Cooling performance investigation of a two-pass rib-roughened channel

Kavas, İsa
The performance of the modern aero-engines is highly dependent on the turbine inlet gas temperature. The higher temperature leads to more compact and efficient machines. Additionally, specific fuel consumption of the engine is decreased for the same thrust rating. However, the turbine inlet temperatures of the today’s engines are already beyond the material structural limits. Hence, the turbine section must be cooled down to acceptable levels. Various types of cooling methods are typically applied to the gas turbine blades like internal cooling, film cooling, impingement cooling etc. The internal cooling channels are embedded inside the turbine blades and often equipped by ribs in order to enhance the turbulence activities and heat transfer area. Cooling channels may form as a single pass or multi-pass channels depending on the design considerations. Current research focuses on vi experimentally and numerically investigating the thermal performance of a 2-pass channel. Especially the performance of U turn section and its effect on the second channel were studied. A rectangular cross section tunnel with two passage and a U-turn section that mimic the modern gas turbine cooling configurations was designed and manufactured. The ribs with square cross section are located on the bottom wall of both passages. The ambient air is sucked to the wind tunnel by using a blower. The bottom wall of the test section was heated by a foil heater which generates uniform heat flux. The wall surface temperature was obtained by means of optical thermography method (IR camera). The heat loss was computed assuming one-dimensional heat conduction through the wall. The experiments were conducted at three Reynolds number by changing the blower speed. Finally the Nusselt number was computed based on the heater power, surface temperature and the mainstream temperature. The results were compared with the smooth wall configuration. The current investigation aims to provide Nusselt numbers and deep understanding of the flow physics of the modern gas turbine cooling configuration both experimentally an numerically. The U-turn section and cooling passage interaction is investigated. The cooling effectiveness improvement by design is addressed at the end of the manuscript. Experimental results are compared with the numerical analysis to come up with a suitable turbulence model.


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Citation Formats
İ. Kavas, “Cooling performance investigation of a two-pass rib-roughened channel,” M.S. - Master of Science, Middle East Technical University, 2015.