端壁运动对自发射流抑制叶尖泄漏影响的数值研究

通过数值手段分析了端壁运动对带有叶尖自发射流的叶栅流场特性、叶顶间隙泄漏流量特性及叶片周向载荷分布特性的影响。结果表明:端壁运动的反向刮削作用会显著影响间隙附近流场,随着端壁运动速度增大,泄漏涡和上通道涡会逐渐向叶片吸力面靠近,同时,泄漏涡强度逐渐削弱,而上通道涡强度逐渐增强,平均总压损失增大;端壁运动对叶尖自发射流抑制泄漏流的效果有放大作用;端壁运动会显著改变叶尖吸力面附近静压系数的分布,使其具有后加载的特性。     

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。     

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.     

扭叶片正弯对叶栅通道内二次流动影响的数值分析

以某汽轮机高压级动叶为研究对象,采用κ-ωSST模型、SIMPLEC算法数值模拟了正弯扭叶片叶顶间隙泄漏涡的形成和发展过程及其对叶栅通道二次流的影响。结果表明:相对于常规扭叶片,汽流在正弯扭叶片吸力面附近形成的泄漏涡的影响范围和对通道主流的扰动变小,且叶顶间隙的增加削弱了正弯扭叶片吸力面的"C"型压力梯度,使得叶片两端部附面层厚度增加,造成了叶片端部损失的增大。     

汽轮机动叶顶部间隙泄漏流动特性的数值模拟

以一个小展弦比轴流透平级为研究对象,采用数值方法对不同动叶顶部间隙情况下的间隙泄漏流动进行了分析,研究了间隙流和间隙涡的形成、发展及其对透平级性能的影响.以三维流线和极限流线为手段,分析了6种间隙尺寸下动叶顶部的泄漏流和泄漏涡造成的损失及其与主流掺混的过程.结果表明:动叶顶部间隙两侧压力面和吸力面之间的压力差使汽流从压力面被吸入间隙,跨过叶顶,进入相邻叶栅通道的吸力面,导致泄漏流动;与无间隙的情况相比,叶顶间隙的存在使上端壁处的流场发生明显变化,引起损失迅速增长;随着间隙的增大,泄漏涡的产生位置提前,强度增大,从而导致更大的流动损失.     

汽轮机叶片正弯对叶顶间隙泄漏流动影响的数值模拟

以某汽轮机高压级动叶为研究对象,采用κ-ε湍流模型,应用SIMPLEC算法对在相同叶顶间隙高度下的常规扭叶片和正弯扭叶片的叶顶间隙流动进行了数值模拟。研究结果表明:与常规扭叶片相比,叶片正弯提高了汽流在叶顶区的最低压力值,减小了叶顶压力边与吸力边的横向压力梯度;汽流在正弯扭叶片吸力面附近形成的泄漏涡的影响范围和对通道主流的扰动弱于在常规扭叶片内形成的影响;正弯扭叶片使汽流在吸力面和压力面上形成了叶顶部正径向压力梯度、叶根部负径向压力梯度的"C"型压力分布,同时降低了叶片上端部附近的总压损失。叶片正弯既降低了叶顶泄漏损失,又降低了叶栅通道内的掺混损失。     

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%。     

采用弯叶片控制高负荷涡轮叶栅内附面层迁移的机理分析

对具有128.5°折转角的高负荷平面涡轮叶栅的内部流场进行了数值模拟.结合前期的实验结果,并利用拓扑学理论,详细分析了弯叶片对叶栅内附面层发展及旋涡运动的影响.结果表明,以通道涡为主的集中涡系在高负荷涡轮叶栅中部强烈掺混,使得中部的能量损失系数(0.56)明显高于端部(0.07),这是反弯叶片能改善此类叶栅整体气动性能的原因.对附面层迁移理论作了进一步讨论后指出,在高负荷涡轮叶栅内采用弯叶片减少二次流损失时应重点考察自由涡层的迁移.     

