潮流能水轮机单向流固耦合计算方法

基于ANSYS和CFX软件实现了垂直轴潮流能水轮机单向流固耦合瞬态计算。将二维CFX流体计算结果作为水轮机受力,将流体与结构中相对应的节点压力施加到结构有限元模型上,从而完成水轮机工作状态主轴应变计算。将计算结果与实验结果进行对比发现二者吻合较好,说明单向流固耦合方法是将流体计算结果传递到结构分析的有效方法,在潮流能水轮机叶片小变形的条件下能够准确的预报结构响应的趋势,有效的计算垂直轴水轮机的结构强度,对其结构校核起到很好的指导作用     

一种小型流体阻尼隔振器的设计与实验

针对惯导敏感元件的振动隔离问题,提出一种小型流体阻尼隔振器,采用金属膜片作为弹性元件,通过黏性流体间隙流动产生阻尼耗能。给出计算金属膜片挠度的解析式,建立隔振器动力学模型,获得刚度-阻尼并联的两参数模型的动刚度表达式,进而分析两参数原理模型的振动传递特性,给出根据隔振性能指标设计刚度、阻尼的方法。根据测试与理论计算结果,二者的加速度传递率曲线吻合良好,且实验结果表明可将共振峰值抑制在6 dB以下。     

潮流能柔性叶片水轮机水动力学特性分析

提出了一种新型海洋潮流能获取装置--潮流能柔性叶片水轮机.其叶片采用柔性材料,可适应流体发生形变,从而它能自动调节攻角,能充分利用流体的升力效应和阻力效应做功,具有独特的水动力学特性.以柔性叶片水轮机获能系数(Cp)为主要研究目标,通过水槽模型实验对其影响因素进行了研究.实验证实了该柔性叶片水轮机的独特水动力学特性,而且证明,叶片形状和水轮机结构形式是其性能的主要影响因素,并通过分析得到了具有较佳水动力学特性的水轮机的叶片形状和水轮机结构形式.     

环境振动试验传感器布置优化方法研究

为了快速获得最优的加速度传感器布置位置,依据电动振动台多点控制原理和夹具传递函数特性,建立了传感器布置优化计算模型。以一夹具为实例建立有限元模型,利用nastran软件求出传递函数,然后,根据所建优化模型获得传感器最优布置位置,最后,通过夹具振动试验测试夹具与试品连接部位处的响应。测试结果表明优化方法所得的响应加速度均方偏离度明显小于传统方法,证明了该优化方法是实用和可行的,并能为环境振动试验中的传感器布置和夹具设计提供实践与理论指导。     

离心泵流体激励力诱发的振动:蜗壳途径与叶轮途径

研究蜗壳、叶轮途径流体力诱发的离心泵振动,分析CFD蜗壳内表面流体力作用下电机-离心泵-机架FEM模型瞬态响应;用Newmark-β算法分析CFD叶轮表面流体合力、合力矩作用下叶轮-转轴-支撑-机架转子动力学模型响应;并对比蜗壳、叶轮两条途径流体力诱发离心泵基座振动。结果表明,泵内表面流体压力脉动为宽频激振源,会诱使离心泵系统产生各阶模态振动;流体力通过叶轮途径诱发离心泵基座振动位移幅值谱最大峰值出现在叶轮转频处,振动加速度幅值谱最大峰值出现在叶轮流道通过频率处,而非叶片通过频率处;流体力通过蜗壳途径诱发的离心泵基座振动远小于叶轮途径诱发的振动,叶轮-转轴-支撑-机架为流体激励诱发离心泵基座振动的主要途径。     

基于输出预估自抗扰策略的加筋壁板结构多模态振动主动控制

针对加筋壁板结构中存在的模型难以精确确定和多模态外界干扰等问题,基于加速度传感器,提出了一种不依赖结构精确数学模型的多模态线性自抗扰振动主动控制(Linear Active Disturbance Rejection Control)策略。由于加速度传感器和压电驱动器的异位配置不可避免地使得整个控制系统存在时延。为解决该问题,利用Smith预估器的原理,引入输出预估器来补偿时延,这样设计的自抗扰振动主动控制器能够很好地解决时延对结构振动性能的影响。基于dSPACE实时仿真平台、利用加速度传感器、压电片驱动器,设计并建立四面固支压电加筋壁板结构实验系统,对提出的控制方法进行试验比较研究。最后的试验结果表明,采用提出的具有输出预估功能的自抗扰振动控制器,能够快速有效地抑制结构的多模态振动。     

