On the Physics of Heat Transfer and Aerodynamic Behavior of Separated Flow Along a Highly Loaded Low Pressure Turbine Blade Under Periodic Unsteady Wake Flow and Varying of Turbulence Intensity

Abstract

This paper attempts to provide a detailed insight into the heat transfer and aerodynamic behavior of a separation zone that is generated as a result of boundary layer development along the suction surface of a highly loaded low pressure turbine blade. This paper experimentally investigates the individual and combined effects of periodic unsteady wake flows and freestream turbulence intensity (Tu) on heat transfer and aerodynamic behavior of the separation zone. Heat transfer experiments were carried out at Reynolds numbers of 110,000, 150,000, and 250,000 based on the suction surface length and the cascade exit velocity. Aerodynamic experiments were performed at Re=110,000. For the above Re numbers, the experimental matrix includes Tu’s of 1.9%, 3.0%, 8.0%, and 13.0% and three different unsteady wake frequencies with the steady inlet flow as the reference configuration. Detailed heat transfer and boundary layer measurements are performed with particular attention paid to the heat transfer and aerodynamic behavior of the separation zone at different Tu’s at steady and periodic unsteady flow conditions. The objectives of the research are (a) to quantify the effect of Tu on the aerothermal behavior of the separation bubble at steady inlet flow conditions, (b) to investigate the combined effects of Tu and the unsteady wake flow on the aerothermal behavior of the separation bubble, and (c) to provide a complete set of heat transfer and aerodynamic data for numerical simulation that incorporates Navier–Stokes and energy equations. The experimental investigations were performed in a large-scale, subsonic, unsteady turbine cascade research facility at the Turbomachinery Performance and Flow Research Laboratory of Texas A&M University.