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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.

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Title: 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.
Authors: Green, Brian R.1 brian.green@ge.com, Mathison, Randall M.2 mathisor.4@osu.edu, Dunn, Michael G.2 dunn.129@osu.edu
Source: Journal of Turbomachinery. Jan2014, Vol. 136 Issue 1, p1-12. 12p.
Subjects: Wind turbine blades, Impellers, Cooling, Computational fluid dynamics, High pressure (Technology), Nozzles, Gas flow, Thermodynamics
Abstract: The detailed mechanisms of purge flow interaction with the hot-gas flow path were inves-tigated 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 commer-cial, 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 intro-duced 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 pres-sure 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 experimen-tal 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 concen-trates 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 addi-tion, the purge flow is weak enough that upon exiting the cavity, it is swept into the main-stream flow and provides no additional cooling benefits on the platform of the rotating blade. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:The detailed mechanisms of purge flow interaction with the hot-gas flow path were inves-tigated 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 commer-cial, 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 intro-duced 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 pres-sure 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 experimen-tal 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 concen-trates 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 addi-tion, the purge flow is weak enough that upon exiting the cavity, it is swept into the main-stream flow and provides no additional cooling benefits on the platform of the rotating blade. [ABSTRACT FROM AUTHOR]
ISSN:0889504X
DOI:10.1115/1.4024776