基于Kriging插值的失谐叶盘气动 结构耦合振动特性分析

以某型航空发动机压气机转子为研究对象,考虑叶盘间动静干涉的影响,对压气机叶盘转子内部的三维流场进行了模拟。通过静频试验引入叶片失谐量,基于Kriging模型完成了耦合界面载荷数据的传递,分析了压气机转子叶片表面非定常气动载荷的分布规律,并讨论了失谐和气动载荷对压气机转子叶盘系统振动特性的影响。结果表明：压气机叶片受到的气动载荷为非定常脉动压力,主导频率为动静干涉频率f0的倍频;在干涉周期T内,压力面和吸力面气动载荷的变化呈相反趋势,且压力面气动载荷的非定常性明显大于吸力面气动载荷的非定常性;失谐和气动载荷的作用加剧了叶盘系统的振动。研究结果为压气机叶盘转子系统的动力学设计提供了理论依据。     

组合压气机中尾迹与势流同频/异频干涉的叠加特性

为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化;当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。      

基于谐波平衡法的跨声速风扇颤振特性数值模拟

由于叶片振动诱发的非定常响应具有时间周期性的特点,采用频域谐波平衡计算技术,结合结构动力学分析方法,基于流固单向耦合的方式数值模拟了振荡叶片下的非定常流场,通过评估结构和流体之间的能量传递关系对叶片的颤振特性进行了预测。针对某两级风扇的第一级转子叶片,通过给定不同的转速和出口背压条件对比研究了叶片的气动弹性稳定性,并给出了叶片的颤振失稳边界,计算结果显示:在100%、95%、90%转速下的非失速工况中叶片存在失稳风险,意味着发生颤振的类型为超音速非失速颤振;不同工况下,激波下游和叶顶前缘附近气流做功的综和效应决定了叶片的气动弹性稳定性。     

动静干涉下低压涡轮非定常气动载荷研究

为研究动静干涉下轴向间距和尾缘锯齿结构对低压涡轮叶片非定常气动载荷的控制作用,对高效节能发动机(energy efficient engine,简称E3)低压涡轮最后一级的内部流场进行了数值仿真,研究了不同轴向间距和静叶尾缘锯齿结构两种情况下,下游动叶表面非定常气动载荷的变化规律。研究发现：增大轴向间距可以加强尾迹与主流的掺混,消除气流不均匀性,削弱下游动叶表面的非定常气动载荷;静叶采用尾缘锯齿结构不仅可以加强尾迹与主流的掺混,同时还会改变尾缘处的涡结构,对下游动叶前缘产生破坏性干涉效应,使其最大载荷波动降低约30%,减少静叶尾迹速度亏损75.7 m/s,还能适当提升涡轮的流通能力和时均效率。与采用直尾缘静叶的模型相比,采用锯齿尾缘静叶不仅能大幅度地改善涡轮的转静干涉效应和气动性能,还能在不影响涡轮效率的前提下,将涡轮轴向间距缩短10%。     

进气总管轮廓优化对轴流风机噪声的影响

针对一般情况下叶轮机械的非定常气流运动,特别是风扇的气动声学,文中测定轴流风机的气动声学特性和上游环境对其影响.在对叶轮机械各种噪声来源进行分析之后,研究了抽吸速度场的扰动所带来的影响,因此分析进气总管轮廓优化前后对轴流风机入口的影响.结果表明,噪声特别是宽带噪声产生于上游气流湍流水平的提高.     

分体滑动导叶可调涡轮激波与载荷波动机制

针对某柴油机用可调涡轮在低速工况下的低效强激波特征,提出并设计了一种分体滑动导叶,并在10%、40%和100% 3个典型开度下进行了定常/非定常数值计算。结果表明：分体滑动导叶在小开度下可实现对间隙泄漏流动的有效抑制,大幅度提高涡轮效率;在10%开度下,分体滑动导叶提高了涡轮10%的峰值效率,同时涡轮效率在40%和全开工况下也有不同程度的提高。此外,通过合理设计转静间距,分体滑动导叶尾缘激波被大幅度削弱。导叶间隙泄漏流和尾缘激波的抑制可有效弱化转子定子干涉强度,降低下游转子叶片表面载荷波动幅值,提高转子叶片的可靠性。     

密流比对压气机叶栅性能影响研究

对高压比跨音轴流压气机转子流动分析,论证了在10％～ 90％叶高范围内转子叶片采用二维设计方法是可行的.采用数值模拟方法,对超音、高亚音转子回转面叶栅进行全工况气动性能计算,研究密流比对于压气机叶栅气动性能的影响规律.结果 表明:密流比增加,超音叶栅总压比和效率均增大,结尾正激波前移,耐反压能力下降;高亚音转子叶栅气流转角增大,低损失气流角及范围增大.     

