An experimental study of heat transfer in the rectangular coolant passages of a gas turbine rotor blade

Abstract

Modern gas turbines have high inlet temperatures to harness maximum power output, which causes different components to experience severe thermal stresses and fatigue. To achieve turbine blade durability goals, the blades are cooled with air extracted from the compressor. The amount of air to be extracted depends on the heat transfer duty required from the turbine rotor blade. But this air extraction process lowers the overall turbine efficiency. This study presents the heat local transfer from a stationary and rotating two-pass rectangular duct (AR=2:1) with and without rib turbulators with two channel orientations (90⁰ and 45⁰ to the direction of rotational plane). In rotation, the Coriolis and buoyancy forces cause different heat transfer patterns from the leading and trailing surfaces. The heat transfers from the first pass trailing and the second pass leading walls are enhanced by rotation. However, the first leading and second pass trailing surfaces show a decrease in heat transfer with rotation, and the difference between the heat transfer coefficient from the leading and trailing surfaces increases with the increase of rotation. The model orientation of the coolant channel has substantial effect on the secondary flow and heat transfer pattern. Rib turbulators with different configurations are placed at an angular (45⁰) fashion to the mainstream flow. These angular ribs not only trip the boundary layers but also produce secondary flows, which cause better enhancement of heat transfer from the surface. These secondary flows from ribs interact with the secondary flows from rotation and create new heat transfer characteristic processes. Form the study it is observed that 45⁰ parallel ribs produce better heat transfer enhancement than that of 45⁰ cross rib configuration does.