from three areas of the Lamtakong weather station in Nakhonratchasima Provice, the Khaokoh weather station in Phetchaboon and the Sirindhorn dam weather station in Ubonratchathani, Thailand. The objective is to design a best aerodynamic configurations for the blade (chord, twist and pitch) using the same airfoil as that of NREL Phase VI wind turbine. Such design is carried out at a design wind speed point. Wind turbine blades were optimized for both maximum annual energy production and minimum cost of energy using a method that take into account aerodynamic and structural considerations. The work will be carried out by the program “SuWiTStat” which was developed by the authors and based on BEM Theory (Blade Element Momentum). Another side issue is the credibility of the Weibull statistic in representing the real wind measurement. This study uses a regression analysis to determine this issue.

NON-DIMENSIONAL DESIGN PARAMETERS FOR FOD TOLERANT FAN BLADES

Non-dimensional design concept for FOD tolerant fan blades is introduced based on the analyses of simplified impact models. The fan blades arc idealized as either beams or plates of elastic or rigid-plastic materials. The case of constant force impact as well as that of mass impact is analyzed. The centrifugal force effects are also considered in the beam models. The critical fracture conditions arc shown in simple npn-dimensional formulae or diagrams for each case.

Structure Design of Turbo-Jet Engine Blade with Feature Based Parametric Modeling

On the platform of UG general CAD system, a customized module dedicated to turbo-jet engine blade design is implemented to support the integration of CAD/CAE/CAM processes and multidisciplinary optimization of structure design. An example is presented to illustrate the related techniques.

气动翼型涡流发生器与风力机翼型同步优化设计

针对目前风力机叶片翼型与涡流发生器相互独立的串行设计方法,导致不能最大限度的设计出气动性能最佳的风力机新叶片加装新型涡流发生器。这里提出带气动翼型的涡流发生器与风力机叶片翼型同步设计方法,利用B样条函数分别表达叶片翼型与涡流发生器气动形状,以最大升阻比及失速前最大升力系数为多目标函数建立优化数学模型,结合CFD技术与粒子群算法对原始叶片翼型DU97-W-300与CLARKY翼型涡流发生器进行同步优化,优化结果表明:相比原始叶片翼段加装CLARKY翼型涡流发生器,优化后的升力系数为2.378,提高了9.3%,升阻比为63.335,提高了7.5%;且对优化前后的流线图及涡量云图进行了对比分析,说明优化后叶片加装涡流发生器翼型可产生更大的诱导涡,能够有效抑制叶片表面流体分离。这里研究对于叶片与涡流发生器的设计及应用具有很好的参考与借鉴意义。

融合多源数据挖掘信息的非轴对称端壁/叶身联合成型设计空间知识挖掘

为厘清联合成型设计空间各造型方法对涡轮叶栅性能提升的贡献,将基于总变差分析的全局敏感性分析方法与平行坐标系及直方图、散点图等可视化技术相结合,提出了将多源数据挖掘信息进行融合的设计空间知识挖掘框架,并利用该框架对某小展弦比叶栅端壁/叶身联合成型设计空间进行知识挖掘。结果表明:叶栅气动损失增减对基元型线微调十分敏感;非轴对称端壁所带来的损失减少量与型线微调接近,但设计空间内不同非轴对称端壁样本性能波动较小,导致其重要性被全局敏感性分析方法低估;虽然单独采用弯叶片难以整体降低小展弦比叶栅损失,但将弯、型线微调和非轴对称端壁造型相结合可获得“1+1+1>3”的性能增益;在端壁/叶身联合成型设计空间内,将基元型线朝着后加载方向微调,并采用喉部附近下凹较深的非轴对称端壁造型及反弯叶片设计,可获得气动损失较小的叶栅设计。研究结果明晰了端壁/叶身联合成型设计空间优化解特征,可为类似小展弦比叶栅设计优化提供借鉴。

