计算多级轴流压气机阻塞系数和减功系数的新方法

讨论了轴流压气机环壁边界层的流量阻塞效应和减功效应,提出了一种工程上可以简便适用波压气机设计和分析用的新的阻塞系数和减功系数计算方法,并应用于二台导叶可调及淡可调的十多级轴流压气机变工况的性能分析计算,结果与实验值吻合良好。     

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以某跨声速轴流压气机单转子为研究对象,应用数值模拟技术,采用全通道 计算方案,利用Jameson有限体积中心差分格式并结合Spalart-Allmaras 湍流模型获得进口畸变条件下该轴流压气机转子性能和内部流动细节,详细分析了进气周向 总压畸变对压气机转子内流场流动结构的影响. 并将计算结果与实验结果进行了比较, 结果表明,数值模拟的结果与实验结果符合较好,计算方案切实可行.     

多级轴流压气机叶栅内三维紊流流场的数值模拟

对多级轴流压气机叶栅内三维紊流流场进行数值模拟,采用高精度高分辨率的三阶ENN格式以保证对激波的捕捉和对紊流特征的正确模拟,利用LU-SGS隐式解法提高了计算速度,从而构成了一种既准确又高效的多级跨声速轴流压气机紊流流动数值求解系统。重点研究了动静网格的交接方法及相应的动静交接面处理模型。计算了某带进口导叶的三级轴流压气机,计算结果与实验数据吻合较好。     

轴流压气机机匣处理研究进展及评述

喘振和旋转失速裕度等稳定性问题是压气机设计者所关心的主要问题之一, 不稳定 流动大多数情况下都是从压气机端部区域开始的, 如果能够延迟端部区域的失速, 就能提高压气机的稳定工作范围. 在过去的30多年中,许多种型式的处理机匣结 构被用于改善端部区域流动, 提高压气机的稳定工作范围. 从机匣处理的实验 研究、理论分析和数值模拟3个方面对轴流压气机机匣处理的研究进行了回顾, 讨 论了处理机匣内部流动机理及其对轴流压气机性能和稳定性的影响, 并指出了机匣 处理研究的发展趋势.     

变几何叶片对压气机特性影响的实验研究及分析

利用带导叶的单级轴流压气机实验台，详细测量了进口导叶无预旋、全叶高预旋2度和叶顶端部预旋2度对压气机总性能、基元性能及失速边界的影响。在设计及非设计转速下，通过对比三种导叶几何条件下的性能曲线，探讨了导叶预旋在非设计转速下的扩稳效果及设计转速下对 气机性能的影响，分析了利用端弯技术扩大压气机稳定工作范围的机理，该研究进一步说明了端弯技术是推迟轴流压气机不稳定流动发生的有效手段之一，可以很方便的用于实际轴流压气机中。     

一种微型轴流风扇扭叶片设计方法及其气动特性的数值研究

本文利用"径向平衡"原理,建立了轴流叶轮出口通流速度沿叶高的分布方程,并基于此提出了一种新的扭叶片设计方法.将该方法运用于某微型风扇的设计,并采用CFD技术,数值研究了不同扭曲形式下该型风扇的气动特点.通过与用传统方法设计的扭叶片及原始直叶片的气动性能的对比发现,按本文提出的方法所设计的扭叶片不仅能扩大微型风扇小流量稳定工况范围,而且其风压明显增加,有助于提高微型风扇的气动性能.     

跨音速压气机级的三维周期性非定常流动计算

对跨音速压气机级动静叶排相干形成的三维非定常流场进行了数值研究，利用时间推进ＬＵ－ＳＧＳ稳式迭代法求解三维非定常欧拉方程，对流项采用高分辨率ＮＮＤ格式离散。对某压气机第一级动静叶排相干非定常流场的计算结果表明，本文方法不仅在收敛速度上明显地优于一般显式方法，而且保持了流场中激波的高分辨率，适于推广到计算量巨大的的多级轴流压气机三维非定常流场的数值分析问题     

轴流压气机级内三维粘性流动的数值模拟

考虑轴流压气机中实际气流沿径向和周向都不均匀的特点,采用亚松弛方法改进传统的混合界面模型,发展了轴流式压气机级内全三维粘性流场的数值计算程序,并以某轴流式双排对转压气机的进口导叶/转子为研究对象,将本文发展的程序与商用 NUMECA 软件的结果进行对比,对本文发展的程序进行了验证。对比结果表明：由于混合界面法引入了“人工掺混”,商业软件计算得出的总压在通过交界面时存在一定的总压损失,而自编程序计算结果保证了总压在交界面处的一致性。流场分析结果表明：该转子叶片在设计工况下处于负攻角状态,在导叶出口轮毂处、压力面50%弦长处、吸力面靠近尾缘处均出现了轻微的流动分离现象。     

