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角区失速预测始终是轴流压气机设计面临的难题之一,尤其当代先进三维弯掠叶片应用使得在设计阶段准确预测角区失速更加困难。探究问题根源,即便目前最成功的Lei预测模型与准则,虽然其综合考虑了逆压梯度和横向二次流影响,但仍因未考虑角区二面角下附面层交汇因素而失效于弯掠叶片角区失速预测。鉴于此,本文采用不同正多边形(包括圆)截面扩张管道计算模型,研究构建了量化表征不同二面角、不同逆压梯度环境下交汇附面层发展状态的Ψ因子,并综合考虑二次流影响建立了预测三维叶片角区失速的DJ因子,然后以NACA65系列叶栅为案例,采用数值模拟方法建立了叶栅性能数据库,据此形成了DJ因子角区分离预测准则。最后,基于国内外公开文献中叶栅、叶片试验结果对DJ准则进行了检验,并分析了DJ因子应用中需要注意的一些问题。 相似文献
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从端壁动态压力场看压气机转子尖区流动 总被引:8,自引:1,他引:7
用高频压力传感器测量了低速单级压气机转子叶尖动态压力场。结果表明,转子叶背附面层径向潜流使得叶背附近存在一个高压带。叶背角区和叶盆角区的气流交混造成通道中部具有甚至不低于叶盆处的高压力。两个高压区都随流量的减小而扩大,并随流向逐渐融合,反映了叶背附面层径向潜流和中部气流交温的发展。设计状态下,泄漏涡是造成转子叶尖压力脉动的主要因素,形成的高水平压力脉动区随流向呈喇叭形逐渐扩大,约在一半弦长处脉动最强。近失速状态下,叶背前部角区中强叶面附面层潜流及与强泄漏流和端壁附面层的交混造成大范围的强压力脉动区,局部扩展到整个通道,通道中部叶背附面层很有可能发生分离。 相似文献
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为探究进口附面层形式对轴流压气机叶栅端区流动特性的影响,本文以某高亚声速压气机叶栅为研究对象,基于数值方法对比分析常规和倾斜两种进口附面层形式对叶栅角区分离和叶尖泄漏流流动特性以及总体性能的影响。结果表明:进口倾斜附面层使端区来流的攻角和进口速度增加。在无叶尖间隙时,倾斜附面层能够缩小角区分离的轴向和周向范围,提高扩压能力,相比常规附面层工况,总压损失降低6.3%;1%叶高间隙下,倾斜附面层能够降低叶尖泄漏流相关损失并减少尾迹与主流的掺混损失,总压损失较常规附面层降低15.3%。 相似文献
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Symmetric and asymmetric self-similar flows of a viscous incompressible fluid along a semi-infinite right-angle dihedral corner with a preset streamwise pressure gradient have been considered. Equations describing such flows in the framework of boundary layer approximation have been derived. The asymptotic behavior of solutions of the derived equations far from the corner edge has been theoretically investigated. A new method of computation of these solutions has been developed. Solutions for two types of asymptotic behavior have been obtained. 相似文献
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A challenge in the study of turbulent boundary layers (TBLs) is to understand the non-equilibrium relaxation process after sep-aration and reattachment due to shock-wave/boundary-layer interaction. The classical boundary layer theory cannot deal with the strong adverse pressure gradient, and hence, the computational modeling of this process remains inaccurate. Here, we report the direct numerical simulation results of the relaxation TBL behind a compression ramp, which reveal the presence of intense large-scale eddies, with significantly enhanced Reynolds stress and turbulent heat flux. A crucial finding is that the wall-normal profiles of the excess Reynolds stress and turbulent heat flux obey a β-distribution, which is a product of two power laws with respect to the wall-normal distances from the wall and from the boundary layer edge. In addition, the streamwise decays of the excess Reynolds stress and turbulent heat flux also exhibit power laws with respect to the streamwise distance from the corner of the compression ramp. These results suggest that the relaxation TBL obeys the dilation symmetry, which is a specific form of self-organization in this complex non-equilibrium flow. The β-distribution yields important hints for the development of a turbulence model. 相似文献
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V. G. Chernorai M. V. Litvinenko Yu. A. Litvinenko V. V. Kozlov E. E. Cherednichenko 《Thermophysics and Aeromechanics》2007,14(4):515-523
In the present study, the flow field near the orifice of a plane wall jet is in focus. Two main flow regions may be distinguished
in the wall jet, i. e., a free shear layer away from the wall and a boundary layer close to the surface. In both of these
layers, streamwise coherent structures are detected by means of smoke visualization and hot-wire measurements. The structures,
which occur naturally, have different spanwise scales and emerge at different distance from the nozzle. Effects of the flow
