Experiment on Linear Compressor Cascade With 3-D Blade Oscillation

An experiment has been carried out to enhance the understanding of 3D blade aeroelastic mechanisms and to produce test data of realistic configurations for validation of advanced 3D aeromechanical methods. A low speed rig with a compressor cascade consisting of seven prismatic blades of controlled diffusion profile has been commissioned. The middle blade is mechanically driven to oscillate in a 3D bending/flapping mode. At a nominal steady flow condition unsteady pressure measurements were performed at six spanwise sections for three different reduced frequencies and two different tip-clearance gaps. Off-board pressure transducers were utilized in conjunction with a transfer-function method to correct tubing distortion errors. The linearity of aerodynamic response is confirmed by the tests with different blade oscillation amplitudes, which enables the tuned cascade results to be constructed by using the Influence Coefficient Method. The measured results illustrate fully three-dimensional unsteady behaviour. Strong spanwise unsteady interaction leads to a non-proportional distribution of pressure amplitude at different spanwise locations. The tests with different tip-clearance gaps (1–2% span) show that the near tip region is destabilised as the tip gap is increased. This may be attributed to the local unloading of the corresponding steady flow. The destabilised region is seen to extend to approximately 20% of the blade span. The total aerodynamic damping at the least stable inter-blade phase angle has been reduced by 27%, when the tip gap is increased from nearly zero to 2% span.

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

10.1115/1.2836694 ◽

1996 ◽

Vol 118 (3) ◽

pp. 492-502 ◽

Cited By ~ 29

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 ◽

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.

Validation Studies of Linear Oscillating Compressor Cascade and Use of Influence Coefficient Method

10.1115/1.4045657 ◽

2020 ◽

Vol 142 (5) ◽

Cited By ~ 1

Author(s):

H. M. Phan ◽

L. He

Keyword(s):

Boundary Layer ◽

Tip Clearance ◽

Influence Coefficient ◽

Far Field ◽

Compressor Cascade ◽

Linear Cascade ◽

Influence Coefficient Method ◽

Blade Tip ◽

Coefficient Method ◽

Blade Tip Clearance

Abstract Advanced predictions of blade flutter have been continually pursued. It is noted however that validation cases of unsteady CFD methods against experimental cases with detailed 3D unsteady pressures are still rather lacking. The main objectives of the present work are two-folds. First, validate and understand the characteristics of blade tip clearance, as well as a bubble-type flow separation for an unsteady CFD solver against a 3D oscillating cascade experiment. And second, examine the applicability of the influence coefficient method (ICM) as widely used in an oscillating linear cascade setup. In the first part, the capability of a widely used commercial solver (CFX) for unsteady flows induced by a 3D oscillating compressor cascade is examined. The present computations have shown consistently a destabilizing effect of increasing blade tip clearance, in agreement with the experiment. More remarkably, the computational analyses reveal a distinctive interplay between the inlet endwall boundary layer and the tip clearance in relation to the aerodynamic damping. Different inlet endwall boundary layer thicknesses are shown to lead to qualitatively different aeroelastic stability characteristics in relation to tip clearance. The aero-damping variation with the tip clearance under the influence of the inlet endwall boundary layer seems to correlate closely to a balancing act between the passage vortex and the tip leakage vortex. The tip clearance aeroelastic behavior seems also in line with a simple quasi-steady analysis. On the other hand, the mid-chord laminar bubble separation on suction surface, though with a clear signature in the local aero-damping, has negligible effects on the overall stability. The second part aims to examine computationally the applicability of the influence coefficient method in a linear cascade setup. The comparison between the cascade-based ICM data and a baseline “tuned cascade” shows that the differences in the sensitivity to the far-field treatment can be significant, depending on inter-blade phase angles. On the other hand, non-linearity effects closely relevant to the basic linear assumption of the ICM are shown to only have a small influence. The present results suggest that extra caution should be exercised when comparing a CFD-based tuned cascade model with a finite cascade-based ICM model, at conditions close to acoustic resonance. The resultant discrepancies may well arise from the inherently different far-field sensitivities between the two models, rather than those typical numerical and physical modeling aspects of interest (e.g., meshing, spatial and temporal discretization errors as well as turbulence modeling).

