分流叶栅及串列叶栅的流场计算

本文用流函数有限差分松驰法求解了分流叶栅及串列叶栅的流场。所求出的轴流式叶栅叶型表面速度分布与文献[1]中试验数据十分相符;同时计算了多分流叶栅流场,计算值与[2]中试验值吻合很好;还对[3]中的串列叶栅流场进行了计算,计算与试验结果也吻合较好;按本方法计算数据优化设计的含分流叶栅的离心式风机的性能较好。     

外来扰动频率对涡轮叶栅流动稳定性的影响

应用非线性PSE方法预测和评价某型超临界蒸汽轮机调节级导叶栅边界层流动的稳定性,研究了扰动频率对叶栅流动稳定性的影响。结果表明,当来流扰动频率变化时,扰动会对叶栅边界层稳定性产生很大的影响,此时存在一个最大扰动频率,在这一频率下流动最容易发生转捩。最大扰动频率受边界层厚度雷诺数的直接影响,其数值沿着流向逐渐减小,即叶片入口流动对高频扰动敏感,叶片出口流动对低频扰动敏感。     

计算跨音速透平叶栅极限进气角的方法

本文提出了一个计算跨音速透平叶栅的极限进气角的方法。该法以叶栅的相对极限环量为根据。用本法计算得到的极限进气角和实验结果吻合较好。     

气膜冷却对高压涡轮叶栅损失特性的影响研究

为获得全气膜气冷涡轮叶栅的损失特性,采用试验及数值仿真方法,研究了不同冷气流量、不同叶栅出口马赫数条件下冷气射流对叶栅损失的影响。通过叶栅槽道静压云图及叶片表面压力分布等试验及数值仿真结果对比,验证了通冷气叶栅性能仿真分析方法的准确性。结果表明：同一冷气流量比下,通冷气叶栅能量损失系数随着马赫数的增大先减小后增大,在设计马赫数附近损失最低;通冷气叶栅能量损失系数随着冷气流量的增大而增大,且前后腔均通冷气时能量损失系数最大,前腔单独通冷气时能量损失系数最小;通冷气叶栅能量损失系数随着冷气与主流温比增大而增大。     

变弯度叶栅的试验研究

对有缝隙的和无缝隙的变尾缘叶栅与变弯度叶栅进行了系统试验研究,取得了这种叶栅的气流转折角和损失以及落后角的变化规律。证实压气机变弯度叶栅可在较小的能量损失下实现较大的气流转折角,其工作特性比可转导叶明显优越。推荐的叶栅构型及其几何参数值可供设计直接使用,它是改善压气机调节性能,防止喘振,扩大稳定工作范围的行之有效的方法。     

大功率汽轮机末级动叶根部叶栅的最优化设计

本文提出了大功率汽轮机末级动叶根部叶栅的最优化设计的方法,并给出设计实例。最优设计所得的叶栅损失系数比原有叶栅的损失系数有明显下降。     

高负荷跨音速透平叶栅气水模拟的试验研究

本文介绍了在我国首次利用气水模拟方法对某高负荷跨音速透平动、静叶栅进行详尽的空气动力学试验研究的结果,并将结果与平面叶栅风洞试验及叶栅绳流的计算结果进行比较。气水模拟方法对跨音速叶栅的方案设计和定性分析具有正确、直观、简便、经济的优点。本方法不仅可替代繁重的平面叶栅高速风洞的试验工作,还可验证跨音速叶栅绕流的计算结果。     

叶片倾斜对叶栅出口流场的影响

通过吹风实验,探讨了在不同径高比和外壁面扩张角的汽轮机环形静叶栅中叶片倾斜对叶栅出口流场的影响.实验结果表明:采用最佳倾斜角叶片能降低叶栅能量损失和改善叶栅出口流场的气动性能.图9参10     

