平面叶栅跨音流动的数值计算及变工况性能的研究

提出一种隐式矢通量分裂差分格式并用来直接求解Ｒｅｙｎｏｌｄｓ平均Ｎ－Ｓ方程组。该方法避开了近似因子分解及矩阵运算，具有精度高、稳定性好、计算量少等优点。在平面叶栅跨音流场的计算中，较好地捕获了激波，与实验比较，结果令人满意。

用高阶隐式矢通量分裂格式求解平面叶栅的跨音流动

本文应用高阶隐式矢通量分裂法直接求解Reynolds平均Navier－Stokes方程组。该方法避开了近似因子分解及矩阵运算，具有精度高、稳定性好、计算量少等优点。在平面叶栅跨音流场的计算中，较好地捕获了激波，与实验比较，结果令人满意。

平面叶栅跨音流动的数值研究

讨论用一种高效、可靠的数值方法来模拟透平叶栅的真实流动，获取大量细致的流动信息，总结出各种实用规律，为现代叶型设计提高一个快速、可靠、实用的依据。数值试验表明，提出的一隐式矢通量二阶差分格式计算透平叶栅具有精度高、计算量小、收敛快的特点。

一先进跨音速离心压气机叶轮内部粘性流动数值模拟

随着计算机和计算技术的发展，三元粘性数值计算被广泛地应用于叶轮机械内部流场分析，本文使用三元Ｎ－Ｓ方程对这一先进跨音速离心压气机叶轮内部流场进行数值模拟，一是对这一成功设计进行分析验证。二是使用数值方法进行内部流场细节的模拟掌握其内部粘性流动特点，为今后设计和改进高压比跨音速离心压气机提供经验。

平面叶栅跨音流场气动特性的数值研究

通过对模型方程的分析，给出了一种新的隐格式构造思想。将它运用到关通量分裂格式中，可得到无近似因子分解、无矩阵运算的高效二阶精度隐式矢通量分裂差分格式，并用来直接求解时间平均Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程组。数值计算标明：该方法具有精度高、稳定性好、计算量少、收敛快等优点，在平面叶栅跨音流场的计算中，较好地捕获了激波，与实验比较，结果令人满意。

用GAO-YONG湍流模式对翼型跨音粘流的数值模拟

应用GAO-YONG可压缩湍流模式,数值模拟了NACA0012,RAE2822翼型的定常跨音速粘流算例.对流项采用三阶ROE格式,扩散项采用二阶中心格式,用多步Runge-Kutta显式时间推进法求解空间离散后的控制方程.计算结果很好地预测了翼型表面的压力系数的分布、激波的位置、马赫数等值线的分布等情况,并且对翼型表面激波与边界层相互干扰以及层流向湍流的转捩问题进行了分析计算.计算结果与实验值符合很好,表明GAO-YONG可压缩湍流模式应用合适的计算方法能够高精度模拟翼型跨音粘性流动问题,并且基于GAO-YONG可压缩湍流模式各向异性湍流粘性的机理,提供了一种预测转捩起始位置的判别方法.

二阶矢通量分裂格式及其对二维跨音流的数值模拟

在前人工作基础上提出了一种二阶精度隐式矢通量分裂一步格式，并将该格式使用到二维喷管和叶栅无粘跨音流动的数值模拟中去，得到了比较满意的计算结果，证实了该格式在激波捕获精度方面的优良性能，也证实了该隐格式构造思想具有一定的普遍意义。

使用GAO-YONG湍流模型数值研究管道凸起流动

用GAO-YONG可压缩湍流方程数值模拟了Delery管道凸起跨音流场中的激波湍流边界层干扰现象,分析了GAO-YONG可压缩湍流方程组对湍流的非平衡、多尺度、各向异性等特性的描述能力。计算中对流项、扩散项分别采用二阶ROE格式和二阶中心差分格式离散,并用多步Runge-Kutta显式时间推进法求解了空间离散后的控制方程。计算很好地模拟到了压力平台区、"λ"波结构等典型激波湍流边界层干扰的流动现象,也得到了壁面压力分布、平均速度剖面以及雷诺应力分布等,并与相应的实验数据进行了对比分析,两者符合很好。

