Title page for ETD etd-12202011-172031

Type of Document Master's Thesis
Author Samal, Nihar Ranjan
Author's Email Address bsamal@vt.edu
URN etd-12202011-172031
Title A wind tunnel facility for the evaluation of a land-based gas turbine diffuser-collector
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Ng, Wing F. Committee Chair
Dancey, Clinton L. Committee Co-Chair
Lowe, Kevin Todd Committee Co-Chair
  • Annular diffuser
  • Diffuser-Collector
  • Exhaust hood
  • Pressure recovery
  • Stereo-PIV
Date of Defense 2011-12-07
Availability unrestricted
A subsonic wind tunnel facility was built and tested as part of a base line test investigating flow within a diffuser-collector. Facility controls allowed the quarter scale model to match both Reynolds number and Mach number. Mass averaged conditions at the diffuser inlet during testing were determined as 1.939 × 106 for Reynolds number based upon diffuser inlet hydraulic diameter, and 0.418 for Mach number. A flow conditioning section prior to test section contained several interchangeable sections. Flow conditioning components were used to create flow characteristic of that leaving the last stage of a land-based gas turbine. The diffuser-collector subsystem was evaluated through the use of wall static pressure measurements, a variety of probe traverse measurements, and Stereo-PIV. Flow within the collector and diffuser were determined to be heavily dependent upon the collector geometry. PIV measurements showed the development of two large counter rotating vortices within the collector. Each symmetric vortex grew and shifted according to the collector geometry while creating complex regions of flow. Pressure recovery within the diffuser was in range of 0.47 to 0.78, and would drop to 0.52 at the collector exit. The drop in pressure recovery was presumed to be a combination of inefficient diffusion in the collector and losses due to the vortices. The baseline test was found to be successful in terms of facility design, and determining the critical flow phenomena. Further testing and experimentation are necessary to evaluate specific details of the collector geometry’s effect upon the pressure recovery and flow development.
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