高压比单级涡轮增压器

评述了高压比下运行的离心式压气机以及轴流式和向心式涡轮能达到的性能。提供了对于运行压比超过4.0:1,总膨胀比3.7:1的涡轮增压器离心式压气机和单级轴流涡轮的性能。强调了在高压比下压气机运行范围的重要问题并详述了对达到广泛范围所加的限制。评述了与现代离心式压气机和轴流式涡轮的设计逐步增载到运行压比5.0:1有关的问题。本述评包含把向心式涡轮引入非汽车涡轮增压器范围的现实性。      

轴流压气机叶片气动设计

本文概述了轴流压气机设计的基本问题和一般的解决途径。叙述了现今叶轮机械气动设计概念中所需要的理论方法和计算机工具。由此给出了将真实流体效应(例如亚音速粘性损失及激波)连系起来并引入设计过程的方法。重点放在叶片气动设计,特别是跨音速风扇和多级压气机的叶片设计上。指出了使压气机气动设计成为一门更严格的科学和将来研究的突出领域所需要增进的知识。      

轴流压气机失速初始扰动的研究进展

在失速主动控制思想的推动下,对轴流压气机失速初始扰动的研究一直是叶轮机械非定常流领域的热点问题之一,同时也是一个尚未认识清楚的难点问题. 本文从失速初始扰动的理论模型、实验研究和机理分析3个方面对轴流压气机失速初始扰动的研究进展进行了回顾.对目前失速初始扰动研究中的集中问题,如低速和高速环境下初始扰动的试验检测方法, 初始扰动类型,以及初始扰动出现的内在流体动力学机理等问题进行了总结. 在此基础上,讨论了叶尖区域的复杂流动特性和失速初始扰动的内在联系,并指出了失速初始扰动研究的发展趋势, 认为今后应进一步深化如下问题:初始扰动形式影响因素的系统研究, 高速压气机中初始扰动新形式研究,初始扰动产生的流体动力学物理机制及其与压气机的设计和运行参数之间的关联性研究.      

Numerical solution of subsonic and transonic cascade flows

In this work a study of the application of the finite element method to transonic flows in axial turbomachines is undertaken. Solution techniques capable of accurately predicting flows from the incompressible regime up to the establishment of shocks in the transonic regime are presented. In the subsonic and shockless transonic regimes a local linearization method capable of very rapid convergence is used. In the full transonic regime the artificial compressibility method is employed to exclude downstream influences in the supersonic regions. The two approaches can be combined in a unified package and appropriate switches introduced to select the relevant method in any flow regime.     

Study of modeling unsteady blade row interaction in a transonic compressor stage part 2: influence of deterministic correlations on time-averaged flow prediction

The average-passage equation system (APES) provides a rigorous mathematical framework for accounting for the unsteady blade row interaction through multistage compressors in steady state environment by introducing deterministic correlations (DC) that need to be modeled to close the equation system.The primary purpose of this study was to provide insight into the DC characteristics and the influence of DC on the time-averaged flow field of the APES.In Part 2 of this two-part paper,the influence of DC on the time-averaged flow field was systematically studied.Several time-averaging computations were conducted with various boundary conditions and DC for the downstream stator in a transonic compressor stage,by employing the CFD solver developed in Part 1 of this two-part paper.These results were compared with the time-averaged unsteady flow field and the steady one.The study indicated that the circumferentialaveraged DC can take into account major part of the unsteady effects on spanwise redistribution of flow fields in compressors.Furthermore,it demonstrated that both deterministic stresses and deterministic enthalpy fluxes are necessary to reproduce the time-averaged flow field.     

Performance evaluation of an inverse integral equation method applied to turbomachine cascades

An improved formulation of the inverse integral equation method proposed in Reference 1 is presented which allows, in particular, a well-posed problem to be ensured. The corresponding computation code is tested in an exhaustive manner for axial and radial compressor and turbine cascades. The agreement between the velocity field obtained with the inverse method and that resulting from a direct calculation is examined for subsonic, transonic and supersonic flows. Accuracy and reliability of the solution to the boundary condition problem are excellent for the subsonic and transonic flows. However, for the supersonic flow, the application of the method seems to be limited by the use of elementary solutions of the Laplace operator.     

