Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design changes to a baseline double circular arc airfoil axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely, high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely, a full forward chordwise sweep (FFCS) rotor and a rotor with gradual stagger angle reduction in the outer span, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower sensitivity of performance and aerodynamic stability to tip clearance.

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Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size

Volume 2A: Turbomachinery ◽

10.1115/gt2015-42746 ◽

2015 ◽

Cited By ~ 2

Author(s):

Engin Erler ◽

Huu Duc Vo ◽

Hong Yu

Keyword(s):

Axial Compressor ◽

Tip Clearance ◽

Aerodynamic Stability ◽

Tip Leakage ◽

Compressor Rotor ◽

Flow Features ◽

Parametric Studies ◽

Compressor Performance ◽

Flow Effects ◽

Stagger Angle

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design change on a baseline double circular arc axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely full forward chordwise sweep and partially low stagger angle, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower performance and aerodynamic stability sensitivity to tip clearance.

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Performance Desensitization for a High-Speed Axial Compressor

Volume 2A: Turbomachinery ◽

10.1115/gt2018-77203 ◽

2018 ◽

Cited By ~ 1

Author(s):

Yassine Souleimani ◽

Huu Duc Vo ◽

Hong Yu

Keyword(s):

High Speed ◽

Numerical Study ◽

Pressure Ratio ◽

Axial Compressor ◽

Tip Clearance ◽

Lower Sensitivity ◽

Tip Leakage Flow ◽

Stall Margin ◽

Casing Treatment ◽

Compressor Rotor

The increase in compressor tip clearance over the lifespan of an aero-engine leads to a long-term degradation in its fuel consumption and operating envelope. A highly promising recent numerical study on a theoretical high-speed axial compressor rotor proposed a novel casing treatment to decrease performance and stall margin sensitivity to tip clearance increase. This paper aims to apply and analyze, through CFD simulations, this casing treatment concept to a representative production axial compressor rotor with inherently lower sensitivity to tip clearance increase and complement the explanation on the mechanism behind the reduction in sensitivity. Simulations of the baseline rotor showed that the lower span region contribute as much to the pressure ratio sensitivity as the tip region which is dominated by tip leakage flow. In contrast, the efficiency sensitivity is mainly driven by losses occurring in the tip region. The novel casing treatment was successfully applied to the baseline rotor through a design refinement. Although the casing treatment causes some penalty in nominal performance, it completely reversed the pressure ratio sensitivity (i.e. pressure ratio increases with tip clearance) and reduced the efficiency sensitivity. The reversed pressure ratio sensitivity is explained by a rotation in the core flow in the lower span region indirectly induced by the flow injection from the casing treatment. The lower efficiency sensitivity comes from a reduction in the amount of fluid that crosses the tip clearance of two adjacent blades, known as double leakage. The casing treatment’s beneficial effect on stall margin sensitivity is less obvious because of the stall inception type of the baseline rotor and its change in the presence of the casing treatment.

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Endwall Blockage in Axial Compressors

Journal of Turbomachinery ◽

10.1115/1.2841344 ◽

1999 ◽

Vol 121 (3) ◽

pp. 499-509 ◽

Cited By ~ 97

Author(s):

S. A. Khalid ◽

A. S. Khalsa ◽

I. A. Waitz ◽

C. S. Tan ◽

E. M. Greitzer ◽

...

Keyword(s):

Tip Clearance ◽

Design Parameters ◽

Tip Clearance Flow ◽

Axial Compressors ◽

Clearance Flow ◽

Flow Features ◽

Physical Insight ◽

Level Loading ◽

Stagger Angle ◽

Insight Into

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.

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Behavior of Tip Leakage Flow Behind an Axial Compressor Rotor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3239889 ◽

1986 ◽

Vol 108 (1) ◽

pp. 7-14 ◽

Cited By ~ 94

Author(s):

M. Inoue ◽

M. Kuroumaru ◽

M. Fukuhara

Keyword(s):

Incidence Angle ◽

Axial Compressor ◽

Performance Testing ◽

Tip Clearance ◽

Vortex Center ◽

Tip Leakage Flow ◽

Flow Measurements ◽

Wall Boundary Layer ◽

Compressor Rotor ◽

Work Done

Performance testing and detailed flow measurements were made in an axial compressor rotor with various tip clearances. The experiments were conducted on the condition of the same incidence angle at midspan. Thus, the effect of tip clearance distinguished from that of incidence angle was investigated on the overall performance, work-done factor, blockage factor, and increases in displacement, momentum, and blade-force-deficit thicknesses of the casing wall boundary layer, The phase-locked flow patterns obtained by the multisampling technique show clear evidence of a leakage vortex core behind the rotor. Behavior of the leakage vortex was clarified for various tip clearances by examining loci of the vortex center, decay characteristics of the vorticity at the center, and the total amount of vorticity shed from the blade tip. These results were compared with the leakage vortex model presented by Lakshminarayana.