草莓大棚开沟起垄刀具数值模拟与工作参数响应面优化

草莓种植要求采用高垄栽培,为了提高开沟质量,现有开沟刀具一般是将旋耕刀具的刀身部分进行简单加宽处理。由于这种改进缺乏设计依据,当前的草莓大棚开沟刀具普遍存在作业质量不高和能耗较大的问题。为了进一步提高草莓大棚开沟刀具的性能,采用LS-DYNA软件建立了开沟刀具土壤旋抛数值仿真模型,并搭建田间实时试验装置,对仿真模型进行了分析验证。在此基础上,采用Box-Behnken响应面分析方法,以刀辊扭矩和残留粒子比例为响应值,建立了刀辊前进速度,刀轴转速和开沟起垄深度的二次回归模型,并对其进行优化。优化结果表明:前进速度0.38 m·s^(-1)、刀轴转速300 r·min^(-1)、开沟起垄深度300 mm,以此参数进行田间试验得到的扭矩为27.9 Nm,模型优化预测结果与田间试验相比相对误差小于5%,验证了优化模型和结果的可靠性。提出的新型的开沟刀具参数化设计方法可为大棚草莓开沟机具的设计优化提供参考。

基于RTCP控制算法的叶片加工六轴砂带磨床优化设计

基于叶片型面磨削工艺参数及工艺过程确定机床各坐标轴运动性能和磨削接触压力,进行叶片加工砂带磨床优化设计和频率分析。采用RTCP算法和传动链独立的算法结构模式,建立转轴数学模型、工件传动链算法库以及刀具传动链算法库。对设计的机床伺服速度进行测试,优化机床结构薄弱环节,满足叶片型面及全特征型面磨削要求。通过有限元分析研究X,Y,Z轴的变形量,计算六轴砂带磨床1阶~6阶的固有振动频率,并进行分析和优化,提高了叶片磨削的轮廓精度,加工经济效益显著。

涡轮钻具定转子三维叶型的设计方法研究

为了研究涡轮三维叶型的水力性能,基于等环量法提出了一种涡轮三维叶型的理论造型方法,并推导出了该涡轮三维叶型的特性参数计算方法。利用ANSYS Fluent对同尺寸下的涡轮三维叶型和二维叶型进行了数值模拟分析其水力特性。研究结果表明:与二维叶型相比,涡轮三维叶型的压降减小约50%,水力效率提高约5%。对比了三维叶型涡轮扭矩的理论计算结果与仿真结果,发现它们的误差在10%左右,在实际工程允许范围内。研究结果可为涡轮三维叶型的设计提供理论依据。

考虑叶片造型的压气机流动稳定性模型研究进展

压气机实际稳定裕度是否达到指标直接决定了发动机是否可以投入使用.目前的压气机气动设计体系中缺乏一种高效、准确的评估失稳边界的工具,导致在设计定型后依然存在实际稳定裕度不足的风险.因此迫切需要发展快速可靠的压气机稳定性预测工具以供设计阶段使用.现代航空压气机叶片的气动设计朝着三维精细化方向发展,如何在设计阶段考虑叶片三维造型的变化对稳定性的影响愈发关键.传统的激盘/半激盘模型难以精细捕捉到三维叶片造型对流动稳定性的影响,而非定常数值模拟方法对计算资源的消耗在压气机设计阶段难以承受.为了在精细考虑叶片造型影响的同时提高计算效率,为气动设计阶段提供稳定性评估工具,本团队首先在2013年提出了叶轮机流动稳定性通用理论,通过分布式叶片力源项建模考虑复杂叶片造型的影响,通过系统特征值描述流动稳定性.继而针对不同的预测目标和应用条件,发展了3种简化模型:子午面模型、流线模型和径向展开模型.其中子午面模型能够准确刻画叶尖间隙、叶片掠和叶片加载方式等关键设计参数对流动稳定性的影响,为设计阶段提供了一种可靠的失稳边界预测工具;流线模型可以快速评估展向各条流线系统的流动稳定性,并定量地给出流动稳定性最为薄弱的区域,从而有针对性地指导叶片扩稳设计;径向展开模型可以快速地预测离心压气机的流动失稳点,定量评估离心压气机流动稳定性.以上模型可以应用于压气机气动设计体系,为设计定型的压气机提供了可靠的稳定性评估方法,为压气机气动/稳定性一体化设计提供了技术储备.