关于“应用功率谱测量振动表面声强”的讨论

在“应用功率谱测量振动表面声强”(刊于《噪声与振动控制》1990年第4期,以下简称“应”)文中引用了[1,2]中振动表面声强谱为质点振速与声压互功率谱的实部,测量中测量仪器两通道的相位差对测量结果有严重影响。两通道的相位差包括声传感器和加速度传感器(测振速用)的相位差和放大通路的相位差,即使两个同类型传感器,其相差也是难以控制,至于两个不同类传感器,由于原理与结构不同,其相差更是难以估计和控制。为了避开这个困难,“应”文作者用声压自功率谱G_p(ω),声压自功率谱梯度(?)G_p/(?)n(?),及振速自功率谱G_u(ω)来估算振动表面声强,这是有意义的设想。     

核岛结构PCS水箱FSI效应简化方法研究

高置冷却水箱是核电厂非能动安全壳冷却系统(PCS)的重要组成部分,在进行动力分析时,必须考虑冷却水与屏蔽厂房之间的流固耦合(FSI)效应。由于FSI效应问题复杂,数值分析耗时较长,因此,在研究核岛结构动力分析时,有必要采用简化方法,在满足计算精度要求的前提下,提高计算效率。基于Housner模型,提出一种考虑液体-水箱相互作用的简化模型。采用ADINA软件分别进行水箱FSI模型和简化模型的核岛结构三向地震反应分析,分析了FSI模型和简化模型结构反应的峰值加速度、楼层反应谱和有效应力相对误差。结果表明:提出的水箱简化模型可用于高置冷却水箱核岛结构三向地震反应分析,能够很好地模拟FSI效应。     

基于卷积神经网络优化的水轮机振动信号识别

提出了一种基于蝙蝠算法优化卷积神经网络的水轮机振动信号识别方法。首先对水轮机时域加速度振动信号进行测量、提取和归一化处理,采用蝙蝠算法对卷积神经网络训练过程中的超参数权值和偏置值进行优化,然后对10 种不同测点的水轮机振动信号进行实验,针对每个测点的振动信号对水轮机8 种不同工况进行区分识别,最后将信号识别过程中各参数对传统卷积神经网络识别结果的影响进行针对性分析。结果表明：所建立的基于蝙蝠算法优化卷积神经网络的识别模型具有良好的稳定性和较高的识别精度,能够准确识别振动信号,识别结果准确率均在94 %以上,与传统卷积神经网络对比,信号识别准确率显著提升,最高达到20.78 %。同时可以看出,振动数据输入长度、样本尺寸和训练次数对传统卷积神经网络训练效果影响显著。研究结论可为水轮机振动识别、工况识别和故障识别提供理论依据。     

轨道随机不平顺影响下高速铁路地基动力分析模型

考虑轨道随机不平顺影响,建立了移动车辆-有砟轨道-路基-层状地基垂向耦合振动解析模型。模型中,将虚拟激励法和解析的波数-频率域法有效结合起来,直接由轨道不平顺的功率谱密度得到准确的动态轮轨力功率谱。将移动列车轴荷载和轨道随机不平顺引起的动态轮轨力考虑为傅里叶级数表示的谐波叠加形式,根据线性系统叠加原理,求得地基动力响应功率谱估计值与时程结果。利用在波数域内直接计算位移频谱、划分合适谐波区间等技术,显著提高了随机振动响应功率谱和时程的计算效率。对比分析了地基表面测点垂向振动加速度时程与频谱的理论计算与现场实测结果,证明了本文模型的合理性。     

