| dc.description.abstract | Three test sections are investigated in the study. One is a three-passage channel with hub turn, another is two-passage channel with tip turn, and the other is a four-passage serpentine channel. The test section with hub turn is a three-passage internal cooling channel with a 180° U-bend at the hub turn portion. The flow is radially inward at the second passage, while it is radially outward at the third passage after the U-bend. Measurement was conducted at the second and the third passages. Aspect ratio of the second passage is 2:1 (AR=2:1), and the third passage is wedge-shaped with side wall slot ejections. Study of heat transfer begins with smooth channel surface. Roughened surface with rib turbulators and pin-fin array is also tested. Tests are conducted for both cases of with and without turning vane at the turn portion. Range of Reynolds numbers is from 10,000 to 40,000, and the corresponding rotation number is from 0 to 0.32.
The test section with tip turn is a two-passage rectangular channel with aspect ratio of 2:1, and two 90° sharp turn at tip. Tests are only conducted with roughened surface. Straight ribs are placed on leading and trailing surfaces of both passages with P/e = 8, e/Dh = 0.1, α = 45°. Ribs are in staggered arrangement between leading and trailing surfaces. With and without vane conditions are both studied. Range of rotation number studied is from 0 to 0.42
The serpentine channel has geometry more close to real engine blades. The aspect ratio of each passage is increasing from leading edge to trailing, while the orientation angle of passage is decreasing. Broken ribs are attached to the leading and trailing surface of the channel and heat transfer is studied. Heat transfer data is compared with previous geometry of straight ribs on the same test section. Rotation numbers studied are 0 and 0.23.
Nu/Nus to rotation number correlation is found on every surface for all geometries of all three test sections. Rotation effect on leading and trailing surfaces is different depending on the flow direction, which is consistent with previous studies. Heat transfer enhancement at tip turn and hub turn are reported. The effect of turning vane is also shown. | en |