Identification of limit cycles for piecewise nonlinear aeroelastic systems

This paper describes two methods for the analysis of aeroelastic systems with complex piecewise nonlinear structural stiffness. These methods are tested and compared for low speed incompressible and transonic flows. The first technique employed in this paper uses a new application of the analytical solution of linear algebraic systems, the second technique utilises logarithmic and tanh functions to both represent discrete nonlinearities and to act as a switch between different nonlinear areas. The transonic aerodynamic models used are generated using an eigenvalue realisation algorithm (ERA) which produces reduced order models (ROMs) from the pulse responses of time linearised Euler simulations. It is shown that such aerodynamic models are well suited to use with continuation methods. Flutter boundaries and limit cycle oscillations can then be rapidly identified with good accuracy.     

基于非线性状态空间辨识的气动弹性模型降阶

高维、非线性气动弹性系统的模型降阶是当前气动弹性力学与控制领域的研究热点之一.然而国内外现有的非线性模型降阶方法仍存在辨识算法复杂、精度有待提高等问题.本研究提出了一种基于非线性状态空间辨识的跨音速气动弹性模型降阶方法. 首先,该方法基于非定常空气动力的单位脉冲响应数据,采用特征系统实现算法对非线性状态空间模型的线性动力学部分进行系统辨识. 其次,引入状态和控制输入的非线性函数, 采用优化算法对非线性函数的系数矩阵进行优化,进而得到考虑非线性效应的空气动力降阶模型.为了验证该降阶模型在预测跨音速气动弹性力学行为的精确性,本文以三维机翼为研究对象,分别从基于非线性降阶模型的气动力辨识、跨声速颤振边界计算和极限环振荡预测三方面进行了算例验证,并与现有的模型降阶方法进行了对比, 进一步说明本文所提出方法的有效性.研究结果表明, 该降阶模型对上述三类问题的计算精度与直接流-固耦合方法相吻合,可用于高效预测飞行器跨声速气动弹性力学行为.      

Study of modeling unsteady blade row interaction in a transonic compressor stage part 1: code development and deterministic correlation analysis

The average-passage equation system (APES) provides a rigorous mathematical framework for accounting for the unsteady blade row interaction through multistage compressors in steady state environment by introducing deterministic correlations (DC) that need to be modeled to close the equation system.The primary purpose of this study is to provide insight into the DC characteristics and the influence of DC on the time-averaged flow field of the APES.In Part 1 of this two-part paper,firstly a 3D viscous unsteady and time-averaging flow CFD solver is developed to investigate the APES technique.Then steady and unsteady simulations are conducted in a transonic compressor stage.The results from both simulations are compared to highlight the significance of the unsteady interactions.Furthermore,the distribution characteristics of DC are studied and the DC at the rotor/stator interface are compared with their spatial correlations (SC).Lastly,steady and time-averaging (employing APES with DC) simulations for the downstream stator alone are conducted employing DC derived from the unsteady results.The results from steady and time-averaging simulations are compared with the time-averaged unsteady results.The comparisons demonstrate that the simulation employing APES with DC can reproduce the time-averaged field and the 3D viscous time-averaging flow solver is validated.     

转子叶尖引射式射流的数值研究

转子叶尖射流能够有效地提高压气机的稳定工作裕度, 但是现有的各种射流器结构复杂, 并使发动机的重量增加. 研究目的在于探索一种新型的射流方式, 以方便在压气机中的实现,并且不增加发动机的重量. 采用对转子叶尖前缘位置机匣进行局部修型的方法, 提高了转子叶尖前缘附近流场的轴向速度, 从而产生类似转子叶尖射流的效果. 在Rotor37上的数值分析发现, 该方法能够提高转子的失速裕度约6.7%, 并能使转子的效率与压比有较小的提升. 对比不同机匣修型方案发现, 修型位置对压气机裕度的影响最为明显. 对转子叶尖流场的分析表明, 该方法能够提高转子叶尖前缘的轴向速度, 并将叶尖泄露涡向下游推移, 减小了转子叶尖的流动堵塞, 从而拓宽了转子的失速裕度.      

跨音速极限环型颤振的高效数值分析方法

事先建立一个低阶的非线性、非定常气动力模型是开展非线性流场中气动弹性问题研究的一个捷径. 基于CFD方法, 通过计算结构在流场中自激振动的响应来获得系统的训练数据. 采用带输出反馈的循环RBF神经网络, 建立时域非线性气动力降阶模型.耦合结构运动方程和非线性气动力降阶模型, 采用杂交的线性多步方法计算结构在不同速度(动压)下的响应历程, 从而获得模型极限环随速度(动压)变化的特性. 两个典型的跨音速极限环型颤振算例表明, 基于气动力降阶模型方法的计算结果与直接CFD仿真结果吻合很好, 与后者相比其将计算效率提高了1~2个数量级.