Experimental Investigations of Corner Stall in a Linear Compressor Cascade

2011 ◽  
Author(s):  
Wei Ma ◽  
Xavier Ottavy ◽  
Lipeng Lu ◽  
Francis Leboeuf ◽  
Feng Gao
Keyword(s):  
Velocity Field ◽  
Flow Field ◽  
Three Dimensional ◽  
Suction Side ◽  
Experimental Results ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Inlet Flow ◽  
Linear Compressor ◽  
Linear Compressor Cascade

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.

Numerical Investigation of Intermittent Corner Separation in a Linear Compressor Cascade

2016 ◽  
Author(s):  
Wei Ma ◽  
Feng Gao ◽  
Xavier Ottavy ◽  
Lipeng Lu ◽  
A. J. Wang
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Leading Edge ◽  
Suction Side ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Corner Separation ◽  
Eddy Simulation ◽  
Linear Compressor Cascade

Recently bimodal phenomenon in corner separation has been found by Ma et al. (Experiments in Fluids, 2013, doi:10.1007/s00348-013-1546-y). Through detailed and accurate experimental results of the velocity flow field in a linear compressor cascade, they discovered two aperiodic modes exist in the corner separation of the compressor cascade. This phenomenon reflects the flow in corner separation is high intermittent, and large-scale coherent structures corresponding to two modes exist in the flow field of corner separation. However the generation mechanism of the bimodal phenomenon in corner separation is still unclear and thus needs to be studied further. In order to obtain instantaneous flow field with different unsteadiness and thus to analyse the mechanisms of bimodal phenomenon in corner separation, in this paper detached-eddy simulation (DES) is used to simulate the flow field in the linear compressor cascade where bimodal phenomenon has been found in previous experiment. DES in this paper successfully captures the bimodal phenomenon in the linear compressor cascade found in experiment, including the locations of bimodal points and the development of bimodal points along a line that normal to the blade suction side. We infer that the bimodal phenomenon in the corner separation is induced by the strong interaction between the following two facts. The first is the unsteady upstream flow nearby the leading edge whose angle and magnitude fluctuate simultaneously and significantly. The second is the high unsteady separation in the corner region.

Investigations of Three-Dimensional Flow Field Development in an Axial Compressor Cascade

2019 ◽  
Author(s):  
Saeed A. El-Shahat ◽  
Hesham M. El-Batsh ◽  
Ali M. A. Attia ◽  
Guojun Li ◽  
Lei Fu
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Computational Results ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Blade Passage ◽  
Field Development ◽  
Hole Pressure ◽  
Sensor Module ◽  
Linear Compressor Cascade

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.

Experimental Investigation in Annular Compressor Cascades at Transonic Flow Conditions

1995 ◽  
Author(s):  
K. Schulz ◽  
P. Dalbert ◽  
A. Bölcs
Keyword(s):  
Flow Field ◽  
Suction Side ◽  
Flow Conditions ◽  
Compressor Cascade ◽  
Flow Measurements ◽  
Inlet Flow ◽  
Blade Passage ◽  
Controlled Diffusion ◽  
Pressure Distributions ◽  
Shock System

The paper describes flow measurements in an annular compressor cascade at sub- and supersonic inlet flow conditions. The investigation is concentrated on the evolution of the flow field along the blade passage. A homogeneous flow could be realized in the test section at midspan with carefully directed suction by a splitter downstream of the blade passage. Two typical compressor cascades (Multiple circular arc profile (MCA) and controlled diffusion (C.D.)) have been investigated at similar inlet flow conditions in the whole operating range with a maximum relative inlet Mach number of about 1.3. Detailed flow measurements have been performed over several axial and radial positions along the whole blade passage. The velocity vectors have been measured with a Laser-2-Focus anemometer and the total pressure with miniature pilot-probes. Cascade overall performance, blade-surface-pressure-distributions and flow-visualization are presented. The obtained results show that the blade shape has a strong influence on the loss behavior especially at off design conditions and on the shock system influencing the whole flow field of the blade row. Different boundary layer evolution on the suction side (measured with Laser-2-Focus) causes the shock to be fixed or in fluctuation resulting in different losses (shock-, profile-, overall losses).

Non-Axisymmetric Endwall Contouring in a Linear Compressor Cascade

2020 ◽  
Author(s):  
Yuchen Ma ◽  
Jinfang Teng ◽  
Mingmin Zhu ◽  
Xiaoqing Qiang
Keyword(s):  
Pressure Loss ◽  
Reverse Flow ◽  
Measurement Techniques ◽  
Suction Side ◽  
Limiting Factor ◽  
Blade Surface ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Endwall Contouring ◽  
Linear Compressor Cascade