Validation Studies of Linear Oscillating Compressor Cascade and Use of Influence Coefficient Method

Volume 7A: Structures and Dynamics ◽

10.1115/gt2019-90941 ◽

2019 ◽

Author(s):

H. M. Phan ◽

L. He

Keyword(s):

Boundary Layer ◽

Tip Clearance ◽

Influence Coefficient ◽

Far Field ◽

Compressor Cascade ◽

Linear Cascade ◽

Influence Coefficient Method ◽

Blade Tip ◽

Coefficient Method ◽

Blade Tip Clearance

Abstract Advanced predictions of blade flutter have been continually pursued. It is noted however that validation cases of unsteady CFD methods against experimental cases with detailed 3D unsteady pressures are still rather lacking. The main objectives of the present work are two-folds. Firstly, validate and understand the characteristics of blade tip clearance, as well as a bubble-type flow separation for an unsteady CFD solver against a 3D oscillating cascade experiment. And secondly, examine the applicability of the Influence Coefficient Method (ICM) as widely used in an oscillating linear cascade setup. In the first part, the capability of a widely used commercial solver (CFX) for unsteady flows induced by a 3D oscillating compressor cascade is examined. The present computations have shown consistently a destabilizing effect of increasing blade tip clearance, in agreement with the experiment. More remarkably, the computational analyses reveal a distinctive interplay between the inlet endwall boundary layer and the tip clearance in relation to the aerodynamic damping. Different inlet endwall boundary layer thicknesses are shown to lead to qualitatively different aeroelastic stability characteristics in relation to tip clearance. The aero-damping variation with the tip-clearance under the influence of the inlet endwall boundary layer seems to correlate closely to a balancing act between the passage vortex and the tip-leakage vortex. The tip clearance aeroelastic behaviour seems also in line with a simple quasi-steady analysis. On the other hand, the mid-chord laminar bubble separation on suction surface, though with a clear signature in the local aero-damping, has negligible effects on the overall stability. The second part aims to examine computationally the applicability of the influence coefficient method in a linear cascade setup. The comparison between the cascade based ICM data and a baseline ‘tuned cascade’ shows that the differences in the sensitivity to the far-field treatment can be significant, depending on interblade phase angles. On the other hand, non-linearity effects closely relevant to the basic linear assumption of the ICM are shown to only have a small influence. The present results suggest that extra caution should be exercised when comparing a CFD-based tuned cascade model with a finite cascade-based ICM model, at conditions close to acoustic resonance. The resultant discrepancies may well arise from the inherently different far-field sensitivities between the two models, rather than those typical numerical and physical modelling aspects of interest (e.g. meshing, spatial and temporal discretization errors as well as turbulence modelling).

Discussion: “Numerical Simulation of Three-Dimensional Viscous Flow in a Linear Compressor Cascade With Tip Clearance” (Kang, S., and Hirsch, C., 1996, ASME J. Turbomach., 118, pp. 492–502)

10.1115/1.2836695 ◽

1996 ◽

Vol 118 (3) ◽

pp. 502-503

Author(s):

N. A. Cumpsty ◽

E. M. Greitzer

Keyword(s):

Numerical Simulation ◽

Viscous Flow ◽

Three Dimensional ◽

Tip Clearance ◽

Compressor Cascade ◽

Linear Compressor ◽

Closure to “Discussion of ‘Numerical Simulation of Three-Dimensional Viscous Flow in a Linear Compressor Cascade With Tip Clearance’” (1996, ASME J. Turbomach., 118, pp. 502–503)

10.1115/1.2836696 ◽

1996 ◽

Vol 118 (3) ◽

pp. 503-505

Author(s):

S. Kang ◽

C. Hirsch

Keyword(s):

Numerical Simulation ◽

Viscous Flow ◽

Three Dimensional ◽

Tip Clearance ◽

Compressor Cascade ◽

Linear Compressor ◽

Experimental Investigation Into the Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade

10.1115/1.4028797 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 6

Author(s):

Andreas Krug ◽

Peter Busse ◽

Konrad Vogeler

Keyword(s):

Flow Field ◽

Experimental Studies ◽

Axial Compressor ◽

Field Measurements ◽

Tip Clearance ◽

Compressor Cascade ◽

Unsteady Interaction ◽

Linear Compressor Cascade ◽

Tip Clearance Vortex ◽

The Impact

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex (TCV) and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step toward the characterization of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions. This paper focuses on experimental studies conducted at the newly designed low-speed cascade wind tunnel in Dresden. The general tunnel configuration and details on the specific cascade setup will be presented. Steady state flow field measurements were carried out using five-hole probe traverses up- and downstream of the cascade and accompanied by static wall pressure readings. 2D-particle image velocimetry (PIV) measurements complemented these results by visualizing the blade-to-blade flow field. Hence, the structure of the evolving secondary flow system is evaluated and compared for all tested configurations.