叶片厚度变化对船用轴流涡轮性能的影响

目的 研究船用轴流涡轮叶片厚度对涡轮性能的影响，为高性能涡轮设计提供参考。方法 基于计算流体力学(CFD)仿真，模拟分析了2种叶片厚度下的叶片压力、涡轮流通特性及效率特性。结果 在相同膨胀比条件下，当叶片厚度从16.12 mm增大至16.61 mm(叶根处宽度)时，折合流量下降。当膨胀比从1.5增大到2时，加厚叶片的折合流量从0.216增长至0.238，未加厚叶片的折合流量从0.219增长至0.243。当膨胀比从2继续增大时，涡轮流量随膨胀比的变化而趋于平缓。当膨胀比约为2时，涡轮效率达到最高。采用加厚叶片时，涡轮效率最高达到0.815;当膨胀比为1.5~2.68时，涡轮效率在0.8以上。当采用未加厚叶片时，涡轮效率最高达到0.808;当膨胀比为1.6~2.38时，涡轮效率才能达到0.8以上。结论 转子叶片的加厚有利于降低能量损失，且叶片表面产生旋转涡流有助于减轻尾缘处的速度冲击，进一步降低了能量损失;但转子叶片过厚会限制流体的通量，使转子的通流面积减小，涡轮的折合流量减小;在大膨胀比条件下，加厚叶片涡轮的堵塞流量明显小于未加厚涡轮的。涡轮效率随膨胀比的增大而先增大后减小。随着叶片厚度的增大，涡轮整体效率增大，高效区范围增大。     

汽轮机叶片动频的转子调频非接触测量法

叶片的共振断裂是叶片损伤的主要形式,为了避免叶片共振,如何准确地测得叶片的动频是保证叶片安全工作的关键。本文提出采用转子调频非接触测量法测量汽轮机叶片的动频。采用该方法只需要在叶片顶部固定支架上安装两只光学传感器及在转子的适当位置安装一只转子旋转同步传感器,就可以测量工作轮上所有叶片的动步,从而克服了传统接触应变片法仅能测量某几个叶片动频、应变片寿命短等缺点,同时也避免了安装多只传感器工艺复杂、费用较高等问题。本文通过实验验证了该方法的可行性。     

汽轮机间隙气流激振力分析

基于流体动力学,应用动量定理研究汽轮机直叶片、短扭叶片、长扭叶片以及汽轮机调节级由于间隙引起的气流激振力问题,综合考虑了叶片的各项设计参数并应用理论分析方法导出普遍适用的计算公式,解决了Alford公式中需人为选取效率系数的困难。数值实验的结果表明,所导出的计算公式是可靠的。     

Vibration based damage detection of rotor blades in a gas turbine engine

This paper describes the problems concerning turbine rotor blade vibration that seriously impact the structural integrity of a developmental aero gas turbine. Experimental determination of vibration characteristics of rotor blades in an engine is very important from fatigue failure considerations. The blades under investigation are fabricated from nickel base super alloy through directionally solidified investment casting process. The blade surfaces are coated with platinum aluminide for oxidation protection. A three dimensional finite element modal analysis on a bladed disk was performed to know the likely blade resonances for a particular design in the speed range of operation. Experiments were conducted to assess vibration characteristics of bladed disk rotor during engine tests. Rotor blade vibrations were measured using non-intrusive stress measurement system, an indirect method of blade vibration measurement utilizing blade tip timing technique. Abnormalities observed in the vibration characteristics of the blade tip timing data measured during engine tests were used to detect the blade damage. Upon disassembly of the engine and subsequent fluorescent penetrant inspection, it was observed that three blades of the rotor assembly were identified to have damaged. These are the blades that exhibited vibration abnormalities as a result of large resonant vibration response while engine tests. Further, fractographic analysis performed on the blades revealed the mechanism of blade failures as fatigue related. The root cause of blade failure is established to be high cycle fatigue from the engine run data history although the blades were put into service for just 6 h of engine operation.     

Accelerated LCF‐creep experimental methodology for durability life evaluation of turbine blade

This paper proposes an accelerated low cycle fatigue (LCF)‐creep experimental methodology in laboratory to investigate the durability life of turbine blades. A typical mission profile of the turbine blade was obtained by means of rain flow counting method, considering both the actual flight condition and ground test data. Finite element analysis (FEA) was conducted to obtain the stress and temperature fields of turbine blade. A test system was constructed to conduct LCF‐creep experiments of turbine blades, simulating the stress and temperature distributions of critical section properly. LCF‐creep experiments of full‐scale turbine blades were performed under a trapezoidal loading spectrum. Experiment results showed that the durability life of turbine blade based on numerical method was longer than that based on this experimental methodology, even an order of magnitude. Furthermore, this experimental methodology helped to extend the service life of this blade safely, and its validity was verified in actual service condition.     

