Time Accurate Evaluation of Shaped Hole Film Cooling Effectiveness Using an Infrared Compensated Pressure Sensitive Paint Technique
| Main Authors: | Spencer Sperling, Randall Mathison |
|---|---|
| Format: | Proceeding Journal |
| Bahasa: | eng |
| Terbitan: |
, 2018
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/1342430 |
Daftar Isi:
- A modified method is proposed to evaluate film cooling performance utilizing high-frequency response polymer ceramic pressure sensitive paint (PSP). This paint offers unique possibilities for measuring the unsteady behavior of cooling jets due to its negligible signal attenuation up to a frequency of 1 kHz and a -3 dB attenuation at 10 kHz, however it is also quite sensitive to temperature variations. It is therefore necessary to correct the results according to the paint surface temperature as well as the gas temperature above the painted surface. Surface temperature is measured with an infrared (IR) camera, and to account for the change in oxygen concentration due to gas temperature the paint is calibrated to density instead of pressure. The ultimate goal of the method under development is to obtain high-speed film cooling measurements in a full-stage transonic turbine tested at design corrected conditions in a short-duration facility. To simulate this, the current study utilizes a medium duration blowdown wind tunnel to investigate the impact of large temperature variations. The film cooling effectiveness is measured for a baseline case of five 7-7-7 diffuser-shaped film cooling holes installed on a flat plate. The flow provided by the blowdown facility is characterized by large changes in total pressure and total temperature, and it provides a challenging trial of the measurement technique before it is subject to the turbine test environment. Unsteady characteristics of the diffuser shaped holes in this experiment, including the tendency of the jet to oscillate and periodically detach from the surface, are captured with a high-speed camera, and the time-averaged film effectiveness is shown to agree well with the performance documented in previous studies