Research Papers

Coriolis Effects on the Flow Field Inside a Rotating Triangular Channel for Leading Edge Cooling

[+] Author and Article Information
Luca Casarsa

Dipartimento di Ingegneria Elettrica,
Gestionale e Meccanica,
University of Udine,
Via delle scienze 206,
Udine 33100, Italy

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received May 24, 2013; final manuscript received September 2, 2013; published online October 25, 2013. Assoc. Editor: Li He.

J. Turbomach. 136(3), 031019 (Oct 25, 2013) (12 pages) Paper No: TURBO-13-1083; doi: 10.1115/1.4025570 History: Received May 24, 2013; Revised September 02, 2013

The flow field inside a rotating smooth radial channel with a triangular shaped cross section is investigated. Test conditions resemble those pertaining to the passages used for the internal cooling of the gas turbine blade's leading edge. Heat transfer data are also available from the literature on the same geometry and at comparable working conditions and have been profitably used for a combined aerothermal analysis. The model consists of a straight smooth channel with an equilateral triangle cross section. The rotation axis is aligned with one of the triangle bisectors. Two dimensional particle image velocimetry (PIV) and stereo-PIV were used in order to characterize the inlet flow (in static conditions) and the rotation-induced secondary flow in the channel cross section at Re = 20,000, Ro = 0.2 and Re = 10,000, Ro = 0.4. A wider range of working conditions (Re = 10,000–40,000, Ro = 0.2–0.6) was explored by means of Reynolds averaged Navier–Stokes (RANS) simulations carefully validated by the available PIV data. The turbulence was modeled by means of the shear stress transport (SST) model with a hybrid near-wall treatment. The results show that the rotation-induced flow structure is rather complicated and show relevant differences compared to the flow models that have been considered thus far. Indeed, the secondary flow turned out to be characterized by the presence of two or more vortex cells, depending on channel location and Ro number. No separation or reattachment of these structures is found on the channel walls but they have been observed at the channel apexes. The stream-wise velocity distribution shows a velocity peak close to the lower apex and the overall flow structure does not reach a steady configuration along the channel length. This evolution is fastened (in space) if the rotation number is increased while changes of the Re number have no effect. Finally, due to the understanding of the flow mechanisms associated with rotation, it was possible to provide a precise justification of the channel thermal behavior.

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Fig. 1

Secondary flow model proposed by Liu et al. [4]

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Fig. 2

Schematic of the test section and localization and nomenclature of the PIV measurement planes (dimensions in mm)

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Fig. 3

Comparison of (a) streamwise U, and (b) spanwise V, velocity profiles from 2D and stereo-PIV extracted at position x = 520 mm and z = 0 mm from planes xy (2D data) and yz1 (stereo data)

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Fig. 4

Overview and details of the computational mesh

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Fig. 5

Comparison of the streamwise velocity profiles from the CFD and 2D-PIV extracted at position x = 120 mm from planes (a) IN3, and (b) IN1-2

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Fig. 6

Computed velocity profiles (top) from meshes with different numbers of elements (bottom). Data extracted at position x = 120 mm from plane IN3.

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Fig. 7

Comparison of (a) numerical, and (b) experimental time-averaged stream tracers in plane yz1 for Re = 20,000, Ro = 0.2

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Fig. 8

Contour map of the pressure distribution on the channel cross section at x = 520 mm obtained by the CFD at Re = 20,000 and Ro = 0.2. The dashed arrows indicate the displacement of the near wall flow caused by the pressure gradient that, locally, is not balanced by the Coriolis forces.

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Fig. 9

Three-dimensional view of the velocity distribution inside the Ekman layers from (a) CFD, and (b) stereo-PIV

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Fig. 10

Comparison of the (a) numerical, and (b) experimental time-averaged streamwise velocity contour map in plane yz1 for Re = 20,000, Ro = 0.2

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Fig. 11

Contour maps of the (a) streamwise, and (b) spanwise velocities at different channel locations from the CFD at Re = 20,000, Ro = 0.2

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Fig. 12

(a) Contour maps of the streamwise velocity and stream tracers at different channel locations, and (b) evolution along the channel of the streamwise and spanwise velocities at point y = 38 mm, z = 24 mm (see the blue line in (a)). The CFD data at Re = 20,000, Ro = 0.4.

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Fig. 13

Contour maps of the streamwise velocity and stream tracers at different channel locations. The CFD data at Re = 20,000, Ro = 0.6.

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Fig. 14

Comparison of contour maps of the streamwise velocity and stream tracers in plane yz1 (x = 520 mm): CFD data at Ro = 0.4 and (a) Re = 40,000, and (b) Re = 10,000; (c) stereo-PIV data at Ro = 0.4 and Re = 10,000

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Fig. 15

Experimental contour maps of flow turbulence intensity in plane yz1 (x = 520 mm) for (a) Re = 20,000, Ro = 0.2, and (b) Re = 10,000, Ro = 0.4

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Fig. 16

Heat transfer data from Liu et al. [4]




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