共查询到17条相似文献,搜索用时 203 毫秒
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弯曲叶片是改善压气机近端壁流动的有效技术手段之一。为探索叶片弯曲对高负荷压气机叶栅流场的影响机理,在初始高负荷直列叶栅的基础上,设计了不同正/反弯曲水平的叶栅,并采用数值模拟方法对系列叶栅进行研究。研究发现:叶片正弯曲形成了中间静压低、两端静压高的"C"形静压分布,可有效改善压气机叶栅近端壁流场,显著抑制角区分离,使得端壁区域扩压能力提高;正弯曲可增大叶展中部区域负荷,恶化叶中流场,增大流动分离;叶片反弯曲形成了中间静压高、两端静压低的反"C"形静压分布,可显著恶化近端壁区流场,角区分离区增大,端壁区域扩压能力降低,叶中流场有所改善。 相似文献
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低展弦比涡轮静叶栅叶片正弯曲作用的试验研究 总被引:2,自引:0,他引:2
对弯曲叶片研究中代表性的HIT涡轮静叶型重新开展了叶片弯曲对低展弦比涡轮静叶栅流场影响的试验研 究。测量了直叶片叶栅、+10°、+20°和+30°弯曲叶片叶栅的进、出口流场,分析了叶片弯曲对叶栅出口二次流、 总压损失和气流角的影响。结果表明:对该叶型叶栅,叶片正弯曲既不能大幅度降低叶栅二次流损失,也不能改 善叶栅出口气流角沿叶高的分布:叶栅出口二次流动、尾缘涡及壁角涡随叶片正弯曲角的增大而增强,而通道涡 强度和位置变化不大;该研究结果同以往有关文献的研究结果完全不同。 相似文献
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为探究端壁造型对涡轮动叶气动性能及流场特性的影响,分析非轴对称端壁造型对涡轮转子叶片的压差作用,开展基于非轴对称端壁造型的理论研究,提出一种涡轮动叶轮毂上凸、下凹的造型方案,研究非轴对称端壁造型对涡轮流场二次流损失的影响。数值模拟分析表明:非轴对称端壁造型对减小横向压差具有重要作用,在动叶轮毂鞍点处进行非轴对称端壁造型,比在通道内造型效果更好;涡轮动叶下端壁不同区间造型可有效降低涡轮动叶通道内的二次流流动损失,使用非轴对称端壁造型方法可有效地减小动叶出口总压损失系数0.132 2%。 相似文献
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在低雷诺数进口条件下,低速涡轮叶片绕流可能存在大范围的层流流动、层流分离流动、边界层转捩和显著的径向二次流动,流动结构复杂,给精确的数值模拟提出挑战。本文对AIST低速轴流单级涡轮内部流动进行数值模拟,其中静叶通道分别采用全层流模型、全湍流模型、AbuGhannamShaw(AGS)转捩模型和分离涡模拟(DES)方法,动叶通道求解RANS方程,湍流模型为Spalrat-Allmaras一方程模型。与实验结果对比显示,层流模型准确地捕捉到了静叶叶片吸力面层流分离的分离位置。三维流动结构分析显示,在很低的雷诺数条件下,静叶吸力面层流分离流产生很大的径向运动,没有再附于叶片表面,被卷入叶片根部的通道涡中。 相似文献
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为探索改善小角度进气条件下叶栅栅前流动周期性的试验控制方法,以某跨音速压气机平面叶栅试验件为研究对象,采用数值模拟方法研究了小角度进气条件下尾板偏移角度和端壁通道宽度对叶栅栅前周期性分布的影响。研究结果发现:叶栅在小角度进气时栅前周期性分布特性较差,调节下尾板角度对栅前周期性具有一定影响,调节上尾板对近端壁通道气流难以起到导流效果;采用全叶片式叶栅进气方案时,仅端壁附近流道的流动受到边界附面层影响,而中间测量通道内的周期性分布得到明显改善;改变近端壁两端通道宽度可以有效改善栅前流场周期性。 相似文献
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Experimental data are presented which describe the effects of a combustor-level high free-stream turbulence on the near-wall
flow structure and heat/mass transfer on the endwall of a linear high-turning turbine rotor cascade. The endwall flow structure
is visualized by employing the partial- and total-coverage oil-film technique, and heat/mass transfer rate is measured by
the naphthalene sublimation method. A turbulence generator is designed to provide a highly-turbulent flow which has free-stream
turbulence intensity and integral length scale of 14.7% and 80mm, respectively, at the cascade entrance. The surface flow
visualizations show that the high free-stream turbulence has little effect on the attachment line, but alters the separation
line noticeably. Under high free-stream turbulence, the incoming near-wall flow upstream of the adjacent separation lines
collides more obliquely with the suction surface. A weaker lift-up force arising from this more oblique collision results
in the narrower suction-side corner vortex area in the high turbulence case. The high free-stream turbulence enhances the
heat/mass transfer in the central area of the turbine passage, but only a slight augmentation is found in the endwall regions
adjacent to the leading and trailing edges. Therefore, the high free-stream turbulence makes the endwall heat load more uniform.
