Experimental investigation of the tip leakage flow in a low-speed multistage axial compressor

Casing pressure measurements and Stereoscopic Particle-Image Velocimetry (SPIV) measurements are used together to characterize the behavior of the rotor tip leakage flow at both the design and near-stall conditions in a low-speed multistage axial compressor. A three-dimensional Navier-Stokes solver is also performed for the multistage compressor and the prediction of tip leakage flow is compared with SPIV data and casing dynamic static pressure data. During the experiment 10 high-frequency Kulite transducers are mounted in the outer casing of the rotor 3 to investigate the complex flow near the compressor casing and Fourier analyses of the dynamic static pressure on the casing of the rotor 3 are carried out to investigate the tip leakage flow characteristics. At the same time, the two CCD cameras are arranged at the same side of the laser light sheet, which is suitable for investigating unsteady tip leakage flow in the multistage axial compressor. The SPIV measurements identify that the tip leakage flow exists in the rotor passage. The influence of tip leakage flow leads to the existence of low axial velocity region in the rotor passage and the alternating regions of positive and negative radial velocity indicates the emergence of tip leakage vortex (TLV). The trajectory of the tip leakage vortex moves from the suction surface toward the pressure surface of adjacent blade, which is aligned close to the rotor at the design point (DP). However, the tip leakage vortex becomes unstable and breaks down at the near-stall point (NS), making the vortex trajectory move upstream in the rotor passage and causing a large blockage in the middle of the passage.

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Characteristics of the Tip Leakage Vortex in a Low-Speed Axial Compressor With Different Rotor Tip Gaps

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-69148 ◽

2012 ◽

Cited By ~ 3

Author(s):

Zhibo Zhang ◽

Xianjun Yu ◽

Baojie Liu

Keyword(s):

Axial Compressor ◽

Pressure Rise ◽

Operating Conditions ◽

Stereoscopic Particle Image Velocimetry ◽

Tip Clearance ◽

Test Facility ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Low Speed ◽

Tip Leakage

The detailed evolutionary processes of the tip leakage flow/vortex inside the rotor passage are still not very clear for the difficulties of investigating of them by both experimental and numerical methods. In this paper, the flow fields near the rotor tip region inside the blade passage with two tip gaps, 0.5% and 1.5% blade height respectively, were measured by using stereoscopic particle image velocimetry (SPIV) in a large-scale low speed axial compressor test facility. The measurements are conducted at four different operating conditions, including the design, middle, maximum static pressure rise and near stall conditions. In order to analyze the variations of the characteristics of the tip leakage vortex (TLV), the trajectory, concentration, size, streamwise velocity, and the blockage parameters are extracted from the ensemble-averaged results and compared at different compressor operating conditions and tip gaps. The results show that the formation of the TLV is delayed with large tip clearance, however, its trajectory moves much faster in an approximately linear way from the blade suction side to pressure side. In the tested compressor, the size of the tip gap has little effects on the scale of the TLV in the spanwise direction, on the contrary, its effects on the pitch-wise direction is very prominent. Breakdown of the TLV were both found at the near-stall condition with different tip gaps. The location of the initiation of the TLV breakdown moves downstream from the 60% chord to 70% chord as the tip gap increases. After the TLV breakdown occurs, the flow blockage near the rotor tip region increases abruptly. The peak value of the blockage effects caused by the TLV breakdown is doubled with the tip gap size increasing from 0.5% to 1.5% blade span.

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Numerical Study on Tip Leakage Flow Structure of an Axial Flow Compressor Rotor

Volume 2A: Turbomachinery ◽

10.1115/gt2014-27291 ◽

2014 ◽

Cited By ~ 2

Author(s):

Chenkai Zhang ◽

Jun Hu ◽

Zhiqiang Wang ◽

Wei Yan ◽

Chao Yin ◽

...

