AN INVESTIGATION OF COMBINED COOLING EFFECTS ON GAS TURBINE BLADES

Document Type : Original Article

Authors

Mechanical Power Engineering Department, Faculty of Engineering, Minoufiya University, Shibin El-Kawm, Egypt.

Abstract

In this paper, experimental measurements of the cascade loss in addition to
the local and overall cooling effectiveness on the suction and pressure surfaces of
a gas turbine blade cascade are presented. The influence of the coolant ratio and
inlet gases temperature on the cooling effectiveness are discussed. The
experiments were performed with seven blades linear cascade of the first stage of
a gas turbine. The experimental data were conducted for three cases; cold air, hot
gas flow without cooling of the blade and hot gas flow with blade cooling. The
combined cooling is achieved by a hole and five jets distributed at the leading
edge. The experiments include the distributions of blade wall-to-gas temperature
ratio and the velocity profiles measurements. The boundary layer parameters,
cooling effectiveness and cascade loss were calculated. The influence of coolant
temperature, inlet conditions of hot gases on the cooling effectiveness, the
boundary layer growth and the cascade losses are investigated. The results
indicated that, the cooling of the blade causes substantial increase in the boundary
layer thickness and the secondary loss compared with that of uncooled blade.
Also, the total loss increases as the flow moves in the direction of downstream and
approaching the trailing edge. The comparison between the combined and internal
cooling indicates that, the boundary layer thickness and the cooling effectiveness
are higher in case of combined cooling which means more efficient in such
applications.

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