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Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650919856541 ◽

2019 ◽

Vol 234 (2) ◽

pp. 127-142

Author(s):

Wei Zhu ◽

Songtao Wang ◽

Longxin Zhang ◽

Jun Ding ◽

Zhongqi Wang

Keyword(s):

Numerical Simulations ◽

Dynamic Balance ◽

Three Dimensional ◽

Axial Compressor ◽

Tip Clearance ◽

Stall Margin ◽

Tip Clearance Flow ◽

Compressor Rotor ◽

Clearance Flow ◽

Flow Phenomena

This study aimed to enhance the understanding of flow phenomena in low-reaction aspirated compressors. Three-dimensional, multi-passage steady and unsteady numerical simulations are performed to investigate the performance sensitivity to tip clearance variation on the first-stage rotor of a multistage low-reaction aspirated compressor. Three kinds of tip clearance sizes including 1.0τ, 2.0τ and 3.0τ are modeled, in which 1.0τ corresponds to the designed tip clearance size of 0.2 mm. The steady numerical simulations show that the overall performance of the rotor moves toward lower mass flow rate when the tip clearance size is increased. Moreover, energy losses, efficiency reduction and stall margin decrease are also observed with increasing tip clearance size. This can be mostly attributed to the damaging impact of intense tip clearance flow. For unsteady simulation, the result shows periodical oscillation of the tip leakage vortex and a “two-passage periodic structure” in the tip region at the near-stall point. The occurrence of the periodical oscillation is due to the severe interaction between the tip clearance flow and the shock wave. However, the rotor operating state is still stable at this working point because a dynamic balance is established between the tip clearance flow and incoming flow.

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Leakage Effects in the Rotor Tip-Clearance Region of a Multistage Axial Compressor: Part 2 — Numerical Modelling

Volume 1: Turbomachinery ◽

10.1115/98-gt-592 ◽

1998 ◽

Author(s):

E. S. Politis ◽

K. C. Giannakoglou ◽

K. D. Papailiou

Keyword(s):

Axial Compressor ◽

Tip Clearance ◽

Navier Stokes ◽

Computational Domain ◽

Loose Coupling ◽

Tip Clearance Flow ◽

Clearance Flow ◽

Flow Effects ◽

Multistage Axial Compressor ◽

Asme Paper

Innovative measurements of tip-clearance flow for the 3rd stage rotor embedded in a four stage Low-Speed Research Compressor are presented in the companion ASME paper. Here, in Part 2, the rotor flow is numerically simulated through a Navier-Stokes solver implementing the k-ε turbulence model. The 3rd stage rows are considered as discrete parts of the same computational domain and the flow in each one of them is treated as steady in the corresponding system of reference. An iterative, though loose, coupling between the rotor exit and the stator inlet is established by artificially increasing the inter-row distance. To model tip-clearance flow effects with sufficient accuracy, a two-block grid system per row is used. Comparisons with measurements published in Part 1 for the average flow quantities at the exit of both rows are presented. Row patterns close to the rotor tip-clearance region are illustrated.

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Blockage Development in a Transonic, Axial Compressor Rotor

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

10.1115/97-gt-394 ◽

1997 ◽

Cited By ~ 5

Author(s):

Kenneth L. Suder

Keyword(s):

Boundary Layer ◽

Axial Compressor ◽

Flow Region ◽

Tip Clearance ◽

Surface Boundary ◽

Core Flow ◽

The Core ◽

Compressor Rotor ◽

Transonic Axial Compressor ◽

The Impact

A detailed experimental investigation to understand and quantify the development of blockage in the flow field of a transonic, axial flow compressor rotor (NASA Rotor 37) has been undertaken. Detailed laser anemometer measurements were acquired upstream, within, and downstream of a transonic, axial compressor rotor operating at 100%, 85%, 80%, and 60% of design speed which provided inlet relative Mach numbers at the blade tip of 1.48, 1.26, 1.18, and 0.89 respectively. The impact of the shock on the blockage development, pertaining to both the shock / boundary layer interactions and the shock / tip clearance flow interactions, is discussed. The results indicate that for this rotor the blockage in the endwall region is 2–3 times that of the core flow region, and the blockage in the core flow region more than doubles when the shock strength is sufficient to separate the suction surface boundary layer.

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Numerical Investigation of Relation Between Unsteady Behavior of Tip Leakage Vortex and Rotating Disturbance in a Transonic Axial Compressor Rotor

Volume 6: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2008-50779 ◽

2008 ◽

Cited By ~ 5

Author(s):

K. Yamada ◽

K. Funazaki ◽

H. Sasaki

Keyword(s):

Vortex Breakdown ◽

Axial Compressor ◽

Tip Clearance ◽

Tip Leakage Vortex ◽

Tip Clearance Flow ◽

Tip Leakage ◽

Compressor Rotor ◽

Clearance Flow ◽

Transonic Axial Compressor ◽

Rotating Instability

The purpose of this study is to have a better understanding of the unsteady behavior of tip clearance flow at near-stall condition from a multi-passage simulation and to clarify the relation between such unsteadiness and rotating disturbance. This study is motivated by the following concern. A single passage simulation has revealed the occurrence of the tip leakage vortex breakdown at near-stall condition in a transonic axial compressor rotor, leading to the unsteadiness of the tip clearance flow field in the rotor passage. These unsteady flow phenomena were similar to those in the rotating instability, which is classified in one of the rotating disturbances. In other words it is possible that the tip leakage vortex breakdown produces a rotating disturbance such as the rotating instability. Three-dimensional unsteady RANS calculation was conducted to simulate the rotating disturbance in a transonic axial compressor rotor (NASA Rotor 37). The four-passage simulation was performed so as to capture a short length scale disturbance like the rotating instability and the spike-type stall inception. The simulation demonstrated that the unsteadiness of tip leakage vortex, which was derived from the vortex breakdown at near-stall condition, invoked the rotating disturbance in the rotor, which is similar to the rotating instability.

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