It is also observed that the heat/mass transfers along the locus of the pressure-side leg of the leading-edge horseshoe vortex
and along the suctionside corner are influenced most strongly by the high free-stream turbulence. In this study, the endwall
surface is classified into seven different regions based on the local heat/mass transfer distribution, and the effects of
the high free-stream turbulence on the local heat/mass transfer in each region are discussed in detail. 相似文献
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Lee Sang Woo Kwon Hyun Goo Park Byung-Kyu 《Journal of Mechanical Science and Technology》2005,19(6):1347-1357
Effects of combustor-level high free-stream turbulence on the blade-surface heat/mass transfer have been investigated in the
three-dimensional flow region near the endwall within a high-turning turbine rotor cascade passage. Free-stream turbulence
intensity and integral length scale in the high turbulence case are 14.7 percents and 80 mm, respectively. The result shows
that there is no considerable discrepancy in the blade heat/mass transfer near the endwall between the low and high turbulence
cases. As departing from the endwall, however, the deviation between the two cases becomes larger, particularly in the region
where flow separation and re-attachment occur. Under the high turbulence, flow disturbances such as boundary-layer separation
and re-attachment seem to be suppressed, which makes the blade heat/mass transfer more uniform. Moreover, there are some evidences
that endwall vortices tend to be weakened under the high turbulence. 相似文献
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Heat/mass transfer characteristics on the near-tip blade surface under combustor-level high inlet turbulence have been investigated
within a high-turning turbine rotor passage by using the naphthalene sublimation technique. The inlet turbulence intensity
and length scale are 14.7% and 80 mm, respectively. The tip gap-to-chord ratio is changed to beh/c = 0.74, 1.47, and 2.94 percents. Increasingh/c results not only in higher heat/mass transfer in the pressure-side tip region but also in more convective transport on the
pressure surface even far away from the tip edge. Severe heat/mass transfer is always observed in the suction-side tip-leakage
flow region which can be divided into two distinct high transport regions. There is a local maximum of heat/mass transfer
along the trailing-edge centerline. This arises from the interaction of a tip-leakage vortex with a trailing-edge vortex shedding.
Comparisons of the present data forh/c = 2.94 percents with the previous low turbulence one show that there is a large discrepancy of heat/mass transfer in the
pressure-side near-tip area, which diminishes with departing from the tip edge. The suction-side heat/mass transfer in the
tip-leakage flow region is less influenced by the high inlet turbulence than that at the mid-span. The leading-edge heat/mass
transfer under the high inlet turbulence is always higher than that in the low turbulence case, while there is no big difference
in the trailing-edge heat/mass transfer between the two cases. 相似文献
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W. Ghopa Wan Aizon Ken-ichi Funazaki Takemitsu Miura 《Journal of Mechanical Science and Technology》2013,27(6):1611-1617
The endwall and blade film cooling systems are the typical solution adopted within gas turbines to allow further increase of turbine inlet temperature, avoiding critical material thermal damages. Due to the complex secondary flow field in the blade passage, endwall is more difficult to be cooled than blade surfaces. In the matter of fact, in endwall film cooling studies, it is necessary to investigate the interaction between coolant air and the secondary flow. In present study, the flow field of high-pressure turbine in linear cascade has been investigated by 5-holes pitot tube to reveal the secondary flows behaviour under the influenced of purge flows through a slot which is located 0.63 Cax upstream of blade leading edge. Both measurement and numerical simulation presented almost similar trend of aerodynamics performance thus enable the authors to excute the flow visualizations accurately. The presence of newly generated vortical structures was considered to be responsible to the additional loss at higher MFR cases. 相似文献
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A numerical analysis has been conducted in order to simulate the characteristics of complex flow through linear cascades of
high performance turbine blade with/without tip clearance by using a pressure-correction based, generalized 3D incompressible
Navier-Stokes CFD code. The development and generation of horseshoe vortex, passage vortex, leakage vortex, tip vortex within
tip clearance, etc. are clearly identified through the present simulation which uses the RNG k-ε turbulent model with wall
function method and a second-order linear upwind scheme for convective terms. The present simulation results are consistent
with the generally known tendency that occurs in the blade passage and tip clearance. A 3D model for secondary and leakage
flows through turbine cascades with/without tip clearance is also suggested from the present simulation results, including
the effects of tip clearance height. 相似文献
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基于环形叶栅理论建立转轮叶片三维模型。采用FLUENT软件对转轮叶片进行了三维定常湍流计算。数值模拟了转轮内部三维湍流流场,得到了叶片表面压力云图、速度矢量图和叶片进出口边附近压力分布图,并估算出水轮机水力效率。结果表明采用环形叶栅理论建立的贯流式水轮机叶片具有可行性。 相似文献