Abstract
The concurrent use of film cooling and internal cooling plays an important role to maintain the life of turbine blades and increase thermal efficiency. Several studies were published on the interaction of these cooling strategies but these are mainly investigations on how internal cooling influences film cooling. The present study contributes to an improved understanding on how the cooling extraction through film cooling holes is influencing internal flow structures and therefore internal cooling. The flow field in an internal cooling channel is investigated by measuring the velocity distribution with 2D-PIV. Heat transfer measurements are performed using the thermochromic liquid crystal technique. The test stand models a rectangular cooling channel (AR=2:1), which is equipped with parallel ribs of four different geometries (90° ribs, 60° ribs, 60°-V-shaped ribs and 60°-Λ-shaped ribs). Bleed holes are placed in the rib segments and are positioned at three positions in streamwise direction. The suction ratio is varied between 0 and 6 and the cooling channel Reynolds number is 30.000.
Highlights
The increasing demands on thermal efficiency in the development of high performance gas turbines imply rising rotor inlet temperatures, which exceed the blades maximum allowable material temperatures
The present study extends the investigations to further rib geometries. 60°, V and Λ ribs are tested with varying cooling hole positions
The rectangular cooling channel of the test rig is equipped with 10 rib segments containing cooling holes
Summary
The increasing demands on thermal efficiency in the development of high performance gas turbines imply rising rotor inlet temperatures, which exceed the blades maximum allowable material temperatures. This requires an effective cooling system to prevent the blades from damage. The combination of internal cooling and film cooling is state of the art technology for blade cooling. Pressurized air from the compressor is extracted and routed through internal passages in the turbine blade to remove heat. The air from the internal passages is ejected through film cooling holes and forms a layer to prevent the blades surface from the hot gas. A representative design of the current generation of turbine rotor blade cooling technology can be found in Town et al (2017)
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