The Impact of Leakage Flow Tangential Velocity on Secondary Losses in a Shrouded Compressor Cascade

2012 ◽  
Author(s):  
J. W. Kim ◽  
J. S. Lee ◽  
S. J. Song ◽  
T. Kim ◽  
H-. W. Shin
Keyword(s):  
Secondary Flow ◽  
Tangential Velocity ◽  
Leading Edge ◽  
Suction Side ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
The Impact

Experimental and numerical studies have been performed to investigate the effects of the leakage flow tangential velocity on the secondary flow and aerodynamic loss in an axial compressor cascade with a labyrinth seal. Six selected leakage flow tangential (vy/Uhub = 0.15, 0.25, 0.35, 0.45, 0.55 and 0.65) have been tested. In addition to the classical “secondary” flow, shroud trailing edge vortex and shroud leading edge vortex are examined. The overall loss decreases with increasing leakage flow tangential velocity. Increased leakage flow tangential velocity underturns the hub endwall flows through the blade passage, weakening the suction side hub corner separation. Due to the suction effect of the downstream cavity, increasing leakage flow tangential velocity weakens the shroud trailing edge vortex. Also, increasing leakage flow tangential velocity strengthens the shroud leading edge vortex, weakening the pressure side leg of the horseshoe vortex, and, in turn, the passage vortex. Thus, the overall loss is reduced with increasing leakage flow tangential velocity.

Control of Leading-Edge Vortex Breakdown by Trailing Edge Injection

2002 ◽  
Vol 39 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Anthony M. Mitchell ◽  
Didier Barberis ◽  
Pascal Molton ◽  
Jean Delery
Keyword(s):  
Vortex Breakdown ◽  
Leading Edge ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex

Influence of the Leakage Flow Tangential Velocity on the Loss Generation and Leakage Flow Kinematics in Shrouded Axial Compressor Cascades

2006 ◽  
Author(s):  
D. W. Sohn ◽  
T. Kim ◽  
S. J. Song
Keyword(s):  
Tangential Velocity ◽  
Axial Compressor ◽  
Suction Side ◽  
Velocity Variation ◽  
Leakage Flow ◽  
Compressor Blades ◽  
Blade Passage ◽  
Leakage Flows ◽  
And Behavior ◽  
The Impact

Although compressor blades have long been shrouded for aerodynamic and structural reasons, the impact of the leakage flow in the shroud cavities on passage flows has only recently been investigated. Furthermore, the tangential velocity of the leakage flow, set by the blading and the relative motion between rotating and stationary surfaces, has a strong influence on the passage flow. Yet the influence of the tangential velocity variation on the kinematics and dynamics (loss) of the leakage flow (from its ingress to egress) in the shrouded cavity and main flow in the blade passage are unknown. Therefore, this paper reports on an experimental investigation of the axial evolution of loss generation in the blade passage and behavior of the leakage flow in the seal cavity in shrouded axial compressor cascades subject to the variation of leakage tangential velocity. The newly found results are as follows. First, increasing tangential velocity of the leakage flow reduces loss at 10% and 50% chordwise locations in the passage. However, most of the blockage and loss reductions occurs in the aft half chord and downstream of the blade passage. Second, the increasing tangential velocity spreads the loss core, which is originally concentrated in the suction side hub corner, in the pitchwise direction. Thus, the loss core becomes more two-dimensional, and the region’s radial extent is reduced. Third, increasing tangential velocity of the leakage flow makes the near hub passage flow more radially uniform. Consequently, the shear and resultant mixing loss between the passage and leakage flows are reduced near the hub, reducing the overall loss. Finally, the leakage flow is ingested through the downstream cavity and makes an abrupt turn at the seal tooth. Thus, two distinct flow regions — downstream and upstream of the single-tooth seal — are found. Before the leakage flow rejoins the mainstream via the upstream cavity trench, the leakage flow circumferentially migrates in the direction of rotation. The magnitude of the circumferential shift depends strongly on the leakage tangential velocity.

Trailing edge flap influence on leading edge vortex flap aerodynamics

1983 ◽  
Vol 20 (2) ◽  
pp. 165-169 ◽  
Author(s):  
Arthur C. Grantz ◽  
J. F. Marchman
Keyword(s):  
Leading Edge ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
Trailing Edge Flap

Effect of Surface Roughness Location and Reynolds Number on Compressor Cascade Performance

2010 ◽  
Author(s):  
Seung Chul Back ◽  
Garth V. Hobson ◽  
Seung Jin Song ◽  
Knox T. Millsaps
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Trailing Edge ◽  
Blade Loading ◽  
Linear Compressor Cascade

An experimental investigation has been conducted to characterize the influence of surface roughness location and Reynolds number on compressor cascade performance. Flow field surveys have been conducted in a low-speed, linear compressor cascade. Pressure, velocity, and flow angles have been measured via a 5-hole probe, pitot probe, and pressure taps on the blades. In addition to the entirely smooth and entirely rough blade cases, blades with roughness covering the leading edge; pressure side; and 5%, 20%, 35%, 50%, and 100% of suction side from the leading edge have been studied. All of the tests have been done for Reynolds number ranging from 300,000 to 640,000.Cascade performance (i.e. blade loading, loss, and deviation) is more sensitive to roughness on the suction side than pressure side. Roughness near the trailing edge of suction side increases loss more than that near the leading edge. When the suction side roughness is located closer to the trailing edge, the deviation and loss increase more rapidly with Reynolds number. For a given roughness location, there exists a Reynolds number at which loss begins to visibly increase. Finally, increasing the area of rough suction surface from the leading edge reduces the Reynolds number at which the loss coefficient begins to increase.

