任意回转面上,可压缩流动轴流式叶栅最佳壁面速度分布的计算方法

本文在边界层理论分析和叶栅损失计算的基础上,通过近代应用数学“最优控制论”的工具,首先提供了一个二元、不可压、稳定流动叶栅壁面最佳速度分布的理论计算方法。又通过一些转换的方法把它推广到了可压缩流动和任意回转面上。同时证明了二元不可压稳定流动叶栅壁面最佳速度分布经推广到可压缩流动任意回转面上去后,仍然是后者叶栅壁面的最佳速度分布。并且可以推广到二元扩压器,喷管以及轴对称细长旋成体表面最佳速度分布的计算。      

超跨声速扩压叶栅未启动堵塞工况计算

本文研究了超跨声速叶栅未启动堵塞工况的运行攻角.在下游节流和轴向密流比变化时,也能算出有用的结果,并获得相应的其他叶栅性能,如总压损失系数、压比、气流折转角等.同国外已有工作比较,本文方法可以考虑更多的变化条件.计算结果的比较说明本方法是可信的.由于方法比较简单,可用来分析叶栅性能,分析叶栅的几何参数和动力参数变化时叶栅性能的变化.     

任意回转面上,可压缩轴流式叶栅损失的理论计算方法

本文提供了在任意回转面上,用叶栅出气边上边界层特征参势表示的可压缩流动轴流式叶栅形面动能损失系数,形面摩擦系数,包含叶栅下游掺混损失在内的总的动能损失系数以及尾迹掺混损失系数的理论计算方法。本文的第一部分推导了上述各种损失系数的数学表达式。第二部分推导了任意回转面上回转叶栅包含离心力影响在内的可压缩索流边界层的冲量积分方程以及通过Mangler变换所得到的轴对称旋成体表面紊流边界层的冲量积分方程,并发现了两者之间流动的相似性。通过这两类边界层流动相似的比拟方法,找到了它们之间解的变换关系。第三部分详细地叙述了一个平面可压缩紊流边界层解的方法和具体的计算步骤。最后通过manglers以及上述的变换关系可以得到任意回转面上,可压缩回转叶栅紊流边界层特征参数以及上述各种损失系数的计算方法。      

RK—AUSM^＋混合格式在跨声速Euler方程计算中的应用

首先在一维AUSM^ 格式的基础上,推导出了AUSM^ 格式在任意曲线坐标下的二维形式,并将其与Runge-Kutta格式结合,对跨声速Euler方程进行求解,最后,为了验证RK-AUSM^ 混合格式的有效性,将典型双圆弧叶栅无粘跨声速流动作为算例,本文计算结果和文献结果符合很好。     

透平叶栅跨音速流动计算中的新型有限元法

将Ｔａｙｌｏｒ－Ｇａｌｅｒｋｉｎ有限元法和多级有限元的思想结合起来，构成了在收敛速度和稳定性两方面均较好的新型有限元算法：多级广义有限元。利用这一方法，分别基于Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程和Ｅｕｌｅｒ方程，研究了透平跨音速叶栅无粘流动和粘性流动，并将计算结果与实验结果作了比较。计算结果表明，本方法是透平机械内部跨音速流动计算的强有力的手段。     

跨音速湿空气非平衡凝结流动的数值研究

跨音速流动条件下湿空气中的水蒸气由于快速膨胀而发生非平衡凝结,凝结潜热对跨音速气流进行加热,会显著改变气流的流动特性。通过对商用计算流体动力学软件FLUENT进行二次开发,建立了湿空气非平衡凝结流动的数值求解方法。该方法可用于二维或三维、粘性或无粘、内流或外流的求解中。采用该方法分剐对缩放喷管、透平叶栅以及绕CA-0.1圆弧翼型的湿空气非平衡凝结流动进行了数值分析。计算结果表明：湿空气凝结手l起缩放喷管中的凝结激波、导致叶橱流动中总压降低;对于翼型周围的流动,在相对湿度分别为50％、57．1％、64.1％时,依次计算得到了单激波、五激波、双激波。     

引入温-粘及压-粘关系式的油膜工作性能数值分析

为了研究温-粘及压-粘效应对液体静压支承系统中油膜工作性能的影响,本文以大尺寸液体静压支承转台为研究对象,建立了三维立体油腔模型,采用有限体积法,模拟计算了引入温-粘及压-粘关系式时,油腔内部流体的承载力及温升变化情况.计算结果表明,温-粘特性及压-粘特性在很大程度上影响油腔内的承载能力和湿升.引入了温-粘及压-粘关系...     

