An Analysis of the Performance of an Axial-Flow Compressor at Low Reynolds Number

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, and turbulence intensity, etc. were carried out at a very low Reynolds number condition, Reout = 3.5 × 104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

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Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number

Journal of Turbomachinery ◽

10.1115/1.2464143 ◽

2006 ◽

Vol 129 (2) ◽

pp. 360-371 ◽

Cited By ~ 20

Author(s):

Takayuki Matsunuma

Keyword(s):

Reynolds Number ◽

Flow Field ◽

Unsteady Flow ◽

Low Reynolds Number ◽

Axial Flow ◽

Turbine Rotor ◽

Frame Of Reference ◽

Flow Angle ◽

Low Reynolds ◽

Secondary Vortices

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, turbulence intensity, etc., were carried out at a very low Reynolds number condition, Reout=3.5×104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

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An Experiment With Aspect Ratio as a Means of Extending the Useful Range of a Transonic Inlet Stage of an Axial Flow Compressor

Journal of Engineering for Power ◽

10.1115/1.3677586 ◽

1964 ◽

Vol 86 (3) ◽

pp. 243-246 ◽

Cited By ~ 1

Author(s):

W. C. Swan

Keyword(s):

Reynolds Number ◽

Aspect Ratio ◽

Axial Flow ◽

Compressor Stage ◽

Axial Flow Compressor ◽

Flow Compressor

An experiment in unstalled range of a transonic axial flow compressor stage is discussed. Two rotors of identical design, but of differing aspect ratio, are compared. The study suggests that some criteria other than blade chord Reynolds number be used to define chord lengths of transonic stages.

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Deformation of a soft helical filament in an axial flow at low Reynolds number

Soft Matter ◽

10.1039/c5sm02625c ◽

2016 ◽

Vol 12 (6) ◽

pp. 1898-1905 ◽

Cited By ~ 5

Author(s):

Mohammad K. Jawed ◽

Pedro M. Reis

Keyword(s):

Reynolds Number ◽

Numerical Investigation ◽

Low Reynolds Number ◽

Axial Flow ◽

Low Reynolds

We perform a numerical investigation of the deformation of a rotating helical filament subjected to an axial flow, under low Reynolds number conditions. This problem is motivated by the propulsion of bacteria that use a helical flagella.

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Effects of Low Reynolds Number on Wake-Generated Unsteady Flow of an Axial-Flow Turbine Rotor

International Journal of Rotating Machinery ◽

10.1155/ijrm.2005.1 ◽

2005 ◽

Vol 2005 (1) ◽

pp. 1-15 ◽

Cited By ~ 8

Author(s):

Takayuki Matsunuma ◽

Yasukata Tsutsui

Keyword(s):

Reynolds Number ◽

Energy Dissipation ◽

Flow Field ◽

Unsteady Flow ◽

Power Law ◽

Turbulence Intensity ◽

Low Reynolds Number ◽

Axial Flow ◽

Reynolds Numbers ◽

Low Reynolds

The unsteady flow field downstream of axial-flow turbine rotors at low Reynolds numbers was investigated experimentally using hot-wire probes. Reynolds number, based on rotor exit velocity and rotor chord lengthReout,RT, was varied from3.2×104to12.8×104at intervals of1.0×104by changing the flow velocity of the wind tunnel. The time-averaged and time-dependent distributions of velocity and turbulence intensity were analyzed to determine the effect of Reynolds number. The reduction of Reynolds number had a marked influence on the turbine flow field. The regions of high turbulence intensity due to the wake and the secondary vortices were increased dramatically with the decreasing Reynolds number. The periodic fluctuation of the flow due to rotor-stator interaction also increased with the decreasing Reynolds number. The energy-dissipation thickness of the rotor midspan wake at the low Reynolds numberReout,RT=3.2×104was1.5times larger than that at the high Reynolds numberReout,RT=12.8×104. The curve of the−0.2power of the Reynolds number agreed with the measured energy-dissipation thickness at higher Reynolds numbers. However, the curve of the−0.4power law fitted more closely than the curve of the−0.2power law at lower Reynolds numbers below6.4×104.

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LDV Measurements of Unsteady Midspan Flow in a Turbine Rotor at Low Reynolds Number

Volume 6: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38468 ◽

2003 ◽

Cited By ~ 2

Author(s):

Takayuki Matsunuma ◽

Yasukata Tsutsui

Keyword(s):

Reynolds Number ◽

Flow Field ◽

Reynolds Stress ◽

Low Reynolds Number ◽

Axial Flow ◽

Turbine Rotor ◽

Mean Flow ◽

Suction Surface ◽

Flow Angle ◽

Low Reynolds

In this study, the unsteady flow field at midspan in an axial-flow turbine rotor at low Reynolds number (Reout,RT = 3.6×104) was investigated experimentally using a laser Doppler velocimetry (LDV) system. The time-averaged and time-dependent distributions of velocity, flow angle, vorticity, turbulence intensity, and Reynolds stress were analyzed in terms of both absolute and relative frames of reference. In the relative frame of reference, the nozzle wake had a slip velocity relative to the mean flow, which caused the wake fluid to migrate across the rotor passage and accumulate on the rotor suction surface. The effect of the nozzle wake on the flow field inside the rotor was determined qualitatively and quantitatively. The flow separation occurred at the rotor suction surface because of the low Reynolds number. The position of the separation onset fluctuated periodically as much as about 10% of the rotor axial-chord by the rotor-stator interaction. The turbulence in the wake region was anisotropy, and it exhibited strong Reynolds stress.

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Stalling Pressure Rise Capability of Axial Flow Compressor Stages

Journal of Engineering for Power ◽

10.1115/1.3230787 ◽

1981 ◽

Vol 103 (4) ◽

pp. 645-656 ◽

Cited By ~ 54

Author(s):

C. C. Koch

Keyword(s):

Experimental Data ◽

Reynolds Number ◽

Axial Flow ◽

Pressure Rise ◽

Tip Clearance ◽

Flow Coefficient ◽

Low Speed ◽

Axial Flow Compressor ◽

Wide Range ◽

Flow Compressor

A procedure for estimating the maximum pressure rise potential of axial flow compressor stages is presented. A simplified stage average pitchline approach is employed so that the procedure can be used during a preliminary design effort before detailed radial distributions of blading geometry and fluid parameters are established. Semi-empirical correlations of low speed experimental data are presented that relate the stalling static-pressure-rise coefficient of a compressor stage to cascade passage geometry, tip clearance, bladerow axial spacing and Reynolds number. Blading aspect ratio is accounted for through its effect on normalized clearances, Reynolds number and wall boundary layer blockage. An unexpectedly strong effect of airfoil stagger and of the resulting flow coefficient of the stage’s vector triangle is observed in the experimental data. This is shown to be caused by the differing ability of different types of stage vector triangles to re-energize incoming low-momentum fluid. Use of a suitable “effective” dynamic head in the pressure rise coefficient gives a good correlation of this effect. Stalling pressure rise data from a wide range of both low speed and high speed compressor stages are shown to be in good agreement with these correlations.

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