机匣切向喷气角对涡轮动叶间隙流动的影响

机匣喷气已被证明是改善动叶流道内二次流分布,提高涡轮效率的有效措施之一。本研究采用数值模拟方法研究机匣切向喷气角度对间隙流动控制的影响。结果显示,当增大机匣切向喷气角时,由于喷气速度在切向上的分量减小,使得喷气孔流体在间隙内轴向上影响范围减小,最大降幅可达50%,导致机匣喷气对间隙流动的阻拦作用降低。同时由于切向角度增大使得上通道涡尺寸增加,涡核强度增大约11%,使得动叶出口截面上流动损失增大。考虑到喷气对动叶输出功的负作用,应当选择适当的切向喷气角度,以达到提高涡轮效率的目的。     

涡轮叶顶间隙内部流动的数值研究

动叶叶顶间隙流动是引起涡轮中流动损失的主要原因之一,但由于间隙尺寸较小,且流动方向与叶片转动方向相同,因此很难通过试验测量间隙内部详细的流动及压力分布。通过对"LISA"1.5级轴流涡轮设计工况进行计算,并与试验测量结果进行对比,进而研究间隙内部压力场、流场的分布情况,同时分析间隙高度变化对间隙内部流动的影响。     

涡轮叶尖间隙流动的数值模拟

采用基于雷诺平均N-S方程的三维CFD计算程序,并结合Spalart-Allmaras-方程或κ-epsilon双方程湍流模型加壁面函数的方法,对涡轮平面叶栅和涡轮级转子的叶尖间隙流场进行了数值计算,详细研究了不同叶尖间隙高度、不同叶尖间隙形式和叶尖间隙有冷气入射时其对涡轮叶尖间隙流场和性能的影响.计算结果表明:叶尖间隙对从大约70%叶高到叶尖位置的叶片损失具有明显的影响;在同样间隙大小情况下,余高间隙叶片等熵效率比平间隙叶片等熵效率约提高了一个百分点;而叶尖间隙有冷气入射时涡轮的等熵效率要比无冷气入射时的等熵效率约提高两个百分点.     

向心涡轮可调导叶间隙流动的数值研究

应用数值方法对某型向心涡轮的可调导叶间隙流动结构及其涡轮性能的影响作了分析,间隙尺寸分别为1%、2%、4%叶高.计算结果表明:间隙加大,涡轮效率下降,流量增加,间隙流动所造成的流动损失是结构阻力型的.间隙对涡轮性能的影响主要来自于叶轮进口气流冲角的增加与叶轮反动度的提高.简单地修正导向叶栅的流动效率,不能反映间隙对涡轮整体性能的影响.     

活塞环闭口间隙的设计对机油消耗及漏气量的影响

为了降低柴油机的机油消耗,一二环闭口间隙的联合设计被得到应用。闭口间隙联合设计的功用在于控制活塞环的轴向运动及调节二环岸间气体压力以达到对机油消耗及漏气量的控制目的。笔者通过降低二环岸间气体压力来达到降低机油消耗的目的,尽管这么做可能引起二环的浮起。同时窜气对机油消耗的影响也有一定的影响。     

汽轮机叶顶间隙内非定常流动的数值分析

为了分析叶顶间隙泄漏涡的影响范围、运行轨迹和强度的变化规律,以某汽轮机高压级为研究对象,采用SSTκ-ω湍流模型,应用PISO算法对叶项间隙内的非定常流动进行了数值模拟．结果表明：叶顶间隙泄漏流是有规律的周期性的非定常流动,泄漏涡的影响范围、运行轨迹和强度随时间和叶顶间隙的变化而变化;泄漏流对主流的影响呈现出从弱到强、再从强到弱的周期性变化规律;叶顶间隙泄漏涡在丁／4时刻的强度和影响范围均达到最大,在T／2时刻,静叶脱落涡和动叶吸力面前部的泄漏涡混合形成新的涡系,而动叶吸力面后部的泄漏涡却与其边界层的脱涡混合,离开吸力面．     

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...     

