Influence of the Tip Clearance on a Compressor Blade Aerodynamic Damping

Besem, Fanny M.; Kielb, Robert E.

doi:10.2514/1.b36121

Cited by 26 publications

(12 citation statements)

References 12 publications

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“…Besem and Kielb [16] investigated computationally the effects of tip clearance for rotor blades oscillating in a torsion mode, but found a non-monotonic variation of aerodamping with tip clearance. The damping initially increased with the tip gap size until it reached a maximum and it then decreased with the further tip gap increases.…”

Section: Introductionmentioning

confidence: 99%

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

Phan

2020

Journal of Turbomachinery

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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).

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Section: Introductionmentioning

confidence: 99%

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

Phan

2020

Journal of Turbomachinery

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“…The tip gap will affect not only the steady performance but also the aeroelastic behaviour [8], [9]. The tip leakage flow significantly influences the steady and aeroelastic behaviours in compressors [10]- [12]. This complex phenomenon needs an experimental facility to provide a standard configuration for numerical studies.…”

Section: Kth Transonic Aeroelastic Compressor Rigmentioning

confidence: 99%

Numerical Investigation on the Pressure Perturbation of a Transonic Aeroelastic Compressor Rig

Tian¹,

Kth²,

Salas³

2020

Proceedings of Global Power &Amp; Propulsion Society

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A linear aeroelastic rig was designed to serve as a validation facility for forced response research in axial compressors. This rig focuses on the study of aerodynamic damping at high-reduced frequencies when the central blade oscillates in a controlled manner. The steady and unsteady flow field of the rig has been numerically investigated previously. This paper aims to understand the pressure perturbation throughout the domain, which will give more insight into the actual transonic linear cascade rig and will improve the design of the test rig in some aspects. Such aspects are the tip gaps of the side blades that with the previously optimized upper inclined wall and tailboards are of importance in keeping flow periodicity. The design process has shown that these components do influence the unsteady pressure distribution, which might reduce the accuracy of the experiments. Thus, the aeroelastic cascade itself needs detailed investigations on the systematic accuracy losses in the unsteady testing due to the current design layout. This paper presents the impacts and mechanisms of tip gaps, upper inclined wall, and bottom tailboard on the test rig's aeroelastic performance. It provides a new validation reference for cascade test results with a perspective on the numerical studies, which can introduce a correction procedure on the existing test rig or on future cascade designs.

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“…Tip gap is another significant factor in the compressor design [9]. The tip leakage flow has a significant influence on the steady and aeroelastic behaviors in compressor [10][11][12]. Tip gap will inevitably cause the redistribution of the wall pressure on the blades.…”

Section: Introductionmentioning

confidence: 99%

Numerical Sensitivity Study on the Design of a Transonic Aeroelastic Compressor Rig

Tian

Salas

2020

Volume 2E: Turbomachinery

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In modern transonic compressors, forced response can occur at high-order modes and at high-reduced frequencies. To understand this phenomenon, a new cascade test-rig is being built to provide configurations and validations for the forced response simulations of transonic compressors. With the aid of Computation Fluid Dynamics (CFD) optimizations, the test section shape was roughly determined before. The purpose of this paper is to provide the finalization process of the cascade test-rig design including a transonic nozzle and blade tip gaps. Hence, the steady and unsteady simulations are employed based on three different geometries: test section, test rig with nozzle, and test rig with 1% tip gap. The simulation results show that the unsteadiness in the test rig is related mainly to the oscillation performance of the shock waves in the passage. The comparison in the test rig with and without tip gap confirms that tip gap can reduce the unsteady pressure. The unsteady pressure reflection due to the tailboards, especially on the bottom tailboards, indicates this problem needs to be thoroughly considered in the installation and testing.

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Influence of the Tip Clearance on a Compressor Blade Aerodynamic Damping

Cited by 26 publications

References 12 publications

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

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

Numerical Investigation on the Pressure Perturbation of a Transonic Aeroelastic Compressor Rig

Numerical Sensitivity Study on the Design of a Transonic Aeroelastic Compressor Rig

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