Keyword(s):

Flow Structure ◽

Large Scale ◽

Numerical Study ◽

Axial Compressor ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Low Speed ◽

Tip Leakage

To deepen the knowledge of tip leakage flow/vortex flow structure in the tip clearance of axial compressor rotors, this paper presents steady numerical studies on a subsonic rotor. The rotor and its related low-speed large-scale repeating-stage axial compressor are used for low-speed model testing of a modern high-pressure compressor. Results were first compared with available experimental data to validate adopted numerical method. Then complex endwall flow structure and flow loss mechanism at design operating point were studied. At last, comparisons were made for tip leakage vortex structure, interface of the leakage flow/main flow, endwall blockage and loss between design and near-stall operating points. Results show that only the spilled flows below 62.5% clearance height at the leading edge will roll into tip leakage vortex for this rotor. In addition, tip leakage vortex plays a secondary important role for higher positions, where secondary leakage flow occurs and occupies broader chordwise range. Although tip leakage vortex would expand and strongly mix with the mainflow when it propagates downstream, which leads to a rapid reduction of the normalized streamwise vorticity, the value of the normalized helicity shows that concentrated vortex feature is still maintained.

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Numerical Investigation of the Behavior of Tip Leakage Flow in a Low-Speed Axial Compressor Rotor at Near-Stall Condition

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-69635 ◽

2012 ◽

Cited By ~ 1

Author(s):

Zhenzhen Duan ◽

Yangwei Liu ◽

Lipeng Lu

Keyword(s):

Axial Compressor ◽

Rotating Stall ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Stall Inception ◽

Low Speed ◽

Tip Leakage ◽

Compressor Rotor ◽

Corner Vortex

In the present work, time-accurate simulations were performed to investigate the unsteady flow fields in the tip region of a low-speed large-scale axial compressor rotor at near-stall condition. Firstly, the steady performance characteristic of the rotor was obtained by steady simulations. Secondly, a series of unsteady simulations were carried out to investigate the physical processes as the rotor approaching stall and the role of complex tip flow mechanism on flow instability in the rotor. The characteristics of tip leakage vortex were compared between design condition and near-stall condition. Detailed analyses were then employed to emphasize the development of stall inception and the comprehensions of the internal flow field. Two flow phenomena, spillage at the leading edge and backflow at the trailing edge, are found beyond the flow solution limit, which are both linked to the tip leakage flow. And the breakdown of the tip leakage vortex has been captured. The flow visualization and the quantification of passage blockage expose that the tip leakage vortex and corner vortex contribute most to the total passage blockage. Therefore, they are considered to be the key flow structures contributing to the rotating stall. Further analyses indicate that, in the current rotor, the interaction of the tip leakage flow and the corner vortex is clarified to be the key factor that leads to the rotating stall. In addition, the very initial disturbances of stall inception are discussed. And the interaction of the boundary layer migration on the blade suction side and the tip leakage vortex also plays a significant role in the stall inception.

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Prediction of Tip Leakage Vortex Dynamics in an Axial Compressor Cascade Using RANS Analyses

Volume 2C: Turbomachinery ◽

10.1115/gt2020-14797 ◽

2020 ◽

Author(s):

Martina Ricci ◽

Roberto Pacciani ◽

Michele Marconcini ◽

Andrea Arnone

Keyword(s):

Vortex Dynamics ◽

Eddy Viscosity ◽

Axial Compressor ◽

Viscosity Model ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Eddy Viscosity Model ◽

