Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor—Part II: Wake-Tip Clearance Vortex Interaction

In this two-part paper, results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference, the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

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Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part II — Wake–Tip Clearance Vortex Interaction

Volume 6: Turbo Expo 2007, Parts A and B ◽

10.1115/gt2007-27211 ◽

2007 ◽

Cited By ~ 1

Author(s):

Ronald Mailach ◽

Ingolf Lehmann ◽

Konrad Vogeler

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Rotor Blade ◽

Pressure Sensors ◽

Tip Clearance ◽

Experimental Investigations ◽

Lower Velocity ◽

Blade Row ◽

Blade Tip ◽

Tip Clearance Vortex

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part II of the paper the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes the tip clearance vortices are separated into different segments. Along the mean vortex trajectory these parts can be characterised by alternating patches of higher and lower velocity and flow turning or subsequent counterrotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

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Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor: Part I — Flow Field at Midspan

Volume 6: Turbo Expo 2007, Parts A and B ◽

10.1115/gt2007-27210 ◽

2007 ◽

Cited By ~ 2

Author(s):

Ronald Mailach ◽

Ingolf Lehmann ◽

Konrad Vogeler

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Pressure Distribution ◽

Rotor Blade ◽

Laser Doppler Anemometry ◽

Pressure Sensors ◽

Stability Limit ◽

Rotor Blades ◽

Experimental Investigations ◽

Blade Row

In this two-part paper results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden Low-Speed Research Compressor are presented. The main part of the experimental investigations was performed using Laser-Doppler-Anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In part I of the paper the flow field at midspan of the rotor blade row will be discussed. Different aspects of the blade row interaction process are considered for the design point and an operating point near the stability limit. The periodical unsteady blade-to-blade velocity field is dominated by the incoming stator wakes, while the potential effect of the stator blades is of minor influence. The inherent vortex structures and the negative jet effect, which is coupled to the wake appearance, are clearly resolved. Furthermore the time-resolved profile pressure distribution of the rotor blades is discussed. Although the negative jet effect within the rotor blade passage is very pronounced the rotor blade pressure distribution is nearly independent from the convectively propagating chopped stator wakes.

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Effects of Tip Clearance on Unsteady Flow Characteristics in an Axial Turbine Stage

Volume 7: Turbomachinery, Parts A and B ◽

10.1115/gt2009-59828 ◽

2009 ◽

Author(s):

Hao Sun ◽

Jun Li ◽

Zhenping Feng

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Rotor Blade ◽

Suction Side ◽

Tip Clearance ◽

Leakage Flow ◽

Turbine Stage ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Blade Tip

The clearance between the rotor blade tip and casing wall in turbomachinery passages induces leakage flow loss and thus degrades aerodynamic performance of the machine. The flow field in turbomachinery is significantly influenced by the rotor blade tip clearance size. To investigate the effects of tip clearance size on the rotor-stator interaction, the turbine stage profile from Matsunuma’s experimental tests was adopted, and the unsteady flow fields with two tip clearance sizes of 0.67% and 2.00% of blade span was numerical simulated based on Harmonic method using NUMECA software. By comparing with the domain scaling method, the accuracy of the harmonic method was verified. The interaction mechanism between the stator wake and the leakage flow was investigated. It is found that the recirculation induced by the stator wake is separated by a significant “interaction line” from the flow field close to the suction side in the clearance region. The trend of the pressure fluctuation is contrary on both sides of the line. When the stator wakes pass by the suction side, the pressure field fluctuates and the intensity of the tip leakage flow varies. With the clearance size increasing, the “interaction line” is more far away from the suction side and the intensity of tip leakage flow also fluctuates more strongly.

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Experimental Study of a 3D Wake Decay and Secondary Flows Behind a Rotor Blade Row of a Low Speed Compressor Stage

Volume 1: Turbomachinery ◽

10.1115/96-gt-415 ◽

1996 ◽

Cited By ~ 4

Author(s):

A. S. Witkowski ◽

T. J. Chmielniak ◽

M. D. Strozik

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Secondary Flow ◽

Rotor Blade ◽

Three Dimensional ◽

Secondary Flows ◽

Operating Conditions ◽

Tip Clearance ◽

Compressor Stage ◽

Blade Row

Detailed measurements have been performed in a low pressure axial flow compressor stage to investigate the structure of the secondary flow field and the three-dimensional wake decay at different axial locations before and behind the rotor. The three dimensional flow field upstream and downstream of the rotor and on the centerline of the stator blade passage have been sampled periodically using a straight and a 90 degree triple-split fiber probe. Radial measurements at 39 radial stations were carried out at chosen axial positions in order to get the span-wise characteristics of the unsteady flow. Taking the experimental values of the unsteady flow velocities and turbulence properties, the effects of the rotor blade wake decay and secondary flow on the blade row spacing and stator passage flow at different operating conditions are discussed. For the normal operating point, the component of radial turbulent intensities in the leakage-flow mixing region is found to be much higher than the corresponding axial and tangential components. But for a higher value of the flow coefficient the relations are different.The results of the experiments show that triple-split fiber probes, straight and 90 degree measurements, combined with the ensemble average technique are a very useful method for the analysis of rotor flow in turbomachinery. Tip clearance vortex, secondary flow near the hub and radial flow in the wake, turbulent intensity and Reynolds stresses and also the decay of the rotor wakes can be obtained by this method.