N-S方程在非结构网格下的求解

在Ｒｏｅ的矢通量差分分裂的基础上，吸收了ＮＮＤ格式的优点，提出了一种非结构网格下求解Ｅｕｌｅｒ方程和Ｎ－Ｓ方程的高分辨率高精度迎风格式．这种格式具有捕捉强激波和滑移线的良好性能．在时间方向上采用了显式和隐式两种解法．文中还给出了自适应技术．最后，成功地完成了ＧＡＭＭ超音速前台阶绕流、二维平板无粘激波反射、三维Ｈｏｂｓｏｎ叶栅流动、ＶＫＩ叶栅流动、Ｃ３Ｘ叶栅流动的数值模拟，得到了满意的结果     

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.      

湿空气非平衡凝结对压气机叶栅性能影响的数值研究

跨音速流动条件下湿空气中的水蒸气由于快速膨胀而发生非平衡凝结,凝结潜热与跨音速气流耦合会显著改变流场结构。本文建立了湿空气非平衡凝结流动的数学物理模型,对三种工况下压气机叶栅内湿空气凝结流动进行计算分析。计算结果表明:湿空气压气机叶栅流动中,湿空气中水蒸气有可能发生非平衡凝结从而对叶栅通道内的流动产生强烈影响,改变流场内的激波结构,叶栅内压力系数减小最大幅度由1.38减小到0.76。     

An inviscid model for the base pressure of transonic turbine cascade

An inviscid base pressure model for transonic turbine blade has been presented. It has been shown that for a given back pressure the base pressure at the trailing edge, and the profile loss of a turbine blade are fixed according to the model and the base pressure can be calculated with the help of an inviscid numerical scheme. A parameteric study on the model shows that a blade profile with positive curvature downstream of the throat is advantageous for generating less loss, whilst the worst situation is when the exit flow reaches the sonic condition.     

Investigation of aerodynamic effects of coolant ejection at the trailing edge of a turbine blade model by PIV and pressure measurements

In order to simulate the thick trailing edges of turbine blades a slotted plate profile together with a newly designed nozzle was installed into the high-speed wind tunnel of the DLR Göttingen. At different supersonic Mach numbers and at four coolant flow rates in the range of 0–2.5% pressure distribution measurements and probe measurements were performed. The flow field was visualized by schlieren photos and the instantaneous velocity field was quantitatively investigated by Particle Image Velocimetry (PIV). The measurements of the velocity field gave an insight into stationary effects, for example the change of shock strength with coolant flow rate, and instationary effects such as the existence of a vortex street in the wake. The PIV technique offers special advantages for the investigation of transonic flow fields, but also yields to special experimental difficulties, which are also described in this article. Measured losses display a maximum at the downstream Mach number 1. This is strongly related to the behaviour of the base pressure. A loss minimum is achieved at moderate coolant flow rates, showing that an optimum coolant flow rate exists. The loss was analysed and separated into the loss contributions from the profile upstream of the trailing edge and the mixing loss due to the coolant flow.     

Conservative calculations of non-isentropic transonic flows

The classical potential formulation of inviscid transonic flows is modified to account for non-isentropic effects. The density is determined in terms of the speed as well as the pressure, which in turn is calculated from a second-order mixed-type equation derived via differentiating the momentum equations. The present model differs in general from the exact inviscid Euler equations since the flow is assumed irrotational. On the other hand, since the shocks are not isentropic, they are weaker and are placed further upstream compared to the classical potential solution. Furthermore, the streamline leaving the aerofoil does not necessarily bisect the trailing edge. Results for the present conservative calculations are presented for non-lifting and lifting aerofoils at subsonic and transonic speeds and compared to potential and Euler solutions.     

Turbulence measurements in a transonic two-passage turbine cascade

This paper presents detailed turbulence measurements in a two-dimensional, transonic, double passage turbine cascade. Particle image velocimetry was used to obtain mean velocity and turbulence measurements all around a single turbine blade within about 2 mm of the blade and wall surfaces. The passage walls were designed using an optimization procedure so that the blade surface pressure distribution matches that of the blade in an infinite cascade. The resulting experimental model captures much of the complexity of a real turbine stage (including high streamline curvature, strong accelerations, and shocks) in a passage with a continuous wall shape, allowing for high measurement resolution and well controlled boundary conditions for comparison to CFD. The measurements show that in the inviscid regions of the passage the absolute level of the turbulent fluctuations does not change significantly as the flow accelerates, while the local turbulence intensity drops rapidly as the flow accelerates. These results provide a benchmark data set that can be used to improve turbulence models.     

Analytical solutions for a single blade in vertical axis turbine motion in two-dimensions

An analytical model for a time dependent two dimensional flow around a moving profile is developed. The model is suitable for fast aerodynamic and aeroelastic coupling calculations. It determines the inviscid pressure distribution in the vicinity of one blade and the force on the blade in arbitrary two dimensional motion. The method is more flexible than previous analysis: it can represent any profile, pitching motion and blade attachment position. The method is based on conformal mapping techniques and Laurent's series decomposition and is faster and more accurate than standard panel methods. A main idea is to directly treat the singularities of the flow in a mapped plane where any geometrical plane is simplified to a circle. The vorticity is assumed to be shed in the form of a continuous vortex sheet near the trailing edge.     