The Impact

Abstract The tip leakage flow in turbine and compressor blade rows is responsible for a relevant fraction of the total loss. It contributes to unsteadiness, and have an important impact on the operability range of compressor stages. Experimental investigations and, more recently, scale-resolving CFD approaches have helped in clarifying the flow mechanism determining the dynamics of the tip leakage vortex. Due to their continuing fundamental role in design verifications, it is important to establish whether RANS/URANS approaches are able to reproduce the effects of such a flow feature, in order to correctly drive the design of the next generation of turbomachinery. Base studies are needed in order to accomplish this goal. In the present work the tip leakage flow in axial compressor rotor blade cascade have been studied. The cascade was tested experimentally in Virginia Tech Low Speed Cascade Wind Tunnel in both stationary and moving endwall configurations. Numerical analyses were performed using the TRAF code, a state-of-the-art in-house-developed 3D RANS/URANS flow solver. The impact of the numerical framework was investigated selecting different advection schemes including a central scheme with artificial dissipation and a high-resolution upwind strategy. In addition, two turbulence models have been used, the Wilcox linear k–ω model and a non-linear eddy viscosity model (Realizable Quadratic Eddy Viscosity Model), which accounts for turbulence anisotropy. The numerical results are scrutinized using the available measurements. A detailed discussion of the vortex evolution inside the blade passage and downstream of the blade trailing edge is presented in terms of streamwise velocity, streamwise vorticity, and turbulent kinetic energy contours. The purpose is to identify guidelines for obtaining the best representation of the vortex dynamics, with the methodologies usually employed in routine design iterations and, at the same time, evidence their weak aspects that need further modelling efforts.

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PIV Maps of Tip Leakage and Secondary Flow Fields on a Low-Speed Turbine Blade Cascade With Moving End Wall

Journal of Turbomachinery ◽

10.1115/1.2437218 ◽

2007 ◽

Vol 130 (1) ◽

Cited By ~ 32

Author(s):

P. Palafox ◽

M. L. G. Oldfield ◽

J. E. LaGraff ◽

T. V. Jones

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Field Measurements ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Low Speed ◽

Tip Leakage ◽

End Wall

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110deg and blade chord of 1.0m. Data were obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0×105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle image velocimetry was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip end-wall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the undertip flow near the end wall due to the moving wall is observed and the effect on the tip leakage vortex examined.

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Tip Leakage Vortex Control in a Low Speed Axial Compressor Using Pulsed Plasma Actuation

Volume 2A: Turbomachinery ◽

10.1115/gt2016-56795 ◽

2016 ◽

Author(s):

Yun Wu ◽

Cai-dong Ma ◽

Si-meng Tian ◽

You-tian Zhou ◽

Jun Li ◽

...

Keyword(s):

Axial Compressor ◽

Pulsed Plasma ◽

Tip Leakage Flow ◽

Control Effect ◽

Stability Range ◽

Tip Leakage Vortex ◽

Low Speed ◽

Tip Leakage ◽

Vortex Control ◽

Plasma Actuation

Plasma actuation is a novel method for axial compressor flow control with advantages of short response time and broad frequency range. Numerical simulation of tip leakage vortex control in a low speed axial compressor with pulsed plasma actuation is performed. Millisecond pulsed dielectric barrier discharge plasma actuation with different frequencies are generated on the inner wall of compressor casing at the rotor leading edge. Scale adaptive hybrid Reynolds-averaged Navier-Stokes/large eddy simulation method based on shear stress transport turbulence model is adopted. The plasma actuation is simplified as a body force in the simulation. Results show that the frequency has a strong influence on the control effect of pulsed plasma actuation. Pulsed plasma actuation with frequency of 0.25 blade passing frequency (BPF), 0.5 BPF and 1.0 BPF extend the compressor’s stability range effectively. The mechanism is tip leakage vortex oscillation in the stream wise direction through coupling between unsteady plasma actuation and tip leakage flow. However, pulsed plasma actuation with frequency of 0.125 BPF, 2 BPF and 3 BPF fails to improve the stability range. The mechanism of pulsed plasma actuation at 2 BPF and 3 BPF is similar to that with steady plasma actuation, which is only stream wise boundary layer acceleration. The oscillation of tip leakage vortex in the stream wise direction can’t occur. For the pulsed plasma actuation at 0.125 BPF, its frequency is too low to get enough control effect.