Abstract Modern axial compressors are designed to be highly loaded in terms of aerodynamics, which can lead to challenges of increasing the compressor efficiency. Losses associated with secondary flow effects are well known to be the major limiting factor of improving the compressor performance. In this study, non-axisymmetric endwall contouring in a linear compressor cascade was generated through the optimization process. Combined with numerical simulation, wind tunnel tests on linear cascades with flat and contoured endwall were performed with various measurement techniques at the design and off-design conditions. The simulation results show that optimal endwall design can provide 3.08% reduction of the total pressure loss at the design condition. The reduction of pressure loss obtained is mainly below 24%span with the size of the high loss region being effectively reduced. At off-design condition, the numerical benefit of the endwall contouring is found less pronounced. The discrepancy is spotted between simulation and experiments. The experimental pressure loss reduction is mainly below 18% at ADP. And the pressure loss for the CEW increases greatly at offdesign condition in experiments. Flow patterns revealed by numerical simulations show that the separation on the blade surface is mitigated with focus point disappearing, and reverse flow on the endwall near the suction side corner is moved away from the blade surface. CFD analysis indicates that the altered pressure distribution on the endwall accelerates the flow at the suction side corner and moves the reverse flow core further downstream. The weakened interaction between the corner vortex and tornado-like vortex from the endwall near the suction side corner is the main control mechanism of the CEW. The performance improvement in the linear compressor is mainly gained from it.

Corner Separation Dynamics in a Linear Compressor Cascade

2016 ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy ◽  
Jochen Kriegseis
Keyword(s):  
Three Dimensional ◽  
Recirculation Region ◽  
Spanwise Direction ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Time Resolved ◽  
Piv Measurements ◽  
Blade Section ◽  
Pod Analysis ◽  
Linear Compressor Cascade

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.

Inverse Design of Centrifugal Compressor Vaned Diffusers in Inlet Shear Flows

1996 ◽  
Vol 118 (2) ◽  
pp. 385-393 ◽  
Author(s):  
M. Zangeneh
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Design Method ◽  
Three Dimensional ◽  
Internal Flow ◽  
Inviscid Flow ◽  
Inverse Design ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Blade Thickness

A three-dimensional inverse design method in which the blade (or vane) geometry is designed for specified distributions of circulation and blade thickness is applied to the design of centrifugal compressor vaned diffusers. Two generic diffusers are designed, one with uniform inlet flow (equivalent to a conventional design) and the other with a sheared inlet flow. The inlet shear flow effects are modeled in the design method by using the so-called “Secondary Flow Approximation” in which the Bernoulli surfaces are convected by the tangentially mean inviscid flow field. The difference between the vane geometry of the uniform inlet flow and nonuniform inlet flow diffusers is found to be most significant from 50 percent chord to the trailing edge region. The flows through both diffusers are computed by using Denton’s three-dimensional inviscid Euler solver and Dawes’ three-dimensional Navier–Stokes solver under sheared in-flow conditions. The predictions indicate improved pressure recovery and internal flow field for the diffuser designed for shear inlet flow conditions.

An Analysis of the Secondary Flow Around a Tandem Blade Under the Presence of a Tip Gap in a High-Speed Linear Compressor Cascade

2021 ◽  
pp. 1-20
Author(s):  
Liesbeth Konrath ◽  
Dieter Peitsch ◽  
Alexander Heinrich
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Tip Clearance ◽  
Compressor Cascade ◽  
Complex Flow ◽  
Flow Topology ◽  
Linear Compressor ◽  
Near Surface ◽  
Oil Flow ◽  
Linear Compressor Cascade

Abstract Tandem blades have often been under investigation, experimentally as well as numerically, but most studies have been about tandem blade stators without tip gap. This work analyzes the influence of a tip gap on the flow field of a tandem blade for engine core compressors. Experiments have been conducted in a high-speed linear compressor cascade on a tandem and a reference geometry. The flow is analyzed using five-hole probe measurements in the wake of the blades and oil flow visualization to show the near surface stream lines. First, the results for design conditions (tandem and conventional blade) are compared to measurements on corresponding blades without tip gap. Similarities and differences in the flow topology due to the tip clearance are analyzed, showing that the introduction of the tip clearance has a similar influence on the loss and turning development for the tandem and the conventional blade. The tandem blade features two tip clearance vortices with a complex flow interaction and the possible formation of a third counter-rotating vortex between them. An incidence variation from 0deg to 5deg for both blades indicates at first a similar behavior. After a separation of the flow field into gap and non-gap half it becomes apparent that the tandem blade shows higher losses on the gap side, while featuring a close-to-constant behavior on the non-gap side. Further investigation of the flow on the gap side shows indicators of the front blade exhibiting tip clearance vortex break down.

Numerical Simulation of Three-Dimensional Viscous Flow in a Linear Compressor Cascade With Tip Clearance

1996 ◽  
Vol 118 (3) ◽  
pp. 492-502 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Viscous Flow ◽  
Flow Structure ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Linear Compressor ◽  
Linear Compressor Cascade

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.

Corner Separation Dynamics in a Linear Compressor Cascade

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy ◽  
Jochen Kriegseis
Keyword(s):  
Three Dimensional ◽  
Recirculation Region ◽  
Spanwise Direction ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Time Resolved ◽  
Piv Measurements ◽  
Blade Section ◽  
Pod Analysis ◽  
Linear Compressor Cascade

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.

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