Numerical Modeling of a Viscous-Gas Flow in a Turbine Cascade with Air Ejection

The gas flow pattern, the local friction coefficients, the profile losses, and the outlet flow angles in a plane turbine cascade are modeled numerically using the 2-D Reynolds equations. For describing the turbulence characteristics, a two-parameter q- turbulence model is used. The flow pattern behind the cascade trailing edge is studied. The calculated values of the local gas pressure and the friction coefficient on the profile contour, the profile losses, and the outlet flow angles are compared with the experimental data for a transonic flow in a nozzle cascade at various reduced gas velocities behind the cascade and relative mass flows of the air ejected.     

Flow and Heat Transfer in a High-Aspect-Ratio Rib-Roughed Cooling Channel with Longitudinal Intersecting Ribs

This paper describes a detailed numerical investigation of a stationary high-aspect-ratio rib-roughed rectangular cooling channel with longitudinal intersecting ribs near the gas turbine blade trailing edge region. In order to overcome the heat transfer performance degeneration in the highaspect- ratio channel, longitudinal intersecting ribs are arranged on the channel bottom surface. The effect of the number of longitudinal intersecting ribs on the flow and heat transfer is systematically studied in the Reynolds number range Re = 10 000–30 000. The results show that a heat transfer augmentation region exists just downstream the junction between the longitudinal rib and the angled rib due to additional secondary flows. With more longitudinal intersecting ribs, the heat transfer distributions on the channel surfaces are more uniform. Though the pressure loss is also enlarged with an increase in the number of longitudinal intersecting ribs, the overall thermal efficiency increases in the entire range of Reynolds numbers investigated. The configuration with two sets of longitudinal intersecting ribs shows the best overall thermal efficiency.     

Development of secondary flows in the stator of a model turbine

Measurements are described which show the development of the secondary flows through the stator blades in a single stage model turbine. The build of the turbine is intended to simulate a stage in the HP cylinder of a steam turbine and three different thicknesses of inlet boundary layers are studied. Flow visualisation of the inlet boundary fluid shows the development of the horseshoe vortex round the blade leading edge. Probe measurements upstream and downstream of the trailing edge plane show how the passage vortices are developed and how they influence the distribution of losses across the annulus.     

钝后缘风力机翼型的环量控制研究

钝后缘风力机翼型具有结构强度高、对表面污染不敏感等优点,但其较大的阻力系数使得翼型的整体气动特性不够理想. 利用环量控制方法对钝后缘风力机翼型进行了流动控制,以改善钝后缘风力机翼型的气动特性,减弱尾迹区脱体涡强度. 通过对钝后缘风力机翼型环量控制方法进行相关的数值模拟,对比研究了环量控制方法的增升减阻效果, 研究了环量控制下翼型升阻力特性随射流动量系数的变化规律,并对不同射流动量系数下环量控制方法的气动品质因子和控制效率进行了分析. 研究结果表明:环量控制方法能够大幅提升钝后缘风力机翼型的升力系数,同时有效地降低翼型的阻力系数; 翼型的升力系数随射流动量系数的增大而增大,表现出很明显的分离控制阶段和超环量控制阶段的变化规律; 射流能耗的功率系数随射流动量系数的增大而增大,且增长速率逐渐增大;实施环量控制方法后叶片的输出功率同样随射流动量系数增大而增大,但增长速率逐渐降低. 总体来说,环量控制方法可以有效地改善钝后缘风力机翼型的气动特性以及功率输出特性,在大型风力机流动控制中具有很好的应用前景.      

DIRECT NUMERICAL SIMULATION OF TURBINE CASCADE FLOW WITH HEAT TRANSFER EFFECTS

低雷诺数流动对高空动力装置, 特别是涡轮部件的性能产生重要的影响. 本文采用具有7阶精度的差分格式, 通过直接求解二维瞬态可压缩Navier-Stokes方程组, 对雷诺数为241 800 (基于叶片弦长)时的叶片表面带有热传导效应的平面涡轮叶栅流动进行了二维直接数值模拟, 对低雷诺数平面涡轮叶栅流动的非定常流动现象作了初步的探索.数值结果表明:在叶栅通道入口处, 流场的非定常性很弱;在叶栅尾缘处, 具有正负涡量的尾涡交替地从压力面和吸力面上脱落;周期性的涡脱落使得叶栅通道内和尾迹区的总压发生(准)周期的变化, 并且, 尾迹区总压变化主频率是通道内总压变化主频率的2倍;在时均流场中, 叶片表面压力的分布与实验值吻合良好, 表征热传导效应的斯坦顿数除湍流区外与实验值基本吻合;尾迹区速度脉动的2阶统计量与圆柱绕流尾迹区速度脉动2阶统计量具有基本相似的分布特征.