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PIV Maps of Tip Leakage and Secondary Flow Fields on a Low Speed Turbine Blade Cascade With Moving Endwall

Volume 6: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68189 ◽

2005 ◽

Cited By ~ 6

Author(s):

P. Palafox ◽

M. L. G. Oldfield ◽

J. E. LaGraff ◽

T. V. Jones

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Field Measurements ◽

Turbine Rotor ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Low Speed ◽

Tip Leakage

New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110 degrees and blade chord of 1.0 m. Data was obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0 × 105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle Image Velocimetry (PIV) was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip endwall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the under-tip flow near the endwall due to the moving wall is observed and the effect on the tip leakage vortex examined.

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Effect of circumferential static pressure nonuniformity caused by volute on tip leakage flow in a centrifugal compressor

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

10.1177/0954410019836905 ◽

2019 ◽

Vol 233 (14) ◽

pp. 5134-5149 ◽

Cited By ~ 2

Author(s):

Li Fu ◽

Ce Yang ◽

Wenrui Bao ◽

Hanzhi Zhang ◽

Changmao Yang ◽

...

Keyword(s):

Pressure Gradient ◽

Centrifugal Compressor ◽

Vortex Core ◽

Static Pressure ◽

Circumferential Direction ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

High Static Pressure

For a centrifugal compressor with volute, the flow field is circumferentially nonuniform because of the volute asymmetrical structure and leads to a circumferential difference in the tip leakage flow. In this work, the compressor performance and the casing wall static pressure distribution are measured, and the results are compared with the time-averaged results of the unsteady calculation to verify the reliability of the simulation. The results show a relationship between the tip leakage vortex trajectory and the high static pressure region in the diffuser, based on which a prediction model is established for the reverse propagation of pressure waves caused by a volute tongue. Influenced by the volute asymmetric structure, the trajectory, shape, and strength of the tip leakage vortex at different circumferential positions differs significantly. The tip leakage vortex trajectory affected by the high static pressure is more inclined to a circumferential direction because the tip leakage flow velocity flowing out of the suction surface is reduced, and the tip leakage flow with low velocity is subjected to the high-pressure gradient in a passage. Moreover, the tip leakage vortex breakdown in different passages differs significantly. A tip leakage vortex core more inclined towards the streamwise direction is more likely to break down than a tip leakage vortex core inclined towards the circumferential direction because of the larger reverse pressure gradient.

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Commencement and Development Processes of Flow Unsteadiness at Tip Clearance Region of a Low Speed Axial Compressor Rotor Blade Row

Periodica Polytechnica Mechanical Engineering ◽

10.3311/ppme.11113 ◽

2017 ◽

Vol 61 (4) ◽

pp. 288

Author(s):

Marhamat Zeinali ◽

Sarallah Abbasi ◽

Abolfazl Hajizadeh Aghdam

Keyword(s):

Three Dimensional ◽

Axial Compressor ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Low Speed ◽

Tip Leakage ◽

Blade Row ◽

Development Processes ◽

Flow Frequency

Commencement and development processes of unsteadiness, caused by blade row tip leakage flow in a low speed axial compressor, are investigated and results are presented in this paper. Analyses are based on results obtained through numerical simulation of unsteady three dimensional viscous flows. Discretization of the Navier-Stokes’s equations has been carried out based on upwind second-order scheme and k-ω-SST turbulence modeling was used for estimation of eddy viscosity.Three different circumstances, including design point and two near stall conditions are considered for investigation and discussion. Tip leakage flow frequency spectrums were examined through surveying instantaneous static pressure signals imposed on the blades surfaces. Focusing on time dependent flow structure results signified existence of some pressure peaks at near stall conditions. These regions, which are created as a result of interaction between main inflow and tip leakage flow, lead to occurrence of self-induced unsteadiness. However, at design condition, flow is more affected by the main inflow instead of the tip leakage flow. By occurrence of self-induced unsteadiness, which occurs at near stall condition, tip leakage vortex flow starts to fluctuate at a frequency about the blade passing frequency. Further decrease in the flow rate up to a specified value showed no significant variations in the leakage flow frequency, but, on the other hand, magnified amplitudes of this unsteadiness.

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