平面叶栅气动试验研究进展与展望

平面叶栅气动试验传统上是验证压气机、涡轮的基元性能的主要手段,近年来国内外研究人员利用平面叶栅开展了大量的流动测量试验,以揭示叶栅内部复杂流动现象的本质和规律、探索减小叶栅内流动损失的方法.本文从试验装置、测试技术和研究内容三个方面,综述了近年来平面叶栅气动试验研究的进展情况.首先介绍了平面叶栅试验装置的发展及提高平面叶栅试验段流场品质的措施;其次介绍了叶栅气动试验采用的部分流场测试技术,包括叶片表面压力场、叶片表面温度场、内流速度场及流场可视化等测试技术,分析了这些测试技术的进展和存在的问题;然后梳理了近年来平面叶栅试验研究的相关科学问题及进展,包括跨音速叶栅中的激波研究,叶顶间隙泄漏流动研究,叶型优化研究,多尺度非定常旋涡结构研究,振动环境下叶栅流场研究等;最后对平面叶栅气动试验研究方向进行了展望.通过了解叶栅内复杂流动现象及本质,为进一步探索和提高压气机、涡轮的气动性能提供技术支撑.

Effects of Heterogeneous Condensation on the Transonic Flow Fields on a Bump Model

In the present study, effect of the heterogeneous condensation on the characteristics of shock wave generated on the bump model in the transonic flow field was investigated numerically. As a result, it was found that, for the flow field with steady adiabatic shock wave on the bump model, the condensation with heterogeneous nucleation has a strong effect on the whole flow field, and it reduced the strength of the shock. Furthermore, the total pressure loss was dependent on the concentration of the solid particles per unit volume.

Transonic Instability in Entrance Part of Mixing Chamber of High-Speed Ejector

The paper deals with experimental and numerical study of flow structure in two-dimensional model of supersonic ejector. Schlieren pictures of flow structure were taken, static pressure distributions on side wall were measured and Fluent software to calculate the flow structure in supersonic ejector was used. For certain region of back pressure ratio pb/p02 and stagnation pressure ratio of both streams p01/p02 the terminal shock wave is close to the trailing edge of the primary flow nozzle and a transonic instability occurs. The instability causes the movement of position of boundary layer separation, the structure of shock waves changes and all flow structure oscillates. The movie of these regimes during schlieren experiments was taken and relevant numerical modelling was performed.

Numerical Investigation of Tip Clearance Effects in an Axial Transonic Compressor

Numerical investigations of the Darmstadt transonic single stage compressor (DTC), in the Rotor1-Stator1 configuration, aimed at advancing the understanding of the effect of different rotor tip gaps and transition modelling on the blade surfaces are presented. Steady three dimensional Reynolds Averaged Navier Stokes (RANS) simulations were performed to obtain the flow fields for the different configurations at different operating conditions using the RANS-Solver TRACE. The stage geometry and the multi-block structured grid were generated by G3DMESH and a grid sensitivity analysis was conducted. For the clearance gap region, a fully gridded special H-grid was chosen. Comparisons were made between the flow characteristic at design speed, representative for a transonic flow regime, and at 65% speed, representative for a subsonic flow regime. The computations were used to analyse the flow phenomena through the tip clearance region for the different configurations and their impact on the performance of the compressor stage.

Transonic Moist Air Flow around a Circular Arc Blade with Bump

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vibration. In recent years, the effect of bump wall on the flow field around an airfoil has been investigated experimentally and as a result, it was observed that the bump wall is effective for the control of shock wave on the airfoil. In the transonic or supersonic flow field, a rapid expansion of moist air or steam gives rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation around a circular arc blade with or without a bump on the blade was investigated numerically. The results showed that the non-equilibrium condensation significantly reduced the flow field unsteadiness such as root mean of pressure oscillation and frequency compared to the case without the non-equilibrium condensation.

Aero-Acoustics of Modern Transonic Fans—— Fan Noise Reduction from Its Sources

The noise of aerodynamics nature from modern transonic fan is examined from its sources with the perspective of noise reduction through aero-acoustics design using advanced Computational Fluid Dynamics (CFD) tools. In particular the problems associated with the forward propagating noise in the front is addressed. It is identified that the shock wave spillage from the leading edge near the fan tip is the main source of the tone noise. Two different approaches have been studied to reduce the forward arc tone noise and two state-of-art transonic fans are designed using the strategies developed. The following rig tests show that while the fans exhibit other noise problems, the primary goals of noise reduction have been achieved through both fans and the novel noise reduction concept vindicated.

Passive Control of Transonic Flow Fields with Shock Wave Using Non-equilibrium Condensation and Porous Wall

When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by the latent heat released. In the present study, in order to control the transonic flow field with shock wave, a condensing flow was produced by an expansion of moist air on a circular bump model and shock waves were occurred in the supersonic parts of the fields. Furthermore, the additional passive technique of shock / boundary layer interaction using the porous wall with a cavity underneath was adopted in this flow field. The effects of these methods on the shock wave characteristics were investigated numerically and experimentally. The result obtained showed that the total pressure loss in the flow fields might be effectively reduced by the suitable combination between non-equilibrium condensation and the position of porous wall.