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Rotating Instabilities in an Axial Compressor Originating From the Fluctuating Blade Tip Vortex

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

10.1115/2000-gt-0506 ◽

2000 ◽

Cited By ~ 8

Author(s):

R. Mailach ◽

I. Lehmann ◽

K. Vogeler

Keyword(s):

Rotor Blade ◽

Laser Doppler Anemometry ◽

Stability Limit ◽

Rotor Blades ◽

Tip Clearance ◽

Tip Vortex ◽

Experimental Investigations ◽

Flow Phenomenon ◽

Low Speed ◽

Blade Tip

Rotating instabilities (RI) have been observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades. The paper describes experimental investigations of RI in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon. RI have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region. Laser-Doppler-Anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex. It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed as rotating instability (RI).

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Rotating Instabilities in an Axial Compressor Originating From the Fluctuating Blade Tip Vortex

Journal of Turbomachinery ◽

10.1115/1.1370160 ◽

2000 ◽

Vol 123 (3) ◽

pp. 453-460 ◽

Cited By ~ 148

Author(s):

R. Mailach ◽

I. Lehmann ◽

K. Vogeler

Keyword(s):

Rotor Blade ◽

Laser Doppler Anemometry ◽

Stability Limit ◽

Rotor Blades ◽

Tip Clearance ◽

Tip Vortex ◽

Experimental Investigations ◽

Flow Phenomenon ◽

Low Speed ◽

Blade Tip

Rotating instabilities (RIs) have been observed in axial flow fans and centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades. The paper describes experimental investigations of RIs in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon. RIs have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region. Laser-Doppler-anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex. It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed a rotating instability.

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CFD Analysis of High Pressure Turbines

Volume 1: Turbomachinery ◽

10.1115/98-gt-453 ◽

1998 ◽

Cited By ~ 1

Author(s):

N. Liamis ◽

J.-M. Duboue

Keyword(s):

High Pressure ◽

Rotor Blade ◽

Tip Clearance ◽

Navier Stokes ◽

Cfd Analysis ◽

Computational Results ◽

High Lift ◽

Blade Row ◽

Blade Tip ◽

Blade Tip Clearance

The purpose of this contribution is to report on the aerodynamical performance calculations carried out around single stage high pressure turbines including rotor blade tip clearance effects. Three different turbine configurations are considered: a low lift case with two different tip gap heights and a high lift case. A multistage approach based on the ONERA-Snecma 3D Navier-Stokes code CANARI is used to investigate the turbine flow behaviour. The computational results are compared with experimental data and with results obtained by single blade row simulations.

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Characteristics of Tip Clearance Flow Instability in a Transonic Compressor

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2010-22101 ◽

2010 ◽

Cited By ~ 5

Author(s):

Chunill Hah ◽

Melanie Voges ◽

Martin Mueller ◽

Heinz-Peter Schiffer

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Flow Instability ◽

Tip Clearance ◽

Piv Measurements ◽

Tip Clearance Flow ◽

Transonic Compressor ◽

Compressor Rotor ◽

Clearance Flow ◽

Tip Clearance Vortex

In the present study, unsteady flow phenomena due to tip clearance flow instability in a modern transonic axial compressor rotor are studied in detail. First, unsteady flow characteristics due the oscillating tip clearance vortex measured with the particle image velocimetry (PIV) and casing-mounted unsteady pressure transducers are analyzed and compared to numerical results with a large eddy simulation (LES). Then, measured characteristic frequencies of the unsteady flow near stall operation are investigated. The overall purpose of the study is to advance the current understanding of the unsteady flow field near the blade tip in an axial transonic compressor rotor near the stall operating condition. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. The currently applied PIV measurements indicate that the flow near the tip region is unsteady even at the design condition. This self-induced unsteadiness increases significantly as the compressor operates toward the stall condition. PIV data show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The spectral analysis of measured end wall and blade surface pressure shows that there are two dominant frequencies near stall. One frequency is about 40–60% of the rotor rotation and the other dominant frequency is about 40–60% of the blade passing frequency (BPF). The first frequency represents the movement of a large blockage over several consecutive blade passages against the rotor rotation. The second frequency represents traditional tip flow instability, which has been widely observed in subsonic compressors. The LES simulations show that the second frequency is due to movement of the instability vortex.

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3D Laser Transit Measurements of the Tip Clearance Vortex in a Compressor Rotor Blade Row

Volume 1: Turbomachinery ◽

10.1115/96-gt-506 ◽

1996 ◽

Cited By ~ 2

Author(s):

Andrew C. Foley ◽

Paul C. Ivey

Keyword(s):

Flow Field ◽

Total Pressure ◽

Tip Clearance ◽

Measured Velocity ◽

Tip Clearance Flow ◽

Pressure Losses ◽

Compressor Rotor ◽

Blade Row ◽

Clearance Flow ◽

Tip Clearance Vortex

This paper describes the structure of the tip clearance flow in a low speed isolated compressor rotor. Pneumatic cobra probes are radially traversed upstream and downstream of the blade row and the time averaged total pressure losses across the blade row calculated. The increase in pressure losses due to the tip clearance flow is clearly seen. The nature of the tip losses is investigated further using a unique 3D laser transit anemometer to measure velocities and turbulence levels. A 3D representation of the resulting flow field is then constructed using the experimentally measured velocity vectors. With the aid of ‘stream particles’ released into this flow field a vortex structure is then visualised. A section through the path of this vortex assists in showing its development through the blade row. Due to the co-location of this vortex and the total pressure losses in the passage, it is this vortex which is believed to be responsible for the excess total pressure losses in the tip region.

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