抑制叶顶间隙泄漏的叶轮机械叶片的流场模拟

根据叶顶间隙流对叶轮机械的性能有重要影响这一特性,设计了一种叶片.该叶片顶部带有"燕尾冠",在叶顶的压力侧和吸力侧都形成"倒钩".通过对带有"燕尾冠"的叶片和一般的叶片的流场进行数值模拟,在同等条件下比较两者之间压气机的总体性能、流场特性以及叶顶间隙的泄漏量的区别,得到优化设计后的"燕尾冠"叶片能较好的保持住叶片表面的压力,削弱了叶顶间隙泄漏涡的产生和减少了通过叶顶间隙的泄漏量.数据结论为改进和提高叶轮机械的运转性能提供参考依据.     

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。     

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.     

Experimental study of effects of one kind of tangentially non-uniform tip clearance on the flow field at an exit of a compressor cascade passage

This paper presents an experimental investigation of effects of one kind of tangentially non-uniform tip clearance on the flow field at an exit of a compressor cascade passage.The tests were performed in a low-speed large-scale cascade with the uniform tip clearance and the non-uniform clearance.The three-dimensional flow field was measured at the exit at three incidence angles of 0°,5°,and 8° using a mini five-hole pressure probe.The measurement results show that the non-uniform tip clearance can moderate the leakage flow and blow down more low-energy fluids at the tip corner and decrease the accumulation of low-energy fluids which cause the flow blockage in the blade passage.In the meantime,the non-uniform clearance can weaken the tangential migration of the low-energy fluids in the endwall boundary layer and reduce the secondary loss and the flow blockage in the tip region.     

Experimental and numerical investigation on compressor cascade flows with tip clearance at a low Reynolds number condition

High flow rate aeroengines typically employ axial flow compressors,where aerodynamic loss is predominantly due to secondary flow features such as tip leakage and corner vortices.In very high altitude missions,turbomachinery operates at low density ambient atmosphere,and the recent trend toward more compact engine core inevitably leads to the reduction of blade size,which in turn increases the relative height of the blade tip clearance.Low Reynolds number flowfield as a result of these two factors amplifies the relative importance of secondary flow effects.This paper focuses on the behavior of tip leakage flow,investigating by use of both experimental and numerical approaches.In order to understand the complex secondary flow behavior,cascade tests are usually conducted using intrusive probes to determine the loss.However relatively few experimental studies are published on tip leakage flows which take into account the interaction between a rotating blade row and its casing wall.Hence a new linear cascade facility has been designed with a moving belt casing in order to reproduce more realistic flowfield as encountered by a rotating compressor row.Numerical simulations were also performed to aid in the understanding of the complex flow features.The experimental results indicate a significant difference in the flowfield when the moving belt casing is present.The numerical simulations reveal that the leakage vortex is pulled by the shearing motion of the endwall toward the pressure side of the adjacent blade.The results highlight the importance of casing wall relative motion in analyzing leakage flow effects.     

不同参数端壁翼刀控制二次流机理的实验研究

不同周向和轴向位置的压气机叶栅上安装1／2轴向弦长翼刀的叶栅出口流场测量结果表明,两种方案的叶栅总损失随翼刀周向位置变化的总体趋势是翼刀靠近压力面时叶栅总损失降低。翼刀安装在流道前半部的最佳周向位置是距离吸力面60％相对节距处;安装在流道后半部的翼刀最佳周向位置是距离吸力面80％相对节距处。通过对比初步探讨了翼刀减小二次流损失的机理：一方面通过降低流道内端壁附面层内横向压力梯度,减弱低能流体向吸力面／壁角区的堆积;另一方面是通过产生的反向翼刀涡限制马蹄涡的压力面分支发展,从而减小通道涡的尺寸和强度。     

Measurement and analysis of tip clearance unsteady flow spectrum in axial-flow fan rotor

The dynamic pressure measurement device and test technology are described in this study. The tip clearance unsteady flow development from the inlet to the outlet of an axial-flow rotor was revealed by analyzing pressure frequency spectrum acquired from measuring the unsteady pressure field of the tip endwall. The experiment provides test basis for thoroughly understanding the tip clearance unsteady flow and building interaction models of tip clearance flow and main flow.     