强耦合流激振动的建模及求解的预测多修正算法

将基于Lagrangian描述的结构振动问题与基于Eulerian描述的不可压缩粘性流动问题通过流-固系统的功率耗散平衡在广义变分原理的框架下统一,建立了描述强耦合流激振动的有限元控制方程。采用将Newmark法和Hughes预测多修正法相结合的求解策略,提出了基于稳定有限元法求解小变形弹性结构强耦合流激振动的计算方法,用于计算复杂边界条件下的流激振动问题。以三维混流式水轮机叶道为例的数值算例表明,模拟结果与试验实测结果吻合较好。     

Aerodynamic design and analysis of a 10 kW horizontal-axis wind turbine for Tainan,Taiwan

The purpose of the present study is to develop a small-scale horizontal-axis wind turbine (HAWT) suitable for the local wind conditions of Tainan, Taiwan. The wind energy potential was first determined through the Weibull wind speed distribution and then was adapted to the design of the turbine blade. Two numerical approaches were adopted in the design and analysis of the HAWT turbine blades. The blade element momentum theory (BEMT) was used to lay out the shape of the turbine blades (S822 and S823 airfoils). The geometry of the root region of the turbine blade was then modified to facilitate integration with a pitch control system. A mathematical model for the prediction of aerodynamic performance of the S822 and S823 airfoils, in which the lift and drag coefficients are calculated using BEMT equations, was then developed. Finally, computational fluid dynamics (CFD) was used to examine the aerodynamic characteristics of the resulting turbine blades. The resulting aerodynamic performance curves obtained from CFD simulation are in agreement with those obtained using BEMT. It is also observed that separation flow occurred at the turbine blade root at the tip speed ratios of 5 and 7.     

Local Buckling Prediction for Large Wind Turbine Blades

Local buckling is a typical failure mode of large scale composite wind turbine blades. A procedure for predicting the onset and location of local buckling of composite wind turbine blades under aerodynamic loads is proposed in this paper. This procedure is distinct from its counterparts in adopting the pressure distributions obtained from Computational Fluid Dynamics (CFD) calculations as the loads. The finite element method is employed to investigate local buckling resistance of the composite blade. To address the mismatch between the unstructured CFD grids of the blade surface and the finite shell elements used during the buckling analysis, an interpolation code is developed, allowing mapping the pressure computed by using CFD to the finite element model. With the well documented National Renewable Energy Laboratory phase VI wind turbine blade, the procedure is demonstrated to be capable of yielding satisfactory results. Comparison with results obtained by using the blade surface pressure distributions calculated using a simple method is also conducted.     

基于Campbell理论的航空发动机涡轮叶片共振裕度分析

针对航空发动机涡轮叶片的共振特性会导致叶片发生疲劳断裂、振动失效等问题,本文以某型号航空发动机涡轮叶片为研究对象,开展共振裕度分析研究。首先基于试验自锤击法和有限元物理仿真计算两种方法同步分析叶片的振动特性,通过提取叶片在两种工作状态下前6阶的模态分析结果,验证了该模型的正确性与实用性。其次在已有模型基础上,通过绘制不同工作转速下的Campbell共振曲线图,结合该型号发动机的实际工况参数,进行了转速共振裕度的校核分析,对叶片上可能发生共振的工作转速进行了解析并提出优化及改进方案。本方法主要是为叶片的前期设计制造及共振安全性检验问题提供了充足的科学依据和方法。     

A computational procedure for prebending of wind turbine blades

Prebending of wind turbine blades constitutes a viable engineering solution to the problem of tower clearance, that is, ensuring that during wind turbine operation there is sufficient distance between the rotor blades and the tower to avoid collision. The prebent shape of the blade must be such that when the turbine rotor is subjected to wind and inertial loads, the blades are straightened into their design configuration. In this paper, we propose a method for accurate prediction of the prebent shape of wind turbine blades. The method relies on a stand‐alone aerodynamics simulation that provides the wind loads on a rigidly spinning rotor, followed by a series of structural mechanics simulations to determine the stress‐free prebent shape of the blade. This procedure involves only one‐way coupling between the fluid and structural mechanics, which avoids the challenges of solving the coupled fluid–structure interaction problem. The proposed methodology, which has no limitations on the blade geometry and structural modeling, is successfully applied to prebending of a 63‐m offshore wind turbine blade. Copyright © 2011 John Wiley & Sons, Ltd.