低转折角叶片弯曲作用的实验研究

在低速平面叶栅风洞上,对具有不同正弯曲角叶片的透平矩形静叶栅进行了吹风实验.叶栅展弦比h/b=0.68,叶片转折角θ=71°.分析了叶片正弯曲对叶栅气动特性的改善作用及减小端部损失的机理.讨论了冲角、叶片弯曲角和出口条件对叶片正弯曲作用的影响.图9参7     

新型极小展弦比叶栅的叶型研究

以数值手段分析研究了具有不同极小展弦比的改型设计的后加载透平叶栅的内部定常三维粘性流动及损失，同时对该透平叶栅在不同出口马赫数和进气角下进行平面叶栅吹风实验。数值分析结果和实验结果表明，后加载叶栅在极小展弦比下能有效控制叶栅内二次流动的形成，具有低的三维叶栅损失。     

Effects of freestream turbulence on bypass transition of separated boundary layer on low-pressure turbine airfoils

This paper presents experimental studies on bypass transition of separated boundary layer on low-pressure turbine airfoils,focusing on the effects of freestream turbulence on the transition process.Hot-wire probe measurements are performed on the suction side of an airfoil in the low-pressure linear turbine cascade at several Reynolds number conditions.Freestream turbulence is enhanced by use of turbulence grid located upstream of the cascade.The results of this experimental study show that the location of boundary layer separation does not strongly de-pend on the freestream turbulence level.However,as the freestream turbulence level increases,the size of separa-tion bubble becomes small and the location of turbulent transition moves upstream.The size of separation bubble becomes small as the Reynolds number increases.At low freestream turbulence intensity,the velocity fluctuation due to Kelvin-Helmholtz instability is observed clearly in the shear layer of the separation bubble.At high frees-tream turbulence intensity,the streak structures appear upstream of the separation location,indicating bypass transition of attached boundary layer occurs at high Reynolds number.     

Experimental Studies on Heat Transfer in the Tip Gap of a Sectorial Turbine Cascade

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Aerodynamic Loading Distribution Effects on the Overall Performance of Ultra-High-Lift L Turbine Cascades简

The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both profile and secondary losses in the aero-engine LP turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading （Zw=1.03）, has been compared with two Ultra-High-Lift profiles with the same Zweifel number （Zw=1.3 for both cascades）, but different velocity peak positions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been experimentally in- vestigated for Reynolds numbers in the range 70000〈Re〈300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency ./＋=0.62 on both profile and secondary flow losses for the three different cascade designs have been studied. Total pressure and velocity distributions have been measured by means of a miniaturized 5-hole probe in a tangential plane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic performance of the blade cascades in terms of profile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When operating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest profile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are present.     

Numerical study of improving aerodynamic performance of low solidity LPT cascade through increasing trailing edge thickness

This paper presents a new idea to reduce the solidity of low-pressure turbine (LPT) blade cascades, while remain the structural integrity of LPT blade. Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness (TET). The solidity of the LPT cascade blade can be reduced by about 12.5% through increasing the TET of the blade without a significant drop in energy efficiency. For the low solidity LPT cascade, increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by 1.86% for Reynolds number (Re) of 25,000 and freestream turbulence intensities (FSTI) of 2.35%. The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented. The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.     

On the inverse heat convection problem of the flow over a cascade of rectangular blades

In this study, an inverse algorithm based on the conjugate gradient method is applied to a steady flow over a cascade of rectangular blades to estimate the inlet flow temperature. The objective is to study the difficulties associated with inverse heat convection problems. Therefore, the measurement quantity has been deliberately placed at five different locations over the domain, each of them covered by a unique flow feature. The computation shows that at very low Reynolds number, the accuracy of the inverse method is not affected by the relative position between the estimated and measurement quantities. At a higher Reynolds number, however, the accuracy of the inverse method strongly depends on the relative position between the two quantities. The inverse method only returns satisfactory estimation for some cases but not others.     

