用粘性体力方法计算轴流叶轮机械内部流场

阐述了一种用于叶轮机械内部三维粘性流场计算程序。该程序以有限体积显式时间推进方法为基础,用Baldwin-Lomax模型模拟湍流流动,用局部时间步长和多重网格方法提高计算效率。使用上述方法计算了NASA 37^#跨音速压气机转子流场,并与实验结果进行了比较,从而证明文中提出的方法能够快速、准确地模拟轴流叶轮机械内部复杂三维流场,该方法具有较强的工程实用意义。     

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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。     

考虑气动热对粘性系数μt影响的压气机流场计算

根据气动热影响叶片壁面附面层粘性系数tμ的理论,把考虑气动热对粘性系数tμ影响的粘性体积力计算方法运用于压气机叶栅三维粘性流场计算。计算时使用有限体积显式时间推进法解算Navier-Stokes方程,用Baldwin-Lomax模型模拟湍流流动。所得结果比不考虑气动热影响的三维计算结果更接近实验结果,能更真实地反映压气机叶栅流场的流动。     

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。     

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。     

使用不等距多重网格技术求解线接触热弹流润滑问题

使用不等距多重网格法求解了线接触热弹流润滑问题 .结果表明 :与等距多重网格法相比 ,新解法虽不能提高数值求解的稳定性 ,却能得到更为精确的压力、膜厚及温度分布 ;计算结果表明中载下第二压力峰是光滑的     

压气机近失速点旋涡流场时空演化分析

为了探索轴流压气机内旋涡流场的时空演化特征, 对一台压气机转子的流场进行了时间精确的数值模拟. 通过对转子不同轴向位置的流量分析发现, 在压气机近失速工况附近, 压气机进口流量波动约为最大流量的2%. 对旋涡流场的进一步分析发现, 叶片尾缘附近吸力面的旋涡流场摆动是导致压气机进口流量波动的主要原因.      

射流元件控制通道流动的三维数值模拟

针对一种射流元件控制通道的复杂结构 ,采用分块对接技术和网格“融合”技术生成计算网格 ,并运用五步显式格式的 Runge-Kutta法和多重网格法对含全 N-S方程、RNG k-ε湍流模型和两层分区壁面模型的流动模型进行数值求解。通过对控制通道内部流动的数值模拟和流场特性分析 ,提出了改进方案     

特征距离和扩充无网格法分析多裂纹相互作用

提出特征距离这一概念对内部基扩充无网格法进行修正,并数值模拟了多裂纹之间的相互作用。特征距离法用于选择内部基扩充无网格Galerkin法的奇异基函数,该方法仅对传统的内部基扩充无网格Galerkin法作了很小的改进,即可方便地应用于求解多裂纹问题;给出了相互作用能量积分计算混合型模式下的应力强度因子,数值模拟了三条内部裂纹和六条边裂纹问题,并与杂交位移不连续边界元法的计算结果进行比较。数值结果表明:修正的内部基扩充无网格法可以方便、有效地求解多裂纹问题,在不增加附加节点和自由度的情况下与杂交位移不连续方法的计算精度非常接近。     

Euler analysis of transonic stator-rotor interaction using a finite volume method

A generalized finite volume method that can solve the Euler equations for the stator and rotor parts of stage flow in similar formulations is presented. The method consists of a new moving grid finite volume formulation applied to the rotor region and the existing fixed grid finite volume method used in the stator region, with the data transfer made by an interpolation procedure at the sliding surface in between. The accuracy of the method has been demonstrated on a simple cascade flow before the time-dependent compressor stage flow is fully investigated. The transonic stator-rotor flow interaction is elucidated within the inviscid and rotational flow limit.     

用扰动涡方法模拟叶轮机内动静叶的相互作用

发展了一种研究叶轮机内动、静叶间的相互作用的新方法———扰动涡方法，它利用全三维的定常解为基础解，并由此给出非定常扰动场的初始解．为计算叶片对扰动场的响应过程，采用拉格朗日方法追踪扰动涡团的对流流动过程，用确定性涡方法来描述流体的粘性扩散过程．发展了代数湍流模型（Ｂａｌｄｗｉｎ Ｌｏｍａｘ湍流模型）在尾迹中的应用方法，克服了其它数值方法中无法准确捕捉尾迹中心线的运动轨迹，以及计算出的边界层外的湍流涡粘性系数偏大的缺陷．利用该方法计算轴流叶轮机内由于动、静叶间的相互作用而引起的非定常流动过程，与实验的对照表明，模拟结果与实验数据吻合得相当好，从而说明本文发展的方法是可信的，为更直观地描述尾迹等非定常因素的流动及叶轮机内的掺混问题提供依据．     

基于流固耦合的跨声速压气机叶片静气动弹性分析

采用时域推进的双向流固耦合方法对一级跨声速压气机叶片流场和固体域进行数值模拟,研究跨声速转子叶片静气动弹性变形及其对气动性能的影响,对比分析了100%转速下转子叶片的气动特性和固有频率的变化.结果表明:转子叶片在气动力和离心惯性力共同作用下的弹性变形以扭转变形为主,气动力对叶尖前缘变形量的影响可达总变形量的20%.转子叶片变形后通道流通能力增强,气动特性曲线向大流量方向偏移.     