Experimental investigation of the leading edge vortex formation on unsteady boundary layer

2017 ◽  
Vol 232 (18) ◽  
pp. 3263-3280
Author(s):  
Ali R Davari ◽  
Rezvan Abdollahi ◽  
Ehsaneddin Azimizadeh
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Unsteady Boundary Layer ◽  
Leading Edge Vortex ◽  
Reduced Frequency ◽  
Blade Section ◽  
Edge Vortex ◽  
The Impact

Extensive experimental studies have been performed to investigate the unsteady boundary layer behavior over a plunging wind turbine blade section. The studies have been undertaken at various combinations of reduced frequencies, Reynolds numbers, and locations. A boundary layer rake has been carefully manufactured and utilized for velocity measurements inside the unsteady boundary layer. The measurement has been conducted in pre-static stall conditions. The reduced frequency and free stream velocity have varied from 0.005 to 0.1, and 30 to 60 m/s, respectively. To cover all possible scenarios, the streamwise positions of measurements have been chosen to be in favorable (x/c = 0.37), almost zero (x/c = 0.47), and adverse pressure gradient (x/c = 0.57) regions, on the blade section. The velocity inside the boundary layer has shown high sensitivity to the reduced frequency in the different pressure gradient regions. In some definite test cases, velocity inside boundary layer has shown beating phenomena, which is the result of the periodical appearance of the leading edge vortex. The impact of the leading edge vortex on the velocity has been observed to be more evident, in some cases, in the form of signal beating. This signature has been more evident, as the rake entered the adverse pressure gradient region. In order to quantify this observed phenomenon, the time-dependent velocity data have been transformed into the frequency domain, utilizing the discrete Fourier transformation. Even though the leading edge vortex has been continuously developed on the profile, and then has shed toward the leading edge, during each cycle on a plunging profile, the dominant frequency throughout this process has been measured to be about 4 Hz for this blade section.

scholarly journals The leading-edge vortex of swift wing-shaped delta wings

2017 ◽  
Vol 4 (8) ◽  
pp. 170077 ◽  
Author(s):  
Rowan Eveline Muir ◽  
Abel Arredondo-Galeana ◽  
Ignazio Maria Viola
Keyword(s):  
Reynolds Number ◽  
Delta Wing ◽  
Leading Edge ◽  
Trailing Edge ◽  
Delta Wings ◽  
Leading Edge Vortex ◽  
Wing Model ◽  
Image Velocimetry ◽  
Edge Vortex ◽  
First Time

Recent investigations on the aerodynamics of natural fliers have illuminated the significance of the leading-edge vortex (LEV) for lift generation in a variety of flight conditions. A well-documented example of an LEV is that generated by aircraft with highly swept, delta-shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge can serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, a model non-slender delta-shaped wing with a sharp leading edge is tested at low Reynolds number, along with a delta wing of the same design, but with a modified trailing edge inspired by the wing of a common swift Apus apus . The effect of the tapering swift wing on LEV development and stability is compared with the flow structure over the unmodified delta wing model through particle image velocimetry. For the first time, a leading-edge vortex system consisting of a dual or triple LEV is recorded on a swift wing-shaped delta wing, where such a system is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the trailing-edge geometry of the swift wing alone does not prevent the common swift from generating an LEV system comparable with that of a delta-shaped wing.

scholarly journals Three-dimensional effects in hovering flapping flight

2012 ◽  
Vol 702 ◽  
pp. 102-125 ◽  
Author(s):  
T. Jardin ◽  
A. Farcy ◽  
L. David
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Flapping Flight ◽  
Length Scale ◽  
Two Dimensional ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Dimensional Flow ◽  
Dimensional Effects ◽  
Edge Vortex

AbstractThis paper aims at understanding the influence of three-dimensional effects in hovering flapping flight. Numerical simulations at a Reynolds number of 1000 are performed to compare two types of flapping kinematics whose plunging phase is characterized by either a rectilinear translation or a revolving motion. In this way, we are able to isolate the three-dimensional effects induced by the free end condition from that induced by the spanwise incident velocity gradient (and the associated implicit Coriolis and centrifugal effects). In the rectilinear translation case, the analysis of the wake and of the aerodynamic loads reveals that the wingspan can be compartmented into three distinct regions whether it is predominantly subjected to an unstable two-dimensional flow, a stable three-dimensional flow or both two-dimensional and three-dimensional effects. It is found that this partitioning exhibits common features for three different aspect ratios of the wing. In conjunction with the previous results of Ringuette, Milano & Gharib (J. Fluid Mech., vol. 581, 2007, pp. 453–468), this suggests that the influence of the tip vortex over the wingspan is driven by a characteristic length scale. In addition, this length scale matches the position of the connecting point between leading and tip vortices observed in the revolving case, providing insight into the connecting process. In both translating and revolving cases, leading edge vortex attachment and strong spanwise velocities are found to be strongly correlated phenomena. Spanwise velocities (that mostly confine at the periphery of the vortices), together with downward velocities, do not only affect the leading edge vortex but also act as an inhibitor for the trailing edge vortex growth. As a consequence, cross-wake interactions between leading and trailing edge vortices are locally limited, hence contributing to flow stabilization.

Sign in / Sign up

Export Citation Format

Share Document