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Title: Blade tip heat transfer measurements in a shroudless, transonic, high pressure turbine
Author: Jackson, Adam James
ISNI:       0000 0004 2720 9234
Awarding Body: Oxford University
Current Institution: University of Oxford
Date of Award: 2011
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To improve the performance of aero-engines manufacturers strive to increase the inlet temperature to the high pressure turbine. The components that are exposed to the hot gas - particularly the over-tip casing and blade tips of shroud less turbines - are vulnerable to heat damage. A previous investigation using the Oxford Rotor Facility demonstrated that a backwards facing casing step - located 20 % of high pressure blade axial chord upstream of the leading edge of the rotor - could mitigate the significant convective heat loads that the over-tip casing must withstand. This thesis describes an investigation into the effect ofthe aforementioned casing step on blade tip heat transfer rates. A second investigation, to determine the effect of the tip gap size on blade tip heat transfer rates, is also reported. These investigations necessitated the acquisition of two sets of experimental measurements. In both instances the casing step was present. The time resolved heat transfer rate data was obtained using thirty- five thin film gauges distributed over three blade tips. A small number of blade relative aerodynamic measurements were also performed. The aerodynamic measurements were valuable in helping to elucidate the mechanisms responsible for the measured changes of heat transfer rate. In order to investigate the effect of the tip gap size it was necessary to modify the over-tip casing before the second set of measurements were made. Detailed measurements of the over-tip casing were made before and after the modifications. It was shown that the mod- ifications reduced the mean tip gap to approximately two thirds ofthe baseline size. Computational fluid dynamics calculations were performed to complement the predomi- nantlyexperimental investigations. The predictive work was undertaken in order to obtain further insight into the mechanisms underpinning the changes of heat transfer rate that were observed in the experiments.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available