HEAT TRANSFER CHARACTERISTICS OF AN INTERNAL COOLING CHANNEL WITH PINFINS USING RECESSED-EXTRUDED ENDWALL COUPLING IN GAS TURBINE BLADE

초록

This work numerically explores the vortices creation and preservation in a channel with pin-fins for two endwall-turbulation systems: the flat endwall and the recessed-extruded endwall, while studying the flow structure therein. The heat transfer characteristics, including Nusselt number, friction factor, and HTEI, are analyzed and compared with the smooth endwall case at Reynolds numbers ranging from 7400 to 36000. The simulations are carried out with the RANS method. It is reported in the results that, with the new endwall configuration, the high heat transfer areas near the pin-fins are noticeably enlarged compared to the flat endwall at all the tested Reynolds numbers. Besides, the new endwall design increases the heat transfer level near the pin-fins, represented by an enhancement of 64.3% of the Nusselt number compared to the flat endwall at Re = 36000. However, the growth in friction factor due to the flow obstruction at all the Reynolds numbers is trivial. It has been discovered that the enhancement in heat transfer capacity is induced mainly by the combination of the indentations and protrusions that the geometry creates. When considering the heat transfer performance, the HTEI of the recessed-extruded endwall is increased by approximately 62.4% at Re = 21500 compared to the flat endwall, with a height of 2.5% channel height. These findings demonstrate the tremendous potential for enhancing the pin-fin's heat transfer by altering the endwall design.

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