研究目的
To study the combined effects of unsteady wakes and oncoming free-stream turbulence intensities on the film cooling effectiveness of a turbine blade using the pressure sensitive paint (PSP) technique.
研究成果
The research concludes that unsteady wakes and high free-stream turbulence generally reduce film cooling effectiveness on turbine blades, with effects varying by surface region and mass flux ratio. High turbulence diminishes the impact of wakes, and the suction surface is more affected than the pressure surface. These findings provide insights for optimizing cooling strategies in gas turbines.
研究不足
The study is limited to a specific blade geometry and scale model; results may not fully represent real turbine conditions. Uncertainty in PSP measurements increases at lower effectiveness values, and the experimental setup may not capture all complex flow interactions in actual engines.
1：Experimental Design and Method Selection:
The study uses a linear cascade setup with a spoke-wheel type wake generator to simulate unsteady wakes. The PSP technique is employed to measure film cooling effectiveness, based on photoluminescence and oxygen quenching principles.
2：Sample Selection and Data Sources:
A scaled-up turbine blade model with specific film hole configurations is used. Mainstream and secondary flows are controlled, with nitrogen as coolant for PSP measurements.
3：List of Experimental Equipment and Materials:
Includes centrifugal blower, compressor, nitrogen tank, flow meter, heater, wake generator, hot-wire probe, pressure taps, PSP paint (UniFIB), CCD camera, excitation light, and turbulence grid.
4：Experimental Procedures and Operational Workflow:
Mainstream air flows through the cascade; secondary flow (nitrogen or air) is injected through film holes. PSP measurements involve four tests under dark, reference, and test conditions to obtain emission intensities. Pressure and turbulence measurements are conducted using pressure taps and hot-wire probes.
5：Data Analysis Methods:
Data is analyzed using the Stern-Volmer equation for PSP calibration and uncertainty analysis based on established methods. Film cooling effectiveness is calculated from oxygen partial pressures.
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Hot-Wire Probe
55P14-type
DANTEC
Used to measure turbulence intensity in the cascade.
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Anemometer System
StreamLine
DANTEC
Connected to the hot-wire probe for turbulence measurements.
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Pressure Sensitive Paint
UniFIB
Used to measure static pressure distribution and film cooling effectiveness on the blade surface via photoluminescence and oxygen quenching.
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Pressure System
NetScannerTM 9816
Used to measure pressure distribution from pressure taps on the blade.
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CCD Camera
Used to capture emitted light intensities during PSP measurements.
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Excitation Light
Used to excite the PSP for photoluminescence.
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Wake Generator
Spoke-wheel type
Simulates upstream unsteady wakes using rotating rods.
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Turbulence Grid
Creates high free-stream turbulence intensity in the mainstream flow.
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Centrifugal Blower
Supplies mainstream air for the cascade.
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Compressor
Supplies secondary air flow for cooling.
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Nitrogen Tank
Supplies nitrogen as coolant for PSP measurements.
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Flow Meter
Measures flow rates of secondary flow.
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Heater
Heats the secondary flow if needed.
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Three-Phase Asynchronous Motor
Drives the wake generator.
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Frequency Converter
Adjusts the rotation speed of the wake generator.
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