Session: 12-01 Experimental studies on film cooling

Paper Number: 123466

123466 - Passage Secondary Flow Effects on Turbine Endwall Discrete Hole Film Cooling - A Review With Unique New Evidence 

Film cooling effectiveness measurement results are discussed for an endwall of a five-blade linear cascade using a high-performance rotor blade profile. The heat/mass transfer analogy is applied. The effects of the interaction of secondary flows naturally occurring in a turbine passage and the ejected coolant from discrete film cooling holes are studied by injecting naphthalene-free and naphthalene-saturated air as coolant to determine the downstream film cooling effectiveness distribution. The film cooling holes are distributed uniformly over the endwall surface. Blowing ratios of 0.75, 1.5, and 2.5 are applied. Endwall surface wall shear fields are documented using oil-dot visualization to indicate the angles between the approach flow to selected coolant holes and their corresponding coolant hole axes. Since the shear fields are taken without holes, the directions accurately apply to only the first row of holes. Results from recent studies in the literature of the interaction of coolant flows and surrounding vortices are applied to develop hypotheses regarding the effects of vortices on passage endwall surface effectiveness data downstream of the holes studied. For a discrete hole located under the pressure leg horseshoe vortex near the passage entry, ejected coolant is swept by the vortex resulting in low surface effectiveness, as documented by the surface effectiveness data. For discrete holes located in the region where the pressure and suction leg horseshoe vortices merge, the shear field (affected by coolant injection) offers only an approximate approach flow angle, but the coolant flow is more strongly influenced by passage vortices. Here, the ejected coolant is lifted by the suction leg horseshoe vortex and is also influenced by the pressure leg horseshoe vortex. As a result, the ejected coolant is partially restrained to be under the pressure leg horseshoe vortex and the surface effectiveness is increased. Also, ejected coolant is partially washed into the suction leg horseshoe vortex, reducing surface effectiveness values further. However, since the suction leg horseshoe vortex is strengthened by the ejected coolant, it can sustain further downstream an up-wash of flow driven by the pressure leg horseshoe vortex and, thus, enhance surface effectiveness downstream.

 

Presenting Author: Ting Wei Chen University of Minnesota, Twin Cities

Presenting Author Biography: Ting-Wei Chen, from Tainan, Taiwan, is pursuing a master's degree in mechancial engineering with a specilization in thermal and fluid science at University of Minnesota, Twin Cities. He graudated from National Cheng Kung University (NCKU) in 2020 with a bacheloar's degree in System and Naval Mechatronic engineering. Afterwards, he worked as a thermal engineering in ASUS Technology concentrated on electronic cooling in the notebook systems. His current research is focused on film cooling and secondary flow in the heating section of the gas turbine.

Authors:

Ting-Wei Chen University of Minnesota, Twin Cities
Matthew Stinson Trane Technologies
Terrence Simon University of Minnesota, Twin Cities