间隙变化对轴流压气机转子近失速工况叶顶流场的影响研究

为研究间隙变化对轴流压气机转子近失速工况下叶顶流场结构的影响,以轴流压气机转子Rotor37为研究对象,对其叶顶流场进行定常和非定常的数值模拟。计算结果表明：随着叶顶间隙的减小,压气机的总压比和等熵效率均有所提高,稳定运行范围扩大;2倍设计间隙下,叶尖泄漏涡经激波作用后发生膨胀破碎,堵塞来流通道,诱发压气机堵塞失速;0.5倍设计间隙下,吸力面流动分离加剧,发生回流,部分回流与来流在压力面前缘上游发生干涉,进口堵塞加剧,致使部分来流从前缘溢出,导致压气机叶尖失速;不同间隙下压气机失速过程的主导因素不同,大间隙下失速由叶尖泄漏涡破碎的非定常波动引起,小间隙下失速主要由流动分离引发的周期性前缘溢流所主导。     

轮毂封严对涡轮端区流动影响的数值研究

为了研究轮毂封严对涡轮端区流动的影响,对转/静叶片之间带有封严腔的某单级涡轮进行三维定常数值模拟。结果表明,封严流量对涡轮效率影响较大,2.0%的封严流量使涡轮级效率降低约1.6%;封严气流受到转子前缘位势场的影响,与主流在径向上存在着动量差,两股气流在转子进口处相互剪切形成剪切诱导涡。剪切诱导涡对轮毂通道涡的贡献较大,是端区二次流损失的主要来源。采用与转子旋转方向相同的喷射方向并增大喷射角度对减小攻角损失以及封严气流与主流的掺混损失是非常有利的。     

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。     

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.     

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…     

Numerical simulation on the effect of tip clearance size on unsteadiness in tip clearance flow

Unsteadiness of tip clearance flow with three different tip clearance sizes is numerically investigated in this paper. NASA Rotor 67 is chosen as the computational model. It is found that among all the simulated cases, the un- steadiness exists when the size of the tip clearance is equal to or larger than design tip clearance size. The relative total pressure coefficient contours indicate that region of influence by tip leakage flow augments with the increase of tip clearance size at a fixed mass flow rate. Root Mean Square contours of static pressure distribution in the rotor tip region are provided to illustrate that for design tip clearance （1.1% tip chord） the strongest fluctuating region is located on pressure side of blade near leading edge, while for the larger tip clearance （2.2% tip chord）, it is in the region of the interaction between the shock wave and the tip leakage flow.     

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. __________ Translated from Compressor, Blower & Fan Technology, 2007, (5): 12–15 [译自: 风机技术]     

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…     

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.     

Numerical analysis of the tip leakage flow field in a transonic axial compressor with circumferential casing treatment

This paper reports on numerical investigations aimed at understanding the influence of
circumferential casing grooves on the tip leakage flow and its resulting vortical structures.The results
and conclusions are based on steady state 3D numerical simulations of the well-known transonic axial
compressor NASA Rotor 37 near stall operating conditions.The calculations carried out on the casing
treatment configuration reveal an important modification of the vortex topology at the rotor tip
clearance.Circumferential grooves limit the expansion of the tip leakage vortex in the direction
perpendicular to the blade chord,but generate a set of secondary tip leakage vortices due to the
interaction with the leakage mass flow.Finally,a deeper investigation of the tip leakage flow is
proposed.     

偏心度与间隙比对轴流泵流动激励力的影响

叶轮偏心将会引起轴流泵叶轮顶部间隙沿周向不均匀,从而导致附加的流动激励和噪声.利用计算流体力学商业软件Fluent模拟不同偏心度和间隙比的轴流泵非定常流场,研究周向非均匀间隙对泵内压强脉动及叶轮激励力的影响.结果表明:壁面压强脉动强度并不是在最小间隙处达到最大,而是出现在偏离最小间隙处约30°~60°的方向,并随着间隙比增大,脉动强度最大值发生位置逐渐向最小间隙处靠拢;同时,偏心造成的非均匀叶顶间隙引起了轴频处的压强脉动,在间隙比为2.5%下偏心度从0%增加到60%,轴频处的压强脉动相对增量为661.54%;叶轮受到的径向激励力时均值与偏心度呈线性关系,其斜率与间隙比的平方根成正比.