端壁相对运动对压气机叶栅间隙流场影响的数值模拟

压气机端壁与叶片间的相对运动是影响叶顶间隙气流流动的重要因素.采用数值模拟的方法考察了端壁运动对不同叶顶间隙压气机叶栅内三维流场的影响.结果表明:端壁相对运动改变了叶栅间隙流场结构,叶栅通道内出现向相邻叶片压力面运动的刮削泄漏涡,上通道涡及叶顶分离涡受到抑制,叶尖负荷增大,间隙泄漏流量增加,叶栅总损失由于叶顶区掺混损失减少而减少.     

具有静止顶部间隙透平叶栅气动特性的实验研究

对具有静止顶部间隙的常规透平直叶栅和透平正弯叶栅的流道和间隙进行了测量，得到流道及间隙内的详细参数。结果表明：顶部间隙的存在对叶栅的气动性能有较大影响，使叶栅上半翼损失明显增高，叶片正弯曲减小了叶顶后的横向压力梯度，削弱了泄漏流与端壁横流及二者的相互作用，降低了叶栅的流动损失，明显改善了叶栅的出口流场。     

叶片弯曲降低泄漏损失的实验研究

应用拓扑学原理分析了叶顶相对间隙为0．036的涡轮直叶栅与正、反弯叶栅的壁面流谱，发现正弯叶片栅与直叶片、反弯叶片栅吸力面上半叶展的拓扑结构明显不同，探讨了差别形成的机理及其对相对漏气量与总流动损失的影响。     

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。     

端壁相对运动对叶顶流动传热特性影响的研究

采用求解三维Reynolds-Averaged Navier-Stokes(RANS)和标准k-w紊流模型的方法数值研究了端壁与动叶相对运动时动叶顶部的气动换热特性。以实验测量的叶栅为研究对象验证了所采用的数值方法和紊流模型的有效性。分析了端壁与叶顶有无相对运动时叶顶间隙高度对动叶顶部气动换热特性的影响。研究结果表明:端壁与叶顶存在相对运动时,叶顶换热系数随着间隙高度的增大而增大。在小叶顶间隙(s=0.2%H)时叶顶表面平均换热系数最小,动叶顶部前缘处的换热系数显著降低且泄漏流方向发生较大偏转。同时近顶部的吸力面侧前缘换热系数较大,随着叶顶间隙高度增大该区域的换热系数降低。端壁与叶顶无相对运动时,随着叶顶间隙高度的增加叶顶换热系数先增大后减小且在叶顶间隙中间弦长处产生大范围流动分离,当s=0.5%H时叶顶平均换热系数最大。小叶顶间隙(s=0.2%H)时端壁与叶顶存在相对运动时,动叶气动效率比端壁与叶顶无相对运动提高0.5%。大叶顶间隙(s=2.0%H)时端壁与叶顶无相对运动时,动叶气动效率比端壁与叶顶存在相对运动提高0.29%。     

带有自发射流的涡轮叶顶间隙流场PIV测量

为了探究叶尖射流对涡轮叶栅流场特性的影响,搭建了一个小尺度低速叶栅风洞实验台,利用粒子成像测速(PIV)技术对带有自发射流的涡轮叶顶间隙流场进行了直接测量,获得了低雷诺数(Re=6.46×103~3.23×104)下射流孔附近的流动图像及速度测量结果,展示了叶顶间隙内层流和紊流2种流态下自发射流与泄漏流的相互作用过程,揭示了低雷诺数工况下(涵盖层流到紊流的转捩)叶尖射流抑制泄漏流的作用机理及影响因素,并对叶尖射流尾迹中出现的类卡门涡街的涡分布现象进行了探讨.结果表明:叶尖射流的引入在泄漏流抑制方面取得一定收益,但同时也进一步加剧了叶顶间隙流动的复杂性.     