轴向间隙对对旋风机气动特性及总性能的影响

以一台矿用对旋风机为对象,采用CFD方法对6种不同轴向间隙方案下风机的气动性能进行了三维非定常数值计算,对不同轴向结构对风机压力脉动特性、性能和流场的影响进行分析研究。研究表明:对旋风机的非定常性受轴向间隙的影响较大,增加间距不仅能较好地削弱下游转子的位势干扰作用,同时也能降低上游转子的叶片尾迹影响;轴向间隙对风机效率、静压升以及两级效率、轴功率均有显著影响;增大轴向间隙会加剧掺混损失对风机性能的影响。     

大型风力机柔性叶片非线性气弹模态分析

针对风力机尺寸增大,叶片刚柔耦合和气弹耦合特性增强,研究大型风力机转动柔性叶片弯曲与扭转耦合变形下的气弹模态及其稳定性。为准确描述柔性叶片的非线性变形特性,采用"超级单元"将柔性叶片离散成若干个刚体,并由运动副与力元连接构成多体系统,而后通过牛顿-欧拉方程建立叶片非线性动力学方程;气动模型则采用叶素动量理论结合修正的B-L (Beddoes-Leishman, B-L)动态失速模型,计算非定常气动载荷;然后基于变分原理,线性化叶片结构与气动载荷动力学方程,构建转动叶片的气弹线性化状态方程。最后以NREL 5 MW叶片为研究对象,在确定尖速比下,分析大型柔性叶片转动条件下的气弹复模态,计算叶片气弹频率与气弹阻尼比,分析叶片气动阻尼对颤振的影响,探究大型叶片颤振失稳机理。     

掠形对高负荷风扇转子失稳机理的影响

以超高负荷两级风扇第一级前掠转子为研究对象,通过定常和非定常数值模拟手段对近失速点叶尖流场进行了深入分析。为探索失稳机理,与同等气动性能下的后掠转子进行了对比。结果表明:前掠转子在近失速工况下泄漏涡涡心并未发生破碎,其流动失稳是由于端壁机匣处的低能流体集聚所致。而后掠转子的泄漏涡与激波干涉导致其向下游发展中发生破碎,表现出与常规转子相似的失速特征。     

静叶尾迹对压气机动叶非定常气动载荷的影响

以某型航空发动机压气机转子系统为研究对象,建立了单级叶盘的三维结构及流场模型。通过对滑移网格(sliding mesh,简称SM)方法与运动坐标系(moving reference frame,简称MRF)方法在计算耗时和收敛性方面的比较,证明了运动坐标系方法的准确性和高效性。考虑前一级静叶尾迹的影响,求解压气机内部在不同时刻的流动特性,得到静叶尾迹对动叶流场的非定常干扰情况。经过对压气机叶顶和轮毂、动叶压力面和吸力面非定常气动载荷的分析发现:在动叶流场的前缘形成了较主流区压力和速度较低的不均匀流场,且在动叶前缘叶顶位置受到的气动载荷最为显著;动叶压力面和吸力面气动载荷的分布规律相反,从叶顶至轮毂、前缘至尾缘,压力面非定常气动载荷的大小和波动幅度逐步递减,而吸力面却与其相反,呈现出逐步递增的趋势。该研究为某型航空发动机压气机叶盘转子系统的动力学设计提供了理论依据。     

Analysis of tiltrotor whirl flutter in time and frequency domain

The whirl flutter phenomenon in a rotor is induced by in-plane hub forces, and imposes a serious limit on the forward speed. In this paper, based on Greenberg’s model, quasi-steady and unsteady aerodynamic forces are formulated to examine the whirl flutter stability for a three-bladed rotor without flexible wing modes. Numerical results are obtained in both time and frequency domains. Generalized eigenvalue solution is utilized to estimate the whirl flutter stability in the frequency domain, and Runge-Kutta method is used to analyze it in time domain. The effects of varying the pylon spring stiffness and the swashplate geometric control coupling upon the flutter boundary are investigated. An optimum pitch-flap coupling parameter is discovered through the parametric study. Aeroelastic stability boundaries are estimated with the three different aerodynamic models. It is found that the analysis with the full unsteady aerodynamics predicts the highest flutter speed.     