数值耗散对压气机流动分离涡模拟的影响研究

分离涡模拟DES是压气机流动模拟中常用的高保真湍流模式。为了使DES准确解析湍流,数值耗散必须限制在合理范围内。然而,当前的压气机流动DES类研究工作中仍然普遍采用高耗散的迎风格式。本文首先基于DES类方法计算的各向同性衰减湍流结果,定量比较了多种不同数值格式的耗散,证实了高耗散迎风格式严重低估中高波数湍流能量。高阶重构格式可以一定程度上改善该问题,但能量耗散仍然过高。本文在高阶重构的基础上,进一步引入自适应耗散函数修改Riemann求解器,构造了自适应耗散格式。该格式在全波数范围都能准确地预测湍流能谱。将该格式配合DES类方法模拟跨声速离心压气机流动,其预测的压比相比于三阶迎风格式,更加接近实验结果。此外,自适应耗散格式显著提高了中小尺度流动结构的分辨率。分析表明,在使用DES类方法模拟压气机流动时,有必要采用数值耗散较低的离散格式,以准确预测压气机总体性能和流动结构。本文构造的自适应耗散格式是一种良好选择。     

用隐式方法和WENO格式计算悬停旋翼跨声速无粘流场

寻找一种能够准确计算以涡为主要特征的复杂流场和克服尾迹耗散问题的数值方法,一直是旋翼空气动力学研究的热点和难点。本文发展了一种基于高阶迎风格式计算悬停旋翼无粘流场的隐式数值方法。无粘通量采用Roe通量差分分裂格式,为提高精度,使用五阶WENO格式进行左右状态插值,并与MUSCL插值进行比较。为提高收敛到定常解的效率,时间推进采用LU-SGS隐式方法。用该方法对一跨声速悬停旋翼无粘流场进行了数值计算,数值结果表明WENO-Roe的激波分辨率高于MUSCL-Roe,体现出了格式精度的提高对计算结果的改善,LU-SGS隐式方法的计算效率比5步Runge-Kutta显式方法的高。     

The challenge of stereo PIV measurements in the tip gap of a transonic compressor rotor with casing treatment

This contribution is aimed at summarizing the effort taken to apply stereoscopic PIV (SPIV) measurements in the tip clearance of a transonic compressor rotor equipped with a casing treatment. A light sheet probe was placed downstream of the stator and aligned to pass the light sheet through a stator passage into the blade tip clearance of the rotor. A setup with three cameras has been used in order to record the entire 2C velocity field and the smaller area of 3C field of view at the same time instance for comparison with earlier 2C PIV results. A homogeneous seeding distribution was achieved by means of a smoke generator. The main emphasis of the SPIV measurement was to establish a data set with high spatial resolution close to the compressor casing, where the aerodynamic effects of a CT are known to be strong. The paper will discuss some major aspects of the utilized PIV data processing and point out a variety of frequently underestimated error sources that influence the overall quality of the recovered data in spite of the fact that the individual PIV recordings seemed to be of very good quality. Thus, the authors will not focus on the PIV results and related interpretation of the flow field, but on the optimization and procedures applied during setup of the experiment and data processing, respectively.     

Rotor wake capture improvement based on high-order spatially accurate schemes and chimera grids

A high-order upwind scheme has been developed to capture the vortex wake of a helicopter rotor in the hover based on chimera grids. In this paper, an improved fifth-order weighted essentially non-oscillatory (WENO) scheme is adopted to interpolate the higher-order left and right states across a cell interface with the Roe Riemann solver updating inviscid flux, and is compared with the monotone upwind scheme for scalar conservation laws (MUSCL). For profitably capturing the wake and enforcing the period boundary condition, the computation regions of flows are discretized by using the structured chimera grids composed of a fine rotor grid and a cylindrical background grid. In the background grid, the mesh cells located in the wake regions are refined after the solution reaches the approximate convergence. Considering the interpolation characteristic of the WENO scheme, three layers of the hole boundary and the interpolation boundary are searched. The performance of the schemes is investigated in a transonic flow and a subsonic flow around the hovering rotor. The results reveal that the present approach has great capabilities in capturing the vortex wake with high resolution, and the WENO scheme has much lower numerical dissipation in comparison with the MUSCL scheme.     

低雷诺数下附面层组合抽吸方案对压气机特性影响的研究

为了分析附面层抽吸流动控制对低雷诺数下压气机特性的影响,本文采用数值方法模拟了低雷诺数下附面层组合抽吸方案对NASA Rotor 37跨音速压气机性能和稳定性的影响特点及作用机理。通过在该压气机转子叶片吸力面和机匣上分别设计附面层抽吸槽,探讨了组合抽吸方案对低雷诺数下(H=20km)压气机性能和稳定性的影响。结果表明:采用组合抽吸方案后,压气机峰值效率提高约1.3%;压气机最大增压比提高约2.5%;压气机转子的近失速点流量减小约14.6%。进一步分析作用机理发现,组合抽吸槽有效抑制了附面层径向涡向叶顶的运动和聚集,使叶顶附面层分离区减少约70%从而有效改善了压气机的流场特性。     

叶轮机械非定常流动研究进展

本文就叶片排进出口流场畸变型动力响应、压缩系统气动稳定性、叶轮机械非定常气动问题的数值模拟以及失速颤振轴流压气机系列转子实验等４个方面问题,从非定常气动力学角度作一概述和展望      

DPIV study of near-stall wake-rotor interactions in a transonic compressor

Wake-rotor interactions at near-stall conditions are studied using digital particle image velocimetry (DPIV) in a transonic compressor at the Compressor Aero Research Lab (CARL) at Wright-Patterson Air Force Base. The wake generators (WGs) are designed to simulate wakes of highly loaded stators without producing flow swirl. Flow visualization, instantaneous, and average velocity field data are presented for near-stall compressor operating conditions. These results describe the interaction of the wake shed from the upstream WG with the downstream potential field of the rotor leading edge for two axial spacings at 75 and 90% span. The advantage of ensemble averaging is demonstrated when operating at challenging conditions such as near-stall, which poses special difficulties in obtaining DPIV data. Ensemble averaging, which is possible because of a natural phase locking provided by the blade potential field, allows robust statistics.