Effects of Low Reynolds Number on Wake-Generated Unsteady Flow of an Axial-Flow Turbine Rotor
<p>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 length <math alttext="$Rea_{ext{out}, ext{RT}$"> <mrow> <...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2005-01-01
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| Series: | International Journal of Rotating Machinery |
| Subjects: | |
| Online Access: | http://www.hindawi.net/access/get.aspx?journal=ijrm&volume=2005&pii=S1023621X04502063 |
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| Summary: | <p>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 length <math alttext="$Rea_{ext{out}, ext{RT}$"> <mrow> <msub> <mrow> <mo>Re</mo> </mrow> <mrow> <mtext>out</mtext><mo>,</mo><mtext>RT</mtext> </mrow> </msub> </mrow> </math>, was varied from <math alttext="$3.2 imes 10^4$"> <mn>3.2</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math> to <math alttext="$12.8imes10^4$"> <mn>12.8</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math> at intervals of <math alttext="$1.6 imes 10^4$"> <mn>1.0</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math> by 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 number <math alttext="$Rea_{ext{out}, ext{RT} = 3.2imes 10^4$"> <msub> <mo>Re</mo> <mrow> <mtext>out</mtext><mo>,</mo><mtext>RT</mtext> </mrow> </msub> <mo>=</mo><mn>3.2</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math> was <math alttext="$1.5$"> <mn>1.5</mn> </math> times larger than that at the high Reynolds number <math alttext="$Rea_{ext{out}, ext{RT} = 12.8 imes 10^4$"> <msub> <mo>Re</mo> <mrow> <mtext>out</mtext><mo>,</mo><mtext>RT</mtext> </mrow> </msub> <mo>=</mo><mn>12.8</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math>. The curve of the <math alttext="$-0.2$"> <mo>−</mo><mn>0.2</mn> </math> power of the Reynolds number agreed with the measured energy-dissipation thickness at higher Reynolds numbers. However, the curve of the <math alttext="$-0.4$"> <mo>−</mo><mn>0.4</mn> </math> power law fitted more closely than the curve of the <math alttext="$-0.2$"> <mo>−</mo><mn>0.2</mn> </math> power law at lower Reynolds numbers below <math alttext="$6.4imes 10^4$"> <mn>6.4</mn><mo>×</mo><msup> <mn>10</mn> <mn>4</mn> </msup> </math>.</p> |
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| ISSN: | 1023-621X |