Performance Enhancement of a Low Speed Axial Compressor Utilizing Simultaneous Tip Injection and Casing Treatment of Groove Type

Rotor blade vibrations observed in the Darmstadt transonic compressor rig are investigated in this paper. The vibrations are nonsynchronous and occur in the near stall (NS) operating region. Rotor tip flow fluctuations traveling near the leading edge (LE) against the direction of rotation (in the rotor relative frame of reference) with about 50% blade tip speed are found to be the reason for the occurrence of the vibrations. The investigations show that the blockage at the rotor tip is an important factor for the aeroelastic stability of the compressor in the NS region. It is found that by application of a recirculating tip injection (TI) casing treatment, the aeroelastic stability increases as a result of reduced blockage in the rotor tip region.

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A Study of Performance and Flow Mechanism of a Slot-Groove Hybrid Casing Treatment in a Low-Speed Compressor

Volume 2C: Turbomachinery ◽

10.1115/gt2015-43920 ◽

2015 ◽

Cited By ~ 2

Author(s):

Juan Du ◽

Fan Li ◽

Jichao Li ◽

Ning Ma ◽

Feng Lin ◽

...

Keyword(s):

Axial Compressor ◽

Suction Side ◽

Tip Leakage Flow ◽

Stall Margin ◽

Low Speed ◽

High Entropy ◽

Casing Treatment ◽

Tip Leakage ◽

Flow Loss ◽

The Difference

A “slot-groove” hybrid casing treatment (CT) is proposed elicited from the recent research on the role of axial location for stall margin improvement (SMI). This combination is expected to display the advantages of both slots and grooves while minimizing their disadvantages. A comparative study is conducted among the “slot-groove”, traditional circumferential groove CT (called the “full-groove” CT) and axial skewed slot CT (known as the “full-slot” CT) to evaluate performance and to explore the stability enhancement and efficiency loss mechanisms of the “slot-groove” CT in a low-speed axial compressor. Results of the combination of laboratory tests and computational fluid dynamics (CFD) data demonstrate that the performance level of the hybrid CT lies in between those two traditional CTs. Simulation results indicate that the difference in the SMIs generated by CTs is closely related to their influences on the vortex trajectory of tip leakage. The stronger and tighter the vortex is, the more the vortex trajectory is inclined toward the blade suction side. Consequently, the interface between tip leakage flow and incoming main flow is pushed downstream and stability is enhanced. The flow loss induced by CTs is explored based on the entropy contours, and the high entropy in the “slot-groove” treated casing produces more efficiency decrease than the “full-groove” CT. Incorporating the “full-slot” CT not only increases entropy generation in the axial skewed slots but also induces considerable flow loss in the blade passage near the casing, thus reducing efficiency most significantly.

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Performance enhancement in transonic axial compressors using blade tip injection coupled with casing treatment

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

10.1243/095765005x28607 ◽

2005 ◽

Vol 219 (5) ◽

pp. 321-331 ◽

Cited By ~ 17

Author(s):

B. H. Beheshti ◽

B Farhanieh ◽

K Ghorbanian ◽

J. A. Teixeira ◽

P. C. Ivey

Keyword(s):

Flow Injection ◽

High Speed ◽

Performance Enhancement ◽

Three Dimensional ◽

Stall Margin ◽

Casing Treatment ◽

Transonic Compressor ◽

Compressor Rotor ◽

Blade Tip ◽

Tip Injection

The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. This paper presents numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection. This is characterized by introducing a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by ∼30 per cent of the tip chord both in the upstream and in the downstream directions. To numerically solve the governing equations, the three-dimensional finite element based finite volume method CFD solver CFX-TASCflow (version 2.12.1) is employed. For a compressible flow with varying density, Reynolds-averaging leads to appearance of complicated correlations. To avoid this, the mass-weighted or Favre-averaging is applied. Using an injected mass flow of 2.4 per cent of the annulus flow, the present design can improve stall margin by up to 7 per cent when compared with a smooth casing compressor without tip injection. This research can lead to an optimum design of recirculating casing treatments or other mechanisms for performance enhancement applying tip flow injection.