Multigrid Navier—Stokes Calculation for Two Dimensional Cascades

INTRODUCTIoNOverthepast2OyearssteadyprogresshasbeenmadeinthedevelopmentofCFDcodesforturboma-chinerybladerows.Thenumericalmethodsthathavebeenthemosthighlydevelopedandhaveprovidedthegreatestadvancementsinturbomachineryfielda-rethetimemarchingsolversbasedonafullyconservativeformofgoverningequation.Theyprovideasin-gleapproachforsubsonic,transonic,andsupersonicflows,andtheyinherentlyprovidenaturalshockcaP-turingcapability.lssuesofsolutionaccuracy,geomet-riccomplexity,speed(cost),unsteadiness,…     

Profile and secondary flow losses in a high-lift LPT blade cascade at different reynolds numbers under steady and unsteady inflow conditions

The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade performance under real engine operating conditions.The Reynolds number has been varied in the range 100000相似文献   

Unsteady inflow effects on the wake shed from a high-lift LPT blade subjected to boundary layer laminar separation

An experimental investigation on the near and far wake of a cascade of high-lift low-pressure turbine blades subjected to boundary layer separation over the suction side surface has been carried out, under steady and unsteady inflows. Two Reynolds number conditions, representative of take-off/landing and cruise operating conditions of the real engine, have been tested. The effect of upstream wake-boundary layer interaction on the wake shed from the profile has been investigated in a three-blade large-scale linear turbine cascade. The comparison between the wakes shed under steady and unsteady inflows has been performed through the analysis of mean velocity and Reynolds stress components measured at midspan of the central blade by means of a two-component crossed miniature hot-wire probe. The wake development has been analyzed in the region between 2% and 100% of the blade chord from the central blade trailing edge, aligned with the blade exit direction. Wake integral parameters, half-width and maximum velocity defects have been evaluated from the mean velocity distributions to quantify the modifications induced on the vane wake by the upstream wake. Moreover the thicknesses of the two wake shear layers have been considered separately in order to identify the effects of Reynolds number and incoming flow on the wake shape. The self-preserving state of the wake has been looked at, taking into account the different thicknesses of the two shear layers. The evaluation of the power density spectra of the velocity fluctuations allowed the study of the wake unsteady behavior, and the detection of the effects induced by the different operating conditions on the trailing edge vortex shedding.     

Experimental investigation of separation and transition processes on a high-lift low-pressure turbine profile under steady and unsteady inflow at low Reynolds number

The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at mid-span. The tested Reynolds number is 70000, typical of the cruise operating condition. The results of the investigations performed under steady and unsteady inflow conditions are analyzed. The unsteady investigations have been performed at the reduced fre- quency off=0.62, representative of the real engine operating condition. Profile aerodynamic loadings as well as boundary layer velocity profiles have been measured to survey the separation and transition processes. Spectral analysis has been also performed to better understand the phenomena associated with the transition process under steady inflow. For the unsteady case, a phase-locked ensemble averaging technique has been employed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal output. The ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakesboundary layer interaction in separation suppression. Time-resolved results are presented in terms of mean velocity and unresolved unsteadiness time-space plots.     

超微涡轮动叶栅叶顶间隙对流场影响的数值模拟

通过数值求解基于雷诺时均的三维定常粘性N-S方程,结合RNGk-ε湍流模型和非平衡壁面函数,对一种超微型向心涡轮动叶栅内的流动情况进行了数值模拟。揭示了具有极低展弦比动叶栅叶顶间隙对流场参数分布和气动损失的影响,为超微涡轮的设计和改进提供了理论依据。模拟结果表明,叶顶间隙的大小对通道内马赫数分布有重要影响,其中顶部间隙射流所引发的泄漏涡与主流的掺混是主流马赫数降低的重要原因;叶顶间隙的存在使得总压损失系数均匀化,即近壁区和主流区的总压损失都较高;动叶栅在叶展方向上的载荷分布均匀,弦向载荷主要由接近尾缘的弧段承担;模拟中还解析出三维的尾迹涡,这主要是动叶栅尾缘过厚所导致,应进行叶型改进。