Tip Leakage Flow in Linear Compressor Cascade

Volume 3B: General ◽

10.1115/93-gt-303 ◽

1993 ◽

Author(s):

S. Kang ◽

C. Hirsch

Keyword(s):

Design Flow ◽

Tip Clearance ◽

Leakage Flow ◽

Compressor Cascade ◽

Tip Leakage Flow ◽

Linear Compressor ◽

Tip Leakage ◽

Flow Mixing ◽

Internal Loss ◽

Tip leakage flow in a linear compressor cascade of NACA 65-1810 profiles is investigated, for tip clearance levels of 1.0, 2.0 and 3.25 percent of chord at design and off-design flow conditions. Data, velocity and pressures, are collected from three transverse sections inside tip clearance and sixteen sections within flow passage. Tip separation vortex influence is identified from the data. Leakage flow mixing is clearly present inside the clearance and has a significant influence on the internal loss.

Numerical Simulation of 3D Viscous Flow in a Linear Compressor Cascade With Tip Clearance

Volume 1: Turbomachinery ◽

10.1115/94-gt-364 ◽

1994 ◽

Author(s):

Shun Kang ◽

Charles Hirsch

Keyword(s):

Viscous Flow ◽

Flow Structure ◽

Leading Edge ◽

Secondary Flows ◽

Tip Clearance ◽

Flow Coefficient ◽

Compressor Cascade ◽

Tip Leakage Flow ◽

Linear Compressor ◽

A Navier-Stokes solver is applied to investigate the 3D 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.

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

Effects of Stator Pressure Field on Upstream Rotor Performance

10.1115/99-gt-099 ◽

1999 ◽

Cited By ~ 8

Author(s):

M. B. Graf ◽

E. M. Greitzer ◽

F. E. Marble ◽

O. P. Sharma

Keyword(s):

Steady Flow ◽

Pressure Field ◽

Three Dimensional ◽

Pressure Rise ◽

Tip Clearance ◽

Navier Stokes ◽

Flow Models ◽

High Pressure Compressor ◽

Rotor Stator Interaction ◽

Rotor Loss

Effects of stator pressure field on upstream rotor performance in a high pressure compressor stage have been assessed using three-dimensional steady and time-accurate Reynolds-averaged Navier-Stokes computations. Emphasis was placed on: (1) determining the dominant features of the flow arising from interaction of the rotor with the stator pressure field, and (2) quantifying the overall effects on time averaged loss, blockage, and pressure rise. The time averaged results showed a 20 to 40% increase in overall rotor loss and a 10 to 50% decrease in tip clearance loss compared to an isolated rotor. The differences were dependent on the operating point and increased as the stage pressure rise, and amplitude of the unsteady back pressure variations, was increased. Motions of the tip leakage vortex on the order of the blade pitch were observed at the rotor exit in all the unsteady flow simulations; these were associated with enhanced mixing in the region. The period of the motion scaled with rotor flow-through time rather than stator passing. Three steady flow approximations for the rotor-stator interaction were assessed with reference to the unsteady computations: an axisymmetric representation of the stator pressure field, an inter-blade row averaging plane method, and a technique incorporating deterministic stresses and bodyforces associated with stator flow field. Differences between steady and unsteady predictions of overall rotor loss, tip region loss, and endwall blockage ranged from 5 to 50% of the time average, but the steady flow models gave overall rotor pressure rise and flow capacity within 5% of the time averaged values.

Study of Three-Dimensional Viscous Flows in an Axial Compressor Cascade Including Tip Leakage Effects Using a SIMPLE-Based Algorithm

10.1115/1.3262024 ◽

1986 ◽

Vol 108 (1) ◽

pp. 51-58 ◽

Cited By ~ 11

Author(s):

M. Pouagare ◽

R. A. Delaney

Keyword(s):

Numerical Simulation ◽

Three Dimensional ◽

Axial Compressor ◽

Simple Algorithm ◽

Suction Side ◽

Tip Clearance ◽

High Loading ◽

Leakage Flow ◽

Compressor Cascade ◽

Flow Phenomena

A multisweep space-marching solver based on a modified version of the SIMPLE algorithm was employed to study the three-dimensional flow field through a linear cascade. Three cases were tested: one with moderate loading, one with high loading, and one with high loading and tip clearance. The results of the numerical simulation were compared with available experimental measurements, and the agreement between the two was found satisfactory. The numerical simulation provided insight into several important endwall flow phenomena such as the interaction between the leakage and passage vortices, the interaction between the leakage vortex and the wake, the effect of leakage flow and loading on losses and secondary kinetic energy, the suction side corner separation, and the blowing of this separation by the leakage flow.