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Experimental and Numerical Investigation of a Circumferential Groove Casing Treatment in a Low-Speed Axial Research Compressor at Different Tip Clearances

Journal of Turbomachinery ◽

10.1115/1.4037822 ◽

2017 ◽

Vol 139 (12) ◽

Cited By ~ 5

Author(s):

Matthias Rolfes ◽

Martin Lange ◽

Konrad Vogeler ◽

Ronald Mailach

Keyword(s):

Total Pressure ◽

Solid Wall ◽

Pressure Ratio ◽

Axial Compressor ◽

Chord Length ◽

Single Stage ◽

Low Speed ◽

Casing Treatment ◽

Operating Range ◽

Circumferential Groove

The demand of increasing pressure ratios for modern high pressure compressors leads to decreasing blade heights in the last stages. As tip clearances (TC) cannot be reduced to any amount and minimum values might be necessary for safety reasons, the TC ratios of the last stages can reach values notably higher than current norms. This can be intensified by a compressor running in transient operations where thermal differences can lead to further growing clearances. For decades, the detrimental effects of large clearances on an axial compressor's operating range and efficiency are known and investigated. The ability of circumferential casing grooves in the rotor casing to improve the compressor's operating range has also been in the focus of research for many years. Their simplicity and ease of installation are one reason for their continuing popularity nowadays, where advanced methods to increase the operating range of an axial compressor are known. In the authors' previous paper, three different circumferential groove casing treatments were investigated in a single-stage environment in the low-speed axial research compressor at TU Dresden. One of these grooves was able to notably improve the operating range and the efficiency of the single stage compressor at very large rotor TC (5% of chord length). In this paper, the results of tests with this particular groove type in a three stage environment in the low-speed axial research compressor are presented. Two different rotor TC sizes of 1.2% and 5% of tip chord length were investigated. At the small TC, the grooves are almost neutral. Only small reductions in total pressure ratio and efficiency compared to the solid wall can be observed. If the compressor runs with large TC, it notably benefits from the casing grooves. Both, total pressure and efficiency can be improved by the grooves in a similar extent as in single stage tests. Five-hole probe measurements and unsteady wall pressure measurements show the influence of the groove on the flow field. With the help of numerical investigations, the different behavior of the grooves at the two TC sizes will be discussed.

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Influence of Rotor Tip Blockage on Near Stall Blade Vibrations in an Axial Compressor Rig

Volume 7B: Structures and Dynamics ◽

10.1115/gt2017-63660 ◽

2017 ◽

Cited By ~ 1

Author(s):

Daniel Möller ◽

Maximilian Jüngst ◽

Heinz-Peter Schiffer ◽

Thomas Giersch ◽

Frank Heinichen

Keyword(s):

Axial Compressor ◽

Leading Edge ◽

Aeroelastic Stability ◽

Casing Treatment ◽

Transonic Compressor ◽

Flow Fluctuations ◽

Operating Region ◽

Blade Vibrations ◽

Blade Tip ◽

Tip Injection

Rotor blade vibrations observed in the Darmstadt transonic compressor rig are investigated in this paper. The vibrations are non-synchronous and occur in the near stall operating region. Rotor tip flow fluctuations traveling near the leading edge against the direction of rotation (in the rotor relative frame of reference) with about 50% blade tip speed are found to be the reason for the occurrence of the vibrations. The investigations show, that the blockage at the rotor tip is an important factor for the aeroelastic stability of the compressor in the near stall region. It is found, that by application of a recirculating tip injection casing treatment, the aeroelastic stability increases as a result of reduced blockage in the rotor tip region.

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Effect of the Foam Metal Casing Treatment on a Low-Speed Axial Compressor

10.1115/1.0002894v ◽

2021 ◽

Author(s):

Jia Li ◽

Dakun Sun ◽

Ruize Xu ◽

Xu Dong ◽

Xiaofeng Sun

Keyword(s):

Axial Compressor ◽

Low Speed ◽

Casing Treatment ◽

Foam Metal ◽

Metal Casing

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Influence of axial skewed slots on the rotating instability of a low-speed axial compressor

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020944331 ◽

2020 ◽

pp. 095441002094433

Author(s):

Tao Li ◽

Yadong Wu ◽

Hua Ouyang

Keyword(s):

Pressure Fluctuations ◽

Flow Characteristics ◽

Axial Compressor ◽

Tip Clearance ◽

Frequency Spectra ◽

Stall Margin ◽

Tip Clearance Flow ◽

Low Speed ◽

Casing Treatment ◽

Rotating Instability

Experimental and numerical analyses were performed on a low-speed axial compressor rotor to investigate the aerodynamic and acoustic effects of axial skewed slots casing treatment on the rotating instability. The experimental results showed that the stall margin could be improved by 8.0% and the frequency broadband hump owing to the rotating instability was suppressed effectively. In the noise spectra, the two dominant broadband humps on both sides of the blade-passing frequency also reduced in amplitude. Full-annulus unsteady computational fluid dynamics simulations were performed near the design condition. Time- and frequency-domain analyses as well as a proper orthogonal decomposition method were applied to obtain the oscillation, frequency, energy and flow characteristics of the rotating instability. Axial skewed slots casing treatment causes a distinct reduction in the amplitude of the pressure fluctuations and frequency spectra with a decrease in the energy of the rotating instability modes. The slots alleviated the tip flow blockage by the periodic injection and removal of the fluid from the passage, which enabled a high tip clearance flow downstream with little impingement on the neighbouring blade tip.

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