Experimental Study of Endwall and Tip Clearance Flows in a Two—Dimensional Turbine Rotor Blade Cascade—Effect of Incidence Angle

IntroductionA ttirbomachinery rotor must have a slhall hilt finite clearance relative to its surrounding casing. Theflow, which leaks thlough this fililte gap, has a surprisingly large effect on the aerodynamics of the flow.The loss produced due to the tip clearance is an.unavoidable loss. The presence of tip clearance ajtersthe endwall flow siglilflcaotly. The normal secondaryflow interacts with the leakage fluid ajs it easts fromthe suction surface. The leakage fluid rolls into whatis known…     

多级轴流压气机模化设计中尺寸缩放对气动性能影响的数值研究

为了研究几何尺寸模化缩放及叶尖间隙对多级轴流压气机气动性能及内部流动的影响,采用Numeca程序对17级轴流压气机开展了数值计算。结果表明：在80%及100%等高转速条件下压气机效率随着模化比例增大而增大,而在50%转速下模化缩放对压气机效率的影响较小。相对于原型压气机,模化放大时,压气机前8级单级压比均有所降低,而后8级压比均提高;模化缩小时,压气机的变化规律则相反。随着压气机几何尺寸的增大,静叶叶根和叶尖区域的总压恢复系数显著提高。同时,叶片叶尖泄漏流区域的熵增减少,从而使各级效率均有所提升。缩放模化中,随着叶尖间隙的增大,泄漏流增多,恶化了动叶叶尖附近的流动分离,降低了动叶后50%弦长区域的相对马赫数,同时扩大了静叶上端壁的流动分离,使压气机效率降低。     

有间隙涡炉叶栅涡系结构的数值模拟

对具有3.6%相对叶顶间隙的锅轮叶栅三维空间流动进行了数值模拟,分析了大间隙涡轮叶栅流场的涡系结构。结果表明在叶顶间隙内部和上半翼展现出了复杂的分离流动,同时由于叶顶间隙的存在,上、下端壁尾缘附近的流动明显不同。     

倒角和间隙对跨音轴流压气机气动性能的影响

通过对一单级跨音速轴流压气机的流场进行数值模拟,研究了动叶根部倒角以及顶部间隙对流场气动性能的影响.结果表明:动叶叶顶间隙会造成顶部区域的通流阻塞并加重顶部分离损失,根部倒角会减小根部的气流折转角,降低做功能力,而且扩大根部分离区,减小根部流量,增大根部分离损失,因此为了提高数值模拟的准确性应考虑动叶叶顶间隙和根部倒角.     

Unsteady tip clearance flow pattern in an isolated axial compressor rotor with micro tip injection

A numerical study of the effect of discrete micro tip injection on unsteady tip clearance flow pattern in an isolatedaxial compressor rotor is presented,intending to better understand the flow mechanism behind stall control meas-ures that act on tip clearance flow.Under the influence of injection the unsteadiness of self-induced tip clearanceflow could be weakened.Also the radial migration of tip clearance vortex is confined to a smaller radial extentnear the rotor tip and the trajectory of tip clearance flow is pushed more downstream,So the injection is benefi-cial to improve compressor stability and increase static pressure rise near rotor tip region.The results of injectionwith different injected mass flow rates show that for the special type of injector adopted in the paper the effect ofinjection on tip clearance flow may be different according to the relative strength between these two streams offlow.For a fixed injected mass flow rate,reducing the injector area to increase injection velocity can improve theeffect of injection on tip clearance flow and thus the compressor stability.A comparison of calculations betweensingle blade passage and multiple blade passages validates the utility of single passage computations to investi-gate the tip clearance flow for the case without injection and its interaction with injected flow for the case with tipinjection.