velocity, upstream perturbations, and acoustic excitation on the generation and characteristics of the streamwise disturbances
are investigated, and especially the interaction between the two layers is studied. In order to resolve the complex 3D flow
by means of hotwires a system for accurate automated traversing and data acquisition has been developed. In each flow case
time-dependent measurements were taken in (X, Y, Z) space of about 3000 to 25,000 points, and it was found that the value of outlet velocity and the frequency of Kelvin — Helmholtz
rolls have a clear influence on the size of the structures. Higher outlet velocities and higher frequencies of triggered two-dimensional
roll-ups lead to a decrease in the size of longitudinal structures. 相似文献
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压气机转子三维紊流流场 总被引:10,自引:3,他引:7
在低速大尺寸压气机试验台上,用单斜热丝、高频压力探针及由旋转四坐标全电动探针位移机构带动的五孔气动探针,测量了单级压气机转子出口和单转子压气机叶片通道尖区在不同流量状态下三维平均和亲流流场。设计状态,叶尖泄漏涡的发展及其与端壁附面层的交混决定了尖区的流动特性。小流量状态,叶片吸力面附面层增厚,近失速状态尖部吸力面附面层发生分离,吸力而附面层内径向潜移强烈,叶尖吸力面角区产生大范围强旋涡,角区部分低能流体移向叶尖通道中部,与端壁附面层、泄漏涡、刮削涡及主流发生交混. 相似文献
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A high order implicit large eddy simulation (ILES) is carried out to study the mechanism of shock induced flow separation reduction under ramp-type MVG control. The mechanism was originally considered as that MVG can generate streamwise vortices which strongly mix boundary layer and the boundary layer becomes more capable to resist strong adverse pressure gradient caused by shock and to keep the boundary layer attached. However, according to our ILES, a chain of ring-like vortices is generated behind the ramp-type MVG and goes further to interact with the shock. When the ring-like vortices pass through the shock, the shock wave is weakened and altered while the vortex structures are quite stable. The instantaneous simulation shows that the spanwise ring-like vortex, not the streamwise vortex, plays a key role to weaken the shock and reduce the shock-induced separation. Detailed investigation on ring-like vortices and shock interaction will be given in this paper. 相似文献
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叶片弦向倾斜对损失发展的影响及叶片反弯降低损失机理的研究 总被引:2,自引:1,他引:1
早在六十年代初期,Smith提出了弦向倾斜叶片 ̄[1]。叶片的这种倾斜集叶片的后掠(叶片展向与气流不垂直)和上反(叶片表面与端壁斜交)于一身。根据理论分析可知,弦向倾斜叶片与周向倾斜叶片比较,在相同倾斜角下,它更能有效地抑制通道涡的形成和发展 ̄[2]。但是,到现在为止还没有实验数据证实这一计算结果。本文继文献 ̄[3]详细测量了弦向倾斜叶片叶栅由栅前至栅后诸截面上的气动参数。实验结果表明,弦向倾斜对损失的发展起到了与周向倾斜相类似的作用,但是前者比后者减小了叶栅进口段的流向逆压梯度,从而降低了二次旋涡损失。本文还测量了大转角常规直叶栅与反弯叶片叶栅端壁与叶片表面上的静压分布,探讨了反弯叶片降低损失的原因,认为:减小叶栅进口段流向逆压梯度,在叶片吸力面前部形成垂直于端壁的平行静压等值线、在中部形成反“C”型静压等值线,以及在流道内建立沿叶高的反“C”型静压分布,是反弯叶片降低损失的三要素。 相似文献
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Direct numerical simulation of the turbulent boundary layer over a sharp cone with 20° cone angle (or 10° half-cone angle)
is performed by using the mixed seventh-order up-wind biased finite difference scheme and sixth-order central difference scheme.
The free stream Mach number is 0.7 and free stream unit Reynolds number is 250000/inch. The characteristics of transition
and turbulence of the sharp cone boundary layer are compared with those of the flat plate boundary layer. Statistics of fully
developed turbulent flow agree well with the experimental and theoretical data for the turbulent flat-plate boundary layer
flow. The near wall streak-like structure is shown and the average space between streaks (normalized by the local wall unit)
keeps approximately invariable at different streamwise locations. The turbulent energy equation in the cylindrical coordinate
is given and turbulent energy budget is studied. The computed results show that the effect of circumferential curvature on
turbulence characteristics is not obvious. 相似文献