Unsteady wake effects on boundary layer transition and heat transfew characteristics of curved plate and turbine blade /
transition and heat transfer characteristics of a turbine blade is analyzed both experimentally and theoretically. Two different test sections, a curved plate under zero pressure gradient and a five-blade turbine cascade, are utilized for experimentation. Comprehensive aerodynamic and heat transfer...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733050131&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | transition and heat transfer characteristics of a turbine blade is analyzed both experimentally and theoretically. Two different test sections, a curved plate under zero pressure gradient and a five-blade turbine cascade, are utilized for experimentation. Comprehensive aerodynamic and heat transfer experiments are conducted on these two different test sections for different wake frequencies that are typical of turbomachinery. Hot-wire anemometry is used for instantaneous velocity measurements inside the boundary layer and steady liquid crystal technique is used for the measurement of heat transfer coefficients. Instantaneous velocities are analyzed for intermittency and scales of turbulence during the transition period. Three parameters are identified for complete specification of intermittency distribution inside the boundary layer under these unsteady flow conditions. They are: (1) maximum intermittency, (2) minimum intermittency and (3) relative intermittency. Minimum intermittency corresponds to the value outside the wake (free stream) and transition process is natural transition. Under natural transition, the intermittency value starts off with a value near 0.0 inside the laminar boundary layer and gradually raises to a maximum value. On the other hand, maximum intermittency corresponds to the intermittency value when high-turbulent wake core is at the point of interest on the blade surface and the transition process under these conditions is induced transition. After going through a minimum near the leading edge portion of the blade, maximum intermittency value again comes back to a value near 1.0 through induced transition. The blade characteristics (skin friction and heat transfer coefficients) change periodically depending on the presence of the wakes on the surface. The ensemble-averaged intermittency is integrated for time-averaged distribution and is modeled for implementation in a numerical boundary layer code. The developed expressions for the three intermittency distributions are implemented in TEXSTAN (a boundary layer code) through mixing length model for transition and the results are in good agreement with the experimental data thereby validating the transition model. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xxii, 210 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 141-148). |