Experimental Study on Linear Compressor Cascade with Three-Dimensional Blade Oscillation

2004 ◽  
Vol 20 (1) ◽  
pp. 180-188 ◽  
Author(s):  
H. Yang ◽  
L. He
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy ◽  
Jochen Kriegseis

This paper considers the inherent unsteady behavior of the three dimensional separation in the corner region of a subsonic linear compressor cascade equipped of thirteen NACA 65-009 profile blades. Detailed experimental measurements were carried out at different sections in spanwise direction achieving, simultaneously, unsteady wall pressure signals on the surface of the blade and velocity fields by time-resolved PIV measurements. Two configurations of the cascade were investigated with an incidence of 4° and 7°, both at Re = 3.8 * 105 and Ma = 0.12 at the inlet of the facility. The intermittent switch between the two statistical preferred sizes of separation, large and almost suppressed, is called bimodal behaviour. The existence of such oscillation, reported at first in previous experimental and numerical works on the same test rig, is confirmed for both incidences. Additionally, the present PIV measurements provide, for the first time, time-resolved flow visualizations of the size switch of the separation with an extended field of view covering the entire blade section. The interaction of random large structures of the incoming boundary layer with the blade is found to be a predominant element that destabilizes the separation boundary. The recirculation region enlarges when these high vorticity perturbations blend with larger eddies situated in the aft part of the blade. Such massive separation persists until the blockage in the passage causes the breakdown of the largest structures in the aft part of the blade. The flow starts again to accelerate and the separation is almost suppressed. Finally, POD analysis is carried out to decompose flow modes and to contribute to the clarification of underlying cause-effect-relations, which predominate the dynamics of the present flow scenario.


Author(s):  
Saeed A. El-Shahat ◽  
Hesham M. El-Batsh ◽  
Ali M. A. Attia ◽  
Guojun Li ◽  
Lei Fu

Abstract This paper presents a complete study about three-dimensional (3-D) flow field development in a linear compressor cascade where flow field in the blade passage has been studied experimentally as well as numerically. In the experimental work, a linear compressor cascade test section was installed in an open loop wind tunnel. The experimental data was acquired for a Reynolds number of 2.98 × 105 based on the blade chord and the inlet flow conditions. The flow field characteristics in blade passage including 3-D flow velocity and velocity magnitude have been measured by using calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system (DAQ). To investigate flow development in the blade passage, velocity coefficient through streamwise planes has been calculated from the measured data. The computational fluid dynamics (CFD) study of the flow field was performed to gain a better understanding of the flow features. Present computational study was first validated with previous experimental and numerical work to check mesh accuracy and give confidence for computational results. Then, two turbulence models, Spalart-Allmaras (S-A) and shear stress transport SST (k-ω) were used for the present work. From both parts of study, the flow field development through the cascade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones such as corner separation that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by the two probes, 5 and 7-hole pressure probes, have been analyzed and compared. The 5-hole pressure probe measurements have showed more agreements with computational results than 7-hole probe. Furthermore S-A turbulence model calculations showed more consistencies with experimental results than SST (k-ω) model.


1996 ◽  
Vol 118 (3) ◽  
pp. 492-502 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch

A Navier–Stokes solver is applied to investigate the three-dimensional viscous flow in a low-speed linear compressor cascade with tip clearance at design and off-design conditions with two different meshes. The algebraic turbulence model of Baldwin–Lomax is used for closure. Relative motion between the blades and wall is simulated for one flow coefficient. Comparisons with experimental data, including flow structure, static and total pressures, velocity profiles, secondary flows and vorticity, are presented for the stationary wall case. It is shown that the code predicts well the flow structure observed in experiments and shows the details of the tip leakage flow and the leading edge horseshoe vortex.


2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy ◽  
Jochen Kriegseis

This paper considers the inherent unsteady behavior of the three-dimensional (3D) separation in the corner region of a subsonic linear compressor cascade equipped of 13 NACA 65-009 profile blades. Detailed experimental measurements were carried out at different sections in spanwise direction achieving, simultaneously, unsteady wall pressure signals on the surface of the blade and velocity fields by time-resolved particle image velocimetry (PIV) measurements. Two configurations of the cascade were investigated with an incidence of 4 deg and 7 deg, both at Re=3.8×105 and Ma = 0.12 at the inlet of the facility. The intermittent switch between two statistical preferred sizes of separation, large, and almost suppressed, is called bimodal behavior. The present PIV measurements provide, for the first time, time-resolved flow visualizations of the separation switch with an extended field of view covering the entire blade section. Random large structures of the incoming boundary layer are found to destabilize the separation boundary. The recirculation region, therefore, enlarges when these high vorticity perturbations blend with larger eddies situated in the aft part of the blade. Such a massive detached region persists until its main constituting vortex suddenly breaks down and the separation almost completely vanishes. The increase of the blockage during the separation growth phase appears to be responsible for this mechanism. Consequently, the proper orthogonal decomposition (POD) analysis is carried out to decompose the flow modes and to contribute to clarify the underlying cause-effect relations, which predominate the dynamics of the present flow scenario.


Author(s):  
Shun Kang ◽  
Ch. Hirsch

Experimental data measured upstream, inside and downstream of a large scale linear compressor cascade with NACA 65-1810 blade profile are presented. The flow is surveyed at 15 traverse planes with 14 (in half span) × 24 (in pitch) points inside a passage, and 14 × 33 points downstream exit plane. The measurements are obtained with a small size five hole probe, and wall static pressure taps. It is observed that the three dimensional flow inside and behind the cascade is characterized, not only by the conventional aspects, such as leading edge horseshoe vortices, passage vortices, trailing edge vortex sheet and corner vortices, but also by two spiral node points, formed from the three dimensional separation lines, on suction surface, and the resulting concentrated vortices.


2011 ◽  
Vol 24 (3) ◽  
pp. 235-242 ◽  
Author(s):  
Wei MA ◽  
Xavier OTTAVY ◽  
Lipeng LU ◽  
Francis LEBOEUF ◽  
Feng GAO

Author(s):  
Wei Ma ◽  
Xavier Ottavy ◽  
Lipeng Lu ◽  
Francis Leboeuf ◽  
Feng Gao

In order to gain a better knowledge of the mechanisms of corner stall and to calibrate computational-fluid-dynamics (CFD) tools including both Reynolds-averaged Navier-stokes and large eddy simulation, a detailed and accurate experiment of three-dimensional flow field through a linear compressor cascade has been set up. Experimental data were acquired for a Reynolds number of 3.82 × 105 based on blade chord and inlet flow conditions. First, inlet flow conditions were surveyed by hot-wire anemometry in boundary layers. Second, in order to investigate the effects of incidence, measurements then were acquired at five incidences from −2° to 6°. The results included the outlet flow variables of the cascade, measured by a five-hole pressure probe, and static pressures on both blade and endwall surfaces, measured by pressure taps. Third, the flow field details were measured at an incidence angle of 4°. In this configuration the corner stall region was large enough to be investigated, and without two-dimensional (2D) separation at mid-span on the blade suction side near the trailing edge. The velocity field was then measured by 2D Particle Image Velocimetry in cross-sections parallel to the endwall. And the velocity field in the vicinity of the blade suction side was measured with 2D Laser Dropper Anemometry. In order to test the performance of CFD and also to validate the experimental results, a series of numerical simulations were carried out and compared with the experimental results. We thus obtained a set of detailed measurements which constitute an original and complete data base and in good agreement with the published experimental results in literature. These data were also compared with CFD results and showed that the improvements needed in turbulence modeling in order to accurately simulate the three-dimensional separation configuration of corner stall.


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