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TECHNICAL PAPERS

Investigation of the Flow Field in a High-Pressure Turbine Stage for Two Stator-Rotor Axial Gaps—Part I: Three-Dimensional Time-Averaged Flow Field

[+] Author and Article Information
P. Gaetani

Dipartimento di Energetica, Politecnico di Milano, Via la Masa 34, I-20158, Italypaolo.gaetani@polimi.it

G. Persico, V. Dossena, C. Osnaghi

Dipartimento di Energetica, Politecnico di Milano, Via la Masa 34, I-20158, Italy

J. Turbomach 129(3), 572-579 (Jul 28, 2006) (8 pages) doi:10.1115/1.2472383 History: Received July 13, 2006; Revised July 28, 2006

An extensive experimental analysis on the subject of unsteady flow field in high-pressure turbine stages was carried out at the Laboratorio di Fluidodinamica delle Macchine (LFM) of Politecnico di Milano. The research stage represents a typical modern HP gas turbine stage designed by means of three-dimensional (3D) techniques, characterized by a leaned stator and a bowed rotor and operating in high subsonic regime. The first part of the program concerns the analysis of the steady flow field in the stator-rotor axial gap by means of a conventional five-hole probe and a temperature sensor. Measurements were carried out on eight planes located at different axial positions, allowing the complete definition of the three-dimensional flow field both in absolute and relative frame of reference. The evolution of the main flow structures, such as secondary flows and vane wakes, downstream of the stator are here presented and discussed in order to evidence the stator aerodynamic performance and, in particular, the different flow field approaching the rotor blade row for the two axial gaps. This results set will support the discussion of the unsteady stator-rotor effects presented in Part II (Gaetani, P., Persico, G., Dossena, V., and Osnaghi, C., 2007, ASME J. Turbomach., 129(3), pp. 580–590). Furthermore, 3D time-averaged measurements downstream of the rotor were carried out at one axial distance and for two stator-rotor axial gaps. The position of the probe with respect to the stator blades is changed by rotating the stator in circumferential direction, in order to describe possible effects of the nonuniformity of the stator exit flow field downstream of the stage. Both flow fields, measured for the nominal and for a very large stator-rotor axial gap, are discussed, and results show the persistence of some stator flow structures downstream of the rotor, in particular, for the minimum axial gap. Finally, the flow fields are compared to evidence the effect of the stator-rotor axial gap on the stage performance from a time-averaged point of view.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of LFM closed-loop test rig

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Figure 2

Meridional view of LFM axial section and axial turbine stage view

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Figure 3

Contours of (a) total pressure loss coefficient, (b) streamwise vorticity, (c) radial Mach number, and (d) blade-to-blade flow angle (x∕bs=0.16)

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Figure 4

Total pressure loss coefficient, streamwise vorticity and radial Mach number contours at (a–c)x∕bs=0.35 and (d–f)x∕bs=0.60

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Figure 5

(a–c) Radial distribution of pitchwise mass averaged loss coefficient, Mach number components, and outlet angle

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Figure 6

Cpt,R contours upstream of the rotor for the minimum gap (a) and the maximum gap (b) and radial distribution of pitchwise averaged rotor incidence for both cases (c)

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Figure 7

Relative total pressure coefficient, rotor deviation angle, and radial Mach number contours at the rotor exit for the case of minimum gap (a–c) and maximum gap (d–f)

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Figure 8

Pitchwise mass-averaged radial distribution of tangential Mach number upstream and downstream of the rotor and efficiency for both axial gaps

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