涡轮叶栅叶顶间隙冷气掺混数值模拟

采用具有三阶精度TVD性质的有限差分格式计算方法,对一具有真实冷气孔形状的涡轮级叶顶间隙冷气掺混流场进行了全三维N-S方程数值模拟,分析了在1%和2%间隙下冷气射流与间隙流动相互作用的运动机理以及冷气射流对间隙和叶栅流场的影响。结果表明,冷气喷射使得泄漏流动速度降低,在小间隙下运动轨迹偏转以及气动参数的变化都非常明显,轮榖表面可以获得低温保护。在大间隙下叶顶表面获得更好的冷却效果。     

150 MW汽轮机高压缸级内流场的数值模拟

采用Numeca软件对带隔板汽封和叶顶间隙汽封的高压缸二、三级叶栅流动进行了数值模拟,并与不带汽封的二、三级叶栅流场进行了比较.结果表明,汽封泄漏损失使级效率显著下降,汽封出口处的低能流体使端壁的附面层变厚,端壁摩擦损失增大;隔板汽封出口处的气体周向速度较小,导致了较大的负攻角流动,它与下排叶栅的横向流动相结合大大促进了下通道涡的发展.     

某小型涡轮不同篦齿封严结构性能分析

通过对某小型涡轮叶顶间隙内的泄漏流动进行数值模拟,分析了不同篦齿形状、高度下叶顶间隙内气流流动特性。结果表明:叶顶泄漏流主要存在于叶片中后部;在保证间隙不变的条件下,梯形篦齿可有效降低泄漏流动;减小篦齿封严间隙可以在一定程度上提高涡轮效率。     

间隙尺寸对涡轮叶栅气动性能影响的实验研究

测量了较大间隙(τ=0．036)下常规直叶栅中分面和上下游及栅内的气动参数，并与黄洪雁博士测量的较小间隙(τ=0．023)下相同叶栅的试验数据进行了详细比较，讨论了间隙尺寸变化对间隙流动和整体叶栅气动特性的影响。     

Experimental Investigation of Aerodynamic Performance due to Blade Tip Clearance in a Gas Turbine Rotor Cascade

This study examines how the complex flow structure within a gas turbine rotor affects aerodynamic loss. An unshrouded linear turbine cascade was built, and velocity and pressure fields were measured using a 5-hole probe. In order to elucidate the effect of tip clearance, the overall aerodynamic loss was evaluated by varying the tip clearance and examining the total pressure field for each case. The tip clearance was varied from 0% to 4.2% of blade span and the chord length based Reynolds number was fixed at 2×10⁵. For the case without tip clearance, a wake downstream of the blade trailing edge is observed, along with hub and tip passage vortices. These flow structures result in profile loss at the center of the blade span, and passage vortex related losses towards the hub and tip. As the tip clearance increases, a tip leakage vortex is formed, and it becomes stronger and eventually alters the tip passage vortex. Because of the interference of the secondary tip leakage flow with the main flow, the streamwise velocity decreases while the total pressure loss increases significantly by tenfold in the last 30% blade span region towards the tip for the 4.2% tip clearance case. It was additionally observed that the overall aerodynamic loss increases linearly with tip clearance.     

Numerical investigation of active tip-clearance control through tip cooling injection in an axial turbine cascade

This paper presents a numerical investigation of an active tip-clearance control method based on cooling injection from the blade tip surface. It aims to study the influences of air injection on controlling tip clearance flow, with emphasis on the effects of the injection location on secondary flow and the potential thermal benefits from the cooling jet. The results show that injection location plays an important role in the redistribution of secondary flow within the cascade passage. Injection located much closer to the pressure-side corner performs better in reducing tip clearance massflow and its associated losses. However, it also intensifies tip passage vortex, due to less restraint deriving from the reduced tip clearance vortex. Lower plenum total pressure is required to inject equivalent amount of cooling air, but the heat transfer condition on the blade tip surface is a bit worse than that with injection from the reattachment region. Thus the optimum location of air injection should be at the tip separation vortex region.     

Experimental Investigations of the Three—Dimensional Flow in a Large Deflection Turbine Cascade with Tip Clearance

INTRoDUCTI0NThetipleakaeflowisnowrecognizedasanimpor-tantsourceoflossesinbothcompressorsandturbines,asasourceofcoolingprobleminturbinesandasourceofinstabilityincomPressorsandfans.Manyturbo-maChinimPellersarenotshroudedandtheleakaeflowthroughthetipgaPofthebladeisanunavoidablefaCtorwhichdeterioratestheperformance.Den-tonandCumpsty[1]melltionedabouttwodistinctandequallyimportantaspects.tothetipclearanceflows.First,thereisareducti0ninthebladeforce,there-fore,theworkdone.Thisoccursbecausethe…     

