Research Papers

Time-Averaged and Time-Accurate Aerodynamic Effects of Rotor Purge Flow for a Modern, One and One-Half Stage High-Pressure Turbine—Part II: Analytical Flow Field Analysis

[+] Author and Article Information
Brian R. Green

GE Aviation,
Cincinnati, OH 45215
e-mail: brian.green@ge.com

Randall M. Mathison

e-mail: mathison.4@osu.edu

Michael G. Dunn

e-mail: dunn.129@osu.edu
Gas Turbine Laboratory,
The Ohio State University,
2300 West Case Rd.,
Columbus, OH 43235

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received July 5, 2012; final manuscript received May 23, 2013; published online September 20, 2013. Editor: David Wisler.

J. Turbomach 136(1), 011009 (Sep 20, 2013) (12 pages) Paper No: TURBO-12-1130; doi: 10.1115/1.4024776 History: Received July 05, 2012; Revised May 23, 2013

The detailed mechanisms of purge flow interaction with the hot-gas flow path were investigated using both unsteady computationally fluid dynamics (CFD) and measurements for a turbine operating at design corrected conditions. This turbine consisted of a single-stage high-pressure turbine and the downstream, low-pressure turbine nozzle row with an aerodynamic design equivalent to actual engine hardware and typical of a commercial, high-pressure ratio, transonic turbine. The high-pressure vane airfoils and inner and outer end walls incorporated state-of-the-art film cooling, and purge flow was introduced into the cavity located between the high-pressure vane and disk. The flow field above and below the blade angel wing was characterized by both temperature and pressure measurements. Predictions of the time-dependent flow field were obtained using a three-dimensional, Reynolds-averaged Navier–Stokes CFD code and a computational model incorporating the three blade rows and the purge flow cavity. The predictions were performed to evaluate the accuracy obtained by a design style application of the code, and no adjustment of boundary conditions was made to better match the experimental data. Part I of this paper compared the predictions to the measurements in and around the purge flow cavity and demonstrated good correlation. Part II of this paper concentrates on the analytical results, looking at the primary gas path ingestion mechanism into the cavity as well as the effects of the rotor purge on the upstream vane and downstream rotor aerodynamics and thermodynamics. Ingestion into the cavity is driven by high static pressure regions downstream of the vane, high-velocity flow coming off the pressure side of the vane, and the blade bow waves. The introduction of the purge flow is seen to have an effect on the static pressure of the vane trailing edge in the lower 5% of span. In addition, the purge flow is weak enough that upon exiting the cavity, it is swept into the mainstream flow and provides no additional cooling benefits on the platform of the rotating blade.

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Fig. 1

Stationary and rotating instrumentation locations in the purge flow cavity (not to scale)

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Fig. 2

Time-averaged cavity streamlines (a) aligned with and (b) away from ingestion zone

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Fig. 3

Rim seal time-averaged vector field (a) aligned with ingestion zone and (b) away from ingestion zone

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Fig. 4

Purge flow forward progressing streamlines for the time-averaged harmonic solution for (a) top looking down view, (b) side view, and (c) forward looking aft side view (not to scale)

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Fig. 5

Instantaneous radial velocity contours on the purge flow cavity and main gas path interface for (a) t = 0, (b) t = 0.055, (c) t = 0.11, (d) t = 0.167, (e) t = 0.22, (f) t = 0.278, (g) t = 0.33, (h) t = 0.389, (i) t = 0.44, and (j) t = 0.5

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Fig. 6

Measured and predicted stationary cavity unsteady static pressure for the (a) PV104 and PV105 location and the (b) PV107 and PV108 location

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Fig. 7

Measured and predicted stationary cavity unsteady static pressure for (a) the PRW70 location, (b) the PRW71 location, and (c) the PRW72

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Fig. 8

Instantaneous static pressure contours on the radial planes of the upper stationary and rotating Kulite gauge locations for time steps 0–0.5 ((a)–(j))

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Fig. 9

Vane exit profiles forward and aft of the cavity

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Fig. 10

Vane hub surface static pressure at 2% span for (a) full wetted distance and (b) aft 40% of wetted distance

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Fig. 11

Vane trailing edge hub static pressure comparison between run 22 and run 28

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Fig. 12

Static pressure for HP blade at 2% span for (a) the full wetted distance, (b) the first 30% of the wetted distance, and (c) leading edge stagnation points




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