1.5级燃气轮机上、下游密封系统非定常流动的数值研究（英文）

For purpose of a more comprehensive understanding of the flow in the disk cavities, the sealing flow in both the upstream and downstream disk-cavity system of a 1.5 stage turbine is investigated by means of CFD methods.The result indicates that the flow structures in the cavity of the unsteady results are less stable than that of the steady results. The comparison of the upstream and downstream results shows that the downstream sealing flow generally is the mirror image of the upstream sealing flow, while the downstream rim seal performs better as the main flow works on the rotor blades. In addition, the proportions of eigenvalues of the first POD mode demonstrates strong unsteady characters of the flow in the rim seal. The frequency spectra of the POD time coefficient indicate that the most prominent frequency of the flow field in the rim seal is caused by the rotor blade.     

离心压缩机扩压器叶片不稳定脉动力及气动噪声预测

参照轴流压气机动叶尾迹衰减规律，利用流动损失系数代替叶栅阻力系数，给出了离心叶轮出口粘性尾迹速度亏缺值及其宽度的计算方法。基于薄机翼理论，每个叶片用一组连续分布涡来代替，把环形叶栅片模化成在圆周上连续分布涡组的等分排列，建立了在离心叶轮粘性尾迹作用下扩压器叶片上不稳定力计算式。在此基础上对离心压缩机气动噪声进行了理论计算。并与实测值进行了比较，二者吻合较好。     

Fast-response total pressure probe for turbomachinery application

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe for the measurement of the total pressure field at the exit of blades. The result of measurement in a one-stage axial turbine is also presented. The fast-response total pressure probe is fabricated by installing a fast-response pressure sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use more than four sensors. The probe is applied to the one-stage axial turbine in order to measure the instantaneous total pressure downstream of rotor blades. The measured instantaneous signal is decomposed to obtain the blade-to-blade pressure distribution. The pressure distribution due to blade passing is clearly captured. Due to the loss generation in the casing region, the total pressure and its amplitude of fluctuation by the blade passing are lower in the shroud and hub region than in mid-span. The total pressure distribution at the exit of the rotor blade is found to be slightly different from blade to blade due to the geometric difference and the different relative positions of the rotor blades and stator vanes. The developed probe successfully measures the accurate total pressure distribution at the rotor exit, and allows the evaluation of the loss distribution and the accurate performance of turbomachinery.     

Nonlinear acoustic diametral modes of pressure pulsations during flutter of rotor blades of a turbocompressor

Features of pressure pulsations of flow during flutter on the bending frequency of rotor blades of an axial turbocompressor, which occurs after incomplete resonance at the torsion frequency of blades with a harmonic of rotor speed, are investigated. The frequency spectrum of nonlinear acoustic diametral modes is predicted, based on Navier-Stokes equations ensemble-averaged. This makes it possible to identify characteristic series determined by the bending frequency of flutter and its second harmonic in the frequency spectrum for recording the pressure pulsation of flow during flutter along with harmonics of rotor speed. The occurrence the second harmonic of the bending frequency is the nonlinear reaction of flow, which locally limits the flutter amplitude in time.     

转速对直叶片升力型风轮动力特性影响数值研究

采用非定常k-ω湍流模型和滑移网格技术,对旋转直径3 m、高3 m和叶片弦长0.44 m的直叶片升力型风轮动力特性进行二维数值研究,分析在三种不同转速下单叶片动力特性、叶轮动力特性及叶片表面压力特性的变化规律。研究发现：随转速增加,上盘面叶片动力矩极高值先增加后减小存在最大值,下盘面动力矩极低值在逐渐减小且范围变广,证明上盘面为风轮的主要做功区域,下盘面对风轮出力贡献少甚至为负值;随转速增加,上盘面叶片表面压力差在增大,吸力面负压增加幅度较明显,压力面增加幅度较缓,证明吸力面对出力增加的贡献更大;叶轮整体出力由上盘面力矩、下盘面力矩和转速三个因素决定,只有均衡三者关系才能增大风轮整体出力。     

Resonance bifurcation during self-oscillations of the rotor blades of a turbocompressor

Bifurcation of the trajectory of the resonance for the blades of an axial rotor, which leads to flutter of the blade cascade, is investigated. For this purpose, a spectral analysis of readouts of the transient period of blade oscillation is performed. As opposed to the resonance with a constant phase difference and excited oscillations of the blades, the shift of the phase of collective synchronous oscillations of the blades during flutter depends on their number and the form of the diametral mode of the blade cascade. The flutter of the blades is associated with one diametral mode of pressure pulsations of the air flow.