基于SPOD方法的压气机转子叶顶区域非定常流动分析

为了研究叶顶区域非定常流动特性,对跨声速轴流压气机转子NASA Rotor37在多工况下进行了三维非定常数值模拟,采用谱本征正交分解（Spectral Proper Orthogonal Decomposition,SPOD）方法从叶顶区域流场中提取出时空耦合的单频相干结构进行分析。研究结果表明：相比于常规分析方法,SPOD方法能够高效地从非定常流场中识别出流动特征,有助于揭示叶顶区域流动规律;在“小流量”工况下叶顶区域流动呈现出强的非定常性,且随着质量流率的减小叶顶区域非定常流动增强、波动范围增加、波动频率呈现出“阶跃式”下降;造成叶顶区域流场非定常周期性波动的主要原因是叶顶间隙泄漏涡破碎区的扰动以及叶顶间隙泄漏涡破碎后与主流相互作用所形成的叶尖二次涡的波动。     

Stereoscopic PIV measurements of the flow field in a turbine cascade

This paper presents experimental measurements of the flow field in a Low-speed Turbine Cascade using a stereoscopic particle-image velocimetry(SPIV). During the measurements, a pair of frame-straddling-based CCD cameras were configured at different sides of the laser light sheet, and appropriate tracing particles(DEHS) were employed. The measurements were conducted at the incidence angle of 0 degree and exit Reynolds number of 1.7 × 105 with the tip clearance 1.18% of blade chord. The tip flow features, such as the evolution and breakdown of tip leakage vortex, the horseshoe vortex, turbulence characteristics of tip leakage flow, were studied for the flow field analysis. The results showed that the tip leakage flow/vortex mainly dominate flow fields in the tip region. The tip leakage vortex performs as a concentrated vortex before its breaking down and splitting into small vortices. The highest turbulence intensity mainly occurs in the tip region along with the trajectory of tip leakage vortex, and when the vortex breaks down, the turbulence intensity reduces rapidly. Additionally, the SPIV with this configuration also shows an advantage in investigating the flow structures and mechanism inside the turbine cascade.     

Unsteady tip clearance flow in an isolated axial compressor rotor

Introduction Background It is well known that the rotor tip clearance flow has profound effects on the performance and stability of axial compressor (Wisler[1], Howard[2]). Numerous studies on the tip clearance flow were carried out in the past fifty years. Rain[3] proposed a model to predict the loss due to tip leakage flow assuming that the kinetic energy of the leakage flow velocity component normal to the mean chamber line would be dissipated. Lakshminarayana[4] developed a model to pre…     

Effect of winglet geometry arrangement and incidence on tip clearance control in a compressor cascade

An experimental study is conducted to investigate the influences of blade tip winglet on the flow field of a compressor cascade. The tests are performed in a low speed linear cascade with stationary endwall, with three blade tip configurations, including the baseline tip, the suction-side winglet tip and the pressure-side winglet tip. The flowfield downstream of the cascade is measured using five-hole probe, from which the three-dimensional velocity field, vorticity field and pressure field are obtained. Static pressure measurements are made on the endwall above the blade row using pressure taps embedded in the plywood endwall. All measurements are made at both design and off-design conditions for tip clearance level of about 2 percent of the blade chord. The results revealed the incidence variation significantly affects the secondary flow and the associated loss field downstream of the cascade, where the tip leakage vortex and passage vortex exist as the major contributors on the field. The winglet geometry arrangements can change the trajectory of the tip leakage vortex. The suction-side winglet tip blade provides a lower overall total pressure loss coefficient when compared to the baseline tip blade and pressure-side winglet tip blade at all incidence angles.     

动力涡轮有冠及无冠动叶栅顶部二次流的数值分析

建立某动力涡轮的流体分析模型,采用三维定常N-S(Navier-Stokes)方程和带转捩的SST(Shear stress transport)湍流模型,对该动力涡轮典型工况下的燃气流动状况进行了数值模拟.针对叶道内的二次流旋涡结构,分别对无冠动叶栅和有冠动叶栅顶部的间隙流、通道涡进行了分析,展示了大展弦比非气冷动叶...