Numerical Investigation of Influence of Tip Leakage Flow on Secondary Flow in Transonic Centrifugal Compressor at Design Condition

In a centrifugal compressor, the leakage flow through the tip clearance generates the tip leakage vortex by the in- teraction with the main flow, and consequently makes the flow in the impeller passage more complex by the inte- raction with the passage vortex. In addition, the tip leakage vortex interacts with the shock wave on the suction surface near the blade tip in the transonic centrifugal compressor impeller. Therefore, the detailed examination for the influence of the tip leakage vortex becomes seriously important to improve the aerodynamic performance cs- pccia｜ly for the transonic centrifugal compressor. In this study, the flows in the transonic centrifugal compressor with and without the tip clearance at the design condition were analyzed numerically by using the commercial CFD code. The computed results revealed that the tip leakage vortex induced by the high loading at the blade tip around the leading edge affected the loss generation by the reduction or the suppression of the shock wave on the suction surface of the blade.

Numerical Modelling of the Aeroelastic Behaviour and Variable Loads for the Turbine Stage in 3D Transonic Flow

In this study presented the algorithm proposed involves the coupled solution of 3-D unsteady flow through a turbine stage and the dynamics problem for rotor-blade motion by the action of aerodynamic forces, without separating the outer and inner flow fluctuations. The partially integrated method involves the solution of the fluid and structural equations separately, but information is exchanged at each time step, so that solution from one domain is used as a boundary condition for the other domain. 3-D transonic gas flow through the stator and rotor blades in relative motion with periodicity on the whole annulus is described by the unsteady Euler conservation equations, which are integrated using the explicit monotonous finite-volume difference scheme of Godunov-Kolgan. The structural analysis uses the modal approach and a 3-D finite element model of a blade. A calculation has been done for the last stage of the steam turbine, under design and off-design regimes. It is shown that the amplitude-frequency spectrum of blade oscillations contains the high frequency harmonics, corresponding to the rotor moving past one stator blade pitch, and low frequency harmonics caused by blade oscillations and flow nonuniformity downstream from the blade row; moreover, the spectrum involves the harmonics which are not multiples of the rotation frequency.

Numerical Investigation of the Unsteady Tip Leakage Flow and Rotating Stall Inception in a Transonic Compressor

It is well known that tip leakage flow has a strong effect on the compressor performance and stability. This paper reports on a numerical investigation of detailed flow structures in an isolated transonic compressor rotor-NASA Rotor 37 at near stall and stalled conditions aimed at improving understanding of changes in 3D tip leakage flow structures with rotating stall inception.Steady and unsteady 3D Navier-Stokes analyses were conducted to investigate flow structures in the same rotor.For steady analysis,the predicted results agree well with the experimental data for the estimation of compressor rotor global performance.For unsteady flow analysis, the unsteady flow nature caused by the breakdown of the tip leakage vortex in blade tip region in the transonic compressor rotor at near stall condition has been captured with a single blade passage.On the other hand, the time-accurate unsteady computations of multi-blade passage at near stall condition indicate that the unsteady breakdown of the tip leakage vortex triggered the short length-scale-spike type rotating stall inception at blade tip region.It was the forward spillage of the tip leakage flow at blade leading edge resulting in the spike stall inception. As the mass flow ratio is decreased,the rotating stall cell was further developed in the blade passage.

Experimental and Analytical Analysis of Perforated Plate Aerodynamics

Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of 'aerodynamic porosity' determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.

3D Flow Past Transonic Turbine Cascade SE 1050-Experiment and Numerical Simulations

This paper is concerned with experimental and numerical research on 3D flow past prismatic turbine cascade SE1050 （known in QNET network as open test case SE1050）. The primary goal was to assess the influence of the inlet velocity profile on the flow structures in the interblade channel and on the flow field parameters at the cascade exit and to compare these findings to results of numerical simulations. Investigations of 3D flow past the cascade with non-uniform inlet velocity profile were carried out both experimentally and numerically at subsonic （M2 = 0.8） and at transonic （M2 = 1.2） regime at design angle of incidence. Experimental data was obtained using a traversing device with a five-hole conical probe. Numerically, the 3D flow was simulated by open source code OpenFOAM and in-house code. Analyses of experimental data and CFD simulations have revealed the development of distinctive vortex structures resulting from non-uniform inlet velocity profile. Origin of these structures results in increased loss of kinetic energy and spanwise shift of kinetic energy loss coefficient distribution. Differences found between the subsonic and the transonic case confirm earlier findings available in the literature. Results of CFD and experiments agree reasonably well.