Detailed film cooling effectiveness distributions were measured on the stationary
blade tip and on the leading edge region of a rotating blade using a Pressure Sensitive
Paint technique. Air and nitrogen gas were used as the film cooling gases and the
oxygen concentration distribution for each case was measured. The film cooling
effectiveness information was obtained from the difference of the oxygen concentration
between air and nitrogen gas cases by applying the mass transfer analogy. In the case of
the stationary blade tip, plane tip and squealer tip blades were used while the film
cooling holes were located (a) along the camber line on the tip or (b) along the span of
the pressure side. The average blowing ratio of the cooling gas was controlled to be 0.5,
1.0, and 2.0. Tests were conducted in a five-bladed linear cascade with a blow down
facility. The free stream Reynolds number, based on the axial chord length and the exit
velocity, was 1,100,000 and the inlet and the exit Mach number were 0.25 and 0.59,
respectively. Turbulence intensity level at the cascade inlet was 9.7%. All
measurements were made at three different tip gap clearances of 1%, 1.5%, and 2.5% of
blade span. Results show that the locations of the film cooling holes and the presence
of squealer have significant effects on surface static pressure and film-cooling effectiveness. Same technique was applied to the rotating turbine blade leading edge
region. Tests were conducted on the first stage rotor of a 3-stage axial turbine. The
Reynolds number based on the axial chord length and the exit velocity was 200,000 and
the total to exit pressure ratio was 1.12 for the first rotor. The effects of the rotational
speed and the blowing ratio were studied. The rotational speed was controlled to be
2400, 2550, and 3000 rpm and the blowing ratio was 0.5, 1.0, and 2.0. Two different
film cooling hole geometries were used; 2-row and 3-row film cooling holes. Results
show that the rotational speed changes the directions of the coolant flows. Blowing
ratio also changes the distributions of the coolant flows. The results of this study will
be helpful in understanding the physical phenomena regarding the film injection and
designing more efficient turbine blades.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4664 |
| Date | 25 April 2007 |
| Creators | Ahn, Jaeyong |
| Contributors | Han, Je-Chin |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 2832713 bytes, electronic, application/pdf, born digital |
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