棉花秸秆无筛粉碎机的设计与试验

针对棉花秸秆因木质化程度较高、韧性强,还掺有棉絮,在有筛粉碎机粉碎过程中排料困难、筛片易堵塞等问题,设计了一种棉花秸秆无筛粉碎机,通过调整出料口面积来实现粉碎室内气体流量的改变,获得不同粉碎粒度的棉花秸秆成品;对粒度分级装置、粉碎刀辊等主要部件的结构进行了确定;阐述了粉碎过程中棉花秸秆的受力过程,确定了L改进型锤片的关键参数,对机具的L改进型锤片和抛送叶片进行了结构和排列设计。Fluent仿真分析结果表明:L改进型锤片相比直刀型锤片更有利于提高棉花秸秆在粉碎室内的流动性并在粉碎室内部形成更大的负压。以L改进型锤片数量、粉碎刀辊转速、出料口面积为试验因素,以棉花秸秆粉碎粒径合格率为试验指标,进行三因素三水平正交试验,确定影响棉花秸秆粉碎粒径合格率显著性的因素由大到小分别为:粉碎刀辊转速、出料口面积和L改进型锤片数量。确定较优参数组合为L改进型锤片数量140把,粉碎刀辊转速2660 r·min^(-1),出料口面积136500 mm^(2)。采用较优参数组合进行样机田间试验,测得棉花秸秆粉碎粒径合格率为93.7%,能够满足棉花秸秆粉碎机实际生产需要。

特大流量潜水贯流泵叶轮水力设计优化研究

针对Q=100 m³/s的特大流量潜水贯流泵装置,对叶轮叶片及导叶进行水力设计,基于正交试验方法进行优化,对最优泵装置方案进行CFD计算,探究机组外特性,并对导叶出口边齐平与不齐平的两种导叶安放型式机组水力性能参数进行了对比分析。研究结果表明:叶轮轮毂比为0.4,叶片数为4,导叶数为6时,泵装置的效率最高,泵装置的最高效率为80.52%;1.0Qd工况下泵装置扬程为2.73 m,效率为74.68%;0.87Qd工况下泵装置扬程为4.50 m,效率为80.14%;1.12Qd工况下泵装置扬程为0.45 m,效率为23.77%;从扬程、效率、导叶段水力损失等参数,得出不齐平的导叶出水边安放型式机组水力性能更优。针对叶轮和导叶的造型方法及正交试验与CFD计算组合的优化方法均提高了水力优化工作效率,适于推广应用,研究成果对低扬程特大流量水泵开展的计算分析工作也为潜水贯流泵大型化发展提供了一定的水力性能参考。

多室连续混合设备桨叶设计参数优化

为优化多室连续混合设备的设计参数,开展多室连续混合设备桨叶多目标优化研究。以混合室单位体积功耗和混合室轴截面有效混合面积为目标函数,峰值剪切应力为约束变量,建立了基于径向基函数的多目标优化模型,采用正交试验设计和遗传算法对桨叶进行了参数优化,并对优化结果进行了CFD仿真和试验验证。结果表明,多室连续混合设备特性参量的显著影响因素为桨叶外径、桨叶-壁面间隙以及桨叶转速。相对于初始设计,优化后单位体积功耗降低了14.90%,混合室轴截面有效混合面积增加了4.10%,二者乘积降低了11.47%,峰值剪切应力降低了21.28%,在混合能力降低较少的情况下安全性获得了较大的提升,证明了基于径向基函数的多目标遗传算法在多室连续混合设备性能优化上的可行性。

采棉机风机叶片优化与流场分析

风机作为采棉机气力输送系统的核心部件,其性能优劣将影响采棉机的作业效率。为提高采棉机气力输送系统的最大风量,针对采棉机用多翼离心风机叶片进行优化设计。为了获得代理模型所需的基本数据,建立了CFD数值模型并采用拉丁超立方实验在设计空间内生成20组样本。基于样本数据,建立了出口风量与设计变量的近似模型,采用智能优化算法获得最优设计方案。优化后的设计方案相较于原型机,出口风速明显增大。CFD数值计算分析风机的动态特性,结果表明,在多转速工况下风量均有明显提升,其在额定转速工况下,风量提升17.27%。

不同叶顶弯曲对离心叶轮性能影响机理

面对现代发动机对离心叶轮性能需求不断提高的背景,叶顶弯曲具备有效改善离心叶轮气动特性的能力,本文通过数值模拟的方式对不同叶顶弯曲方向、弯曲形式、弯曲程度的压气机性能进行预测,基于仿真结果对不同流动状态下压气机内部流场进行分析,给出了叶顶弯曲压气机性能变化机理。结果显示:负弯叶轮有助于提升压气机峰值效率,提高压气机堵塞流量。正弯叶轮则在损失部分效率的情况下,使压气机失速裕度得到提升。弯曲叶轮主要通过改善叶顶前缘载荷,重构叶轮通道内静压分布,从而削弱激波强度、减少二次流损失、抑制低能涡发展,达到提升压气机性能的目的。本文研究结果可为离心压气机叶片改型设计提供参考。